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Sample records for acoustic transducer array

  1. Analog circuit for controlling acoustic transducer arrays

    DOEpatents

    Drumheller, Douglas S.

    1991-01-01

    A simplified ananlog circuit is presented for controlling electromechanical transducer pairs in an acoustic telemetry system. The analog circuit of this invention comprises a single electrical resistor which replaces all of the digital components in a known digital circuit. In accordance with this invention, a first transducer in a transducer pair of array is driven in series with the resistor. The voltage drop across this resistor is then amplified and used to drive the second transducer. The voltage drop across the resistor is proportional and in phase with the current to the transducer. This current is approximately 90 degrees out of phase with the driving voltage to the transducer. This phase shift replaces the digital delay required by the digital control circuit of the prior art.

  2. Electret Acoustic Transducer Array For Computerized Ultrasound Risk Evaluation System

    DOEpatents

    Moore, Thomas L.; Fisher, Karl A.

    2005-08-09

    An electret-based acoustic transducer array is provided and may be used in a system for examining tissue. The acoustic transducer array is formed with a substrate that has a multiple distinct cells formed therein. Within each of the distinct cells is positioned an acoustic transducing element formed of an electret material. A conductive membrane is formed over the distinct cells and may be flexible.

  3. Acoustic transducer

    DOEpatents

    Drumheller, Douglas S.

    2000-01-01

    An active acoustic transducer tool for use down-hole applications. The tool includes a single cylindrical mandrel including a shoulder defining the boundary of a narrowed portion over which is placed a sandwich-style piezoelectric tranducer assembly. The piezoelectric transducer assembly is prestressed by being placed in a thermal interference fit between the shoulder of the mandrel and the base of an anvil which is likewise positioned over the narrower portion of the mandrel. In the preferred embodiment, assembly of the tool is accomplished using a hydraulic jack to stretch the mandrel prior to emplacement of the cylindrical sandwich-style piezoelectric transducer assembly and anvil. After those elements are positioned and secured, the stretched mandrel is allowed to return substantially to its original (pre-stretch) dimensions with the result that the piezoelectric transducer elements are compressed between the anvil and the shoulder of the mandrel.

  4. Acoustic transducer

    DOEpatents

    Drumheller, D.S.

    1997-12-30

    An acoustic transducer is described comprising a one-piece hollow mandrel into the outer surface of which is formed a recess with sides perpendicular to the central axis of the mandrel and separated by a first distance and with a bottom parallel to the central axis and within which recess are a plurality of washer-shaped discs of a piezoelectric material and at least one disc of a temperature-compensating material with the discs being captured between the sides of the recess in a pre-stressed interference fit, typically at 2,000 psi of compressive stress. The transducer also includes a power supply and means to connect to a measurement device. The transducer is intended to be used for telemetry between a measurement device located downhole in an oil or gas well and the surface. The transducer is of an construction that is stronger with fewer joints that could leak fluids into the recess holding the piezoelectric elements than is found in previous acoustic transducers. 4 figs.

  5. Acoustic transducer

    DOEpatents

    Drumheller, Douglas S.

    1997-01-01

    An acoustic transducer comprising a one-piece hollow mandrel into the outer surface of which is formed a recess with sides perpendicular to the central axis of the mandrel and separated by a first distance and with a bottom parallel to the central axis and within which recess are a plurality of washer-shaped discs of a piezoelectric material and at least one disc of a temperature-compensating material with the discs being captured between the sides of the recess in a pre-stressed interference fit, typically at 2000 psi of compressive stress. The transducer also includes a power supply and means to connect to a measurement device. The transducer is intended to be used for telemetry between a measurement device located downhole in an oil or gas well and the surface. The transducer is of an construction that is stronger with fewer joints that could leak fluids into the recess holding the piezoelectric elements than is found in previous acoustic transducers.

  6. Acoustic Field Calculation of Ultrasonic Linear Phased Array Transducers with Curve Surface

    NASA Astrophysics Data System (ADS)

    Xu, Chunguang; Wang, Lijiu; Xiao, Dingguo; Zhou, Shiyuan

    2011-06-01

    The focus law and acoustic field computation method about circular arc linear phased array have been discussed in the paper. Acoustic field of transducers is given by the use of the coordinate transformation and an approximation with rectangle element instead of circular arc element, and was validated using Rayleigh-Sommerfeld Integral and nonparallel multiple Gaussian beam model respectively. The results of two methods match well.

  7. Frequency steerable acoustic transducers

    NASA Astrophysics Data System (ADS)

    Senesi, Matteo

    Structural health monitoring (SHM) is an active research area devoted to the assessment of the structural integrity of critical components of aerospace, civil and mechanical systems. Guided wave methods have been proposed for SHM of plate-like structures using permanently attached piezoelectric transducers, which generate and sense waves to evaluate the presence of damage. Effective interrogation of structural health is often facilitated by sensors and actuators with the ability to perform electronic, i.e. phased array, scanning. The objective of this research is to design an innovative directional piezoelectric transducer to be employed for the localization of broadband acoustic events, or for the generation of Lamb waves for active interrogation of structural health. The proposed Frequency Steerable Acoustic Transducers (FSATs) are characterized by a spatial arrangement of active material which leads to directional characteristics varying with frequency. Thus FSATs can be employed both for directional sensing and generation of guided waves without relying on phasing and control of a large number of channels. The analytical expression of the shape of the FSATs is obtained through a theoretical formulation for continuously distributed active material as part of a shaped piezoelectric device. The FSAT configurations analyzed in this work are a quadrilateral array and a geometry which corresponds to a spiral in the wavenumber domain. The quadrilateral array is experimentally validated, confirming the concept of frequency-dependent directionality. Its limited directivity is improved by the Wavenumber Spiral FSAT (WS-FSAT), which, instead, is characterized by a continuous frequency dependent directionality. Preliminary validations of the WS-FSAT, using a laser doppler vibrometer, are followed by the implementation of the WS-FSAT as a properly shaped piezo transducer. The prototype is first used for localization of acoustic broadband sources. Signal processing

  8. Acoustic Doppler velocity measurement system using capacitive micromachined ultrasound transducer array technology.

    PubMed

    Shin, Minchul; Krause, Joshua S; DeBitetto, Paul; White, Robert D

    2013-08-01

    This paper describes the design, fabrication, modeling, and characterization of a small (1 cm(2) transducer chip) acoustic Doppler velocity measurement system using microelectromechanical systems capacitive micromachined ultrasound transducer (cMUT) array technology. The cMUT sensor has a 185 kHz resonant frequency to achieve a 13° beam width for a 1 cm aperture. A model for the cMUT and the acoustic system which includes electrical, mechanical, and acoustic components is provided. Furthermore, this paper shows characterization of the cMUT sensor with a variety of testing procedures including Laser Doppler Vibrometry (LDV), beampattern measurement, reflection testing, and velocity testing. LDV measurements demonstrate that the membrane displacement at the center point is 0.4 nm/V(2) at 185 kHz. The maximum range of the sensor is 60 cm (30 cm out and 30 cm back). A velocity sled was constructed and used to demonstrate measureable Doppler shifts at velocities from 0.2 to 1.0 m/s. The Doppler shifts agree well with the expected frequency shifts over this range.

  9. Acoustic Doppler velocity measurement system using capacitive micromachined ultrasound transducer array technology.

    PubMed

    Shin, Minchul; Krause, Joshua S; DeBitetto, Paul; White, Robert D

    2013-08-01

    This paper describes the design, fabrication, modeling, and characterization of a small (1 cm(2) transducer chip) acoustic Doppler velocity measurement system using microelectromechanical systems capacitive micromachined ultrasound transducer (cMUT) array technology. The cMUT sensor has a 185 kHz resonant frequency to achieve a 13° beam width for a 1 cm aperture. A model for the cMUT and the acoustic system which includes electrical, mechanical, and acoustic components is provided. Furthermore, this paper shows characterization of the cMUT sensor with a variety of testing procedures including Laser Doppler Vibrometry (LDV), beampattern measurement, reflection testing, and velocity testing. LDV measurements demonstrate that the membrane displacement at the center point is 0.4 nm/V(2) at 185 kHz. The maximum range of the sensor is 60 cm (30 cm out and 30 cm back). A velocity sled was constructed and used to demonstrate measureable Doppler shifts at velocities from 0.2 to 1.0 m/s. The Doppler shifts agree well with the expected frequency shifts over this range. PMID:23927100

  10. Modeling of phased array transducers.

    PubMed

    Ahmad, Rais; Kundu, Tribikram; Placko, Dominique

    2005-04-01

    Phased array transducers are multi-element transducers, where different elements are activated with different time delays. The advantage of these transducers is that no mechanical movement of the transducer is needed to scan an object. Focusing and beam steering is obtained simply by adjusting the time delay. In this paper the DPSM (distributed point source method) is used to model the ultrasonic field generated by a phased array transducer and to study the interaction effect when two phased array transducers are placed in a homogeneous fluid. Earlier investigations modeled the acoustic field for conventional transducers where all transducer points are excited simultaneously. In this research, combining the concepts of delayed firing and the DPSM, the phased array transducers are modeled semi-analytically. In addition to the single transducer modeling the ultrasonic fields from two phased array transducers placed face to face in a fluid medium is also modeled to study the interaction effect. The importance of considering the interaction effect in multiple transducer modeling is discussed, pointing out that neighboring transducers not only act as ultrasonic wave generators but also as scatterers.

  11. Acoustic transducer for acoustic microscopy

    DOEpatents

    Khuri-Yakub, B.T.; Chou, C.H.

    1990-03-20

    A shear acoustic transducer-lens system is described in which a shear polarized piezoelectric material excites shear polarized waves at one end of a buffer rod having a lens at the other end which excites longitudinal waves in a coupling medium by mode conversion at selected locations on the lens. 9 figs.

  12. Acoustic transducer for acoustic microscopy

    DOEpatents

    Khuri-Yakub, Butrus T.; Chou, Ching H.

    1990-01-01

    A shear acoustic transducer-lens system in which a shear polarized piezoelectric material excites shear polarized waves at one end of a buffer rod having a lens at the other end which excites longitudinal waves in a coupling medium by mode conversion at selected locations on the lens.

  13. Development of electromagnetic acoustic transducer (EMAT) phased arrays for SFR inspection

    SciTech Connect

    Le Bourdais, Florian; Marchand, Benoît

    2014-02-18

    A long-standing problem for Sodium cooled Fast Reactor (SFR) instrumentation is the development of efficient under-sodium visualization systems adapted to the hot and opaque sodium environment. Electromagnetic Acoustic Transducers (EMAT) are potential candidates for a new generation of Ultrasonic Testing (UT) probes well-suited for SFR inspection that can overcome drawbacks of classical piezoelectric probes in sodium environment. Based on the use of new CIVA simulation tools, we have designed and optimized an advanced EMAT probe for under-sodium visualization. This has led to the development of a fully functional L-wave EMAT sensing system composed of 8 elements and a casing withstanding 200° C sodium inspection. Laboratory experiments demonstrated the probe's ability to sweep an ultrasonic beam to an angle of 15 degrees. Testing in a specialized sodium facility has shown that it was possible to obtain pulse-echo signals from a target under several different angles from a fixed position.

  14. Development of electromagnetic acoustic transducer (EMAT) phased arrays for SFR inspection

    NASA Astrophysics Data System (ADS)

    Le Bourdais, Florian; Marchand, Benoît

    2014-02-01

    A long-standing problem for Sodium cooled Fast Reactor (SFR) instrumentation is the development of efficient under-sodium visualization systems adapted to the hot and opaque sodium environment. Electromagnetic Acoustic Transducers (EMAT) are potential candidates for a new generation of Ultrasonic Testing (UT) probes well-suited for SFR inspection that can overcome drawbacks of classical piezoelectric probes in sodium environment. Based on the use of new CIVA simulation tools, we have designed and optimized an advanced EMAT probe for under-sodium visualization. This has led to the development of a fully functional L-wave EMAT sensing system composed of 8 elements and a casing withstanding 200° C sodium inspection. Laboratory experiments demonstrated the probe's ability to sweep an ultrasonic beam to an angle of 15 degrees. Testing in a specialized sodium facility has shown that it was possible to obtain pulse-echo signals from a target under several different angles from a fixed position.

  15. Electromagnetic acoustic transducer

    DOEpatents

    Alers, George A.; Burns, Jr., Leigh R.; MacLauchlan, Daniel T.

    1988-01-01

    A noncontact ultrasonic transducer for studying the acoustic properties of a metal workpiece includes a generally planar magnetizing coil positioned above the surface of the workpiece, and a generally planar eddy current coil between the magnetizing coil and the workpiece. When a large current is passed through the magnetizing coil, a large magnetic field is applied to the near-surface regions of the workpiece. The eddy current coil can then be operated as a transmitter by passing an alternating current therethrough to excite ultrasonic waves in the surface of the workpiece, or operated as a passive receiver to sense ultrasonic waves in the surface by measuring the output signal. The geometries of the two coils can be varied widely to be effective for different types of ultrasonic waves. The coils are preferably packaged in a housing which does not interfere with their operation, but protects them from a variety of adverse environmental conditions.

  16. Quantitative shear wave optical coherence elastography (SW-OCE) with acoustic radiation force impulses (ARFI) induced by phase array transducer

    NASA Astrophysics Data System (ADS)

    Song, Shaozhen; Le, Nhan Minh; Wang, Ruikang K.; Huang, Zhihong

    2015-03-01

    Shear Wave Optical Coherence Elastography (SW-OCE) uses the speed of propagating shear waves to provide a quantitative measurement of localized shear modulus, making it a valuable technique for the elasticity characterization of tissues such as skin and ocular tissue. One of the main challenges in shear wave elastography is to induce a reliable source of shear wave; most of nowadays techniques use external vibrators which have several drawbacks such as limited wave propagation range and/or difficulties in non-invasive scans requiring precisions, accuracy. Thus, we propose linear phase array ultrasound transducer as a remote wave source, combined with the high-speed, 47,000-frame-per-second Shear-wave visualization provided by phase-sensitive OCT. In this study, we observed for the first time shear waves induced by a 128 element linear array ultrasound imaging transducer, while the ultrasound and OCT images (within the OCE detection range) were triggered simultaneously. Acoustic radiation force impulses are induced by emitting 10 MHz tone-bursts of sub-millisecond durations (between 50 μm - 100 μm). Ultrasound beam steering is achieved by programming appropriate phase delay, covering a lateral range of 10 mm and full OCT axial (depth) range in the imaging sample. Tissue-mimicking phantoms with agarose concentration of 0.5% and 1% was used in the SW-OCE measurements as the only imaging samples. The results show extensive improvements over the range of SW-OCE elasticity map; such improvements can also be seen over shear wave velocities in softer and stiffer phantoms, as well as determining the boundary of multiple inclusions with different stiffness. This approach opens up the feasibility to combine medical ultrasound imaging and SW-OCE for high-resolution localized quantitative measurement of tissue biomechanical property.

  17. Acoustic Levitation With One Transducer

    NASA Technical Reports Server (NTRS)

    Barmatz, Martin B.

    1987-01-01

    Higher resonator modes enables simplification of equipment. Experimental acoustic levitator for high-temperature containerless processing has round cylindrical levitation chamber and only one acoustic transducer. Stable levitation of solid particle or liquid drop achieved by exciting sound in chamber to higher-order resonant mode that makes potential well for levitated particle or drop at some point within chamber.

  18. Acoustic transducer for nuclear reactor monitoring

    DOEpatents

    Ahlgren, Frederic F.; Scott, Paul F.

    1977-01-01

    A transducer to monitor a parameter and produce an acoustic signal from which the monitored parameter can be recovered. The transducer comprises a modified Galton whistle which emits a narrow band acoustic signal having a frequency dependent upon the parameter being monitored, such as the temperature of the cooling media of a nuclear reactor. Multiple locations within a reactor are monitored simultaneously by a remote acoustic receiver by providing a plurality of transducers each designed so that the acoustic signal it emits has a frequency distinct from the frequencies of signals emitted by the other transducers, whereby each signal can be unambiguously related to a particular transducer.

  19. Acoustic coupling in capacitive microfabricated ultrasonic transducers: modeling and experiments.

    PubMed

    Caronti, Alessandro; Savoia, Alessandro; Caliano, Giosuè; Pappalardo, Massimo

    2005-12-01

    In the design of low-frequency transducer arrays for active sonar systems, the acoustic interactions that occur between the transducer elements have received much attention. Because of these interactions, the acoustic loading on each transducer depends on its position in the array, and the radiated acoustic power may vary considerably from one element to another. Capacitive microfabricated ultrasonic transducers (CMUT) are made of a two-dimensional array of metallized micromembranes, all electrically connected in parallel, and driven into flexural motion by the electrostatic force produced by an applied voltage. The mechanical impedance of these membranes is typically much lower than the acoustic impedance of water. In our investigations of acoustic coupling in CMUTs, interaction effects between the membranes in immersion were observed, similar to those reported in sonar arrays. Because CMUTs have many promising applications in the field of medical ultrasound imaging, understanding of cross-coupling mechanisms and acoustic interaction effects is especially important for reducing cross-talk between array elements, which can produce artifacts and degrade image quality. In this paper, we report a finite-element study of acoustic interactions in CMUTs and experimental results obtained by laser interferometry measurements. The good agreement found between finite element modeling (FEM) results and optical displacement measurements demonstrates that acoustic interactions through the liquid represent a major source of cross coupling in CMUTs.

  20. Piezoelectric materials used in underwater acoustic transducers

    SciTech Connect

    Li, Huidong; Deng, Zhiqun; Carlson, Thomas J.

    2012-07-07

    Piezoelectric materials have been used in underwater acoustic transducers for nearly a century. In this paper, we reviewed four different types of piezoelectric materials: piezoelectric ceramics, single crystals, composites, and polymers, which are widely used in underwater acoustic transducers nowadays. Piezoelectric ceramics are the most dominant material type and are used as a single-phase material or one of the end members in composites. Piezoelectric single crystals offer outstanding electromechanical response but are limited by their manufacturing cost. Piezoelectric polymers provide excellent acoustic impedance matching and transducer fabrication flexibility although their piezoelectric properties are not as good as ceramics and single crystals. Composites combined the merits of ceramics and polymers and are receiving increased attention. The typical structure and electromechanical properties of each type of materials are introduced and discussed with respect to underwater acoustic transducer applications. Their advantages and disadvantages are summarized. Some of the critical design considerations when developing underwater acoustic transducers with these materials are also touched upon.

  1. Acoustic transducer with damping means

    DOEpatents

    Smith, Richard W.; Adamson, Gerald E.

    1976-11-02

    An ultrasonic transducer specifically suited to high temperature sodium applications is described. A piezoelectric active element is joined to the transducer faceplate by coating the faceplate and juxtaposed active element face with wetting agents specifically compatible with the bonding procedure employed to achieve the joint. The opposite face of the active element is fitted with a backing member designed to assure continued electrical continuity during adverse operating conditions which can result in the fracturing of the active element. The fit is achieved employing a spring-loaded electrode operably arranged to electrically couple the internal transducer components, enclosed in a hermetically sealed housing, to accessory components normally employed in transducer applications. Two alternative backing members are taught for assuring electrical continuity. The first employs a resilient, discrete multipoint contact electrode in electrical communication with the active element face. The second employs a resilient, elastomeric, electrically conductive, damped member in electrical communication with the active element face in a manner to effect ring-down of the transducer. Each embodiment provides continued electrical continuity within the transducer in the event the active element fractures, while the second provides the added benefit of damping.

  2. Opto-acoustic transducer for medical applications

    DOEpatents

    Benett, W.; Celliers, P.; Da Silva, L.; Glinsky, M.; London, R.; Maitland, D.; Matthews, D.; Krulevich, P.; Lee, A.

    1999-08-31

    This invention is an optically activated transducer for generating acoustic vibrations in a biological medium. The transducer is located at the end of a fiber optic which may be located within a catheter. Energy for operating the transducer is provided optically by laser light transmitted through the fiber optic to the transducer. Pulsed laser light is absorbed in the working fluid of the transducer to generate a thermal pressure and consequent adiabatic expansion of the transducer head such that it does work against the ambient medium. The transducer returns to its original state by a process of thermal cooling. The motion of the transducer within the ambient medium couples acoustic energy into the medium. By pulsing the laser at a high repetition rate (which may vary from CW to 100 kHz) an ultrasonic radiation field can be established locally in the medium. This method of producing ultrasonic vibrations can be used in vivo for the treatment of stroke-related conditions in humans, particularly for dissolving thrombus. The catheter may also incorporate anti-thrombolytic drug treatments as an adjunct therapy and it may be operated in conjunction with ultrasonic detection equipment for imaging and feedback control. 7 figs.

  3. Opto-acoustic transducer for medical applications

    DOEpatents

    Benett, William; Celliers, Peter; Da Silva, Luiz; Glinsky, Michael; London, Richard; Maitland, Duncan; Matthews, Dennis; Krulevich, Peter; Lee, Abraham

    1999-01-01

    This invention is an optically activated transducer for generating acoustic vibrations in a biological medium. The transducer is located at the end of a fiber optic which may be located within a catheter. Energy for operating the transducer is provided optically by laser light transmitted through the fiber optic to the transducer. Pulsed laser light is absorbed in the working fluid of the transducer to generate a thermal pressure and consequent adiabatic expansion of the transducer head such that it does work against the ambient medium. The transducer returns to its original state by a process of thermal cooling. The motion of the transducer within the ambient medium couples acoustic energy into the medium. By pulsing the laser at a high repetition rate (which may vary from CW to 100 kHz) an ultrasonic radiation field can be established locally in the medium. This method of producing ultrasonic vibrations can be used in vivo for the treatment of stroke-related conditions in humans, particularly for dissolving thrombus. The catheter may also incorporate anti-thrombolytic drug treatments as an adjunct therapy and it may be operated in conjunction with ultrasonic detection equipment for imaging and feedback control.

  4. Opto-acoustic transducer for medical applications

    DOEpatents

    Benett, William; Celliers, Peter; Da Silva, Luiz; Glinsky, Michael; London, Richard; Maitland, Duncan; Matthews, Dennis; Krulevich, Peter; Lee, Abraham

    2002-01-01

    This invention is an optically activated transducer for generating acoustic vibrations in a biological medium. The transducer is located at the end of a fiber optic which may be located within a catheter. Energy for operating the transducer is provided optically by laser light transmitted through the fiber optic to the transducer. Pulsed laser light is absorbed in the working fluid of the transducer to generate a thermal pressure and consequent adiabatic expansion of the transducer head such that it does work against the ambient medium. The transducer returns to its original state by a process of thermal cooling. The motion of the transducer within the ambient medium couples acoustic energy into the medium. By pulsing the laser at a high repetition rate (which may vary from CW to 100 kHz) an ultrasonic radiation field can be established locally in the medium. This method of producing ultrasonic vibrations can be used in vivo for the treatment of stroke-related conditions in humans, particularly for dissolving thrombus. The catheter may also incorporate anti-thrombolytic drug treatments as an adjunct therapy and it may be operated in conjunction with ultrasonic detection equipment for imaging and feedback control.

  5. Multilayer Array Transducer for Nonlinear Ultrasound Imaging

    NASA Astrophysics Data System (ADS)

    Owen, Neil R.; Kaczkowski, Peter J.; Li, Tong; Gross, Dan; Postlewait, Steven M.; Curra, Francesco P.

    2011-09-01

    The properties of nonlinear acoustic wave propagation are known to be able to improve the resolution of ultrasound imaging, and could be used to dynamically estimate the physical properties of tissue. However, transducers capable of launching a wave that becomes nonlinear through propagation do not typically have the necessary bandwidth to detect the higher harmonics. Here we present the design and characterization of a novel multilayer transducer for high intensity transmit and broadband receive. The transmit layer was made from a narrow-band, high-power piezoceramic (PZT), with nominal frequency of 2.0 MHz, that was diced into an array of 32 elements. Each element was 0.300 mm wide and 6.3 mm in elevation, and with a pitch of 0.400 mm the overall aperture width was 12.7 mm. A quarter-wave matching layer was attached to the PZT substrate to improve transmit efficiency and bandwidth. The overlaid receive layer was made from polyvinylidene fluoride (PVDF) that had gold metalization on one side. A custom two-sided flex circuit routed electrical connections to the PZT elements and patterned the PVDF elements; the PZT and PVDF elements had identical apertures. A low viscosity and electrically nonconductive epoxy was used for all adhesion layers. Characterization of electrical parameters and acoustic output were performed per standard methods, where transmit and receive events were driven by a software-controlled ultrasound engine. Echo data, collected from ex vivo tissue and digitized at 45 MS/s, exhibited frequency content up to the 4th harmonic of the 2 MHz transmit frequency.

  6. Acoustic transducer apparatus with reduced thermal conduction

    NASA Technical Reports Server (NTRS)

    Lierke, Ernst G. (Inventor); Leung, Emily W. (Inventor); Bhat, Balakrishna T. (Inventor)

    1990-01-01

    A horn is described for transmitting sound from a transducer to a heated chamber containing an object which is levitated by acoustic energy while it is heated to a molten state, which minimizes heat transfer to thereby minimize heating of the transducer, minimize temperature variation in the chamber, and minimize loss of heat from the chamber. The forward portion of the horn, which is the portion closest to the chamber, has holes that reduce its cross-sectional area to minimize the conduction of heat along the length of the horn, with the entire front portion of the horn being rigid and having an even front face to efficiently transfer high frequency acoustic energy to fluid in the chamber. In one arrangement, the horn has numerous rows of holes extending perpendicular to the length of horn, with alternate rows extending perpendicular to one another to form a sinuous path for the conduction of heat along the length of the horn.

  7. Thermal dispersion method for an ultrasonic phased-array transducer

    NASA Astrophysics Data System (ADS)

    Choi, Euna; Lee, Wonseok; Roh, Yongrae

    2016-07-01

    When the driving voltage of an ultrasonic transducer is increased to improve the quality of ultrasound images, heat is generated inside the transducer, which can burn the patient’s skin and degrade transducer performance. In this study, the method to disperse the heat inside an ultrasonic phased-array transducer has been examined. The mechanism of temperature rise due to heat generation inside the transducer was investigated by numerical analysis and the effects of the thermal properties of the components of the transducer such as specific heat and thermal conductivity on the temperature rise were analyzed. On the basis of the results, a heat-dispersive structure was devised to reduce the temperature at the surface of the acoustic lens of the transducer. Prototype transducers were fabricated to check the efficacy of the heat-dispersive structure. By experiments, we have confirmed that the new heat-dispersive structure can reduce the internal temperature by as much as 50% in comparison with the conventional structure, which confirms the validity of the thermal dispersion mechanism developed in this work.

  8. Robust Acoustic Transducers for Bubble Chambers

    NASA Astrophysics Data System (ADS)

    Wells, Jonathan

    2015-04-01

    The PICO collaboration utilizes bubble chambers filled with various superheated liquids as targets for dark matter. Acoustic sensors have proved able to distinguish nuclear recoils from radioactive background on an event-by-event basis. We have recently produced a more robust transducer which should be able to operate for years, rather than months, in the challenging environment of a heated high pressure hydraulic fluid outside these chambers. Indiana University South Bend.

  9. Transducer Development and Characterization for Underwater Acoustic Neutrino Detection Calibration.

    PubMed

    Saldaña, María; Llorens, Carlos D; Felis, Ivan; Martínez-Mora, Juan Antonio; Ardid, Miguel

    2016-01-01

    A short bipolar pressure pulse with "pancake" directivity is produced and propagated when an Ultra-High Energy (UHE) neutrino interacts with a nucleus in water. Nowadays, acoustic sensor networks are being deployed in deep seas to detect this phenomenon as a first step toward building a neutrino telescope. In order to study the feasibility of the method, it is critical to have a calibrator that is able to mimic the neutrino signature. In previous works the possibility of using the acoustic parametric technique for this aim was proven. In this study, the array is operated at a high frequency and, by means of the parametric effect, the emission of the low-frequency acoustic bipolar pulse is generated mimicking the UHE neutrino acoustic pulse. To this end, the development of the transducer to be used in the parametric array is described in all its phases. The transducer design process, the characterization tests for the bare piezoelectric ceramic, and the addition of backing and matching layers are presented. The efficiencies and directivity patterns obtained for both primary and parametric beams confirm that the design of the proposed calibrator meets all the requirements for the emitter.

  10. Transducer Development and Characterization for Underwater Acoustic Neutrino Detection Calibration.

    PubMed

    Saldaña, María; Llorens, Carlos D; Felis, Ivan; Martínez-Mora, Juan Antonio; Ardid, Miguel

    2016-01-01

    A short bipolar pressure pulse with "pancake" directivity is produced and propagated when an Ultra-High Energy (UHE) neutrino interacts with a nucleus in water. Nowadays, acoustic sensor networks are being deployed in deep seas to detect this phenomenon as a first step toward building a neutrino telescope. In order to study the feasibility of the method, it is critical to have a calibrator that is able to mimic the neutrino signature. In previous works the possibility of using the acoustic parametric technique for this aim was proven. In this study, the array is operated at a high frequency and, by means of the parametric effect, the emission of the low-frequency acoustic bipolar pulse is generated mimicking the UHE neutrino acoustic pulse. To this end, the development of the transducer to be used in the parametric array is described in all its phases. The transducer design process, the characterization tests for the bare piezoelectric ceramic, and the addition of backing and matching layers are presented. The efficiencies and directivity patterns obtained for both primary and parametric beams confirm that the design of the proposed calibrator meets all the requirements for the emitter. PMID:27490547

  11. Transducer Development and Characterization for Underwater Acoustic Neutrino Detection Calibration

    PubMed Central

    Saldaña, María; Llorens, Carlos D.; Felis, Ivan; Martínez-Mora, Juan Antonio; Ardid, Miguel

    2016-01-01

    A short bipolar pressure pulse with “pancake” directivity is produced and propagated when an Ultra-High Energy (UHE) neutrino interacts with a nucleus in water. Nowadays, acoustic sensor networks are being deployed in deep seas to detect this phenomenon as a first step toward building a neutrino telescope. In order to study the feasibility of the method, it is critical to have a calibrator that is able to mimic the neutrino signature. In previous works the possibility of using the acoustic parametric technique for this aim was proven. In this study, the array is operated at a high frequency and, by means of the parametric effect, the emission of the low-frequency acoustic bipolar pulse is generated mimicking the UHE neutrino acoustic pulse. To this end, the development of the transducer to be used in the parametric array is described in all its phases. The transducer design process, the characterization tests for the bare piezoelectric ceramic, and the addition of backing and matching layers are presented. The efficiencies and directivity patterns obtained for both primary and parametric beams confirm that the design of the proposed calibrator meets all the requirements for the emitter. PMID:27490547

  12. Optically selective, acoustically resonant gas detecting transducer

    NASA Technical Reports Server (NTRS)

    Dimeff, J. (Inventor)

    1977-01-01

    A gas analyzer is disclosed which responds to the resonant absorption or emission spectrum of a specific gas by producing an acoustic resonance in a chamber containing a sample of that gas, and which measures the amount of that emission or absorption by measuring the strength of that acoustic resonance, e.g., the maximum periodic pressure, velocity or density achieved. In the preferred embodiment, a light beam is modulated periodically at the acoustical resonance frequency of a closed chamber which contains an optically dense sample of the gas of interest. Periodic heating of the absorbing gas by the light beam causes a cyclic expansion, movement, and pressure within the gas. An amplitude is reached where the increased losses were the cyclic radiation energy received. A transducing system is inclined for converting the pressure variations of the resonant gas into electronic readout signals.

  13. Electromechanical transducer for acoustic telemetry system

    DOEpatents

    Drumheller, Douglas S.

    1993-01-01

    An improved electromechanical transducer is provided for use in an acoustic telemetry system. The transducer of this invention comprises a stack of ferroelectric ceramic disks interleaved with a plurality of spaced electrodes which are used to electrically pole the ceramic disks. The ceramic stack is housed in a metal tubular drill collar segment. The electrodes are preferably alternatively connected to ground potential and driving potential. This alternating connection of electrodes to ground and driving potential subjects each disk to an equal electric field; and the direction of the field alternates to match the alternating direction of polarization of the ceramic disks. Preferably, a thin metal foil is sandwiched between electrodes to facilitate the electrical connection. Alternatively, a thicker metal spacer plate is selectively used in place of the metal foil in order to promote thermal cooling of the ceramic stack.

  14. Electromechanical transducer for acoustic telemetry system

    DOEpatents

    Drumheller, D.S.

    1993-06-22

    An improved electromechanical transducer is provided for use in an acoustic telemetry system. The transducer of this invention comprises a stack of ferroelectric ceramic disks interleaved with a plurality of spaced electrodes which are used to electrically pole the ceramic disks. The ceramic stack is housed in a metal tubular drill collar segment. The electrodes are preferably alternatively connected to ground potential and driving potential. This alternating connection of electrodes to ground and driving potential subjects each disk to an equal electric field; and the direction of the field alternates to match the alternating direction of polarization of the ceramic disks. Preferably, a thin metal foil is sandwiched between electrodes to facilitate the electrical connection. Alternatively, a thicker metal spacer plate is selectively used in place of the metal foil in order to promote thermal cooling of the ceramic stack.

  15. Optoacoustic tomography of breast cancer with arc-array transducer

    NASA Astrophysics Data System (ADS)

    Andreev, Valeri G.; Karabutov, Alexander A.; Solomatin, Sergey V.; Savateeva, Elena V.; Aleinikov, Vadim; Zhulina, Yulia V.; Fleming, R. Declan; Oraevsky, Alexander A.

    2000-05-01

    The second generation of the laser optoacoustic imaging system for breast cancer detection, localization and characterization using a 32-element arc-shaped transducer array was developed and tested. Each acoustic transducer was made of 110-micrometers thick SOLEF PVDF film with dimensions of 1mm X 12.5mm. The frequency band of transducer array provided 0.4-mm axial in-depth resolution. Cylindrical shape of this 10-cm long transducer array provided an improved lateral resolution of 1.0 mm. Original and compact design of low noise preamplifiers and wide band amplifiers was employed. The system sensitivity was optimized by choosing limited bandwidth of ultrasonic detection 20-kHz to 2-MHz. Signal processing was significantly improved and optimized resulting in reduced data collection time of 13 sec. The computer code for digital signal processing employed auto- gain control, high-pass filtering and denoising. An automatic recognition of the opto-acoustic signal detected from the irradiated surface was implemented in order to visualize the breast surface and improve the accuracy of tumor locations. Radial back-projection algorithm was used for image reconstruction. Optimal filtering of image was employed to reduce low and high frequency noise. The advantages and limitations of various contrast-enhancing filters applied to the entire image matrix were studied and discussed. Time necessary for image reconstruction was reduced to 32 sec. The system performance was evaluated initially via acquisition of 2D opto-acoustic images of small absorbing spheres in breast-tissue-like phantoms. Clinical ex-vivo studies of mastectomy specimen were also performed and compared with x-ray radiography and ultrasound.

  16. Resonant acoustic transducer system for a well drilling string

    DOEpatents

    Kent, William H.; Mitchell, Peter G.

    1981-01-01

    For use in transmitting acoustic waves propagated along a well drilling string, a piezoelectric transducer is provided operating in the relatively low loss acoustic propagation range of the well drilling string. The efficiently coupled transmitting transducer incorporates a mass-spring-piezoelectric transmitter combination permitting resonant operation in the desired low frequency range.

  17. Resonant acoustic transducer system for a well drilling string

    DOEpatents

    Nardi, Anthony P.

    1981-01-01

    For use in transmitting acoustic waves propated along a well drilling string, a piezoelectric transducer is provided operating in the relatively low loss acoustic propagation range of the well drilling string. The efficiently coupled transmitting transducer incorporates a mass-spring-piezoelectric transmitter combination permitting a resonant operation in the desired low frequency range.

  18. Acoustic-speed correction of photoacoustic tomography by ultrasonic computed tomography based on optical excitation of elements of a full-ring transducer array

    NASA Astrophysics Data System (ADS)

    Xia, Jun; Huang, Chao; Maslov, Konstantin; Anastasio, Mark A.; Wang, Lihong V.

    2014-03-01

    Photoacoustic computed tomography (PACT) is a hybrid technique that combines optical excitation and ultrasonic detection to provide high resolution images in deep tissues. In the image reconstruction, a constant speed of sound (SOS) is normally assumed. This assumption, however, is often not strictly satisfied in deep tissue imaging, due to acoustic heterogeneities within the object and between the object and coupling medium. If these heterogeneities are not accounted for, they will cause distortions and artifacts in the reconstructed images. In this paper, we incorporated ultrasonic computed tomography (USCT), which measures the SOS distribution within the object, into our full-ring array PACT system. Without the need for ultrasonic transmitting electronics, USCT was performed using the same laser beam as for PACT measurement. By scanning the laser beam on the array surface, we can sequentially fire different elements. As a first demonstration of the system, we studied the effect of acoustic heterogeneities on photoacoustic vascular imaging. We verified that constant SOS is a reasonable approximation when the SOS variation is small. When the variation is large, distortion will be observed in the periphery of the object, especially in the tangential direction.

  19. Linear Array Ultrasonic Transducers: Sensitivity and Resolution Study

    NASA Astrophysics Data System (ADS)

    Kramb, V. A.

    2005-04-01

    The University of Dayton Research Institute (UDRI) under contract by the US Air Force has designed and integrated a fully automated inspection system for the inspection of turbine engines that incorporates linear phased array ultrasonic transducers. Phased array transducers have been successfully implemented into weld and turbine blade root inspections where the defect types are well known and characterized. Embedded defects in aerospace turbine engine components are less well defined, however. In order to determine the applicability of linear arrays to aerospace inspections the sensitivity of array transducers to embedded defects in engine materials must be characterized. In addition, the implementation of array transducers into legacy inspection procedures must take into account any differences in sensitivity between the array transducer and that of the single element transducer currently used. This paper discusses preliminary results in a study that compares the sensitivity of linear array and conventional single element transducers to synthetic hard alpha defects in a titanium alloy.

  20. A frequency selective acoustic transducer for directional Lamb wave sensing.

    PubMed

    Senesi, Matteo; Ruzzene, Massimo

    2011-10-01

    A frequency selective acoustic transducer (FSAT) is proposed for directional sensing of guided waves. The considered FSAT design is characterized by a spiral configuration in wavenumber domain, which leads to a spatial arrangement of the sensing material producing output signals whose dominant frequency component is uniquely associated with the direction of incoming waves. The resulting spiral FSAT can be employed both for directional sensing and generation of guided waves, without relying on phasing and control of a large number of channels. The analytical expression of the shape of the spiral FSAT is obtained through the theoretical formulation for continuously distributed active material as part of a shaped piezoelectric device. Testing is performed by forming a discrete array through the points of the measurement grid of a scanning laser Doppler vibrometer. The discrete array approximates the continuous spiral FSAT geometry, and provides the flexibility to test several configurations. The experimental results demonstrate the strong frequency dependent directionality of the spiral FSAT and suggest its application for frequency selective acoustic sensors, to be employed for the localization of broadband acoustic events, or for the directional generation of Lamb waves for active interrogation of structural health. PMID:21973344

  1. Porous silicon bulk acoustic wave resonator with integrated transducer

    PubMed Central

    2012-01-01

    We report that porous silicon acoustic Bragg reflectors and AlN-based transducers can be successfully combined and processed in a commercial solidly mounted resonator production line. The resulting device takes advantage of the unique acoustic properties of porous silicon in order to form a monolithically integrated bulk acoustic wave resonator. PMID:22776697

  2. Multi-particle trapping and manipulation by a high-frequency array transducer

    SciTech Connect

    Yoon, Changhan; Kang, Bong Jin; Lee, Changyang; Kim, Hyung Ham Shung, K. Kirk

    2014-11-24

    We report the multiple micro-particle trapping and manipulation by a single-beam acoustic tweezer using a high-frequency array transducer. A single acoustic beam generated by a 30 MHz ultrasonic linear array transducer can entrap and transport multiple micro-particles located at the main lobe and the grating lobes. The distance between trapped particles can be adjusted by changing the transmit arrangement of array-based acoustic tweezers and subsequently the location of grating lobes. The experiment results showed that the proposed method can trap and manipulate multiple particles within a range of hundreds of micrometers. Due to its simplicity and low acoustic power, which is critical to protect cells from any thermal and mechanical damages, the technique may be used for transportation of cells in cell biology, biosensors, and tissue engineering.

  3. Acoustic trapping with a high frequency linear phased array

    NASA Astrophysics Data System (ADS)

    Zheng, Fan; Li, Ying; Hsu, Hsiu-Sheng; Liu, Changgeng; Tat Chiu, Chi; Lee, Changyang; Ham Kim, Hyung; Shung, K. Kirk

    2012-11-01

    A high frequency ultrasonic phased array is shown to be capable of trapping and translating microparticles precisely and efficiently, made possible due to the fact that the acoustic beam produced by a phased array can be both focused and steered. Acoustic manipulation of microparticles by a phased array is advantageous over a single element transducer since there is no mechanical movement required for the array. Experimental results show that 45 μm diameter polystyrene microspheres can be easily and accurately trapped and moved to desired positions by a 64-element 26 MHz phased array.

  4. Acoustic trapping with a high frequency linear phased array.

    PubMed

    Zheng, Fan; Li, Ying; Hsu, Hsiu-Sheng; Liu, Changgeng; Tat Chiu, Chi; Lee, Changyang; Ham Kim, Hyung; Shung, K Kirk

    2012-11-19

    A high frequency ultrasonic phased array is shown to be capable of trapping and translating microparticles precisely and efficiently, made possible due to the fact that the acoustic beam produced by a phased array can be both focused and steered. Acoustic manipulation of microparticles by a phased array is advantageous over a single element transducer since there is no mechanical movement required for the array. Experimental results show that 45 μm diameter polystyrene microspheres can be easily and accurately trapped and moved to desired positions by a 64-element 26 MHz phased array.

  5. Linear-array ultrasonic waveguide transducer for under sodium viewing.

    SciTech Connect

    Sheen, S. H.; Chien, H. T.; Wang, K.; Lawrence, W. P.; Engel, D.; Nuclear Engineering Division

    2010-09-01

    In this report, we first present the basic design of a low-noise waveguide and its performance followed by a review of the array transducer technology. The report then presents the concept and basic designs of arrayed waveguide transducers that can apply to under-sodium viewing for in-service inspection of fast reactors. Depending on applications, the basic waveguide arrays consist of designs for sideway and downward viewing. For each viewing application, two array geometries, linear and circular, are included in design analysis. Methods to scan a 2-D target using a linear array waveguide transducer are discussed. Future plan to develop a laboratory array waveguide prototype is also presented.

  6. Performance, Thermal, and Vibration Qualification Testing of Zetec Acoustic Transducers, Model Z0002659-2, Sondicator Probes

    SciTech Connect

    Jacobson, G; Gemberling, S; Lavietes, A

    2006-03-10

    This report is a result of Qualification Test Plan No.001 prepared by Anthony Lavietes. The Qualification Test Plan outlines a list of requirements for thermal and vibrational testing of Zetac's Z0002659-2 Sondicator Probe acoustic transducers (hereafter called ''transducers''). The Zetec transducers are used in a system that employs an array of 7 acoustic transducers. Qualification testing of these transducers was required since they are a modified version of a standard catalog item from the manufacturer. This report documents the thermal, vibrational, and performance testing that was performed on a sampling of these transducers in order to qualify them for flight. A total of 14 transducers were tested. All 14 passed qualification testing with no failures.

  7. Equivalent Circuit Models for Large Arrays of Curved and Flat Piezoelectric Micromachined Ultrasonic Transducers.

    PubMed

    Akhbari, Sina; Sammoura, Firas; Lin, Liwei

    2016-03-01

    Equivalent circuit models of large arrays of curved (spherical shape) and flat piezoelectric micromachined ultrasonic transducers (pMUTs) have been developed for complex pMUT arrays design and analysis. The exact solutions for circuit parameters in the electromechanical domain, such as mechanical admittance, input electrical impedance, and electromechanical transformer ratio, were analytically derived. By utilizing the array solution methods previously established for the thickness-mode piezoelectric devices and capacitive micromachined ultrasonic transducers (cMUTs), the single pMUT circuit model can be extended to models for array structures. The array model includes both the self- and mutual-acoustic radiation impedances of individual transducers in the acoustic medium. Volumetric displacement, induced piezoelectric current, and pressure field can be derived with respect to the input voltage matrix, material, and geometrical properties of each individual transducer and the array structure. As such, the analytical models presented here can be used as a guideline for analyses and design evaluations of large arrays of curved and flat pMUTs efficiently and can be further generalized to evaluate other pMUT architectures in the form of single devices or arrays. PMID:26863658

  8. Equivalent Circuit Models for Large Arrays of Curved and Flat Piezoelectric Micromachined Ultrasonic Transducers.

    PubMed

    Akhbari, Sina; Sammoura, Firas; Lin, Liwei

    2016-03-01

    Equivalent circuit models of large arrays of curved (spherical shape) and flat piezoelectric micromachined ultrasonic transducers (pMUTs) have been developed for complex pMUT arrays design and analysis. The exact solutions for circuit parameters in the electromechanical domain, such as mechanical admittance, input electrical impedance, and electromechanical transformer ratio, were analytically derived. By utilizing the array solution methods previously established for the thickness-mode piezoelectric devices and capacitive micromachined ultrasonic transducers (cMUTs), the single pMUT circuit model can be extended to models for array structures. The array model includes both the self- and mutual-acoustic radiation impedances of individual transducers in the acoustic medium. Volumetric displacement, induced piezoelectric current, and pressure field can be derived with respect to the input voltage matrix, material, and geometrical properties of each individual transducer and the array structure. As such, the analytical models presented here can be used as a guideline for analyses and design evaluations of large arrays of curved and flat pMUTs efficiently and can be further generalized to evaluate other pMUT architectures in the form of single devices or arrays.

  9. Piezoelectric transducer design for a miniaturized injectable acoustic transmitter

    DOE PAGES

    Li, Huidong; Jung, Ki Won; Deng, Zhiqun D.

    2015-10-07

    Acoustic telemetry has been an important tool in the last 20 years for studying fish survival and migration behaviors during and after dam passage. This technology uses implantable acoustic transmitters as tags to three-dimensionally track the movement of fish. However, the relatively large weights and sizes of commercially available transmitters limit the populations of fish that could be studied. The surgical implantation procedures required may also injure fish and also incur a significant amount of labor. Therefore, a smaller, lighter, and injectable tag was needed, and similar or better acoustic performance and service life over that provided by existing commercialmore » tags was desired. To develop such a small transmitter, a number of technical challenges, including design optimization of the piezoelectric transducer, needed to be overcome. The goal of our efforts to optimize the transducer focused on improving the average source level in the 180° range in which the transmitter was facing the receiving hydrophone, so as to increase the transmitter’s detection probability. This paper reports the techniques that were explored and developed to achieve this goal. We found that a novel off-center tube transducer improved the average source level of the front half of the transducer by 1.5 dB. An acoustic reflector attached to the back of the transducer also improved the source level by 3 dB when the transducer was pointed toward the receiving hydrophone, although the source level on the sides of the transducer was reduced. We found that too small a gap between the transducer and the component placed behind it resulted in distortion of the beam pattern. To overcome that issue, we connected a tuning inductor in series with the transducer to help optimize the source level. Furthermore, the findings and techniques developed in this work contributed to the successful development and implementation of a new injectable transmitter.« less

  10. Piezoelectric transducer design for a miniaturized injectable acoustic transmitter

    SciTech Connect

    Li, Huidong; Jung, Ki Won; Deng, Zhiqun D.

    2015-10-07

    Acoustic telemetry has been an important tool in the last 20 years for studying fish survival and migration behaviors during and after dam passage. This technology uses implantable acoustic transmitters as tags to three-dimensionally track the movement of fish. However, the relatively large weights and sizes of commercially available transmitters limit the populations of fish that could be studied. The surgical implantation procedures required may also injure fish and also incur a significant amount of labor. Therefore, a smaller, lighter, and injectable tag was needed, and similar or better acoustic performance and service life over that provided by existing commercial tags was desired. To develop such a small transmitter, a number of technical challenges, including design optimization of the piezoelectric transducer, needed to be overcome. The goal of our efforts to optimize the transducer focused on improving the average source level in the 180° range in which the transmitter was facing the receiving hydrophone, so as to increase the transmitter’s detection probability. This paper reports the techniques that were explored and developed to achieve this goal. We found that a novel off-center tube transducer improved the average source level of the front half of the transducer by 1.5 dB. An acoustic reflector attached to the back of the transducer also improved the source level by 3 dB when the transducer was pointed toward the receiving hydrophone, although the source level on the sides of the transducer was reduced. We found that too small a gap between the transducer and the component placed behind it resulted in distortion of the beam pattern. To overcome that issue, we connected a tuning inductor in series with the transducer to help optimize the source level. Furthermore, the findings and techniques developed in this work contributed to the successful development and implementation of a new injectable transmitter.

  11. Apparatus for acoustically coupling an ultrasonic transducer with a body

    NASA Technical Reports Server (NTRS)

    Marshall, Scot H. (Inventor)

    1993-01-01

    An apparatus for acoustically coupling an ultrasonic transducer with a body along whose surface waves are to be transmitted includes a wedge having a first surface for acoustically contacting a subject surface area of a body to be measured, on which surface waves are to be transmitted, and a second surface for accoustically contacting an ultrasonic transducer. The wedge includes a cylinder in which the second surface is present and which is movably disposed in a recess in a block in which the first surface is present, for orienting the first surface and the second surface relative to each other so that ultrasonic waves emitted by the ultrasonic transducer generate surface waves which travel on the subject surface area of the body when the ultrasonic transducer is in acoustic contact with the second surface and the first surface is in acoustic contact with the subject surface area of the body. In the preferred embodiment, there is a third surface which is orientable relative to the first surface so that ultrasonic waves emitted by an ultrasonic transducer in contact with the third surface generate surface waves which travel on the subject surface area of the body when the first surface is an acoustic contact with the subject surface area of the body.

  12. Wideband acoustic activation and detection of droplet vaporization events using a capacitive micromachined ultrasonic transducer.

    PubMed

    Novell, Anthony; Arena, Christopher B; Oralkan, Omer; Dayton, Paul A

    2016-06-01

    An ongoing challenge exists in understanding and optimizing the acoustic droplet vaporization (ADV) process to enhance contrast agent effectiveness for biomedical applications. Acoustic signatures from vaporization events can be identified and differentiated from microbubble or tissue signals based on their frequency content. The present study exploited the wide bandwidth of a 128-element capacitive micromachined ultrasonic transducer (CMUT) array for activation (8 MHz) and real-time imaging (1 MHz) of ADV events from droplets circulating in a tube. Compared to a commercial piezoelectric probe, the CMUT array provides a substantial increase of the contrast-to-noise ratio. PMID:27369143

  13. Piezoelectric transducer design for a miniaturized injectable acoustic transmitter

    NASA Astrophysics Data System (ADS)

    Li, H.; Jung, K. W.; Deng, Z. D.

    2015-11-01

    Implantable acoustic transmitters have been used in the last 20 years to track fish movement for fish survival and migration behavior studies. However, the relatively large weights and sizes of commercial transmitters limit the populations of studied fish. The surgical implantation procedures may also affect fish adversely and incur a significant amount of labor. Therefore, a smaller, lighter, and injectable transmitter was needed, and similar or better acoustic performance and service life over those provided by existing commercial transmitters was desired. To develop such a small transmitter, a number of technical challenges, including design optimization of the piezoelectric transducer, needed to be overcome. Our efforts to optimize the transducer focused on improving the average source level in the 180° range in which the signal was not blocked by the transmitter body. We found that a novel off-center tube transducer improved the average source level by 1.5 dB. An acoustic reflector attached to the back of the transducer also improved the source level by 1.3 dB. We found that too small a gap between the transducer and the component placed behind it resulted in distortion of the beam pattern. Lastly, a tuning inductor in series with the transducer was used to help optimize the source level. The findings and techniques developed in this work contributed to the successful development and implementation of a new injectable transmitter.

  14. An ultrasonic transducer array for velocity measurement in underwater vehicles.

    PubMed

    Boltryk, P; Hill, M; Keary, A; Phillips, B; Robinson, H; White, P

    2004-04-01

    A correlation velocity log (CVL) is an ultrasonic navigation aid for marine applications, in which velocity is estimated using an acoustic transmitter and a receiver array. CVLs offer advantages over Doppler velocity logs (DVLs) in many autonomous underwater vehicle (AUV) applications, since they can achieve high accuracy at low velocities even during hover manoeuvres. DVLs require narrow beam widths, whilst ideal CVL transmitters have wide beam widths. This gives CVLs the potential to use lower frequencies thus permitting operation in deeper water, reducing power requirements for the same depth, or allowing the use of smaller transducers. Moving patterns in the wavefronts across a 2D receiver array are detected by calculating correlation coefficients between bottom reflections from consecutive transmitted pulses, across all combinations of receiver pairings. The position of the peak correlation value, on a surface representing receiver-pairing separations, is proportional to the vessel's displacement between pulses. A CVL aimed primarily for AUVs has been developed. Its acoustical and signal processing design has been optimised through sea trials and computer modelling of the sound field. This computer model is also used to predict how the distribution of the correlation coefficients varies with distance from the peak position. Current work seeks to increase the resolution of the peak estimate using surface fitting methods. Numerical simulations suggest that peak estimation methods significantly improve system precision when compared with simply identifying the position of the maximum correlation coefficient in the dataset. The peak position may be estimated by fitting a quadratic model to the measured data using least squares or maximum likelihood estimation. Alternatively, radial basis functions and Gaussian processes successfully predict the peak position despite variation between individual correlation datasets. This paper summarises the CVL's main acoustical

  15. Capacitive Ultrasonic Transducer Development for Acoustic Anemometry on Mars

    NASA Astrophysics Data System (ADS)

    Leonard-Pugh, Eurion; Wilson, C.; Calcutt, S.; Davis, L.

    2012-10-01

    Previous Mars missions have used either mechanical or thermal anemometry techniques. The moving parts of mechanical anemometers are prone to damage during launch and landing and their inertia makes them unsuited for turbulence studies. Thermal anemometers have been used successfully on Mars but are difficult to calibrate and susceptible to varying ambient temperatures. In ultrasonic anemometry, wind speed and sound speed are calculated from two-way time-of-flight measurements between pairs of transducers; three pairs of transducers are used to return a 3-D wind vector. These high-frequency measurements are highly reliable and immune from drift. Piezo-electric ultrasonic anemometers are widely used on Earth due to their full-range accuracy and high measurement frequency. However these transducers have high acoustic impedances and would not work on Mars. We are developing low-mass capacitive ultrasonic transducers for Mars missions which have significantly lower acoustic impedances and would therefore have a much stronger coupling to the Martian atmosphere. These transducers consist of a metallised polymer film pulled taught against a machined metal backplane. The film is drawn towards the backplane by a DC bias voltage. A varying signal is used on top of the DC bias to oscillate the film; generating acoustic waves. This poster will look at the operation of such sensors and the developments necessary to operate the devices under Martian conditions. Transducer performance is determined primarily by two elements; the front film and the backplane. The sensitivity of the transducer is affected by the thickness of the front film; as well as the diameter, curvature and roughness of the metal backplane. We present data on the performance of the sensors and instrument design considerations including signal shapes and transducer arrangements.

  16. Manipulation of Liquids Using Phased Array Generation of Acoustic Radiation Pressure

    NASA Technical Reports Server (NTRS)

    Oeftering, Richard C. (Inventor)

    2000-01-01

    A phased array of piezoelectric transducers is used to control and manipulate contained as well as uncontained fluids in space and earth applications. The transducers in the phased array are individually activated while being commonly controlled to produce acoustic radiation pressure and acoustic streaming. The phased array is activated to produce a single pulse, a pulse burst or a continuous pulse to agitate, segregate or manipulate liquids and gases. The phased array generated acoustic radiation pressure is also useful in manipulating a drop, a bubble or other object immersed in a liquid. The transducers can be arranged in any number of layouts including linear single or multi- dimensional, space curved and annular arrays. The individual transducers in the array are activated by a controller, preferably driven by a computer.

  17. Liquid-membrane coupling response of submersible electrostatic acoustic transducer

    NASA Technical Reports Server (NTRS)

    Cantrell, John H.; Yost, William T.

    1989-01-01

    A mathematical model was developed for the liquid-membrane coupling response of the submersible electrostatic acoustic transducer (ESAT) described by Cantrell et al. (1979). The model accounts for the ESAT's rolloff response and predicts the essential features of the ESAT frequency response. Model predictions were found to agree well with measurements taken over the frequency range from 1 to 11 MHz.

  18. Characterization of HIFU transducers designed for sonochemistry application: Acoustic streaming.

    PubMed

    Hallez, L; Touyeras, F; Hihn, J-Y; Bailly, Y

    2016-03-01

    Cavitation distribution in a High Intensity Focused Ultrasound sonoreactors (HIFU) has been extensively described in the recent literature, including quantification by an optical method (Sonochemiluminescence SCL). The present paper provides complementary measurements through the study of acoustic streaming generated by the same kind of HIFU transducers. To this end, results of mass transfer measurements (electrodiffusional method) were compared to optical method ones (Particle Image Velocimetry). This last one was used in various configurations: with or without an electrode in the acoustic field in order to have the same perturbation of the wave propagation. Results show that the maximum velocity is not located at the focal but shifted near the transducer, and that this shift is greater for high powers. The two cavitation modes (stationary and moving bubbles) are greatly affect the hydrodynamic behavior of our sonoreactors: acoustic streaming and the fluid generated by bubble motion. The results obtained by electrochemical measurements show the same low hydrodynamic activity in the transducer vicinity, the same shift of the active focal toward the transducer, and the same absence of activity in the post-focal axial zone. The comparison with theoretical Eckart's velocities (acoustic streaming in non-cavitating media) confirms a very high activity at the "sonochemical focal", accounted for by wave distortion, which induced greater absorption coefficients. Moreover, the equivalent liquid velocities are one order of magnitude larger than the ones measured by PIV, confirming the enhancement of mass transfer by bubbles oscillation and collapse close to the surface, rather than from a pure streaming effect.

  19. A new approach to calculate the field radiated from arbitrarily structured transducer arrays.

    PubMed

    Piwakowski, B; Sbai, K

    1999-01-01

    A efficient time-domain algorithm, based on the spatial pulse response approach, is proposed for the determination of the acoustic fields radiated by means of acoustical sources. The computations are performed by the discrete representation array modelling (DREAM) procedure, specially adapted to study the planar and arbitrarily structured multielement transducer arrays. DREAM, based on the discrete representation computational concept, acts as the generator of the array velocity potential impulse response, and thus, does not require any analytical solutions prior to the computations. The computations are valid for all field regions and may be performed for any excitation form. Apart from the classic case of rigid baffle conditions, the free and soft planar baffle also can be considered. The use of the time-domain solution for causal Green's function for lossy media enables the wideband absorption effects to be modeled. The accuracy of computations depends on temporal and spatial discretization and can be obtained as required. The quantitative rules, which determine the required discretizations to be predicted, are proposed. The computational examples show that DREAM allows the different and various transducers to be modeled. Its possibilities are illustrated by computations for the multielement transducers, including the beam-steered, amplitude-weighted sonar array, the focusing annular transducer, and the diverging and converging cylindrical array.

  20. Acoustically driven arrayed waveguide grating.

    PubMed

    Crespo-Poveda, A; Hernández-Mínguez, A; Gargallo, B; Biermann, K; Tahraoui, A; Santos, P V; Muñoz, P; Cantarero, A; de Lima, M M

    2015-08-10

    We demonstrate compact tunable phased-array wavelength-division multiplexers driven by surface acoustic waves (SAWs) in the low GHz range. The devices comprise two couplers, which respectively split and combine the optical signal, linked by an array of single-mode waveguides (WGs). Two different layouts are presented, in which multi-mode interference couplers or free propagating regions were separately employed as couplers. The multiplexers operate on five equally distributed wavelength channels, with a spectral separation of 2 nm. A standing SAW modulates the refractive index of the arrayed WGs. Each wavelength component periodically switches paths between the output channel previously asigned by the design and the adjacent channels, at a fixed applied acoustic power. The devices were monolithically fabricated on (Al,Ga)As. A good agreement between theory and experiment is achieved.

  1. MEMS Based Acoustic Array

    NASA Technical Reports Server (NTRS)

    Sheplak, Mark (Inventor); Nishida, Toshikaza (Inventor); Humphreys, William M. (Inventor); Arnold, David P. (Inventor)

    2006-01-01

    Embodiments of the present invention described and shown in the specification aid drawings include a combination responsive to an acoustic wave that can be utilized as a dynamic pressure sensor. In one embodiment of the present invention, the combination has a substrate having a first surface and an opposite second surface, a microphone positioned on the first surface of the substrate and having an input and a first output and a second output, wherein the input receives a biased voltage, and the microphone generates an output signal responsive to the acoustic wave between the first output and the second output. The combination further has an amplifier positioned on the first surface of the substrate and having a first input and a second input and an output, wherein the first input of the amplifier is electrically coupled to the first output of the microphone and the second input of the amplifier is electrically coupled to the second output of the microphone for receiving the output sinual from the microphone. The amplifier is spaced from the microphone with a separation smaller than 0.5 mm.

  2. Bonding and impedance matching of acoustic transducers using silver epoxy.

    PubMed

    Son, Kyu Tak; Lee, Chin C

    2012-04-01

    Silver epoxy was selected to bond transducer plates on glass substrates. The properties and thickness of the bonding medium affect the electrical input impedance of the transducer. Thus, the thickness of the silver epoxy bonding layer was used as a design parameter to optimize the structure for the transducer input impedance to match the 50 Ω output impedance of most radio frequency (RF) generators. Simulation and experimental results show that nearly perfect matching is achieved without using any matching circuit. At the matching condition, the transducer operates at a frequency band a little bit below the half-wavelength resonant frequency of the piezoelectric plate. In experiments, lead titanate (PT) piezoelectric plates were employed. Both full-size, 11.5 mm × 2 mm × 0.4 mm, and half-size, 5.75 mm × 2 mm × 0.4 mm, can be well matched using optimal silver epoxy thickness. The transducer assemblies demonstrate high efficiency. The conversion loss from electrical power to acoustic power in soda-lime glass is 4.3 dB. This loss is low considering the fact that the transducers operate at off-resonance by 12%. With proper choice of silver epoxy thickness, the transducer can be matched at the fundamental, the 3rd and 5th harmonic frequencies. This leads to the possible realization of triple-band transducers. Reliability was assessed with thermal cycling test according to Telcordia GR-468-Core recommendation. Of the 30 transducer assemblies tested, none broke until 2900 cycles and 27 have sustained beyond 4050 cycles.

  3. Acoustic characterization of multi-element, dual-frequency transducers for high-intensity contact ultrasound therapy

    NASA Astrophysics Data System (ADS)

    Burtnyk, M.; N'Djin, W. A.; Persaud, L.; Bronskill, M.; Chopra, R.

    2012-10-01

    High-intensity contact ultrasound therapy can generate precise volumes of thermal damage in deep-seated tissue using interstitial or intracavitary devices. Multi-element, dual-frequency transducers offer increased spatial control of the heating pattern by enabling modulation of ultrasound power and frequency along the device. The performance and acoustic coupling between elements of simple, multi-element, dual-frequency transducers was measured. Transducer arrays were fabricated by cutting halfway through a rectangular plate of PZT, creating individual 4 × 5 mm segments with fundamental frequency (4.1 MHz) and third harmonic (13.3 MHz). Coupling between elements was investigated using a scanning laser vibrometer to measure transducer surface displacements at each frequency and different acoustic powers (0, 10, 20 W/cm2). The measured acoustic power was proportional to the input electrical power with no hysteresis and efficiencies >50% at both frequencies. Maximum transducer surface displacements were observed near element centers, reducing to ˜1/3-maximum near edges. The power and frequency of neighboring transducer segments had little impact on an element's output. In the worst case, an element operating at 4.1 MHz and 20 W/cm2 coupled only 1.5 W/cm2 to its immediate neighboring element. Multi-element, dual-frequency transducers were successfully constructed using a simple dicing method. Coupling between elements was minor, therefore the power and frequency of each transducer element could be considered independent.

  4. Waveguide piezoelectric micromachined ultrasonic transducer array for short-range pulse-echo imaging

    NASA Astrophysics Data System (ADS)

    Lu, Y.; Tang, H.; Wang, Q.; Fung, S.; Tsai, J. M.; Daneman, M.; Boser, B. E.; Horsley, D. A.

    2015-05-01

    This paper presents an 8 × 24 element, 100 μm-pitch, 20 MHz ultrasound imager based on a piezoelectric micromachined ultrasonic transducer (PMUT) array having integrated acoustic waveguides. The 70 μm diameter, 220 μm long waveguides function both to direct acoustic waves and to confine acoustic energy, and also to provide mechanical protection for the PMUT array used for surface-imaging applications such as an ultrasonic fingerprint sensor. The imager consists of a PMUT array bonded with a CMOS ASIC using wafer-level conductive eutectic bonding. This construction allows each PMUT in the array to have a dedicated front-end receive amplifier, which together with on-chip analog multiplexing enables individual pixel read-out with high signal-to-noise ratio through minimized parasitic capacitance between the PMUT and the front-end amplifier. Finite element method simulations demonstrate that the waveguides preserve the pressure amplitude of acoustic pulses over distances of 600 μm. Moreover, the waveguide design demonstrated here enables pixel-by-pixel readout of the ultrasound image due to improved directivity of the PMUT by directing acoustic waves and creating a pressure field with greater spatial uniformity at the end of the waveguide. Pulse-echo imaging experiments conducted using a one-dimensional steel grating demonstrate the array's ability to form a two-dimensional image of a target.

  5. A novel serrated columnar phased array ultrasonic transducer

    NASA Astrophysics Data System (ADS)

    Zou, Cheng; Sun, Zhenguo; Cai, Dong; Song, Hongwei; Chen, Qiang

    2016-02-01

    Traditionally, wedges are required to generate transverse waves in a solid specimen and mechanical rotation device is needed for interrogation of a specimen with a hollow bore, such as high speed railway locomotive axles, turbine rotors, etc. In order to eliminate the mechanical rotation process, a novel array pattern of phased array ultrasonic transducers named as serrated columnar phased array ultrasonic transducer (SCPAUT) is designed. The elementary transducers are planar rectangular, located on the outside surface of a cylinder. This layout is aimed to generate electrically rotating transverse waveforms so as to inspect the longitudinal cracks on the outside surface of a specimen which has a hollow bore at the center, such as the high speed railway locomotive axles. The general geometry of the SCPAUT and the inspection system are illustrated. A FEM model and mockup experiment has been carried out. The experiment results are in good agreement with the FEM simulation results.

  6. Piezoelectric micromachined ultrasound transducer (PMUT) arrays for integrated sensing, actuation and imaging.

    PubMed

    Qiu, Yongqiang; Gigliotti, James V; Wallace, Margeaux; Griggio, Flavio; Demore, Christine E M; Cochran, Sandy; Trolier-McKinstry, Susan

    2015-04-03

    Many applications of ultrasound for sensing, actuation and imaging require miniaturized and low power transducers and transducer arrays integrated with electronic systems. Piezoelectric micromachined ultrasound transducers (PMUTs), diaphragm-like thin film flexural transducers typically formed on silicon substrates, are a potential solution for integrated transducer arrays. This paper presents an overview of the current development status of PMUTs and a discussion of their suitability for miniaturized and integrated devices. The thin film piezoelectric materials required to functionalize these devices are discussed, followed by the microfabrication techniques used to create PMUT elements and the constraints the fabrication imposes on device design. Approaches for electrical interconnection and integration with on-chip electronics are discussed. Electrical and acoustic measurements from fabricated PMUT arrays with up to 320 diaphragm elements are presented. The PMUTs are shown to be broadband devices with an operating frequency which is tunable by tailoring the lateral dimensions of the flexural membrane or the thicknesses of the constituent layers. Finally, the outlook for future development of PMUT technology and the potential applications made feasible by integrated PMUT devices are discussed.

  7. Piezoelectric Micromachined Ultrasound Transducer (PMUT) Arrays for Integrated Sensing, Actuation and Imaging

    PubMed Central

    Qiu, Yongqiang; Gigliotti, James V.; Wallace, Margeaux; Griggio, Flavio; Demore, Christine E. M.; Cochran, Sandy; Trolier-McKinstry, Susan

    2015-01-01

    Many applications of ultrasound for sensing, actuation and imaging require miniaturized and low power transducers and transducer arrays integrated with electronic systems. Piezoelectric micromachined ultrasound transducers (PMUTs), diaphragm-like thin film flexural transducers typically formed on silicon substrates, are a potential solution for integrated transducer arrays. This paper presents an overview of the current development status of PMUTs and a discussion of their suitability for miniaturized and integrated devices. The thin film piezoelectric materials required to functionalize these devices are discussed, followed by the microfabrication techniques used to create PMUT elements and the constraints the fabrication imposes on device design. Approaches for electrical interconnection and integration with on-chip electronics are discussed. Electrical and acoustic measurements from fabricated PMUT arrays with up to 320 diaphragm elements are presented. The PMUTs are shown to be broadband devices with an operating frequency which is tunable by tailoring the lateral dimensions of the flexural membrane or the thicknesses of the constituent layers. Finally, the outlook for future development of PMUT technology and the potential applications made feasible by integrated PMUT devices are discussed. PMID:25855038

  8. Design and Characterization of Dual-Curvature 1.5-Dimensional High-Intensity Focused Ultrasound Phased-Array Transducer

    PubMed Central

    Chen, Gin-Shin; Lin, Che-Yu; Jeong, Jong Seob; Cannata, Jonathan M.; Lin, Win-Li; Chang, Hsu; Shung, K. Kirk

    2013-01-01

    A dual-curvature focused ultrasound phased-array transducer with a symmetric control has been developed for noninvasive ablative treatment of tumors. The 1.5-D array was constructed in-house and the electro-acoustic conversion efficiency was measured to be approximately 65%. In vitro experiments demonstrated that the array uses 256 independent elements to achieve 2-D wide-range high-intensity electronic focusing. PMID:22293745

  9. Design and fabrication of a 40-MHz annular array transducer

    PubMed Central

    Ketterling, Jeffrey A.; Lizzi, Frederic L.; Aristizábal, Orlando; Turnbull, Daniel H.

    2006-01-01

    This paper investigates the feasibility of fabricating a 5-ring, focused annular array transducer operating at 40 MHz. The active piezoelectric material of the transducer was a 9-μm thick polyvinylidene fluoride (PVDF) film. One side of the PVDF was metallized with gold and forms the ground plane of the transducer. The array pattern of the transducer and electrical traces to each annulus were formed on a copper-clad polyimide film. The PVDF and polyimide were bonded with a thin layer of epoxy, pressed into a spherically curved shape, and then back filled with epoxy. A 5-ring transducer with equal area elements and 100 μm kerfs between annuli was fabricated and tested. The transducer had a total aperture of 6 mm and a geometric focus of 12 mm. The pulse/echo response from a quartz plate located at the geometric focus, two-way insertion loss (IL), complex impedance, electrical cross-talk, and lateral beamwidth were all measured for each annulus. The complex impedance data from each element were used to perform electrical matching and the measurements were repeated. After impedance matching, fc ≈ 36 MHz and BWs ranged from 31 to 39%. The ILs for the matched annuli ranged from −28 to −38 dB. PMID:16060516

  10. A Beamforming Study for Implementation of Vibro-acoustography with a 1.75D Array Transducer

    PubMed Central

    Urban, Matthew W.; Chalek, Carl; Haider, Bruno; Thomenius, Kai E.; Fatemi, Mostafa; Alizad, Azra

    2013-01-01

    Vibro-acoustography (VA) is an ultrasound-based imaging modality that uses radiation force produced by two cofocused ultrasound beams separated by a small frequency difference, Δf, to vibrate tissue at Δf. An acoustic field is created by the object vibration and measured with a nearby hydrophone. This method has recently been implemented on a clinical ultrasound system using one-dimensional (1D) linear array transducers. In this article, we discuss VA beamforming and image formation using a 1.75D array transducer. A 1.75D array transducer has several rows of elements in the elevation direction which can be controlled independently for focusing. The advantage of the 1.75D array over a 1D linear array transducer is that multiple rows of elements can be used for improving elevation focus for imaging formation. Six configurations for subaperture design for the two ultrasound beams necessary for VA imaging were analyzed. The point-spread functions for these different configurations were evaluated using a numerical simulation model. Four of these configurations were then chosen for experimental evaluation with a needle hydrophone as well as for scanning two phantoms. Images were formed by scanning a urethane breast phantom and an ex vivo human prostate. VA imaging using a 1.75D array transducer offers several advantages over scanning with a linear array transducer including improved image resolution and contrast due to better elevation focusing of the imaging point-spread function. PMID:23475919

  11. Broadband electrostatic acoustic transducer for ultrasonic measurements in liquids.

    PubMed

    Cantrell, J H; Heyman, J S; Yost, W T; Torbett, M A; Breazeale, M A

    1979-01-01

    A broadband capacitive electrostatic acoustic transducer (ESAT) has been developed for use in a liquid environment at megahertz frequencies. The ESAT basically consists of a thin conductive membrane stretched over a metallic housing. The membrane functions as the ground plate of a parallel plate capacitor, the other plate being a dc biased electrode recessed approximately 10 mum from the electrically grounded membrane. An ultrasonic wave incident on the membrane varies the membrane-electrode gap spacing and generates an electrical signal proportional to the wave amplitude. The entire assembly is sealed for immersion in a liquid environment. Calibration of the ESAT with incident ultrasonic waves of constant displacement amplitude from 1 to 15 MHz reveals a decrease in signal response with increasing frequency independent of membrane tension. The use of the ESAT as a broadband ultrasonic transducer in liquids with a predictable frequency response is promising.

  12. Breast ultrasound tomography with two parallel transducer arrays

    NASA Astrophysics Data System (ADS)

    Huang, Lianjie; Shin, Junseob; Chen, Ting; Lin, Youzuo; Gao, Kai; Intrator, Miranda; Hanson, Kenneth

    2016-03-01

    Breast ultrasound tomography is an emerging imaging modality to reconstruct the sound speed, density, and ultrasound attenuation of the breast in addition to ultrasound reflection/beamforming images for breast cancer detection and characterization. We recently designed and manufactured a new synthetic-aperture breast ultrasound tomography prototype with two parallel transducer arrays consisting of a total of 768 transducer elements. The transducer arrays are translated vertically to scan the breast in a warm water tank from the chest wall/axillary region to the nipple region to acquire ultrasound transmission and reflection data for whole-breast ultrasound tomography imaging. The distance of these two ultrasound transducer arrays is adjustable for scanning breasts with different sizes. We use our breast ultrasound tomography prototype to acquire phantom and in vivo patient ultrasound data to study its feasibility for breast imaging. We apply our recently developed ultrasound imaging and tomography algorithms to ultrasound data acquired using our breast ultrasound tomography system. Our in vivo patient imaging results demonstrate that our breast ultrasound tomography can detect breast lesions shown on clinical ultrasound and mammographic images.

  13. Tunable optical lens array using viscoelastic material and acoustic radiation force

    SciTech Connect

    Koyama, Daisuke Kashihara, Yuta; Matsukawa, Mami; Hatanaka, Megumi; Nakamura, Kentaro

    2015-10-28

    A movable optical lens array that uses acoustic radiation force was investigated. The lens array consists of a glass plate, two piezoelectric bimorph transducers, and a transparent viscoelastic gel film. A cylindrical lens array with a lens pitch of 4.6 mm was fabricated using the acoustic radiation force generated by the flexural vibration of the glass plate. The focal point and the positioning of the lenses can be changed using the input voltage and the driving phase difference between the two transducers, respectively.

  14. Optical vibration measurements of cross coupling effects in capacitive micromachined ultrasonic transducer arrays

    NASA Astrophysics Data System (ADS)

    Leirset, Erlend; Aksnes, Astrid

    2011-05-01

    Optical vibration measurement systems are excellent tools for characterizing ultrasonic transducers. This paper presents measurements on immersed arrays of capacitive ultrasonic transducers (CMUTs) using a heterodyne interferometer. The interferometer allows measurements of vibrations from DC up to 1 GHz with a noise floor of ~1pm/√Hz. Previously CMUTs have been characterized in air. The transducer is intended for intravascular use. Therefore the CMUTs were characterized in the transparent fluids kerosene and rapeseed oil that have acoustic properties closer to blood. The optical measurements on immersed CMUTs were validated by assessing the measurement errors caused by the acousto optic effects in the fluid. When immersed there is significant cross coupling between individual CMUTs within an array. Simulations presented here indicate that this causes an acoustic wave mode that is bound to the interface between the CMUTs and the fluid. This is confirmed by measurements of the phase velocity and attenuation coefficient of this wave. The measurement results indicate that the wave exists up to a maximum frequency and that the attenuation constant increases with increasing frequency. Rapeseed oil causes a significantly larger attenuation coefficient than kerosene, which most probably is due to a considerable difference in fluid viscosities. There was a mismatch between the simulated and measured phase velocity for low frequencies. It is likely that the cause of this is coupling between the fluid CMUT interface waves and Lamb waves in the substrate of the CMUT array. Measurements performed with the heterodyne interferometer have confirmed the presence of dispersive waves bound to the surface of the transducer by directly showing their propagation along the array. The setup has also characterized the bound waves by measuring dispersion relations.

  15. Application of electromagnetic acoustic transducers to coarse-grained material

    SciTech Connect

    Alers, G.A. )

    1991-07-01

    Electromagnetic Acoustic Transducers (EMATs) have certain advantages over piezoelectric transducers because they do not require a coupling medium between the part and the transducer and they can be designed to generate and detect focused sound waves of types unavailable to conventional probes. This program investigated a 500 kHz EMAT designed to focus Shear Horizontal ultrasonic waves onto the interior of centrifugally cast stainless steel (CCSS) in the hope that the large attenuation caused by scattering from the large grains could be minimized and reflections from small defects could be more easily detected. The results demonstrated that synthetic aperture focusing had to be used to distinguish flaw echoes from backscattered noise'' but that flaw detection by a pulse-echo technique was still difficult because of the attenuation of the signal as it propagated to and from the focal point. The ability to control the angle of injection of the sound beam by simply changing the frequency was demonstrated. 4 refs., 10 figs.

  16. Manipulating Liquids With Acoustic Radiation Pressure Phased Arrays

    NASA Technical Reports Server (NTRS)

    Oeftering, Richard C.

    1999-01-01

    High-intensity ultrasound waves can produce the effects of "Acoustic Radiation Pressure" (ARP) and "acoustic streaming." These effects can be used to propel liquid flows and to apply forces that can be used to move or manipulate floating objects or liquid surfaces. NASA's interest in ARP includes the remote-control agitation of liquids and the manipulation of bubbles and drops in liquid experiments and propellant systems. A high level of flexibility is attained by using a high-power acoustic phased array to generate, steer, and focus a beam of acoustic waves. This is called an Acoustic Radiation Pressure Phased Array, or ARPPA. In this approach, many acoustic transducer elements emit wavelets that converge into a single beam of sound waves. Electronically coordinating the timing, or "phase shift," of the acoustic waves makes it possible to form a beam with a predefined direction and focus. Therefore, a user can direct the ARP force at almost any desired point within a liquid volume. ARPPA lets experimenters manipulate objects anywhere in a test volume. This flexibility allow it to be used for multiple purposes, such as to agitate liquids, deploy and manipulate drops or bubbles, and even suppress sloshing in spacecraft propellant tanks.

  17. Diffraction aperture non-ideal behaviour of air coupled transducers array elements designed for NDT.

    PubMed

    Prego Borges, J L; Montero de Espinosa, F; Salazar, J; Garcia-Alvarez, J; Chávez, J A; Turó, A; Garcia-Hernandez, M J

    2006-12-22

    Air coupled piezoelectric ultrasonic array transducers are a novel tool that could lead to interesting advances in the area of non-contact laminar material testing using Lamb wave's propagation techniques. A key issue on the development of such transducers is their efficient coupling to air media (impedance mismatch between the piezoelectric material and air is 90 dB or more). Adaptation layers are used in order to attain good matching and avoid possible serious signal degradation. However, the introduction of these matching layers modify the transducer surface behaviour and, consequently, radiation characteristics are altered, making the usual idealization criteria (of uniform surface movement) adopted for field simulation purposes inaccurate. In our system, we have a concave linear-array transducer of 64 elements (electrically coupled by pairs) working at 0.8 MHz made of PZ27 rectangular piezoceramics (15 mm x 0.3 mm) with two matching layers made of polyurethane and porous cellulose bonded on them. Experimental measurements of the acoustic aperture of single excited array elements have shown an increment on the geometrical dimensions of its active surface. A sub-millimeter vibrometer laser scan has revealed an extension of the aperture beyond the supposed physical single array element dimensions. Non-uniform symmetric apodized velocity surface vibration amplitude profile with a concave delay contour indicates the presumed existence of travelling wave phenomena over the surface of the outer array matching layer. Also, asymptotic propagation velocities around 2500 m/s and attenuation coefficient between 15 and 20 dB/mm has been determined for the travelling waves showing clear tendencies. Further comparisons between the experimental measurements of single array element field radiation diagram and simulated equivalent aperture counterpart reveal good agreement versus the ideal (uniform displaced) rectangular aperture. For this purpose an Impulse Response Method

  18. High-Temperature Surface-Acoustic-Wave Transducer

    NASA Technical Reports Server (NTRS)

    Zhao, Xiaoliang; Tittmann, Bernhard R.

    2010-01-01

    Aircraft-engine rotating equipment usually operates at high temperature and stress. Non-invasive inspection of microcracks in those components poses a challenge for the non-destructive evaluation community. A low-profile ultrasonic guided wave sensor can detect cracks in situ. The key feature of the sensor is that it should withstand high temperatures and excite strong surface wave energy to inspect surface/subsurface cracks. As far as the innovators know at the time of this reporting, there is no existing sensor that is mounted to the rotor disks for crack inspection; the most often used technology includes fluorescent penetrant inspection or eddy-current probes for disassembled part inspection. An efficient, high-temperature, low-profile surface acoustic wave transducer design has been identified and tested for nondestructive evaluation of structures or materials. The development is a Sol-Gel bismuth titanate-based surface-acoustic-wave (SAW) sensor that can generate efficient surface acoustic waves for crack inspection. The produced sensor is very thin (submillimeter), and can generate surface waves up to 540 C. Finite element analysis of the SAW transducer design was performed to predict the sensor behavior, and experimental studies confirmed the results. One major uniqueness of the Sol-Gel bismuth titanate SAW sensor is that it is easy to implement to structures of various shapes. With a spray coating process, the sensor can be applied to surfaces of large curvatures. Second, the sensor is very thin (as a coating) and has very minimal effect on airflow or rotating equipment imbalance. Third, it can withstand temperatures up to 530 C, which is very useful for engine applications where high temperature is an issue.

  19. Arrayed Ultrasonic Transducers on Arc Surface for Plane Wave Synthesis

    NASA Astrophysics Data System (ADS)

    Kim, Jung-Soon; Kim, Jung-Ho; Kim, Moo-Joon; Ha, Kang-Lyeol; Yamada, Akira

    2004-05-01

    In ultrasonic computed tomography (UCT), it is necessary to synthesize a plane wave using waves emitted from sound sources arranged in the interior surface of a cylinder. In order to transmit a plane wave into a cylindrical surface, an ultrasonic transducer which has many vibrating elements with piezoelectric transverse effect arrayed on an arc surface is proposed. To achieve a wide beam width, the elements should have a small radiation area with a much narrow width. The measured electroacoustic efficiency for the elements was approximately 40% and the beam width defined by -3 dB level from the maximum was as wide as 120 deg. It was confirmed that plane wave synthesis is possible using the proposed transducer array.

  20. Laser-scanning photoacoustic microscopy with ultrasonic phased array transducer.

    PubMed

    Zheng, Fan; Zhang, Xiangyang; Chiu, Chi Tat; Zhou, Bill L; Shung, K Kirk; Zhang, Hao F; Jiao, Shuliang

    2012-11-01

    In this paper, we report our latest progress on proving the concept that ultrasonic phased array can improve the detection sensitivity and field of view (FOV) in laser-scanning photoacoustic microscopy (LS-PAM). A LS-PAM system with a one-dimensional (1D) ultrasonic phased array was built for the experiments. The 1D phased array transducer consists of 64 active elements with an overall active dimension of 3.2 mm × 2 mm. The system was tested on imaging phantom and mouse ear in vivo. Experiments showed a 15 dB increase of the signal-to-noise ratio (SNR) when beamforming was employed compared to the images acquired with each single element. The experimental results demonstrated that ultrasonic phased array can be a better candidate for LS-PAM in high sensitivity applications like ophthalmic imaging.

  1. Acoustic pressure-vector sensor array

    NASA Astrophysics Data System (ADS)

    Huang, Dehua; Elswick, Roy C.; McEachern, James F.

    2001-05-01

    Pressure-vector sensors measure both scalar and vector components of the acoustic field. December 2003 measurements at the NUWC Seneca Lake test facility verify previous observations that acoustic ambient noise spectrum levels measured by acoustic intensity sensors are reduced relative to either acoustic pressure or acoustic vector sensor spectrum levels. The Seneca measurements indicate a reduction by as much as 15 dB at the upper measurement frequency of 2500 Hz. A nonlinear array synthesis theory for pressure-vector sensors will be introduced that allows smaller apertures to achieve narrow beams. The significantly reduced ambient noise of individual pressure-vector elements observed in the ocean by others, and now at Seneca Lake, should allow a nonlinearly combined array to detect significantly lower levels than has been observed in previous multiplicative processing of pressure sensors alone. Nonlinear array synthesis of pressure-vector sensors differs from conventional super-directive algorithms that linearly combine pressure elements with positive and negative weights, thereby reducing the sensitivity of conventional super-directive arrays. The much smaller aperture of acoustic pressure-vector sensor arrays will be attractive for acoustic systems on underwater vehicles, as well as for other applications that require narrow beam acoustic receivers. [The authors gratefully acknowledge the support of ONR and NUWC.

  2. Dynamic response of an insonified sonar window interacting with a Tonpilz transducer array.

    PubMed

    Hull, Andrew J

    2007-08-01

    This paper derives and evaluates an analytical model of an insonified sonar window in contact with an array of Tonpilz transducers operating in receive mode. The window is fully elastic so that all wave components are present in the analysis. The output of the model is a transfer function of a transducer element output voltage divided by input pressure versus arrival angle and frequency. This model is intended for analysis of sonar systems that are to be built or modified for broadband processing. The model is validated at low frequency with a comparison to a previously derived thin plate model. Once this is done, an example problem is studied so that the effects of higher order wave interaction with acoustic reception can be understood. It was found that these higher order waves cause multiple nulls in the region where the array detects acoustic energy and that their locations in the arrival angle-frequency plane can be determined. The effects of these nulls in the beam patterns of the array are demonstrated.

  3. A Low Frequency Broadband Flextensional Ultrasonic Transducer Array.

    PubMed

    Savoia, Alessandro Stuart; Mauti, Barbara; Caliano, Giosuè

    2016-01-01

    In this paper, we propose the design and the fabrication of a multicell, piezoelectrically actuated, flextensional transducer array structure, characterized by a low mechanical impedance, thus allowing wideband and high-sensitivity immersion operation in the low ultrasonic frequency range. The transducer structure, consisting of a plurality of circular elementary cells orderly arranged according to a periodic hexagonal tiling, features a high flexibility in the definition of the active area shape and size. We investigate, by finite element modeling (FEM), the influence of different piezoelectric and elastic materials for the flexural plate, for the plate support and for the backing, on the transducer electroacoustic behavior. We carry out the dimensioning of the transducer components and cell layout, in terms of materials and geometry, respectively, by aiming at a circular active area of 80-mm diameter and broadband operation in the 30-100-kHz frequency range in immersion. PZT-5H ceramic disks and a calibrated thickness stainless steel plate are chosen for the vibrating structure, and FR-4 laminates and a brass plate, respectively, for the plate support and the backing. The diameter of the individual cells is set to 6 mm resulting in 121 cells describing a quasi-circular area, and the total thickness of the transducer is less than 10 mm. We report on the fabrication process flow for the accurate assembly of the transducer, based, respectively, on epoxy resin and wire bonding for the mechanical and electrical interconnection of the individual parts. The results of the electrical impedance and transmit pressure field characterization are finally reported and discussed. PMID:26540680

  4. A top-crossover-to-bottom addressed segmented annular array using piezoelectric micromachined ultrasonic transducers

    NASA Astrophysics Data System (ADS)

    Jung, Joontaek; Lee, Wonjun; Kang, Woojin; Hong, Hyeryung; Yuen Song, Hi; Oh, Inn-yeal; Park, Chul Soon; Choi, Hongsoo

    2015-11-01

    We design and fabricate segmented annular arrays (SAAs) using piezoelectric micromachined ultrasonic transducers (pMUTs) to demonstrate the feasibility of acoustic focusing of ultrasound. The fabricated SAAs have 25 concentric top-electrode signal lines and eight bottom-electrodes for grounding to enable electronic steering of selectively grouped ultrasonic transducers from 2393 pMUT elements. Each element in the array is connected by top-crossover-to-bottom metal bridges, which reduce the parasitic capacitance. Circular-shaped pMUT elements, 120 μm in diameter, are fabricated using 1 μm-thick sol-gel lead zirconate titanate on a silicon wafer. To utilize the high-density pMUT array, a deep reactive ion etching process is used for anisotropic silicon etching to realize the transducer membranes. The resonant frequency and effective coupling coefficient of the elements, measured with an impedance analyzer, yields 1.517 MHz and 1.29%, respectively, in air. The SAAs using pMUTs are packaged on a printed circuit board and coated with parylene C for acoustic intensity measurements in water. The ultrasound generated by each segmented array is focused on a selected point in space. When a 5 Vpp, 1.5 MHz square wave is applied, the maximum spatial peak temporal average intensity ({{I}\\text{spta}} ) is found to be 79 mW cm-2 5 mm from the SAAs’ surface without beamforming. The beam widths (-3 dB) of ultrasonic radiation patterns in the elevation and azimuth directions are recorded as 3 and 3.4 mm, respectively. The results successfully show the feasibility of focusing ultrasound on a small area with SAAs using pMUTs.

  5. A novel, flat, electronically-steered phased array transducer for tissue ablation: preliminary results.

    PubMed

    Ellens, Nicholas P K; Lucht, Benjamin B C; Gunaseelan, Samuel T; Hudson, John M; Hynynen, Kullervo H

    2015-03-21

    Flat, λ/2-spaced phased arrays for therapeutic ultrasound were examined in silico and in vitro. All arrays were made by combining modules made of 64 square elements with 1.5 mm inter-element spacing along both major axes. The arrays were designed to accommodate integrated, co-aligned diagnostic transducers for targeting and monitoring. Six arrays of 1024 elements (16 modules) and four arrays of 6144 elements (96 modules) were modelled and compared according to metrics such as peak pressure amplitude, focal size, ability to be electronically-steered far off-axis and grating lobe amplitude. Two 1024 element prototypes were built and measured in vitro, producing over 100 W of acoustic power. In both cases, the simulation model of the pressure amplitude field was in good agreement with values measured by hydrophone. Using one of the arrays, it was shown that the peak pressure amplitude dropped by only 24% and 25% of the on-axis peak pressure amplitude when steered to the edge of the array (40 mm) at depths of 30 mm and 50 mm. For the 6144 element arrays studied in in silico only, similarly high steerability was found: even when steered 100 mm off-axis, the pressure amplitude decrease at the focus was less than 20%, while the maximum pressure grating lobe was only 20%. Thermal simulations indicate that the modules produce more than enough acoustic power to perform rapid ablations at physiologically relevant depths and steering angles. Arrays such as proposed and tested in this study have enormous potential: their high electronic steerability suggests that they will be able to perform ablations of large volumes without the need for any mechanical translation.

  6. Photoacoustic Imaging of Animals with an Annular Transducer Array

    NASA Astrophysics Data System (ADS)

    Yang, Di-Wu; Zhou, Zhi-Bin; Zeng, Lv-Ming; Zhou, Xin; Chen, Xing-Hui

    2014-07-01

    A photoacoustic system with an annular transducer array is presented for rapid, high-resolution photoacoustic tomography of animals. An eight-channel data acquisition system is applied to capture the photoacoustic signals by using multiplexing and the total time of data acquisition and transferring is within 3 s. A limited-view filtered back projection algorithm is used to reconstruct the photoacoustic images. Experiments are performed on a mouse head and a rabbit head and clear photoacoustic images are obtained. The experimental results demonstrate that this imaging system holds the potential for imaging the human brain.

  7. Packaging and modular assembly of large-area and fine-pitch 2-D ultrasonic transducer arrays.

    PubMed

    Lin, Der-Song; Wodnicki, Robert; Zhuang, Xuefeng; Woychik, Charles; Thomenius, Kai E; Fisher, Rayette A; Mills, David M; Byun, Albert J; Burdick, William; Khuri-Yakub, Pierre; Bonitz, Barry; Davies, Todd; Thomas, Glen; Otto, Bernd; Töpper, Michael; Fritzsch, Thomas; Ehrmann, Oswin

    2013-07-01

    A promising transducer architecture for largearea arrays employs 2-D capacitive micromachined ultrasound transducer (CMUT) devices with backside trench-frame pillar interconnects. Reconfigurable array (RA) application-specified integrated circuits (ASICs) can provide efficient interfacing between these high-element-count transducer arrays and standard ultrasound systems. Standard electronic assembly techniques such as flip-chip and ball grid array (BGA) attachment, along with organic laminate substrate carriers, can be leveraged to create large-area arrays composed of tiled modules of CMUT chips and interface ASICs. A large-scale, fully populated and integrated 2-D CMUT array with 32 by 192 elements was developed and demonstrates the feasibility of these techniques to yield future large-area arrays. This study demonstrates a flexible and reliable integration approach by successfully combining a simple under-bump metallization (UBM) process and a stacked CMUT/interposer/ASIC module architecture. The results show high shear strength of the UBM (26.5 g for 70-μm balls), high interconnect yield, and excellent CMUT resonance uniformity (s = 0.02 MHz). A multi-row linear array was constructed using the new CMUT/interposer/ASIC process using acoustically active trench-frame CMUT devices and mechanical/ nonfunctional Si backside ASICs. Imaging results with the completed probe assembly demonstrate a functioning device based on the modular assembly architecture. PMID:25004504

  8. Numerical analysis of acoustic impedance microscope utilizing acoustic lens transducer to examine cultured cells.

    PubMed

    Gunawan, Agus Indra; Hozumi, Naohiro; Takahashi, Kenta; Yoshida, Sachiko; Saijo, Yoshifumi; Kobayashi, Kazuto; Yamamoto, Seiji

    2015-12-01

    A new technique is proposed for non-contact quantitative cell observation using focused ultrasonic waves. This technique interprets acoustic reflection intensity into the characteristic acoustic impedance of the biological cell. The cells are cultured on a plastic film substrate. A focused acoustic beam is transmitted through the substrate to its interface with the cell. A two-dimensional (2-D) reflection intensity profile is obtained by scanning the focal point along the interface. A reference substance is observed under the same conditions. These two reflections are compared and interpreted into the characteristic acoustic impedance of the cell based on a calibration curve that was created prior to the observation. To create the calibration curve, a numerical analysis of the sound field is performed using Fourier Transforms and is verified using several saline solutions. Because the cells are suspended by two plastic films, no contamination is introduced during the observation. In a practical observation, a sapphire lens transducer with a center frequency of 300 MHz was employed using ZnO thin film. The objects studied were co-cultured rat-derived glial (astrocyte) cells and glioma cells. The result was the clear observation of the internal structure of the cells. The acoustic impedance of the cells was spreading between 1.62 and 1.72 MNs/m(3). Cytoskeleton was indicated by high acoustic impedance. The introduction of cytochalasin-B led to a significant reduction in the acoustic impedance of the glioma cells; its effect on the glial cells was less significant. It is believed that this non-contact observation method will be useful for continuous cell inspections.

  9. A comparison of methods for focusing the field of a HIFU array transducer through human ribs.

    PubMed

    Gélat, P; Ter Haar, G; Saffari, N

    2014-06-21

    A forward model, which predicts the scattering by human ribs of a multi-element high-intensity focused ultrasound transducer, was used to investigate the efficacy of a range of focusing approaches described in the literature. This forward model is based on the boundary element method and was described by Gélat et al (2011 Phys. Med. Biol. 56 5553-81; 2012 Phys. Med. Biol. 57 8471-97). The model has since been improved and features a complex surface impedance condition at the surface of the ribs. The inverse problem of focusing through the ribs was implemented on six transducer array-rib topologies and five methods of focusing were investigated, including spherical focusing, binarized apodization based on geometric ray tracing, phase conjugation and the decomposition of the time-reversal operator method. The excitation frequency was 1 MHz and the array was of spherical-section type. Both human and idealized rib topologies were considered. The merit of each method of focusing was examined. It was concluded that the constrained optimization approach offers greater potential than the other focusing methods in terms of maximizing the ratio of acoustic pressure magnitudes at the focus to those on the surface of the ribs whilst taking full advantage of the dynamic range of the phased array.

  10. High-overtone self-focusing acoustic transducers for high-frequency ultrasonic Doppler.

    PubMed

    Zhu, Jie; Lee, Chuangyuan; Kim, Eun Sok; Wu, Dawei; Hu, Changhong; Zhou, Qifa; Shung, K Kirk; Wang, Gaofeng; Yu, Hongyu

    2010-05-01

    This work reports the potential use of high-overtone self-focusing acoustic transducers for high-frequency ultrasonic Doppler. By using harmonic frequencies of a thick bulk Lead Zirconate Titanate (PZT) transducer with a novel air-reflector Fresnel lens, we obtained strong ultrasound signals at 60 MHz (3rd harmonic) and 100 MHz (5th harmonic). Both experimental and theoretical analysis has demonstrated that the transducers can be applied to Doppler systems with high frequencies up to 100 MHz.

  11. A Spherically-Shaped PZT Thin Film Ultrasonic Transducer with an Acoustic Impedance Gradient Matching Layer Based on a Micromachined Periodically Structured Flexible Substrate

    PubMed Central

    Feng, Guo-Hua; Liu, Wei-Fan

    2013-01-01

    This paper presents the microfabrication of an acoustic impedance gradient matching layer on a spherically-shaped piezoelectric ultrasonic transducer. The acoustic matching layer can be designed to achieve higher acoustic energy transmission and operating bandwidth. Also included in this paper are a theoretical analysis of the device design and a micromachining technique to produce the novel transducer. Based on a design of a lead titanium zirconium (PZT) micropillar array, the constructed gradient acoustic matching layer has much better acoustic transmission efficiency within a 20–50 MHz operation range compared to a matching layer with a conventional quarter-wavelength thickness Parylene deposition. To construct the transducer, periodic microcavities are built on a flexible copper sheet, and then the sheet forms a designed curvature with a ball shaping. After PZT slurry deposition, the constructed PZT micropillar array is released onto a curved thin PZT layer. Following Parylene conformal coating on the processed PZT micropillars, the PZT micropillars and the surrounding Parylene comprise a matching layer with gradient acoustic impedance. By using the proposed technique, the fabricated transducer achieves a center frequency of 26 MHz and a −6 dB bandwidth of approximately 65%. PMID:24113683

  12. Design of Optimal Directional Parametric Acoustic Arrays in Air

    NASA Astrophysics Data System (ADS)

    Garner, Glenwood, III

    The nonlinear interaction of propagating acoustic waves in air is exploited as a means of generating highly directional sound beams at both audio frequencies and ultrasonic frequencies. A solution for the third-order intermodulation (IM3) products generated by the nonlinearity of air with a two-tone source waveform is derived by using cascaded secondorder nonlinearities. This method is applied to collinear sources as well as noncollinear sources. With collinear sources, the third-order interaction of two ultrasonic primary tones, where one is approximately the second harmonic of the other, produces an IM3 tone in the audio band. This IM3 tone is shown both theoretically and experimentally to have greater directivity than the difference tone produced by a traditional parametric array which utilizes second-order effects. With noncollinear sources, the third-order interaction of two ultrasonic primary tones closely spaced in frequency produces IM3 upper and IM3 lower tones that are also closely spaced in frequency to the primary tones. The IM3 upper and IM3 lower tones are shown both theoretically and experimentally to have greater directivity than either of the primary tones. Third-order intermodulation distortion generated by the electronic amplifiers and piezoelectric transducers is also shown to contribute to the third-order intermodulation products generated by air. The nonlinear contributions of the amplifier and transducer are modeled using power series expansions and measurements are performed to determine the power series coefficients. A new geometry for the optimum placement of ultrasonic transducers in a multi-element array is derived using the genetic algorithm and results in sparsely packed transducer elements. For primary ultrasonic tones closely spaced in frequency, the sparsely packed array is shown both theoretically and experimentally to produce a difference tone with greater directivity than obtained with a traditional densely packed hexagonal array

  13. Grating lobe reduction in transducer arrays through structural filtering of supercritical plates

    NASA Astrophysics Data System (ADS)

    Anderson, Brian Eric

    The effect of placing a structural acoustic filter between the water medium and the transducer elements of an array is investigated, in this thesis, to help reduce undesirable grating lobes. A plate is mounted to transducer elements with a thin decoupling polyurethane layer between the transducers and the plate. The plate acts as a radiation/incidence angle filter to pass energy at angles near normal incidence, but suppress energy at large incidence angles. The plate must possess a very high bending stiffness while maintaining low mass to achieve optimal results. Grating lobe reduction is achieved at the expense of limiting the available steering of the main lobe. Within this steer angle limit the main lobe beams can be steered as normal while the grating lobe level is reduced by the plate's angular filtering. The insertion of a plate structural filter provides an inexpensive and easily implemented approach to extend usable frequency bandwidth with reduced level grating lobes, without increasing the number of array elements. Even though some data matches theory well, a practical material has yet to be found that possesses optimal material properties. To the author's knowledge, this thesis represents the first attempt to advantageously utilize a plate to provide angular dependent sound transmission filtering above the plate's critical frequency (the supercritical frequency region). Theoretical analysis, numerical analysis, and extensive experimental results have been performed and a comparison will be presented in this thesis. The angular dependence of sound transmission through a plate is reviewed, followed by design considerations to optimize a plate for angular filtering. The optimal thickness for a plate depends on the plate's material properties. Equivalent circuit modeling and finite element modeling was applied, and is compared to. Extensive experimental results conducted with bars and a plate will be shown. Good agreement with theory and modeling is achieved

  14. Frequency dependence of the acoustic field generated from a spherical cavity transducer with open ends

    SciTech Connect

    Li, Faqi; Zeng, Deping; He, Min; Wang, Zhibiao E-mail: wangzhibiao@haifu.com.cn; Song, Dan; Lei, Guangrong; Lin, Zhou; Zhang, Dong E-mail: wangzhibiao@haifu.com.cn; Wu, Junru

    2015-12-15

    Resolution of high intensity focused ultrasound (HIFU) focusing is limited by the wave diffraction. We have developed a spherical cavity transducer with two open ends to improve the focusing precision without sacrificing the acoustic intensity (App Phys Lett 2013; 102: 204102). This work aims to theoretically and experimentally investigate the frequency dependence of the acoustic field generated from the spherical cavity transducer with two open ends. The device emits high intensity ultrasound at the frequency ranging from 420 to 470 kHz, and the acoustic field is measured by a fiber optic probe hydrophone. The measured results shows that the spherical cavity transducer provides high acoustic intensity for HIFU treatment only in its resonant modes, and a series of resonant frequencies can be choosen. Furthermore, a finite element model is developed to discuss the frequency dependence of the acoustic field. The numerical simulations coincide well with the measured results.

  15. Development of high frequency focused transducers for single beam acoustic tweezers

    NASA Astrophysics Data System (ADS)

    Hsu, Hsiu-Sheng

    Contactless particle trapping and manipulation have found many potential applications in diverse fields, especially in biological and medical research. Among the various methods, optical tweezers is the most well-known and extensively investigated technique. However, there are some limitations for particle manipulation based on optical tweezers. Due to the conceptual similarity with the optical tweezers and recent advances in high frequency ultrasonic transducer, a single beam acoustic tweezer using high frequency (≥ 20 MHz) focused transducer has recently been considered, and its feasibility was theoretically and experimentally investigated. This dissertation mainly describes the development of high frequency focused ultrasonic transducers for single beam acoustic tweezers applications. Three different types of transducers were fabricated. First, a 60 MHz miniature focused transducer (<1 mm) was made using press-focusing technique. The single beam acoustic trapping experiment was performed to manipulate 15 microm polystyrene microspheres using this transducer. In vitro ultrasonic biomicroscopy imaging on the rabbit eye was also obtained with this device. Second approach is to build a 200 MHz self-focused ZnO transducer by sputtering ZnO film on a curved surface of the aluminum backing material. An individual 10 microm microsphere was effectively manipulated in two dimensions by this type of transducer. Another ultrahigh frequency focused transducer based on silicon lens design has also been developed, where a 330 MHz silicon lens transducer was fabricated and evaluated. Microparticle trapping experiment was carried out to demonstrate that silicon lens transducer can manipulate a single microsphere as small as 5 microm. The realization of single beam acoustic tweezers using high frequency focused transducers can offer wide range of applications in biomedical and chemical sciences including intercellular kinetics studies and cell stimulation. Additionally, we

  16. Continuous Surveillance Technique for Flow Accelerated Corrosion of Pipe Wall Using Electromagnetic Acoustic Transducer

    NASA Astrophysics Data System (ADS)

    Kojima, F.; Kosaka, D.; Umetani, K.

    2011-06-01

    In this paper, we propose a on-line monitoring technique using electromagnetic acoustic transducer (EMAT). In the series of laboratory experiments, carbon steel pipes were used and each sample was fabricated to simulate FAC. Electromagnetic acoustic resonance method (EMAR) is successfully tested for pipe wall thickness measurements. The validity and the feasibility of our method are also demonstrated through the laboratory experiments.

  17. Resonant acoustic transducer and driver system for a well drilling string communication system

    DOEpatents

    Chanson, Gary J.; Nicolson, Alexander M.

    1981-01-01

    The acoustic data communication system includes an acoustic transmitter and receiver wherein low frequency acoustic waves, propagating in relatively loss free manner in well drilling string piping, are efficiently coupled to the drill string and propagate at levels competitive with the levels of noise generated by drilling machinery also present in the drill string. The transmitting transducer incorporates a mass-spring piezoelectric transmitter and amplifier combination that permits self-oscillating resonant operation in the desired low frequency range.

  18. A 1372-element Large Scale Hemispherical Ultrasound Phased Array Transducer for Noninvasive Transcranial Therapy

    SciTech Connect

    Song, Junho; Hynynen, Kullervo

    2009-04-14

    Noninvasive transcranial therapy using high intensity focused ultrasound transducers has attracted high interest as a promising new modality for the treatments of brain related diseases. We describe the development of a 1372 element large scale hemispherical ultrasound phased array transducer operating at a resonant frequency of 306 kHz. The hemispherical array has a diameter of 31 cm and a 15.5 cm radius of curvature. It is constructed with piezoelectric (PZT-4) tube elements of a 10 mm in diameter, 6 mm in length and 1.4 mm wall thickness. Each element is quasi-air backed by attaching a cork-rubber membrane on the back of the element. The acoustic efficiency of the element is determined to be approximately 50%. The large number of the elements delivers high power ultrasound and offers better beam steering and focusing capability. Comparisons of sound pressure-squared field measurements with theoretical calculations in water show that the array provides good beam steering and tight focusing capability over an efficient volume of approximately 100x100x80 mm{sup 3} with nominal focal spot size of approximately 2.3 mm in diameter at -6 dB. We also present its beam steering and focusing capability through an ex vivo human skull by measuring pressure-squared amplitude after phase corrections. These measurements show the same efficient volume range and focal spot sizes at -6 dB as the ones in water without the skull present. These results indicate that the array is sufficient for use in noninvasive transcranial ultrasound therapy.

  19. Solid Micro Horn Array (SMIHA) for Acoustic Matching

    NASA Technical Reports Server (NTRS)

    Sherrit, S.; Bao, X.; Bar-Cohen, Y.

    2008-01-01

    Transduction of electrical signals to mechanical signals and vice-versa in piezoelectric materials is controlled by the material coupling coefficient. In general in a loss-less material the ratio of energy conversion per cycle is proportional to the square of the coupling coefficient. In practical transduction however the impedance mismatch between the piezoelectric material and the electrical drive circuitry or the mechanical structure can have a significant impact on the power transfer. This paper looks at novel methods of matching the acoustic impedance of structures to the piezoelectric material in an effort to increase power transmission and efficiency. In typical methods the density and acoustic velocity of the matching layer is adjusted to give good matching between the transducer and the load. The approach discussed in this paper utilizes solid micro horn arrays in the matching layer which channel the stress and increase the strain in the layer. This approach is found to have potential applications in energy harvesting, medical ultrasound and in liquid and gas coupled transducers.

  20. Excitation and detection of shear horizontal waves with electromagnetic acoustic transducers for nondestructive testing of plates

    NASA Astrophysics Data System (ADS)

    Ma, Qingzeng; Jiao, Jingpin; Hu, Ping; Zhong, Xi; Wu, Bin; He, Cunfu

    2014-03-01

    The fundamental shear horizontal(SH0) wave has several unique features that are attractive for long-range nondestructive testing(NDT). By a careful design of the geometric configuration, electromagnetic acoustic transducers(EMATs) have the capability to generate a wide range of guided wave modes, such as Lamb waves and shear-horizontal(SH) waves in plates. However, the performance of EMATs is influenced by their parameters. To evaluate the performance of periodic permanent magnet(PPM) EMATs, a distributed-line-source model is developed to calculate the angular acoustic field cross-section in the far-field. Numerical analysis is conducted to investigate the performance of such EMATs with different geometric parameters, such as period and number of magnet arrays, and inner and outer coil widths. Such parameters have a great influence on the directivity of the generated SH0 waves that arises mainly in the amplitude and width of both main and side lobes. According to the numerical analysis, these parameters are optimized to obtain better directivity. Optimized PPM EMATs are designed and used for NDT of strip plates. Experimental results show that the lateral boundary of the strip plate has no perceivable influence on SH0-wave propagation, thus validating their used in NDT. The proposed model predicts the radiation pattern of PPM EMATs, and can be used for their parameter optimization.

  1. Acoustic positioning using multiple microphone arrays.

    PubMed

    Liu, Hui; Milios, Evangelos

    2005-05-01

    Passive acoustic techniques are presented to solve the localization problem of a sound source in three-dimensional space using off-the-shelf hardware. Multiple microphone arrays are employed, which operate independently, in estimating the direction of arrival of sound, or, equivalently, a direction vector from the array's geometric center towards the source. Direction vectors and array centers are communicated to a central processor, where the source is localized by finding the intersection of the direction lines defined by the direction vectors and the associated array centers. The performance of the method in the air is demonstrated experimentally and compared with a state-of-the-art method that requires centralized digitization of the signals from the microphones of all the arrays. PMID:15957748

  2. Three-dimensional ghost imaging using acoustic transducer

    NASA Astrophysics Data System (ADS)

    Zhang, Chi; Guo, Shuxu; Guan, Jian; Cao, Junsheng; Gao, Fengli

    2016-06-01

    We propose a novel three-dimensional (3D) ghost imaging method using unfocused ultrasonic transducer, where the transducer is used as the bucket detector to collect the total photoacoustic signal intensity from spherical surfaces with different radius circling the transducer. This collected signal is a time sequence corresponding to the optic absorption information on the spherical surfaces, and the values at the same moments in all the sequences are used as the bucket signals to restore the corresponding spherical images, which are assembled as the object 3D reconstruction. Numerical experiments show this method can effectively accomplish the 3D reconstruction and by adding up each sequence on time domain as a bucket signal it can also realize two dimensional (2D) ghost imaging. The influence of the measurement times on the 3D and 2D reconstruction is analyzed with Peak Signal to Noise Ratio (PSNR) as the yardstick, and the transducer as a bucket detector is also discussed.

  3. Circumferential phased array of shear-horizontal wave magnetostrictive patch transducers for pipe inspection.

    PubMed

    Kim, Hoe Woong; Lee, Joo Kyung; Kim, Yoon Young

    2013-02-01

    Several investigations report effective uses of magnetostrictive patch transducers to generate and measure longitudinal and torsional guided waves in a pipe. They can be used to form a phased array for the circumferential inspection of pipes. Although there are circumferential phased arrays employing piezoelectric transducers or EMAT's, no magnetostrictive patch transducer based array system has been attempted. In this investigation, we aim to develop a circumferential phased magnetostrictive patch transducer (PMPT) array that can focus shear-horizontal waves at any target point on a cylindrical surface of a pipe. For the development, a specific configuration of a PMPT array employing six magnetostrictive patch transducers is proposed. A wave simulation model is also developed to determine time delays and amplitudes of signals generated by the transducers of the array. This model should be able to predict accurately the angular profiles of shear-horizontal waves generated by the transducers. For wave focusing, the time reversal idea will be utilized. The wave focusing ability of the developed PMPT array is tested with multiple-crack detection experiments. Imaging of localized surface inspection regions is also attempted by using wave signals measured by the developed PMPT array system.

  4. Underwater Acoustic Wavefront Visualization by Scanning Laser Doppler Vibrometer for the Characterization of Focused Ultrasonic Transducers

    PubMed Central

    Longo, Roberto; Vanlanduit, Steve; Arroud, Galid; Guillaume, Patrick

    2015-01-01

    The analysis of acoustic wave fields is important for a large number of engineering designs, communication and health-related reasons. The visualization of wavefronts gives valuable information about the type of transducers and excitation signals more suitable for the test itself. This article is dedicated to the development of a fast procedure for acoustic fields visualization in underwater conditions, by means of laser Doppler vibrometer measurements. The ultrasonic probe is a focused transducer excited by a chirp signal. The scope of this work is to evaluate experimentally the properties of the sound beam in order to get reliable information about the transducer itself to be used in many kinds of engineering tests and transducer design. PMID:26287197

  5. Underwater Acoustic Wavefront Visualization by Scanning Laser Doppler Vibrometer for the Characterization of Focused Ultrasonic Transducers.

    PubMed

    Longo, Roberto; Vanlanduit, Steve; Arroud, Galid; Guillaume, Patrick

    2015-08-13

    The analysis of acoustic wave fields is important for a large number of engineering designs, communication and health-related reasons. The visualization of wavefronts gives valuable information about the type of transducers and excitation signals more suitable for the test itself. This article is dedicated to the development of a fast procedure for acoustic fields visualization in underwater conditions, by means of laser Doppler vibrometer measurements. The ultrasonic probe is a focused transducer excited by a chirp signal. The scope of this work is to evaluate experimentally the properties of the sound beam in order to get reliable information about the transducer itself to be used in many kinds of engineering tests and transducer design.

  6. Acoustic sensor array extracts physiology during movement

    NASA Astrophysics Data System (ADS)

    Scanlon, Michael V.

    2001-08-01

    An acoustic sensor attached to a person's neck can extract heart and breath sounds, as well as voice and other physiology related to their health and performance. Soldiers, firefighters, law enforcement, and rescue personnel, as well as people at home or in health care facilities, can benefit form being remotely monitored. ARLs acoustic sensor, when worn around a person's neck, picks up the carotid artery and breath sounds very well by matching the sensor's acoustic impedance to that of the body via a gel pad, while airborne noise is minimized by an impedance mismatch. Although the physiological sounds have high SNR, the acoustic sensor also responds to motion-induced artifacts that obscure the meaningful physiology. To exacerbate signal extraction, these interfering signals are usually covariant with the heart sounds, in that as a person walks faster the heart tends to beat faster, and motion noises tend to contain low frequency component similar to the heart sounds. A noise-canceling configuration developed by ARL uses two acoustic sensor on the front sides of the neck as physiology sensors, and two additional acoustic sensor on the back sides of the neck as noise references. Breath and heart sounds, which occur with near symmetry and simultaneously at the two front sensor, will correlate well. The motion noise present on all four sensor will be used to cancel the noise on the two physiology sensors. This report will compare heart rate variability derived from both the acoustic array and from ECG data taken simultaneously on a treadmill test. Acoustically derived breath rate and volume approximations will be introduced as well. A miniature 3- axis accelerometer on the same neckband provides additional noise references to validate footfall and motion activity.

  7. GHz-range surface acoustic wave interdigital transducers and applications

    NASA Astrophysics Data System (ADS)

    Yamanouchi, Kazuhiko

    1989-11-01

    GHz-range interdigital transducers (IDTs) with nanometer electrodes fabricated by using a new method of direct electron beam lithography and O2-plasma ashing techniques are examined. Various kinds of unidirectional transducers for low-loss devices are described and a new fabrication technology for higher operating frequencies using a lift-off anodic oxidation method is presented. Electrode separations are obtained by dielectric thin film fabricated by anodic oxidation of the edge of an Al film covered by the photoresist. Various kinds of GHz-range unidirectional IDTs using the lift-off anodic oxidation method are described.

  8. A lightweight push-pull acoustic transducer composed of a pair of dielectric elastomer films.

    PubMed

    Sugimoto, Takehiro; Ando, Akio; Ono, Kazuho; Morita, Yuichi; Hosoda, Kosuke; Ishii, Daisaku; Nakamura, Kentaro

    2013-11-01

    A lightweight push-pull acoustic transducer using dielectric elastomer films was proposed for use in advanced audio systems in homes. The push-pull structure consists of two dielectric elastomer films developed to serve as an electroactive polymer. The transducer utilizes the change in the surface area of the dielectric elastomer film, induced by an electric-field-induced change in the thickness, for sound generation. The resonance frequency of the transducer was derived from modeling the push-pull configuration to estimate the lower limit of the frequency range. Measurement results presented an advantage of push-pull driving in the suppression of harmonic distortion. PMID:24181987

  9. Electromagnetic-acoustic-transducer synthetic-aperture system for thick-weld inspection

    NASA Astrophysics Data System (ADS)

    Fortunko, C. M.; Schramm, R. E.; Moulder, J. C.; McColskey, J. D.

    1984-05-01

    A system is described based on electromagnetic acoustic transducers (EMATs) as an approach to automated nondestructive evaluation of thick weldments. Applications include a new type of ultrasonic inspection system for thick, butt welds used in ship construction. A minicomputer controlled transducer positioned and acquired the digitized ultrasonic waveforms for synthetic aperture processing. The synthetic aperture technique further improved signal quality and yielded flaw localization through the weld thickness. Details include the design of the transducers and electronics, as well as the mechanical positioner, signal processing algorithms, and complete computer program listings.

  10. Detection of acoustic emission from composite laminates using PVF2 transducers

    NASA Technical Reports Server (NTRS)

    Stiffler, R.; Henneke, E. G., II; Herakovich, C. T.

    1983-01-01

    Polyvinylidene fluoride (PVF2), a semicrystalline polymer exhibiting piezoelectricity, is presently used as a sensing transducer in acoustic emission (AE) monitoring of several different composite laminate materials in order to obtain both quasi-static and fatigue loading results. AE signals obtained from PVF2 transducers are compared with those obtained by standard AE sensors. It is noted that PVF2 transducers may, through the application of spectral signal analysis, be able to distinguish between two distinct failure modes which have been observed in two composite laminates of the same material, but employing different lamina stacking sequences.

  11. Acoustic transmission through compound subwavelength slit arrays

    NASA Astrophysics Data System (ADS)

    Ward, G. P.; Hibbins, A. P.; Sambles, J. R.; Smith, J. D.

    2016-07-01

    The angular dependence of the transmission of sound in air through four types of two-dimensional slit arrays formed of aluminium slats is explored, both experimentally and numerically. For a simple, subwavelength periodic slit array, it is well known that Fabry-Perot-like waveguide resonances, supported by the slit cavities, coupled to diffracted evanescent waves, result in enhanced acoustic transmission at frequencies determined by the length, width, and separation of each slit cavity. We demonstrate that altering the spacing or width of some of the slits to form a compound array (i.e., an array having a basis comprised of more than one slit) results in sharp dips in the transmission spectra, which may have a strong angular dependence. These features correspond to phase resonances, which have been studied extensively in the electromagnetic case. This geometry allows for additional near-field configurations compared to the simple array, whereby the field in adjacent cavities can be out of phase. Several types of compound slit arrays are investigated; one such structure is optimized to minimize the effect of boundary-layer loss mechanisms present in each slit cavity, thereby achieving a deep, sharp transmission minimum in a broad maximum.

  12. Breast ultrasound tomography with two parallel transducer arrays: preliminary clinical results

    NASA Astrophysics Data System (ADS)

    Huang, Lianjie; Shin, Junseob; Chen, Ting; Lin, Youzuo; Intrator, Miranda; Hanson, Kenneth; Epstein, Katherine; Sandoval, Daniel; Williamson, Michael

    2015-03-01

    Ultrasound tomography has great potential to provide quantitative estimations of physical properties of breast tumors for accurate characterization of breast cancer. We design and manufacture a new synthetic-aperture breast ultrasound tomography system with two parallel transducer arrays. The distance of these two transducer arrays is adjustable for scanning breasts with different sizes. The ultrasound transducer arrays are translated vertically to scan the entire breast slice by slice and acquires ultrasound transmission and reflection data for whole-breast ultrasound imaging and tomographic reconstructions. We use the system to acquire patient data at the University of New Mexico Hospital for clinical studies. We present some preliminary imaging results of in vivo patient ultrasound data. Our preliminary clinical imaging results show promising of our breast ultrasound tomography system with two parallel transducer arrays for breast cancer imaging and characterization.

  13. Effect of surface acoustic waves on the catalytic decomposition of ethanol employing a comb transducer for ultrasonic generation

    SciTech Connect

    S. J. Reese; D. H. Hurley; H.W. Rollins

    2006-04-01

    The effect of surface acoustic waves, generated on a silver catalyst using a comb transducer, on the catalytic decomposition of ethanol is examined. The comb transducer employs purely mechanical means for surface acoustic wave (SAW) transduction. Unlike interdigital SAW transducers on piezoelectric substrates, the complicating effects of heat generation due to electromechanical coupling, high electric fields between adjacent electrodes, and acoustoelectric currents are avoided. The ethanol decomposition reactions are carried out at 473 K. The rates of acetaldehyde and ethylene production are retarded when acoustic waves are applied. The rates recover to varying degrees when acoustic excitation ceases.

  14. Dynamic response of an array of flexural plates in acoustic medium

    PubMed Central

    Park, Kwan Kyu; Khuri-Yakub, Brutus T.

    2012-01-01

    The dynamic response of a transducer array made up of circular flexural plates in immersion is analytically calculated. The calculation method includes three steps: (1) the calculation of parallel resonant frequency and the velocity profile of each plate, (2) the calculation of mutual acoustic impedance between the plates, and (3) the calculation of velocity response, including the mechanical and acoustic impedance. The calculation method is validated by both finite element analysis and measurement results of a fabricated capacitive micromachined ultrasonic transducer. Based on the calculated velocity, the near-field pressure and the near-to-far field radiation patterns are presented. The flexural plate array in immersion displays two modes of operation. At low frequency, the mode shape of the transducer array is similar to that of a suspended plate and, at certain frequencies, two groups of plates move in opposite phase, which results in the cancellation of the average velocity. At high frequency, the mode shape is similar to that of a piston transducer; however, the near-field pressure distribution is similar to that of a resilient disk. PMID:23039426

  15. Micromachining techniques in developing high-frequency piezoelectric composite ultrasonic array transducers.

    PubMed

    Liu, Changgeng; Djuth, Frank T; Zhou, Qifa; Shung, K Kirk

    2013-12-01

    Several micromachining techniques for the fabrication of high-frequency piezoelectric composite ultrasonic array transducers are described in this paper. A variety of different techniques are used in patterning the active piezoelectric material, attaching backing material to the transducer, and assembling an electronic interconnection board for transmission and reception from the array. To establish the feasibility of the process flow, a hybrid test ultrasound array transducer consisting of a 2-D array having an 8 × 8 element pattern and a 5-element annular array was designed, fabricated, and assessed. The arrays are designed for a center frequency of ~60 MHz. The 2-D array elements are 105 × 105 μm in size with 5-μm kerfs between elements. The annular array surrounds the square 2-D array and provides the option of transmitting from the annular array and receiving with the 2-D array. Each annular array element has an area of 0.71 mm(2) with a 16-μm kerf between elements. The active piezoelectric material is (1 - x) Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT)/epoxy 1-3 composite with a PMN-PT pillar lateral dimension of 8 μm and an average gap width of ~4 μm, which was produced by deep reactive ion etching (DRIE) dry etching techniques. A novel electric interconnection strategy for high-density, small-size array elements was proposed. After assembly, the array transducer was tested and characterized. The capacitance, pulse-echo responses, and crosstalk were measured for each array element. The desired center frequency of ~60 MHz was achieved and the -6-dB bandwidth of the received signal was ~50%. At the center frequency, the crosstalk between adjacent 2-D array elements was about -33 dB. The techniques described herein can be used to build larger arrays containing smaller elements. PMID:24297027

  16. Cylindrical transducer for producing an acoustic spiral wave for underwater navigation (L).

    PubMed

    Brown, David A; Aronov, Boris; Bachand, Corey

    2012-12-01

    A cylindrical piezoceramic transducer using two orthogonal dipoles driven in phase quadrature to create an acoustic spiral wave, having constant amplitude and phase that varies linearly with azimuthal angle, is considered as a source for an underwater acoustic navigation system. Comparison of the spiral-wave signal with an omnidirectional reference signal having a constant phase originating from the same or co-located source provides a means for an underwater vehicle to determine its bearing angle relative to the signaling beacon [B. Hefner and B. Dzikowicz, J. Acoust. Soc. Am. 129(6), 3630-3639 (2011)]. An alternative proof-of-principle transducer along with experimental results including transmit frequency response, directional factors, and computed versus measured bearing angle are presented. PMID:23231092

  17. A four-quadrant PVDF transducer for surface acoustic wave detection.

    PubMed

    Lu, Zimo; Dorantes-Gonzalez, Dante J; Chen, Kun; Yang, Fei; Jin, Baoyin; Li, Yanning; Chen, Zhi; Hu, Xiaotang

    2012-01-01

    In this paper, a polyvinylidene fluoride (PVDF) piezoelectric transducer was developed to detect laser-induced surface acoustic waves in a SiO(2)-thin film-Si-substrate structure. In order to solve the problems related to, firstly, the position of the probe, and secondly, the fact that signals at different points cannot be detected simultaneously during the detection process, a four-quadrant surface acoustic wave PVDF transducer was designed and constructed for the purpose of detecting surface acoustic waves excited by a pulse laser line source. The experimental results of the four-quadrant piezoelectric detection in comparison with the commercial nanoindentation technology were consistent, the relative error is 0.56%, and the system eliminates the piezoelectric surface wave detection direction deviation errors, improves the accuracy of the testing system by 1.30%, achieving the acquisition at the same time at different testing positions of the sample. PMID:23112612

  18. Cylindrical transducer for producing an acoustic spiral wave for underwater navigation (L).

    PubMed

    Brown, David A; Aronov, Boris; Bachand, Corey

    2012-12-01

    A cylindrical piezoceramic transducer using two orthogonal dipoles driven in phase quadrature to create an acoustic spiral wave, having constant amplitude and phase that varies linearly with azimuthal angle, is considered as a source for an underwater acoustic navigation system. Comparison of the spiral-wave signal with an omnidirectional reference signal having a constant phase originating from the same or co-located source provides a means for an underwater vehicle to determine its bearing angle relative to the signaling beacon [B. Hefner and B. Dzikowicz, J. Acoust. Soc. Am. 129(6), 3630-3639 (2011)]. An alternative proof-of-principle transducer along with experimental results including transmit frequency response, directional factors, and computed versus measured bearing angle are presented.

  19. Nondestructive Evaluation of Double Bevel T-Joint by Tandem Array Ultrasonic Transducer

    NASA Astrophysics Data System (ADS)

    Shirahata, H.; Miki, C.; Yamaguchi, R.

    2003-03-01

    The double bevel T-joint is one of the most fundamental joints of steel bridges. Double bevel T-joint can be seen at beam-column connection of bridge pier. In the Japanese specifications, the welding should be full penetration. However, weld defect of incomplete penetration could be left in the joint due to the lack of quality control in welding. Fatigue cracks can be propagated from the weld defects. The authors developed a tandem array transducer. The tandem array transducer consists of 10 elements aligned in the same direction. Tandem scanning can be simulated by the transducer. Image reconstruction of incomplete penetration by synthetic aperture focusing technique was carried out. The test results showed sufficient detectability of incomplete penetration by the tandem array transducer. Height of incomplete of penetration could be estimated.

  20. Semicylindrical acoustic transducer from a dielectric elastomer film with compliant electrodes.

    PubMed

    Sugimoto, Takehiro; Ono, Kazuho; Ando, Akio; Morita, Yuichi; Hosoda, Kosuke; Ishii, Daisaku

    2011-08-01

    A semicylindrical acoustic transducer was constructed using a dielectric elastomer film with compliant electrodes that is an electroactive polymer composed of a polyurethane elastomer base and polyethylene dioxythiophene/polystyrene sulfonate electrodes. The use of this dielectric elastomer is advantageous because polyurethane is a common material that keeps its shape without any rigid frame. Because the dielectric elastomer films are essentially incompressible, electric-field-induced thickness changes are usually translated into much larger changes of the film area and side length. Here it is proposed that this change in side length can be utilized for sound generation when the film is bent into a semicylindrical shape. Accordingly, a semicylindrical acoustic transducer was fabricated using a film of thickness of 300 μm and its acoustic characteristics were investigated. The transducer can be operated at low applied voltages by reducing the film thickness, as long as the film is thick enough to generate sufficient force to overcome sound radiation impedance. The second harmonic distortion of the transducer was also investigated as a function of the ratio of the direct current bias voltage to the alternating current audio signal amplitude. PMID:21877790

  1. Calibration of ipsilateral stimulus transducer for acoustic reflex measurements.

    PubMed

    Olsen, S; Osterhammel, P A; Rasmussen, A N; Nielsen, L H

    1995-01-01

    Pure-tone Reference Equivalent Threshold Sound Pressure Level (RETSPL) of the ipsilateral stimulus receiver for acoustic reflex measurements on Madsen Electronics type Zodiac 901 impedance audiometer is provided. The results, obtained from 20 normal-hearing subjects, are achieved by comparing hearing threshold levels measured using a TDH 39 telephone (calibrated to ISO 389) with thresholds recorded using the ipsilateral stimulus insert phone. The calibration is referenced to an IEC-711 ear simulator and comprises the following frequencies: 125, 250, 500, 750, 1000, 1500, 2000, 3000, 4000, 6000, 8000 Hz.

  2. Acoustic streaming in the transducer plane in ultrasonic particle manipulation devices.

    PubMed

    Lei, Junjun; Glynne-Jones, Peter; Hill, Martyn

    2013-06-01

    In acoustofluidic manipulation and sorting devices, Rayleigh streaming flows are typically found in addition to the acoustic radiation forces. However, experimental work from various groups has described acoustic streaming that occurs in planar devices in a plane parallel to the transducer face. This is typically a four-quadrant streaming pattern with the circulation parallel to the transducer. Understanding its origins is essential for creating designs that limit or control this phenomenon. The cause of this kind of streaming pattern has not been previously explained as it is different from the well-known classical streaming patterns such as Rayleigh streaming and Eckart streaming, whose circulation planes are generally perpendicular to the face of the acoustic transducer. In order to gain insight into these patterns we present a numerical method based on Nyborg's limiting velocity boundary condition that includes terms ignored in the Rayleigh analysis, and verify its predictions against experimental PIV results in a simple device. The results show that the modelled particle trajectories match those found experimentally. Analysis of the dominant terms in the driving equations shows that the origin of this kind of streaming pattern is related to the circulation of the acoustic intensity.

  3. Arbitrary shaped, liquid filled reverberators with non-resonant transducers for broadband focusing of ultrasound using Time Reversed Acoustics.

    PubMed

    Sarvazyan, A; Fillinger, L

    2009-03-01

    The ability to generate short focused ultrasonic pulses with duration on the order of one period of carrier frequency depends on the bandwidth of the transmitter as the pulse duration is inversely proportional to the bandwidth. Conventional focusing arrays used for focusing ultrasound have limited bandwidth due to the resonant nature of the piezoelements generating ultrasound. Theoretically it is possible to build a broadband phased array composed of "non-resonant" elements: wedge-shaped or flat-concave piezotransducers, though there are numerous technical difficulties in designing arrays with hundreds of elements of complex shape. This task is much easier to realize in an alternative technique of ultrasound focusing based on the principles of Time Reversed Acoustics (TRA) because in TRA systems, effective focusing can be achieved with just a few, or even one, transducers. The goal of this study is to demonstrate the possibility of broadband focusing of ultrasonic waves using a TRA system with non-resonant transducers and to explore the factors affecting the performance of such a system. A new type of TRA reverberators, such as water-filled thin-wall plastic vessels, which can be used with the submersible piezotransducers fixed internally in the reverberator, are proposed and tested. The experiments are conducted in a water tank with the walls and bottom covered by a sound absorbing lining. A needle hydrophone mounted on a 3D positioning system is used as a beacon for the TRA focusing and then for measuring the spatial distribution of the focused ultrasound field. The bandwidth and spatial distribution of the signal focused by the TRA system using a single channel with the resonant versus non-resonant transducers have been analyzed. Two types of non-resonant transducers were tested: a flat-concave transducer with a diameter of 30 mm, and a thickness varying from 2 mm in the center to 11 mm at the edge, and a specially designed submersible transducer having an

  4. Arbitrary shaped, liquid filled reverberators with non-resonant transducers for broadband focusing of ultrasound using Time Reversed Acoustics.

    PubMed

    Sarvazyan, A; Fillinger, L

    2009-03-01

    The ability to generate short focused ultrasonic pulses with duration on the order of one period of carrier frequency depends on the bandwidth of the transmitter as the pulse duration is inversely proportional to the bandwidth. Conventional focusing arrays used for focusing ultrasound have limited bandwidth due to the resonant nature of the piezoelements generating ultrasound. Theoretically it is possible to build a broadband phased array composed of "non-resonant" elements: wedge-shaped or flat-concave piezotransducers, though there are numerous technical difficulties in designing arrays with hundreds of elements of complex shape. This task is much easier to realize in an alternative technique of ultrasound focusing based on the principles of Time Reversed Acoustics (TRA) because in TRA systems, effective focusing can be achieved with just a few, or even one, transducers. The goal of this study is to demonstrate the possibility of broadband focusing of ultrasonic waves using a TRA system with non-resonant transducers and to explore the factors affecting the performance of such a system. A new type of TRA reverberators, such as water-filled thin-wall plastic vessels, which can be used with the submersible piezotransducers fixed internally in the reverberator, are proposed and tested. The experiments are conducted in a water tank with the walls and bottom covered by a sound absorbing lining. A needle hydrophone mounted on a 3D positioning system is used as a beacon for the TRA focusing and then for measuring the spatial distribution of the focused ultrasound field. The bandwidth and spatial distribution of the signal focused by the TRA system using a single channel with the resonant versus non-resonant transducers have been analyzed. Two types of non-resonant transducers were tested: a flat-concave transducer with a diameter of 30 mm, and a thickness varying from 2 mm in the center to 11 mm at the edge, and a specially designed submersible transducer having an

  5. Design factors of intravascular dual frequency transducers for super-harmonic contrast imaging and acoustic angiography

    NASA Astrophysics Data System (ADS)

    Ma, Jianguo; Martin, K. Heath; Li, Yang; Dayton, Paul A.; Shung, K. Kirk; Zhou, Qifa; Jiang, Xiaoning

    2015-05-01

    Imaging of coronary vasa vasorum may lead to assessment of the vulnerable plaque development in diagnosis of atherosclerosis diseases. Dual frequency transducers capable of detection of microbubble super-harmonics have shown promise as a new contrast-enhanced intravascular ultrasound (CE-IVUS) platform with the capability of vasa vasorum imaging. Contrast-to-tissue ratio (CTR) in CE-IVUS imaging can be closely associated with low frequency transmitter performance. In this paper, transducer designs encompassing different transducer layouts, transmitting frequencies, and transducer materials are compared for optimization of imaging performance. In the layout selection, the stacked configuration showed superior super-harmonic imaging compared with the interleaved configuration. In the transmitter frequency selection, a decrease in frequency from 6.5 MHz to 5 MHz resulted in an increase of CTR from 15 dB to 22 dB when receiving frequency was kept constant at 30 MHz. In the material selection, the dual frequency transducer with the lead magnesium niobate-lead titanate (PMN-PT) 1-3 composite transmitter yielded higher axial resolution compared to single crystal transmitters (70 μm compared to 150 μm pulse length). These comparisons provide guidelines for the design of intravascular acoustic angiography transducers.

  6. Design factors of intravascular dual frequency transducers for super-harmonic contrast imaging and acoustic angiography

    PubMed Central

    Ma, Jianguo; Martin, K. Heath; Li, Yang; Dayton, Paul A.; Shung, K. Kirk; Zhou, Qifa; Jiang, Xiaoning

    2015-01-01

    Imaging of coronary vasa vasorum may lead to assessment of the vulnerable plaque development in diagnosis of atherosclerosis diseases. Dual frequency transducers capable of detection of microbubble super-harmonics have shown promise as a new contrast-enhanced intravascular ultrasound (CE-IVUS) platform with the capability of vasa vasorum imaging. Contrast-to-tissue ratio (CTR) in CE-IVUS imaging can be closely associated with the low frequency transmitter performance. In this paper, transducer designs encompassing different transducer layouts, transmitting frequencies, and transducer materials are compared for optimization of imaging performance. In the layout selection, the stacked configuration showed superior super-harmonic imaging compared with the interleaved configuration. In the transmitter frequency selection, a decrease in frequency from 6.5 MHz to 5 MHz resulted in an increase of CTR from 15 dB to 22 dB when receiving frequency was kept constant at 30 MHz. In the material selection, the dual frequency transducer with the lead magnesium niobate-lead titanate (PMN-PT) 1-3 composite transmitter yielded higher axial resolution compared to single crystal transmitters (70 μm compared to 150 μm pulse length). These comparisons provide guidelines for design of intravascular acoustic angiography transducers. PMID:25856384

  7. Design factors of intravascular dual frequency transducers for super-harmonic contrast imaging and acoustic angiography.

    PubMed

    Ma, Jianguo; Martin, K Heath; Li, Yang; Dayton, Paul A; Shung, K Kirk; Zhou, Qifa; Jiang, Xiaoning

    2015-05-01

    Imaging of coronary vasa vasorum may lead to assessment of the vulnerable plaque development in diagnosis of atherosclerosis diseases. Dual frequency transducers capable of detection of microbubble super-harmonics have shown promise as a new contrast-enhanced intravascular ultrasound (CE-IVUS) platform with the capability of vasa vasorum imaging. Contrast-to-tissue ratio (CTR) in CE-IVUS imaging can be closely associated with low frequency transmitter performance. In this paper, transducer designs encompassing different transducer layouts, transmitting frequencies, and transducer materials are compared for optimization of imaging performance. In the layout selection, the stacked configuration showed superior super-harmonic imaging compared with the interleaved configuration. In the transmitter frequency selection, a decrease in frequency from 6.5 MHz to 5 MHz resulted in an increase of CTR from 15 dB to 22 dB when receiving frequency was kept constant at 30 MHz. In the material selection, the dual frequency transducer with the lead magnesium niobate-lead titanate (PMN-PT) 1-3 composite transmitter yielded higher axial resolution compared to single crystal transmitters (70 μm compared to 150 μm pulse length). These comparisons provide guidelines for the design of intravascular acoustic angiography transducers. PMID:25856384

  8. Investigation of the Sintering Process Using Non-Contact Electromagnetic Acoustic Transducers

    SciTech Connect

    James C. Foley; David K. Rehbein; Daniel J. Barnard

    2001-05-30

    In-situ characterizations of green state part density and sintering state have long been desired in the powder metal community. Recent advances in non-contact electromagnetic acoustic transducer (EMAT) technology have enabled in-situ monitoring of acoustic amplitude and velocity as sintering proceeds. Samples were made from elemental powders of Al (99.99%), Al (99.7%), Ag, (99.99%), Cu (99.99%) and Fe (99.9%). The powders were pressed in a uniaxial die and examined with acoustic waves for changes in velocity and amplitude during sintering for the samples containing Al, Ag, and Cu. The changes in acoustic properties were correlated with sample microstructures and mechanical properties. Evolution of a series of reverberating echoes during sintering is shown to provide information on the state of sintering, and changes in sintering kinetics as well as having the potential for detection of interior flaws.

  9. Confocal acoustic radiation force optical coherence elastography using a ring ultrasonic transducer

    SciTech Connect

    Qi, Wenjuan; Li, Rui; Ma, Teng; Kirk Shung, K.; Zhou, Qifa; Chen, Zhongping

    2014-03-24

    We designed and developed a confocal acoustic radiation force optical coherence elastography system. A ring ultrasound transducer was used to achieve reflection mode excitation and generate an oscillating acoustic radiation force in order to generate displacements within the tissue, which were detected using the phase-resolved optical coherence elastography method. Both phantom and human tissue tests indicate that this system is able to sense the stiffness difference of samples and quantitatively map the elastic property of materials. Our confocal setup promises a great potential for point by point elastic imaging in vivo and differentiation of diseased tissues from normal tissue.

  10. Ultrasonic fingerprint sensor using a piezoelectric micromachined ultrasonic transducer array integrated with complementary metal oxide semiconductor electronics

    SciTech Connect

    Lu, Y.; Fung, S.; Wang, Q.; Horsley, D. A.; Tang, H.; Boser, B. E.; Tsai, J. M.; Daneman, M.

    2015-06-29

    This paper presents an ultrasonic fingerprint sensor based on a 24 × 8 array of 22 MHz piezoelectric micromachined ultrasonic transducers (PMUTs) with 100 μm pitch, fully integrated with 180 nm complementary metal oxide semiconductor (CMOS) circuitry through eutectic wafer bonding. Each PMUT is directly bonded to a dedicated CMOS receive amplifier, minimizing electrical parasitics and eliminating the need for through-silicon vias. The array frequency response and vibration mode-shape were characterized using laser Doppler vibrometry and verified via finite element method simulation. The array's acoustic output was measured using a hydrophone to be ∼14 kPa with a 28 V input, in reasonable agreement with predication from analytical calculation. Pulse-echo imaging of a 1D steel grating is demonstrated using electronic scanning of a 20 × 8 sub-array, resulting in 300 mV maximum received amplitude and 5:1 contrast ratio. Because the small size of this array limits the maximum image size, mechanical scanning was used to image a 2D polydimethylsiloxane fingerprint phantom (10 mm × 8 mm) at a 1.2 mm distance from the array.

  11. Nonparaxial multi-Gaussian beam models and measurement models for phased array transducers.

    PubMed

    Zhao, Xinyu; Gang, Tie

    2009-01-01

    A nonparaxial multi-Gaussian beam model is proposed in order to overcome the limitation that paraxial Gaussian beam models lose accuracy in simulating the beam steering behavior of phased array transducers. Using this nonparaxial multi-Gaussian beam model, the focusing and steering sound fields generated by an ultrasonic linear phased array transducer are calculated and compared with the corresponding results obtained by paraxial multi-Gaussian beam model and more exact Rayleigh-Sommerfeld integral model. In addition, with help of this novel nonparaxial method, an ultrasonic measurement model is provided to investigate the sensitivity of linear phased array transducers versus steering angles. Also the comparisons of model predictions with experimental results are presented to certify the accuracy of this provided measurement model.

  12. Development of an electromagnetic acoustic transducer (EMAT) for the noncontact excitation of guided ultrasonic waves

    NASA Astrophysics Data System (ADS)

    Fromme, P.

    2015-03-01

    Fatigue damage can develop in aerospace structures at locations of stress concentration, such as fasteners. For the safe operation of the aircraft fatigue cracks need to be detected before reaching a critical length. Guided ultrasonic waves offer an efficient method for the detection and characterization of such defects in large aerospace structures. Noncontact excitation of guided waves was achieved using electromagnetic acoustic transducers (EMAT). The transducer development for the specific excitation of the A0 Lamb wave mode is explained. The radial and angular dependency of the excited guided wave pulses at different frequencies were measured using a noncontact laser interferometer. Based on the induced eddy currents in the plate a theoretical model was developed and reasonably good agreement with the measured transducer performance was achieved. The developed transducers were employed for defect detection in aluminum components using fully noncontact guided wave measurements. Excitation of the A0 Lamb wave mode was achieved using the developed EMAT transducer and the guided wave propagation and scattering was measured using a noncontact laser interferometer. These results provide the basis for the defect characterization in aerospace structures using noncontact guided wave sensors.

  13. Annular spherically focused ring transducers for improved single-beam acoustical tweezers

    NASA Astrophysics Data System (ADS)

    Mitri, F. G.

    2016-02-01

    The use of ultrasonic transducers with a central hollow is suggested for improved single-beam acoustical tweezers applications. Within the framework of the Fresnel-Kirchhoff parabolic approximation, a closed-form partial-wave series expansion (PWSE) for the incident velocity potential (or pressure) field is derived for an annular spherically focused ring (asfr) with uniform vibration across its surface in spherical coordinates. The Rayleigh-Sommerfeld diffraction integral and the addition theorems for the Legendre and spherical wave functions are used to obtain the PWSE assuming a weakly focused beam (with a focusing angle α ≤ 20°). The PWSE allows evaluating the incident field from the finite asfr in 3D. Moreover, the obtained solution allows computing efficiently the acoustic scattering and radiation force on a sphere centered on the beam's axis of wave propagation. The analytical solution is valid for wavelengths largely exceeding the radius of the asfr and when the viscosity of the surrounding fluid can be neglected. Numerical predictions for the beam-forming, scattering, and axial time-averaged radiation force are performed with particular emphasis on the asfr thickness, the axial distance separating the sphere from the center of the transducer, the (non-dimensional) size of the transducer, as well as the sphere's elastic properties without restriction to the long- (i.e., Rayleigh) or the short-wavelength (i.e., ray acoustics) regimes. Potential applications of the present solution are in beam-forming design, particle tweezing, and manipulation due to negative forces using ultrasonic asfr transducers.

  14. Micromachining Techniques in Developing High-Frequency Piezoelectric Composite Ultrasonic Array Transducers

    PubMed Central

    Liu, Changgeng; Djuth, Frank T.; Zhou, Qifa; Shung, K. Kirk

    2014-01-01

    Several micromachining techniques for the fabrication of high-frequency piezoelectric composite ultrasonic array transducers are described in this paper. A variety of different techniques are used in patterning the active piezoelectric material, attaching backing material to the transducer, and assembling an electronic interconnection board for transmission and reception from the array. To establish the feasibility of the process flow, a hybrid test ultrasound array transducer consisting of a 2-D array having an 8 × 8 element pattern and a 5-element annular array was designed, fabricated, and assessed. The arrays are designed for a center frequency of ~60 MHz. The 2-D array elements are 105 × 105 μm in size with 5-μm kerfs between elements. The annular array surrounds the square 2-D array and provides the option of transmitting from the annular array and receiving with the 2-D array. Each annular array element has an area of 0.71 mm2 with a 16-μm kerf between elements. The active piezoelectric material is (1 − x) Pb(Mg1/3Nb2/3)O3−xPbTiO3 (PMN-PT)/epoxy 1–3 composite with a PMN-PT pillar lateral dimension of 8 μm and an average gap width of ~4 μm, which was produced by deep reactive ion etching (DRIE) dry etching techniques. A novel electric interconnection strategy for high-density, small-size array elements was proposed. After assembly, the array transducer was tested and characterized. The capacitance, pulse–echo responses, and crosstalk were measured for each array element. The desired center frequency of ~60 MHz was achieved and the −6-dB bandwidth of the received signal was ~50%. At the center frequency, the crosstalk between adjacent 2-D array elements was about −33 dB. The techniques described herein can be used to build larger arrays containing smaller elements. PMID:24297027

  15. Manipulation of acoustic focusing with an active and configurable planar metasurface transducer

    PubMed Central

    Zhao, Jiajun; Ye, Huapeng; Huang, Kun; Chen, Zhi Ning; Li, Baowen; Qiu, Cheng-Wei

    2014-01-01

    It has a pivotal role in medical science and in industry to concentrate the acoustic energy created with piezoelectric transducers (PTs) into a specific area. However, previous researches seldom consider the focal resolution, whose focal size is much larger than one wavelength. Furthermore, there is to date no such design method of PTs that allows a large degree of freedom to achieve designed focal patterns. Here, an active and configurable planar metasurface PT prototype is proposed to manipulate the acoustic focal pattern and the focal resolution freely. By suitably optimized ring configurations of the active metasurface PT, we demonstrate the manipulation of focal patterns in acoustic far fields, such as the designed focal needle and multi foci. Our method is also able to manipulate and improve the cross-sectional focal resolution from subwavelength to the extreme case: the deep sub-diffraction-limit resolution. Via the acoustic Rayleigh-Sommerfeld diffraction integral (RSI) cum the binary particle swarm optimization (BPSO), the free manipulation of focusing properties is achieved in acoustics for the first time. Our approach may offer more initiatives where the strict control of acoustic high-energy areas is demanding. PMID:25174409

  16. Self-Characterization of Commercial Ultrasound Probes in Transmission Acoustic Inverse Scattering: Transducer Model and Volume Integral Formulation

    PubMed Central

    Haynes, Mark; Verweij, Sacha A. M.; Moghaddam, Mahta; Carson, Paul L.

    2014-01-01

    A self-contained source characterization method for commercial ultrasound probes in transmission acoustic inverse scattering is derived and experimentally tested. The method is based on modified scattered field volume integral equations that are linked to the source-scattering transducer model. The source-scattering parameters are estimated via pair-wise transducer measurements and the nonlinear inversion of an acoustic propagation model that is derived. This combination creates a formal link between the transducer characterization and the inverse scattering algorithm. The method is tested with two commercial ultrasound probes in a transmission geometry including provisions for estimating the probe locations and aligning a robotic rotator. The transducer characterization results show that the nonlinear inversion fit the measured data well. The transducer calibration and inverse scattering algorithm are tested on simple targets. Initial images show that the recovered contrasts are physically consistent with expected values. PMID:24569251

  17. A Preliminary Evaluation of Near-Transducer Velocities Collected with Low-Blank Acoustic Doppler Current Profiler

    USGS Publications Warehouse

    Gartner, J.W.; Ganju, N.K.

    2002-01-01

    Many streams and rivers for which the US Geological Survey must provide discharge measurements are too shallow to apply existing acoustic Doppler current profiler techniques for flow measurements of satisfactory quality. Because the same transducer is used for both transmitting and receiving acoustic signals in most Doppler current profilers, some small time delay is required for acoustic "ringing" to be damped out of transducers before meaningful measurements can be made. The result of that time delay is that velocity measurements cannot be made close to the transducer thus limiting the usefulness of these instruments in shallow regions. Manufacturers and users are constantly striving for improvements to acoustic instruments which would permit useful discharge measurements in shallow rivers and streams that are still often measured with techniques and instruments more than a century old. One promising area of advance appeared to be reduction of time delay (blank) required between transmitting and receiving signals during acoustic velocity measurements. Development of a low- or zero-blank transducer by RD Instruments3 held promise that velocity measurements could be made much closer to the transducer and thus in much shallower water. Initial experience indicates that this is not the case; limitation of measurement quality appears to be related to the physical presence of the transducer itself within the flow field. The limitation may be the result of changes to water flow pattern close to the transducer rather than transducer ringing characteristics as a function of blanking distance. Results of field experiments are discussed that support this conclusion and some minimum measurement distances from transducer are suggested based on water current speed and ADCP sample modes.

  18. A row-column addressed micromachined ultrasonic transducer array for surface scanning applications.

    PubMed

    Wong, Lawrence L P; Chen, Albert I H; Li, Zhenhao; Logan, Andrew S; Yeow, John T W

    2014-12-01

    Row-column addressed arrays for ultrasonic non-destructive testing (NDT) applications are analyzed and demonstrated in this paper. Simulation and experimental results of a row-column addressed 32 by 32 capacitive micromachined ultrasonic transducer (CMUT) array are presented. The CMUT array, which was designed for medical imaging applications, has a center frequency of 5.3MHz. The CMUT array was used to perform C-scans on test objects with holes that have diameters of 1.0mm and 0.5mm. The array transducer has an aperture size of 4.8mm by 4.8mm, and it was used to scan an area of 4.0mm by 4.0mm. Compared to an N by N fully addressed 2-D array, a row-column addressed array of the same number of elements requires fewer (N instead of N(2)) pairs of interconnection and supporting electronic components such as pulsers and amplifiers. Even though the resulting field of view is limit by the aperture size, row-column addressed arrays and the row-column addressing scheme can be an alternative option of 2-D arrays for NDT applications.

  19. Acoustic field and array response uncertainties in stratified ocean media.

    PubMed

    Hayward, Thomas J; Dhakal, Sagar

    2012-07-01

    The change-of-variables theorem of probability theory is applied to compute acoustic field and array beam power probability density functions (pdfs) in uncertain ocean environments represented by stratified, attenuating ocean waveguide models. Computational studies for one and two-layer waveguides investigate the functional properties of the acoustic field and array beam power pdfs. For the studies, the acoustic parameter uncertainties are represented by parametric pdfs. The field and beam response pdfs are computed directly from the parameter pdfs using the normal-mode representation and the change-of-variables theorem. For two-dimensional acoustic parameter uncertainties of sound speed and attenuation, the field and beam power pdfs exhibit irregular functional behavior and singularities associated with stationary points of the mapping, defined by acoustic propagation, from the parameter space to the field or beam power space. Implications for the assessment of orthogonal polynomial expansion and other methods for computing acoustic field pdfs are discussed.

  20. Noncontact excitation of guided waves (A0 mode) using an electromagnetic acoustic transducer (EMAT)

    NASA Astrophysics Data System (ADS)

    Fromme, Paul

    2016-02-01

    Fatigue damage can develop in aircraft structures at locations of stress concentration, such as fasteners, and has to be detected before reaching a critical size to ensure safe aircraft operation. Guided ultrasonic waves offer an efficient method for the detection and characterization of such defects in large aerospace structures. Electromagnetic acoustic transducers (EMAT) for the noncontact excitation of guided ultrasonic waves were developed. The transducer development for the specific excitation of the A0 Lamb wave mode with an out-of-plane Lorentz force is explained. The achieved radial and angular dependency of the excited guided wave pulses were measured using a noncontact laser interferometer. Based on the induced eddy currents in the plate a theoretical model was developed. The application of the developed transducers for defect detection in aluminum components using fully noncontact guided wave measurements was demonstrated. Excitation of the A0 Lamb wave mode was achieved using the developed EMAT transducer and the guided wave propagation and scattering was measured using a noncontact laser interferometer.

  1. Parametric acoustic arrays: A state of the art review

    NASA Technical Reports Server (NTRS)

    Fenlon, F. H.

    1976-01-01

    Following a brief introduction to the concept of parametric acoustic interactions, the basic properties of parametric transmitting and receiving arrays are considered in the light of conceptual advances resulting from experimental and theoretical investigations that have taken place since 1963.

  2. Transversal Anderson localization of sound in acoustic waveguide arrays.

    PubMed

    Ye, Yangtao; Ke, Manzhu; Feng, Junheng; Wang, Mudi; Qiu, Chunyin; Liu, Zhengyou

    2015-04-22

    We present designs of one-dimensional acoustic waveguide arrays and investigate wave propagation inside. Under the condition of single identical waveguide mode and weak coupling, the acoustic wave motion in waveguide arrays can be modeled with a discrete mode-coupling theory. The coupling constants can be retrieved from simulations or experiments as the function of neighboring waveguide separations. Sound injected into periodic arrays gives rise to the discrete diffraction, exhibiting ballistic or extended transport in transversal direction. But sound injected into randomized waveguide arrays readily leads to Anderson localization transversally. The experimental results show good agreement with simulations and theoretical predictions.

  3. Angular Spectrum Method for the Focused Acoustic Field of a Linear Transducer

    NASA Astrophysics Data System (ADS)

    Belgroune, D.; de Belleval, J. F.; Djelouah, H.

    Applications involving non-destructive testing or acoustical imaging are more and more sophisticated. In this context, a model based on the angular spectrum approach is tackled in view to calculate the focused impulse field radiated by a linear transducer through a plane fluid-solid interface. It is well known that electronic focusing, based on a cylindrical delay law, like for the classical cases (lenses, curved transducer), leads to an inaccurate focusing in the solid due to geometric aberrations errors affecting refraction. Generally, there is a significant difference between the acoustic focal distance and the geometrical focal due to refraction. In our work, an optimized delay law, based on the Fermat's principle is established, particularly at an oblique incidence where the geometrical considerations, relatively simple in normal incidence, become quickly laborious. Numerical simulations of impulse field are judiciously carried out. Subsequently, the input parameters are optimally selected in order to achieve good computation accuracy and a high focusing. The overall results, involving compression and shear waves, have highlighted the focusing improvement in the solid when compared to the currently available approaches. Indeed, the acoustic focal distance is very close to geometrical focal distance and then, allows better control of the refracted angular beam profile (refraction angle, focusing depth and focal size).

  4. A perturbative analysis of surface acoustic wave propagation and reflection in interdigital transducers

    NASA Astrophysics Data System (ADS)

    Thoma, Carsten Hilmar

    1997-12-01

    The coupling of stress and strain fields to electric fields present in anisotropic piezoelectric crystals makes them ideal for use as electromechanical transducers in a wide variety of applications. In recent years such crystals have been utilized to produce surface acoustic wave devices for signal processing applications, in which an applied metallic grating both transmits and receives, through the piezoelectric effect, electromechanical surface waves. The design of such interdigital transducers requires an accurate knowledge of wave propagation and reflection. The presence of the metal grating in addition to its ideal transduction function, by means of electrical and mechanical loading, also introduces a velocity shift as well as reflection into substrate surface waves. We seek to obtain a consistent formulation of the wave behavior due to the electrical and mechanical loading of the substrate crystal by the metallic grating. A perturbative solution up to second order in h//lambda is developed, where h is the maximum grating height and λ the acoustic wavelength. For the operating frequencies and physical parameters of modern surface acoustic wave devices such an analysis will provide an adequate description of device behavior in many cases, thereby circumventing the need for more computationally laborious methods. Numerical calculations are presented and compared with available experimental data.

  5. Phantom evaluation of stacked-type dual-frequency 1-3 composite transducers: A feasibility study on intracavitary acoustic angiography.

    PubMed

    Kim, Jinwook; Li, Sibo; Kasoji, Sandeep; Dayton, Paul A; Jiang, Xiaoning

    2015-12-01

    In this paper, we present phantom evaluation results of a stacked-type dual-frequency 1-3 piezoelectric composite transducer as a feasibility study for intracavitary acoustic angiography. Our previous design (6.5/30 MHz PMN-PT single crystal transducer) for intravascular contrast ultrasound imaging exhibited a contrast-to-tissue ratio (CTR) of 12 dB with a penetration depth of 2.5 mm. For improved penetration depth (>3 mm) and comparable contrast-to-tissue ratio (>12 dB), we evaluated a lower frequency 2/14 MHz PZT 1-3 composite transducer. Superharmonic imaging performance of this transducer and a detailed characterization of key parameters for acoustic angiography are presented. The 2/14 MHz arrangement demonstrated a -6 dB fractional bandwidth of 56.5% for the transmitter and 41.8% for the receiver, and produced sufficient peak-negative pressures (>1.5 MPa) at 2 MHz to induce a strong nonlinear harmonic response from microbubble contrast agents. In an in-vitro contrast ultrasound study using a tissue mimicking phantom and 200 μm cellulose microvessels, higher harmonic microbubble responses, from the 5th through the 7th harmonics, were detected with a signal-to-noise ratio of 16 dB. The microvessels were resolved in a two-dimensional image with a -6dB axial resolution of 615 μm (5.5 times the wavelength of 14 MHz waves) and a contrast-to-tissue ratio of 16 dB. This feasibility study, including detailed explanation of phantom evaluation and characterization procedures for key parameters, will be useful for the development of future dual-frequency array transducers for intracavitary acoustic angiography. PMID:26112426

  6. Phantom evaluation of stacked-type dual-frequency 1-3 composite transducers: A feasibility study on intracavitary acoustic angiography.

    PubMed

    Kim, Jinwook; Li, Sibo; Kasoji, Sandeep; Dayton, Paul A; Jiang, Xiaoning

    2015-12-01

    In this paper, we present phantom evaluation results of a stacked-type dual-frequency 1-3 piezoelectric composite transducer as a feasibility study for intracavitary acoustic angiography. Our previous design (6.5/30 MHz PMN-PT single crystal transducer) for intravascular contrast ultrasound imaging exhibited a contrast-to-tissue ratio (CTR) of 12 dB with a penetration depth of 2.5 mm. For improved penetration depth (>3 mm) and comparable contrast-to-tissue ratio (>12 dB), we evaluated a lower frequency 2/14 MHz PZT 1-3 composite transducer. Superharmonic imaging performance of this transducer and a detailed characterization of key parameters for acoustic angiography are presented. The 2/14 MHz arrangement demonstrated a -6 dB fractional bandwidth of 56.5% for the transmitter and 41.8% for the receiver, and produced sufficient peak-negative pressures (>1.5 MPa) at 2 MHz to induce a strong nonlinear harmonic response from microbubble contrast agents. In an in-vitro contrast ultrasound study using a tissue mimicking phantom and 200 μm cellulose microvessels, higher harmonic microbubble responses, from the 5th through the 7th harmonics, were detected with a signal-to-noise ratio of 16 dB. The microvessels were resolved in a two-dimensional image with a -6dB axial resolution of 615 μm (5.5 times the wavelength of 14 MHz waves) and a contrast-to-tissue ratio of 16 dB. This feasibility study, including detailed explanation of phantom evaluation and characterization procedures for key parameters, will be useful for the development of future dual-frequency array transducers for intracavitary acoustic angiography.

  7. Simulation study of a chaotic cavity transducer based virtual phased array used for focusing in the bulk of a solid material.

    PubMed

    Delrue, Steven; Van Den Abeele, Koen; Matar, Olivier Bou

    2016-04-01

    In acoustic and ultrasonic non-destructive testing techniques, it is sometimes beneficial to concentrate sound energy at a chosen location in space and at a specific instance in time, for example to improve the signal-to-noise ratio or activate the nonlinearity of damage features. Time Reversal (TR) techniques, taking advantage of the reversible character of the wave equation, are particularly suited to focus ultrasonic waves in time and space. The characteristics of the energy focusing in solid media using principles of time reversed acoustics are highly influenced by the nature and dimensions of the medium, the number of transducers and the length of the received signals. Usually, a large number of transducers enclosing the domain of interest is needed to improve the quality of the focusing. However, in the case of highly reverberant media, the number of transducers can be reduced to only one (single-channel TR). For focusing in a non-reverberant medium, which is impossible when using only one source, an adaptation of the single-channel reciprocal TR procedure has been recently suggested by means of a Chaotic Cavity Transducer (CCT), a single element transducer glued on a cavity of chaotic shape. In this paper, a CCT is used to focus elastic energy, at different times, in different points along a predefined line on the upper surface of a thick solid sample. Doing so, all focusing points can act as a virtual phased array transducer, allowing to focus in any point along the depth direction of the sample. This is impossible using conventional reciprocal TR, as you need to have access to all points in the bulk of the material for detecting signals to be used in the TR process. To asses and provide a better understanding of this concept, a numerical study has been developed, allowing to verify the basic concepts of the virtual phased array and to illustrate multi-component time reversal focusing in the bulk of a solid material. PMID:26845370

  8. Simulation study of a chaotic cavity transducer based virtual phased array used for focusing in the bulk of a solid material.

    PubMed

    Delrue, Steven; Van Den Abeele, Koen; Matar, Olivier Bou

    2016-04-01

    In acoustic and ultrasonic non-destructive testing techniques, it is sometimes beneficial to concentrate sound energy at a chosen location in space and at a specific instance in time, for example to improve the signal-to-noise ratio or activate the nonlinearity of damage features. Time Reversal (TR) techniques, taking advantage of the reversible character of the wave equation, are particularly suited to focus ultrasonic waves in time and space. The characteristics of the energy focusing in solid media using principles of time reversed acoustics are highly influenced by the nature and dimensions of the medium, the number of transducers and the length of the received signals. Usually, a large number of transducers enclosing the domain of interest is needed to improve the quality of the focusing. However, in the case of highly reverberant media, the number of transducers can be reduced to only one (single-channel TR). For focusing in a non-reverberant medium, which is impossible when using only one source, an adaptation of the single-channel reciprocal TR procedure has been recently suggested by means of a Chaotic Cavity Transducer (CCT), a single element transducer glued on a cavity of chaotic shape. In this paper, a CCT is used to focus elastic energy, at different times, in different points along a predefined line on the upper surface of a thick solid sample. Doing so, all focusing points can act as a virtual phased array transducer, allowing to focus in any point along the depth direction of the sample. This is impossible using conventional reciprocal TR, as you need to have access to all points in the bulk of the material for detecting signals to be used in the TR process. To asses and provide a better understanding of this concept, a numerical study has been developed, allowing to verify the basic concepts of the virtual phased array and to illustrate multi-component time reversal focusing in the bulk of a solid material.

  9. Large Volume Coagulation Utilizing Multiple Cavitation Clouds Generated by Array Transducer Driven by 32 Channel Drive Circuits

    NASA Astrophysics Data System (ADS)

    Nakamura, Kotaro; Asai, Ayumu; Sasaki, Hiroshi; Yoshizawa, Shin; Umemura, Shin-ichiro

    2013-07-01

    High-intensity focused ultrasound (HIFU) treatment is a noninvasive treatment, in which focused ultrasound is generated outside the body and coagulates a diseased tissue. The advantage of this method is minimal physical and mental stress to the patient, and the disadvantage is the long treatment time caused by the smallness of the therapeutic volume by a single exposure. To improve the efficiency and shorten the treatment time, we are focusing attention on utilizing cavitation bubbles. The generated microbubbles can convert the acoustic energy into heat with a high efficiency. In this study, using the class D amplifiers, which we have developed, to drive the array transducer, we demonstrate a new method to coagulate a large volume by a single HIFU exposure through generating cavitation bubbles distributing in a large volume and vibrating all of them. As a result, the coagulated volume by the proposed method was 1.71 times as large as that of the conventional method.

  10. Numerical and experimental analysis of unidirectional meander-line coil electromagnetic acoustic transducers.

    PubMed

    Wang, Shujuan; Su, Riliang; Chen, Xiaoyang; Kang, Lei; Zhai, Guofu

    2013-12-01

    The elastic waves generated by traditional meander-line coil electromagnetic acoustic transducers (EMATs) propagate in two directions, overlapping the echo signals from defects with the same distances, and the defect echo signal is hard to distinguish from the edge-reflected signal when the EMATs are near the edge of a specimen. In this paper, a unidirectional EMAT with two meander-line coils is proposed. A finite element model is used to simulate the directivity of the Rayleigh and shear vertical waves generated by these EMATs. Six transducers are fabricated using the printed circuit technique. The unidirectional Rayleigh wave and shear vertical wave are tested, and the results agree well with the simulation.

  11. Multi-view Hilbert transformation in full-ring-transducer-array based photoacoustic computed tomography (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Li, Lei; Li, Guo; Zhu, Liren; Xia, Jun; Wang, Lihong V.

    2016-03-01

    Photoacoustic tomography (PAT) exploits optical contrast and ultrasonic detection principles to form images of absorbed optical energy density within tissue. Based on the photoacoustic effect, PAT directly and quantitatively measures specific optical absorption. A full-ring ultrasonic transducer array based photoacoustic computed tomography (PACT) system was recently developed for small animal whole-body imaging with a full-view detection angle and high in-plane resolution (100 µm). However, due to the band-pass frequency response of the piezoelectric transducer elements, the reconstructed images present bipolar (both positive and negative) pixel values, which is artificial and counterintuitive for physicians and biologists seeking to interpret the image. Moreover, bipolar pixel values hinder quantification of physiological parameters, such as oxygen saturation and blood flow speed. Unipolar images can be obtained by deconvolving the raw channel data with the transducer's electrical impulse response and applying non-negativity during iteration, but this process requires complex transducer modeling and time-consuming computation. Here, we present a multi-view Hilbert transformation method to recover the unipolar initial pressure for full-ring PACT. Multi-view Hilbert transformation along the acoustic wave propagation direction minimizes reconstruction artifacts during envelope extraction and maintains the signal-to-noise ratio of the reconstructed images. The in-plane isotropic spatial resolution of this method was quantified to 168 μm within a 20 × 20 mm2 field of view. The effectiveness of the proposed algorithm was first validated by numerical simulations and then demonstrated with ex-vivo mouse brain structural imaging and in-vivo mouse wholebody imaging.

  12. Time reversed acoustics techniques for elastic imaging in reverberant and nonreverberant media: An experimental study of the chaotic cavity transducer concept

    NASA Astrophysics Data System (ADS)

    Van Damme, Bart; Van Den Abeele, Koen; Li, YiFeng; Matar, Olivier Bou

    2011-05-01

    In view of emerging imaging technologies based on the combination of Time Reversed Acoustics (TRA) with Nonlinear Elastic Wave Spectroscopy (NEWS) for the detection and localization of micro-damage in solids, we have investigated the benefits of chirped source signal excitation, inverse filtering techniques, and the implementation of chaotic cavity transducers to improve the quality of energy focusing, especially for weakly reverberant media. Chaotic cavity transducer focusing is defined as the hardware-software combination of a piezoelectric ceramic glued on a cavity of chaotic shape on the one hand with the reciprocal Time Reversal (or Inverse Filter) technique on the other hand. Experimental data for reverberant and nonreverberant composite plates show that the use of chirps, inverse filtering and chaotic cavity transducers significantly enhances the focusing process, and enables focusing in a nonreverberant medium using only one transducer. As a potential exploitation, the application of the chaotic cavity transducer concept for synthetic imaging is examined, revealing several properties similar to phased arrays.

  13. Large aperture acoustic arrays in support of reverberation studies

    NASA Astrophysics Data System (ADS)

    Hildebrand, John A.

    1990-04-01

    In preparation for a major field experiment this report addresses the development of acoustic arrays which are needed in order to make carefully controlled and well-documented measurements of bottom reverberation. The purpose of these measurements is to study the physics of the backscattering process and to quantify backscattering characteristics as a function of physically meaningful parameters (e.g., ensonified area, grazing angle, bottom material properties, bottom roughness, etc.). Specific array systems which are addressed include the following: (1) towed horizontal array, (2) horizontal and vertical array, (3) ship-tethered 64-element vertical array, and (4) self-contained, 16-element vertical array.

  14. Preliminary work of real-time ultrasound imaging system for 2-D array transducer.

    PubMed

    Li, Xu; Yang, Jiali; Ding, Mingyue; Yuchi, Ming

    2015-01-01

    Ultrasound (US) has emerged as a non-invasive imaging modality that can provide anatomical structure information in real time. To enable the experimental analysis of new 2-D array ultrasound beamforming methods, a pre-beamformed parallel raw data acquisition system was developed for 3-D data capture of 2D array transducer. The transducer interconnection adopted the row-column addressing (RCA) scheme, where the columns and rows were active in sequential for transmit and receive events, respectively. The DAQ system captured the raw data in parallel and the digitized data were fed through the field programmable gate array (FPGA) to implement the pre-beamforming. Finally, 3-D images were reconstructed through the devised platform in real-time. PMID:26405923

  15. Hybrid Seminumerical Simulation Scheme to Predict Transducer Outputs of Acoustic Microscopes.

    PubMed

    Nierla, Michael; Rupitsch, Stefan J

    2016-02-01

    We present a seminumerical simulation method called SIRFEM, which enables the efficient prediction of high-frequency transducer outputs. In particular, this is important for acoustic microscopy where the specimen under investigation is immersed in a coupling fluid. Conventional finite-element (FE) simulations for such applications would consume too much computational power due to the required spatial and temporal discretization, especially for the coupling fluid between ultrasonic transducer and specimen. However, FE simulations are in most cases essential to consider the mode conversion at and inside the solid specimen as well as the wave propagation in its interior. SIRFEM reduces the computational effort of pure FE simulations by treating only the solid specimen and a small part of the fluid layer with FE. The propagation in the coupling fluid from transducer to specimen and back is processed by the so-called spatial impulse response (SIR). Through this hybrid approach, the number of elements as well as the number of time steps for the FE simulation can be reduced significantly, as it is presented for an axis-symmetric setup. Three B-mode images of a plane 2-D setup-computed at a transducer center frequency of 20 MHz-show that SIRFEM is, furthermore, able to predict reflections at inner structures as well as multiple reflections between those structures and the specimen's surface. For the purpose of a pure 2-D setup, the SIR of a curved-line transducer is derived and compared to the response function of a cylindrically focused aperture of negligible extend in the third spatial dimension.

  16. Acoustic Source Localization in Aircraft Interiors Using Microphone Array Technologies

    NASA Technical Reports Server (NTRS)

    Sklanka, Bernard J.; Tuss, Joel R.; Buehrle, Ralph D.; Klos, Jacob; Williams, Earl G.; Valdivia, Nicolas

    2006-01-01

    Using three microphone array configurations at two aircraft body stations on a Boeing 777-300ER flight test, the acoustic radiation characteristics of the sidewall and outboard floor system are investigated by experimental measurement. Analysis of the experimental data is performed using sound intensity calculations for closely spaced microphones, PATCH Inverse Boundary Element Nearfield Acoustic Holography, and Spherical Nearfield Acoustic Holography. Each method is compared assessing strengths and weaknesses, evaluating source identification capability for both broadband and narrowband sources, evaluating sources during transient and steady-state conditions, and quantifying field reconstruction continuity using multiple array positions.

  17. The electrical properties of a planar coil electromagnetic acoustic transducer and their implications for noise performance

    NASA Astrophysics Data System (ADS)

    Seher, Matthias; Challis, Richard

    2016-02-01

    This paper is concerned with the electrical properties of an electromagnetic acoustic transducer (EMAT) formed of a flat spiral coil coupled to steel sheet components and operating over a narrow band of frequencies around 50 kHz, well below significant resonances. The electromagnetic skin effect is a significant contributor to the terminal impedance of the EMAT and hence to signal sensitivity, Johnson noise generation and the achievable signal-to-noise ratios (SNR). A transformer model is developed to simulate these effects and to assist in the optimization of the SNR. In this analysis Johnson noise in the system is compared to the unknown emf generated in the eddy current path by an incident acoustic wave to yield a fundamental SNR. The attainable SNR of the whole system is normalized to this in the form of a noise figure.

  18. Detection of Volatile Organics Using a Surface Acoustic Wave Array System

    SciTech Connect

    ANDERSON, LAWRENCE F.; BARTHOLOMEW, JOHN W.; CERNOSEK, RICHARD W.; COLBURN, CHRISTOPHER W.; CROOKS, R.M.; MARTINEZ, R.F.; OSBOURN, GORDON C.; RICCO, A.J.; STATON, ALAN W.; YELTON, WILLIAM G.

    1999-10-14

    A chemical sensing system based on arrays of surface acoustic wave (SAW) delay lines has been developed for identification and quantification of volatile organic compounds (VOCs). The individual SAW chemical sensors consist of interdigital transducers patterned on the surface of an ST-cut quartz substrate to launch and detect the acoustic waves and a thin film coating in the SAW propagation path to perturb the acoustic wave velocity and attenuation during analyte sorption. A diverse set of material coatings gives the sensor arrays a degree of chemical sensitivity and selectivity. Materials examined for sensor application include the alkanethiol-based self-assembled monolayer, plasma-processed films, custom-synthesized conventional polymers, dendrimeric polymers, molecular recognition materials, electroplated metal thin films, and porous metal oxides. All of these materials target a specific chemical fi.mctionality and the enhancement of accessible film surface area. Since no one coating provides absolute analyte specificity, the array responses are further analyzed using a visual-empirical region-of-influence (VERI) pattern recognition algorithm. The chemical sensing system consists of a seven-element SAW array with accompanying drive and control electronics, sensor signal acquisition electronics, environmental vapor sampling hardware, and a notebook computer. Based on data gathered for individual sensor responses, greater than 93%-accurate identification can be achieved for any single analyte from a group of 17 VOCs and water.

  19. Thermal-independent properties of PIN-PMN-PT single-crystal linear-array ultrasonic transducers.

    PubMed

    Chen, Ruimin; Wu, Jinchuan; Ho Lam, Kwok; Yao, Liheng; Zhou, Qifa; Tian, Jian; Han, Pengdi; Shung, K Kirk

    2012-12-01

    In this paper, low-frequency 32-element linear-array ultrasonic transducers were designed and fabricated using both ternary Pb(In(1/2)Nb(1/2))-Pb(Mg(1/3)Nb(2/3))-PbTiO(3) (PIN-PMN-PT) and binary Pb(Mg(1/3)Nb(2/3))-PbTiO(3) (PMNPT) single crystals. Performance of the array transducers was characterized as a function of temperature ranging from room temperature to 160°C. It was found that the array transducers fabricated using the PIN-PMN-PT single crystal were capable of satisfactory performance at 160°C, having a -6-dB bandwidth of 66% and an insertion loss of 37 dB. The results suggest that the potential of PIN-PMN-PT linear-array ultrasonic transducers for high-temperature ultrasonic transducer applications is promising. PMID:23221227

  20. 2D array transducers for real-time 3D ultrasound guidance of interventional devices

    NASA Astrophysics Data System (ADS)

    Light, Edward D.; Smith, Stephen W.

    2009-02-01

    We describe catheter ring arrays for real-time 3D ultrasound guidance of devices such as vascular grafts, heart valves and vena cava filters. We have constructed several prototypes operating at 5 MHz and consisting of 54 elements using the W.L. Gore & Associates, Inc. micro-miniature ribbon cables. We have recently constructed a new transducer using a braided wiring technology from Precision Interconnect. This transducer consists of 54 elements at 4.8 MHz with pitch of 0.20 mm and typical -6 dB bandwidth of 22%. In all cases, the transducer and wiring assembly were integrated with an 11 French catheter of a Cook Medical deployment device for vena cava filters. Preliminary in vivo and in vitro testing is ongoing including simultaneous 3D ultrasound and x-ray fluoroscopy.

  1. A nano-power energy harvesting IC for arrays of piezoelectric transducers

    NASA Astrophysics Data System (ADS)

    Dini, M.; Filippi, M.; Romani, A.; Bottarel, V.; Ricotti, G.; Tartagni, M.

    2013-05-01

    This paper describes a multi-source energy harvester IC for arrays of independent transducers, designed in a 0.32μm STMicroelectronics BCD technology, that can manage up to 5 AC-DC channels (e.g. piezoelectric transducers). The IC implements a boost converter based on synchronous electrical charge extraction. A single external inductor is time-shared among all transducers and access conflicts are handled by an arbiter circuit implemented as an asynchronous FSM. The designed converter is fully autonomous and suitable for battery-less operation. The circuit area is 4.6 mm2 and has a power consumption of 175 nW/source at 2.5 V while efficiency ranges between 70% and over than 85%.

  2. Acoustic imaging system

    DOEpatents

    Smith, Richard W.

    1979-01-01

    An acoustic imaging system for displaying an object viewed by a moving array of transducers as the array is pivoted about a fixed point within a given plane. A plurality of transducers are fixedly positioned and equally spaced within a laterally extending array and operatively directed to transmit and receive acoustic signals along substantially parallel transmission paths. The transducers are sequentially activated along the array to transmit and receive acoustic signals according to a preestablished sequence. Means are provided for generating output voltages for each reception of an acoustic signal, corresponding to the coordinate position of the object viewed as the array is pivoted. Receptions from each of the transducers are presented on the same display at coordinates corresponding to the actual position of the object viewed to form a plane view of the object scanned.

  3. Concrete filled steel pipe inspection using electro magnetic acoustic transducer (EMAT)

    NASA Astrophysics Data System (ADS)

    Na, Won-Bae; Kundu, Tribikram; Ryu, Yeon-Sun; Kim, Jeong-Tae

    2005-05-01

    Concrete-filled steel pipes are usually exposed in hostile environments such as seawater and deicing materials. The outside corrosion of the steel pipe can reduce the wall thickness and the corrosion-induced delamination of internal concrete can increase internal volume or pressure. In addition, the void that can possibly exist in the pipe reduces the bending resistance. To avoid structural failure due to this type of deterioration, appropriate inspection and repair techniques are to be developed. Guided wave techniques have strong potentials for this kind of inspection because of long-distance inspection capability. Among different transducer-coupling mechanism, electro-magnetic acoustic transducers (EMATs) give relatively consistent results in comparison to piezoelectric transducers since they do not need any couplant. In this study EMATs are used for transmitting and receiving cylindrical guided waves through concrete-filled steel pipes. Through time history curves and wavelet transform, it is shown that EMAT-generated cylindrical guided wave techniques have good potential for the interface inspection of concrete-filled steel pipes.

  4. Calibration of a broadband acoustic transducer with a standard spherical target in the near field.

    PubMed

    Chu, Dezhang; Eastland, Grant C

    2015-04-01

    This paper investigates the applicability of calibrating a broadband acoustic system in the near field. The calibration was performed on a single transducer with a mono-static configuration using a single standard target, a 25-mm tungsten carbide sphere in the nearfield of both the transducer and the sphere. A theoretical model was developed to quantify the nearfield effect. Numerical simulations revealed that the frequency responses at different distances varied significantly, the null positions were essentially invariant-a unique characteristic for determination of the compressional and shear wave speeds in the calibration sphere. The calibration curves obtained in the near field could be applied to farfield once the nearfield effects were accounted for. Since the transducer was located in the near field, the signal-to-noise ratio was high, resulting in a much wider useable bandwidth than the nominal bandwidth. The resultant calibration uncertainty, i.e., root-mean-square uncertainty over the entire usable frequency band was 1.05 dB and reduces to 0.33 dB when the regions corresponding to nulls were excluded. The methods reported here could potentially be applied to the calibration of multibeam and broadband echosounder/sonar systems since it is difficult to meet the farfield condition for outermost beams when shipboard calibrations are needed.

  5. Feasibility of a phased acoustic array for monitoring acoustic signatures from meshing gear teeth.

    PubMed

    Hood, Adrian A; Pines, Darryll J

    2002-12-01

    This paper investigates the feasibility of sensing damage emanating from rotating drivetrain elements such as bearings, gear teeth, and drive shafts via airborne paths. A planar phased acoustic array is evaluated as a potential fault detection scheme for detecting spatially filtered acoustic signatures radiating from gearbox components. Specifically, the use of beam focusing and steering to monitor individual tooth mesh dynamics is analyzed taking into consideration the constraints of the array/gearbox geometry and the spectral content of typical gear noise. Experimental results for a linear array are presented to illustrate the concepts of adaptive beam steering and spatial acoustic filtering. This feasibility study indicates that the planar array can be used to track the acoustic signatures at higher harmonics of the gear mesh frequency.

  6. Saft-reconstruction in ultrasonic immersion technique using phased array transducers

    NASA Astrophysics Data System (ADS)

    Kitze, J.; Prager, J.; Boehm, R.; Völz, U.; Montag, H.-J.

    2012-05-01

    The two main preconditions for the application of the Synthetic Aperture Focusing Technique (SAFT) are: (i) a large divergence of the sound beam of the transducer and (ii) an exact knowledge about the sound propagation path. These requirements are easily fulfilled for point sources directly mounted on the surface of the specimen. In many cases, however, the transducer is wedge mounted and/or coupled using a water delay line, e.g. in immersion technique. These delay lines change the beam index and the propagation path has to be evaluated for each pixel separately considering Fermat's principle. Using phased array transducers, a sector scan can improve the divergence of the sound beam. The introduced method combines the advantages of using a phased array transducer in immersion technique to improve SAFT reconstruction. An algorithm is presented accounting the influence of the delay line on the reconstruction method. The applicability of the algorithm is shown by validation with simulated echo responses and with experimental results collected from a specimen with artificial flaws.

  7. A preliminary evaluation work on a 3D ultrasound imaging system for 2D array transducer

    NASA Astrophysics Data System (ADS)

    Zhong, Xiaoli; Li, Xu; Yang, Jiali; Li, Chunyu; Song, Junjie; Ding, Mingyue; Yuchi, Ming

    2016-04-01

    This paper presents a preliminary evaluation work on a pre-designed 3-D ultrasound imaging system. The system mainly consists of four parts, a 7.5MHz, 24×24 2-D array transducer, the transmit/receive circuit, power supply, data acquisition and real-time imaging module. The row-column addressing scheme is adopted for the transducer fabrication, which greatly reduces the number of active channels . The element area of the transducer is 4.6mm by 4.6mm. Four kinds of tests were carried out to evaluate the imaging performance, including the penetration depth range, axial and lateral resolution, positioning accuracy and 3-D imaging frame rate. Several strong reflection metal objects , fixed in a water tank, were selected for the purpose of imaging due to a low signal-to-noise ratio of the transducer. The distance between the transducer and the tested objects , the thickness of aluminum, and the seam width of the aluminum sheet were measured by a calibrated micrometer to evaluate the penetration depth, the axial and lateral resolution, respectively. The experiment al results showed that the imaging penetration depth range was from 1.0cm to 6.2cm, the axial and lateral resolution were 0.32mm and 1.37mm respectively, the imaging speed was up to 27 frames per second and the positioning accuracy was 9.2%.

  8. Acousto-optic effect compensation for optical determination of the normal velocity distribution associated with acoustic transducer radiation.

    PubMed

    Foote, Kenneth G; Theobald, Peter D

    2015-09-01

    The acousto-optic effect, in which an acoustic wave causes variations in the optical index of refraction, imposes a fundamental limitation on the determination of the normal velocity, or normal displacement, distribution on the surface of an acoustic transducer or optically reflecting pellicle by a scanning heterodyne, or homodyne, laser interferometer. A general method of compensation is developed for a pulsed harmonic pressure field, transmitted by an acoustic transducer, in which the laser beam can transit the transducer nearfield. By representing the pressure field by the Rayleigh integral, the basic equation for the unknown normal velocity on the surface of the transducer or pellicle is transformed into a Fredholm equation of the second kind. A numerical solution is immediate when the scanned points on the surface correspond to those of the surface area discretization. Compensation is also made for oblique angles of incidence by the scanning laser beam. The present compensation method neglects edge waves, or those due to boundary diffraction, as well as effects due to baffles, if present. By allowing measurement in the nearfield of the radiating transducer, the method can enable quantification of edge-wave and baffle effects on transducer radiation. A verification experiment has been designed. PMID:26428801

  9. A compact array calibrator to study the feasibility of acoustic neutrino detection

    NASA Astrophysics Data System (ADS)

    Ardid, M.; Camarena, F.; Felis, I.; Herrero, A.; Llorens, C. D.; Martínez-Mora, J.; Saldaña, M.

    2016-04-01

    Underwater acoustic detection of ultra-high-energy neutrinos was proposed already in 1950s: when a neutrino interacts with a nucleus in water, the resulting particle cascade produces a pressure pulse that has a bipolar temporal structure and propagates within a flat disk-like volume. A telescope that consists of thousands of acoustic sensors deployed in the deep sea can monitor hundreds of cubic kilometres of water looking for these signals and discriminating them from acoustic noise. To study the feasibility of the technique it is critical to have a calibrator able to mimic the neutrino "signature" that can be operated from a vessel. Due to the axial-symmetry of the signal, their very directive short bipolar shape and the constraints of operating at sea, the development of such a calibrator is very challenging. Once the possibility of using the acoustic parametric technique for this aim was validated with the first compact array calibrator prototype, in this paper we describe the new design for such a calibrator composed of an array of piezo ceramic tube transducers emitting in axial direction.

  10. A Longitudinal Mode Electromagnetic Acoustic Transducer (EMAT) Based on a Permanent Magnet Chain for Pipe Inspection.

    PubMed

    Cong, Ming; Wu, Xinjun; Qian, Chunqiao

    2016-01-01

    A new electromagnetic acoustic transducer (EMAT) design, employing a special structure of the permanent magnet chain, is proposed to generate and receive longitudinal guided waves for pipe inspection based on the magnetostriction mechanism. Firstly, a quantitative analysis of the excitation forces shows the influence of the radial component can be ignored. Furthermore, as the axial component of the static magnetic field is dominant, a method of solenoid testing coils connected in series is adopted to increase the signal amplitude. Then, two EMAT configurations are developed to generate and receive the L(0,2) guided wave mode. The experimental results show the circumferential notch can be identified and located successfully. Finally, a detailed investigation of the performance of the proposed EMATs is given. Compared to the conventional EMAT configuration, the proposed configurations have the advantages of small volume, light weight, easy installation and portability, which is helpful to improve inspection efficiency. PMID:27213400

  11. High Temperature Shear Horizontal Electromagnetic Acoustic Transducer for Guided Wave Inspection.

    PubMed

    Kogia, Maria; Gan, Tat-Hean; Balachandran, Wamadeva; Livadas, Makis; Kappatos, Vassilios; Szabo, Istvan; Mohimi, Abbas; Round, Andrew

    2016-04-22

    Guided Wave Testing (GWT) using novel Electromagnetic Acoustic Transducers (EMATs) is proposed for the inspection of large structures operating at high temperatures. To date, high temperature EMATs have been developed only for thickness measurements and they are not suitable for GWT. A pair of water-cooled EMATs capable of exciting and receiving Shear Horizontal (SH₀) waves for GWT with optimal high temperature properties (up to 500 °C) has been developed. Thermal and Computational Fluid Dynamic (CFD) simulations of the EMAT design have been performed and experimentally validated. The optimal thermal EMAT design, material selection and operating conditions were calculated. The EMAT was successfully tested regarding its thermal and GWT performance from ambient temperature to 500 °C.

  12. Absolute ultrasonic displacement amplitude measurements with a submersible electrostatic acoustic transducer

    NASA Technical Reports Server (NTRS)

    Yost, William T.; Cantrell, John H.

    1992-01-01

    An experimental technique for absolute measurement of ultrasonic wave particle displacement amplitudes in liquids is reported. The technique is capable of measurements over a frequency range of two decades with a sensitivity less than one angstrom. The technique utilizes a previously reported submersible electrostatic acoustic transducer (ESAT) featuring a conductive membrane stretched over a recessed electrode. An uncertainty analysis shows that the displacement amplitude of an ultrasonic plane wave incident on the ESAT can be experimentally determined to better than 2.3-4 percent, depending on frequency, in the frequency range of 0.5-15 MHz. Membranes with lower and more uniform areal densities can improve the accuracy and extend the operation to higher frequencies.

  13. A Longitudinal Mode Electromagnetic Acoustic Transducer (EMAT) Based on a Permanent Magnet Chain for Pipe Inspection

    PubMed Central

    Cong, Ming; Wu, Xinjun; Qian, Chunqiao

    2016-01-01

    A new electromagnetic acoustic transducer (EMAT) design, employing a special structure of the permanent magnet chain, is proposed to generate and receive longitudinal guided waves for pipe inspection based on the magnetostriction mechanism. Firstly, a quantitative analysis of the excitation forces shows the influence of the radial component can be ignored. Furthermore, as the axial component of the static magnetic field is dominant, a method of solenoid testing coils connected in series is adopted to increase the signal amplitude. Then, two EMAT configurations are developed to generate and receive the L(0,2) guided wave mode. The experimental results show the circumferential notch can be identified and located successfully. Finally, a detailed investigation of the performance of the proposed EMATs is given. Compared to the conventional EMAT configuration, the proposed configurations have the advantages of small volume, light weight, easy installation and portability, which is helpful to improve inspection efficiency. PMID:27213400

  14. High Temperature Shear Horizontal Electromagnetic Acoustic Transducer for Guided Wave Inspection

    PubMed Central

    Kogia, Maria; Gan, Tat-Hean; Balachandran, Wamadeva; Livadas, Makis; Kappatos, Vassilios; Szabo, Istvan; Mohimi, Abbas; Round, Andrew

    2016-01-01

    Guided Wave Testing (GWT) using novel Electromagnetic Acoustic Transducers (EMATs) is proposed for the inspection of large structures operating at high temperatures. To date, high temperature EMATs have been developed only for thickness measurements and they are not suitable for GWT. A pair of water-cooled EMATs capable of exciting and receiving Shear Horizontal (SH0) waves for GWT with optimal high temperature properties (up to 500 °C) has been developed. Thermal and Computational Fluid Dynamic (CFD) simulations of the EMAT design have been performed and experimentally validated. The optimal thermal EMAT design, material selection and operating conditions were calculated. The EMAT was successfully tested regarding its thermal and GWT performance from ambient temperature to 500 °C. PMID:27110792

  15. Guided Wave Inspection of Supported Pipe Locations Using Electromagnetic Acoustic Transducers

    NASA Astrophysics Data System (ADS)

    Andruschak, Nicholas

    The goal of the work in this thesis is to develop a rapid and reliable NDT system to detect hidden corrosion at pipe-support interfaces using Electromagnetic Acoustic Transducers (EMATs). Since there are often many support interfaces over a piping run, information is needed on the support interface conditions to optimize subsequent detailed inspections. In this work it is important to be able to isolate the effects produced from the support interface and the incident guided wave. To do this an optimum EMAT operating point is first selected, then the support interfaces and wall loss type defects are independently analyzed through experimentally validated finite element models. It is found that operating the SH1 plate wave mode near the `knee' of its dispersion curve gives a high sensitivity to wall loss type defects while experiencing a minimal effect from the support contact region.

  16. Simulation of ultrasound two-dimensional array transducers using a frequency domain model.

    PubMed

    Rao, Min; Varghese, Tomy; Zagzebski, James A

    2008-07-01

    Ultrasound imaging with two-dimensional (2D) arrays has garnered broad interest from scanner manufacturers and researchers for real time three-dimensional (3D) applications. Previously the authors described a frequency domain B-mode imaging model applicable for linear and phased array transducers. In this paper, the authors extend this model to incorporate 2D array transducers. Further approximations can be made based on the fact that the dimensions of the 2D array element are small. The model is compared with the widely used ultrasound simulation program FIELD II, which utilizes an approximate form of the time domain impulse response function. In a typical application, errors in simulated RF waveforms are less than 4% regardless of the steering angle for distances greater than 2 cm, yet computation times are on the order of 1/35 of those incurred using FIELD II. The 2D model takes into account the effects of frequency-dependent attenuation, backscattering, and dispersion. Modern beam-forming techniques such as apodization, dynamic aperture, dynamic receive focusing, and 3D beam steering can also be simulated.

  17. A Novel Device for Total Acoustic Output Measurement of High Power Transducers

    NASA Astrophysics Data System (ADS)

    Howard, S.; Twomey, R.; Morris, H.; Zanelli, C. I.

    2010-03-01

    The objective of this work was to develop a device for ultrasound power measurement applicable over a broad range of medical transducer types, orientations and powers, and which supports automatic measurements to simplify use and minimize errors. Considering all the recommendations from standards such as IEC 61161, an accurate electromagnetic null-balance has been designed for ultrasound power measurements. The sensing element is placed in the water to eliminate errors due to surface tension and water evaporation, and the motion and detection of force is constrained to one axis, to increase immunity to vibration from the floor, water sloshing and water surface waves. A transparent tank was designed so it could easily be submerged in a larger tank to accommodate large transducers or side-firing geometries, and can also be turned upside-down for upward-firing transducers. A vacuum lid allows degassing the water and target in situ. An external control module was designed to operate the sensing/driving loop and to communicate to a local computer for data logging. The sensing algorithm, which incorporates temperature compensation, compares the feedback force needed to cancel the motion for sources in the "on" and "off" states. These two states can be controlled by the control unit or manually by the user, under guidance by a graphical user interface (the system presents measured power live during collection). Software allows calibration to standard weights, or to independently calibrated acoustic sources. The design accommodates a variety of targets, including cone, rubber, brush targets and an oil-filled target for power measurement via buoyancy changes. Measurement examples are presented, including HIFU sources operating at powers from 1 to 100.

  18. Seismo-acoustic array installed in Vrancea seismogenic area

    NASA Astrophysics Data System (ADS)

    Ionescu, Constantin; Moldovan, Adrian-Septimiu; Moldovan, Iren-Adelina; Ghica, Daniela

    2010-05-01

    The National Institute for Earth Physics (NIEP) has installed two infrasound networks: a four-element seismo-acoustic array with an 1.2 km aperture (IPLOR) and a three-element array with a 400m aperture (IOANE). Both arrays are installed in Vrancea seismogenic area. Each array element of IPLOR consists of three sensors (a seismic 3C broad-band instrument with 1000V/m/s sensitivity, an accelerometer +/-2g EpiSensor type, and an infrasound Chaparral type sensor) and a 24-bit digitizer (Quanterra Q330). The BB sensors and accelerometers are located in 3 meters deep boreholes, while the infrasound sensors are installed in a plastic 1 mc container connected to a porous flexible pipe or plastic tube (for the central element). Inter-array communication is achieved by radio link (2.4 GHz frequency band) which transmits the data from the six-channel digitizers to the local acquisition system. Each power array element consisted of a 12 V DC source powered by the commercial power line or solar panels. The data acquisition system is based on the Seiscomp3 software; a sampling rate of 100 samples per second is applied for BB seismic instruments and accelerometers, whilst for the infrasound sensor a 20 sps rate is used. Each array element of IPLOR consists of a MBAZEL2007 microbarometer and a 24-bit digitizer. Inter-array communication is achieved by a fiber optic link. The sampling rate is 10 sps. The Vrancea seismo-acoustic array is used to identify and locate events associated with industrial blasts, to detect local and regional events, as well for the complex studies on the Vrancea seismogenic area. Moreover, the array data accelerometers are used in the early warning system for Bucharest. At NIEP, several programs are running to analyze each type of data (seismic and acoustic): for BB seismic data, a software for event detection and characterization, kindly provided by NORSAR, is applied, acceleration data recorded by the episensors are processed with a software developed

  19. Two-dimensional ultrasound receive array using an angle-tuned Fabry-Perot polymer film sensor for transducer field characterization and transmission ultrasound imaging.

    PubMed

    Beard, Paul Christopher

    2005-06-01

    A 2-D optical ultrasound receive array has been investigated. The transduction mechanism is based upon the detection of acoustically induced changes in the optical thickness of a thin polymer film acting as a Fabry-Perot sensing interferometer (FPI). By illuminating the sensor with a large-area laser beam and mechanically scanning a photodiode across the reflected output beam, while using a novel angle-tuned phase bias control system to optimally set the FPI working point, a notional 2-D ultrasound array was synthesized. To demonstrate the concept, 1-D and 2-D ultrasound field distributions produced by planar 3.5-MHz and focused 5-MHz PZT ultrasound transducers were mapped. The system was also evaluated by performing transmission ultrasound imaging of a spatially calibrated target. The "array" aperture, defined by the dimensions of the incident optical field, was elliptical, of dimensions 16 x 12 mm and spatially sampled in steps of 0.1 mm or 0.2 mm. Element sizes, defined by the photodiode aperture, of 0.8, 0.4, and 0.2 mm were variously used for these experiments. Two types of sensor were evaluated. One was a discrete 75-microm-thick polyethylene terephthalate FPI bonded to a polymer backing stub which had a wideband peak noise-equivalent pressure of 6.5 kPa and an acoustic bandwidth 12 MHz. The other was a 40-microm Parylene film FPI which was directly vacuum-deposited onto a glass backing stub and had an NEP of 8 kPa and an acoustic bandwidth of 17.5 MHz. It is considered that this approach offers an alternative to piezoelectric ultrasound arrays for transducer field characterization, transmission medical and industrial ultrasound imaging, biomedical photoacoustic imaging, and ultrasonic nondestructive testing.

  20. Experimental Study on Ultrasonic Computed Tomography Using Transducers Arrayed on the Internal Surface of a Cylinder

    NASA Astrophysics Data System (ADS)

    Kim, Jung-Soon; Kim, Moo-Joon; Kim, Jung-Ho; Ha, Kang-Lyeol

    2005-06-01

    In this study, ultrasonic array transducers with 32 vibrators arranged on the internal surface of a part of a cylinder were fabricated. The vibrators were operated by the piezoelectric transverse effect. By controlling the phase of the input signal for every vibrator, a quasi plane wave was synthesized. Using the fabricated array, inverse scattering ultrasonic computed tomography (UCT) was carried out with a phantom specimen after checking the plane wave generation. It was confirmed that the plane wave was synthesized successfully and a sound velocity image of the phantom was obtained by the plane wave. Consequently, it was noted that the array could be employed as a transmitter and receiver for data acquisition in UCT.

  1. Simulation of Temperature Field Induced by 8-Element Phased Array HIFU Transducer with Concave Spherical Surface

    NASA Astrophysics Data System (ADS)

    Sun, Wujun; Zhang, Ping; Zhang, Xiaojing; Jian, Xiqi; Li, Zhihua

    2011-09-01

    Multi-element High Intensity Focused Ultrasound (HIFU) transducers can change their focal lengths and form multi-foci. In this paper the Westervelt formula and Pennes bio-heat transfer equation have been used along, with the Finite Difference Time Domain (FDTD) method, to study the temperature distribution induced by an 8-element phased array HIFU transducer inside the human body. We evaluated the effects of the gap in the arc between two rings, the frequency of excitation function and pre-focal length on the temperature field. For HIFU therapy, skin burns were caused by high frequency, small pre-focal length, or a big gap between two rings. The focal region may be no longer an ellipsoid due to high frequency. In addition, the actual focal length is slightly different from the pre-focal length.

  2. On the acoustic radiation modes of compact regular polyhedral arrays of independent loudspeakers.

    PubMed

    Pasqual, Alexander Mattioli; Martin, Vincent

    2011-09-01

    Compact spherical loudspeaker arrays can be used to provide control over their directivity pattern. Usually, this is made by adjusting the gains of preprogrammed spatial filters corresponding to a finite set of spherical harmonics, or to the acoustic radiation modes of the loudspeaker array. Unlike the former, the latter are closely related to the radiation efficiency of the source and span the subspace of the directivities it can produce. However, the radiation modes depend on frequency for arbitrary distributions of transducers on the sphere, which yields complex directivity filters. This work focuses on the most common loudspeaker array configurations, those following the regular shape of the Platonic solids. It is shown that the radiation modes of these sources are frequency independent, and simple algebraic expressions are derived for their radiation efficiencies. In addition, since such modes are vibration patterns driven by electrical signals, the transduction mechanism of compact multichannel sources is also investigated, which is an important issue, especially if the transducers interact inside a shared cabinet. For Platonic solid loudspeakers, it is shown that the common enclosure does not lead to directivity filters that depend on frequency.

  3. Acoustic Array Development for Wind Turbine Noise Characterization

    SciTech Connect

    Buck, S.; Roadman, J.; Moriarty, P.; Palo, S.

    2013-11-01

    This report discusses the design and use of a multi-arm, logarithmic spiral acoustic array by the National Renewable Energy Laboratory (NREL) for measurement and characterization of wind turbine-generated noise. The array was developed in collaboration with a team from the University of Colorado Boulder. This design process is a continuation of the elliptical array design work done by Simley. A description of the array system design process is presented, including array shape design, mechanical design, design of electronics and the data acquisition system, and development of post-processing software. System testing and calibration methods are detailed. Results from the initial data acquisition campaign are offered and discussed. Issues faced during this initial deployment of the array are presented and potential remedies discussed.

  4. Optimal Transducer Arrangement for Temperature Distribution Measurement in Arbitrary Convex-Shaped Space by Acoustic Computerized Tomography

    NASA Astrophysics Data System (ADS)

    Ayumu Minamide,; Naoto Wakatsuki,; Koichi Mizutani,

    2010-07-01

    We study the optimal transducer arrangement for measuring temperature distribution in an arbitrary convex-shaped space by acoustic computerized tomography (A-CT) using flexibly arranged transducers. The transducer arrangement is optimized by the combined use of two methods, namely, real-coded genetic algorithm (RCGA) and simulated annealing (SA). By RCGA, the optimized arrangement is globally searched and then locally searched by SA. A fitness function of these methods is defined to evaluate the distribution of projection data in θ-r space. By use of this function, we aim to obtain better projection data sets by two-dimensionally interpolating the projection data. By numerical simulations, we confirmed the adequacy of our method and the optimized transducer arrangement.

  5. VHF-induced thermoacoustic imaging of fresh human prostates using a clinical ultrasound transducer array

    NASA Astrophysics Data System (ADS)

    Patch, S. K.; See, W. A.

    2016-03-01

    The purpose of this work was to demonstrate that a clinical ultrasound transducer array can practically detect thermoacoustic pulses induced by irradiation by very high frequency (VHF) electromagnetic energy. This is an important step because thermoacoustic signal strength is directly proportional to the specific absorption rate (SAR), which is lower in the VHF regime than in microwave or optical regimes. A 96-channel transducer array (P4-1) providing 3 cm coverage was incorporated into a benchtop thermoacoustic imaging system for imaging fresh surgical specimens. Thermoacoustic signal was generated by 700 ns irradiation pulses with 11 kV/m electric field strength and 108 MHz carrier frequency. To improve SNR 1024 pulses were averaged at a 250 Hz repetition rate. Two sets of sinograms were acquired, separated by a 2 cm translation along the tomographic axis and reconstructed over a 6 x 6 x 5 cm3 volume. Contrast and in-plane resolution were measured by imaging a homogeneous cylindrical phantom and an 80- micron wire designed to highlight E-field polarization effects. FWHM of the in-plane point spread function varied from 250 microns to 1.1 mm, depending upon transducer used and phantom orientation relative to the electric field. Several fresh human prostates were imaged immediately after surgery. Rudimentary comparison to histology was performed and volumetric reconstruction of the multi-channel P4-1 data visualizes anatomic features that are rarely seen in ultrasound, CT, or MRI. The single element transducer provided superior image contrast, but with inferior resolution.

  6. New fabrication techniques for ring-array transducers for real-time 3D intravascular ultrasound.

    PubMed

    Light, Edward D; Lieu, Victor; Smith, Stephen W

    2009-10-01

    We have previously described miniature 2D array transducers integrated into a Cook Medical, Inc. vena cava filter deployment device. While functional, the fabrication technique was very labor intensive and did not lend itself well to efficient fabrication of large numbers of devices. We developed two new fabrication methods that we believe can be used to efficiently manufacture these types of devices in greater than prototype numbers. One transducer consisted of 55 elements operating near 5 MHz. The interelement spacing is 0.20 mm. It was constructed on a flat piece of copper-clad polyimide and then wrapped around an 11 French catheter of a Cook Medical, Inc. inferior vena cava (IVC) filter deployment device. We used a braided wiring technology from Tyco Electronics Corp. to connect the elements to our real-time 3D ultrasound scanner. Typical measured transducer element bandwidth was 20% centered at 4.7 MHz and the 50 Omega round trip insertion loss was --82 dB. The mean of the nearest neighbor cross talk was -37.0 dB. The second method consisted of a 46-cm long single layer flex circuit from MicroConnex that terminates in an interconnect that plugs directly into our system cable. This transducer had 70 elements at 0.157 mm interelement spacing operating at 4.8 MHz. Typical measured transducer element bandwidth was 29% and the 50 Omega round trip insertion loss was -83 dB. The mean of the nearest neighbor cross talk was -33.0 dB. PMID:20458877

  7. Numerical simulation of electromagnetic acoustic transducers using distributed point source method.

    PubMed

    Eskandarzade, M; Kundu, T; Liebeaux, N; Placko, D; Mobadersani, F

    2010-05-01

    In spite of many advances in analytical and numerical modeling techniques for solving different engineering problems, an efficient solution technique for wave propagation modeling of an electromagnetic acoustic transducer (EMAT) system is still missing. Distributed point source method (DPSM) is a newly developed semi-analytical technique developed since 2000 by Placko and Kundu (2007) [12] that is very powerful and straightforward for solving various engineering problems, including acoustic and electromagnetic modeling problems. In this study DPSM has been employed to model the Lorentz type EMAT with a meander line and flat spiral type coil. The problem of wave propagation has been solved and eddy currents and Lorentz forces have been calculated. The displacement field has been obtained as well. While modeling the Lorentz force the effect of dynamic magnetic field has been considered that most current analyses ignore. Results from this analysis have been compared with the finite element method (FEM) based predictions. It should be noted that with the current state of knowledge this problem can be solved only by FEM.

  8. Evaluation of adhesive-free crossed-electrode poly(vinylidene fluoride) copolymer array transducers for high frequency imaging

    NASA Astrophysics Data System (ADS)

    Wagle, Sanat; Decharat, Adit; Habib, Anowarul; Ahluwalia, Balpreet S.; Melandsø, Frank

    2016-07-01

    High frequency crossed-electrode transducers have been investigated, both as single and dual layer transducers. Prototypes of these transducers were developed for 4 crossed lines (yielding 16 square elements) on a polymer substrate, using a layer-by-layer deposition method for poly(vinylidene fluoride–trifluoroethylene) [P(VDF–TrFE)] with intermediate sputtered electrodes. The transducer was characterized using various methods [LCR analyzer, a pulse–echo experimental setup, and a numerical Finite element method (FEM) model] and evaluated in terms of uniformity of bandwidth and acoustical energy output. All 16 transducer elements produced broad-banded ultrasonic spectra with small variation in central frequency and ‑6 dB bandwidth. The frequency responses obtained experimentally were verified using a numerical model.

  9. Scaling of membrane-type locally resonant acoustic metamaterial arrays.

    PubMed

    Naify, Christina J; Chang, Chia-Ming; McKnight, Geoffrey; Nutt, Steven R

    2012-10-01

    Metamaterials have emerged as promising solutions for manipulation of sound waves in a variety of applications. Locally resonant acoustic materials (LRAM) decrease sound transmission by 500% over acoustic mass law predictions at peak transmission loss (TL) frequencies with minimal added mass, making them appealing for weight-critical applications such as aerospace structures. In this study, potential issues associated with scale-up of the structure are addressed. TL of single-celled and multi-celled LRAM was measured using an impedance tube setup with systematic variation in geometric parameters to understand the effects of each parameter on acoustic response. Finite element analysis was performed to predict TL as a function of frequency for structures with varying complexity, including stacked structures and multi-celled arrays. Dynamic response of the array structures under discrete frequency excitation was investigated using laser vibrometry to verify negative dynamic mass behavior. PMID:23039544

  10. Design and Modeling of High Power Density Acoustic Transducer Materials for Autonomous Undersea Vehicles

    NASA Astrophysics Data System (ADS)

    Heitmann, Adam Arthur

    electromechanical properties of ferroelectric solid solutions based on barium titanate and lead titanate. From the computed binary solid solution phase diagrams, the theory is extended to ternary systems. The ternary solid solutions of PMN-PZT and PZN-PZT are explored, electromechanical properties of targeted compositions for use in next generation acoustic transducers are computed, and the predictive capability of the theory is established. In addition, thermal and electromechanical properties are measured for several compositions adjacent to the morphotropic boundary in the ferroelectric solid solution PZN-PT and used to verify the core assumptions of the theory.

  11. Applications of Flexible Ultrasonic Transducer Array for Defect Detection at 150 °C

    PubMed Central

    Shih, Jeanne-Louise; Wu, Kuo-Ting; Jen, Cheng-Kuei; Chiu, Chun-Hsiung; Tzeng, Jing-Chi; Liaw, Jiunn-Woei

    2013-01-01

    In this study, the feasibility of using a one dimensional 16-element flexible ultrasonic transducer (FUT) array for nondestructive testing at 150 °C is demonstrated. The FUT arrays were made by a sol-gel sprayed piezoelectric film technology; a PZT composite film was sprayed on a titanium foil of 75 μm thickness. Since the FUT array is flexible, it was attached to a steel pipe with an outer diameter of 89 mm and a wall thickness of 6.5 mm at 150 °C. Using the ultrasonic pulse-echo mode, pipe thickness measurements could be performed. Moreover, using the ultrasonic pulse-echo and pitch-catch modes of each element of FUT array, the defect detection was performed on an Al alloy block of 30 mm thickness with a side-drilled hole (SDH) of ϕ3 mm at 150 °C. In addition, a post-processing algorithm based on the total focusing method was used to process the full matrix of these A-scan signals of each single transmitter and multi-receivers, and then the phase-array image was obtained to indicate this defect- SDH. Both results show the capability of FUT array being operated at 150 °C for the corrosion and defect detections. PMID:23322101

  12. Investigation and optimization of a finite element simulation of transducer array systems for 3D ultrasound computer tomography with respect to electrical impedance characteristics

    NASA Astrophysics Data System (ADS)

    Kohout, B.; Pirinen, J.; Ruiter, N. V.

    2012-03-01

    The established standard screening method to detect breast cancer is X-ray mammography. However X-ray mammography often has low contrast for tumors located within glandular tissue. A new approach is 3D Ultrasound Computer Tomography (USCT), which is expected to detect small tumors at an early stage. This paper describes the development, improvement and the results of Finite Element Method (FEM) simulations of the Transducer Array System (TAS) used in our 3D USCT. The focus of this work is on researching the influence of meshing and material parameters on the electrical impedance curves. Thereafter, these findings are used to optimize the simulation model. The quality of the simulation was evaluated by comparing simulated impedance characteristics with measured data of the real TAS. The resulting FEM simulation model is a powerful tool to analyze and optimize transducer array systems applied for USCT. With this simulation model, the behavior of TAS for different geometry modifications was researched. It provides a means to understand the acoustical performances inside of any ultrasound transducer represented by its electrical impedance characteristic.

  13. Detection of foreign body using fast thermoacoustic tomography with a multielement linear transducer array

    SciTech Connect

    Nie Liming; Xing Da; Yang Diwu; Zeng Lvming; Zhou Quan

    2007-04-23

    Current imaging modalities face challenges in clinical applications due to limitations in resolution or contrast. Microwave-induced thermoacoustic imaging may provide a complementary modality for medical imaging, particularly for detecting foreign objects due to their different absorption of electromagnetic radiation at specific frequencies. A thermoacoustic tomography system with a multielement linear transducer array was developed and used to detect foreign objects in tissue. Radiography and thermoacoustic images of objects with different electromagnetic properties, including glass, sand, and iron, were compared. The authors' results demonstrate that thermoacoustic imaging has the potential to become a fast method for surgical localization of occult foreign objects.

  14. The design of a focused ultrasound transducer array for the treatment of stroke: a simulation study

    NASA Astrophysics Data System (ADS)

    Pajek, Daniel; Hynynen, Kullervo

    2012-08-01

    High intensity focused ultrasound (HIFU) is capable of mechanically disintegrating blood clots at high pressures. Safe thrombolysis may require frequencies higher than those currently utilized by transcranial HIFU. Since the attenuation and focal distortion of ultrasound in bone increases at higher frequencies, resulting focal pressures are diminished. This study investigated the feasibility of using transcranial HIFU for the non-invasive treatment of ischemic stroke. The use of large aperture, 1.1-1.5 MHz phased arrays in targeting four clinically relevant vessel locations was simulated. Resulting focal sizes decreased with frequency, producing a maximum -3 dB depth of field and lateral width of 2.0 and 1.2 mm, respectively. Mean focal gains above an order of magnitude were observed in three of four targets and transducer intensities required to achieve thrombolysis were determined. Required transducer element counts are about an order of magnitude higher than what currently exists and so, although technically feasible, new arrays would need to be developed to realize this as a treatment modality for stroke.

  15. Capacitive Micromachined Ultrasonic Transducer Arrays for Integrated Diagnostic/Therapeutic Catheters

    NASA Astrophysics Data System (ADS)

    Wong, Serena H.; Wygant, Ira O.; Yeh, David T.; Zhuang, Xuefeng; Bayram, Baris; Kupnik, Mario; Oralkan, Omer; Ergun, A. Sanli; Yaralioglu, Goksen G.; Khuri-Yakub, Butrus T.

    2006-05-01

    In recent years, medical procedures have become increasingly non-invasive. These include endoscopic procedures and intracardiac interventions (e.g., pulmonary vein isolation for treatment of atrial fibrillation and plaque ablation for treatment of arteriosclerosis). However, current tools suffer from poor visualization and difficult coordination of multiple therapeutic and imaging devices. Dual-mode (imaging and therapeutic) ultrasound arrays provide a solution to these challenges. A dual-mode transducer can provide focused, noncontact ultrasound suitable for therapy and can be used to provide high quality real-time images for navigation and monitoring of the procedure. In the last decade, capacitive micromachined ultrasonic transducers (CMUTs), have become an attractive option for ultrasonic imaging systems due to their fabrication flexibility, improved bandwidth, and integration with electronics. The CMUT's potential in therapeutic applications has also been demonstrated by surface output pressures as high as 1MPa peak to peak and continuous wave (CW) operation. This paper reviews existing interventional CMUT arrays, demonstrates the feasibility of CMUTs for high intensity focused ultrasound (HIFU), and presents a design for the next-generation CMUTs for integrated imaging and HIFU endoscopic catheters.

  16. Improving the Performance of a 1-D Ultrasound Transducer Array by Subdicing.

    PubMed

    Janjic, Jovana; Shabanimotlagh, Maysam; van Soest, Gijs; van der Steen, Antonius F W; de Jong, Nico; Verweij, Martin D

    2016-08-01

    In medical ultrasound transducer design, the geometry of the individual elements is crucial since it affects the vibration mode of each element and its radiation impedance. For a fixed frequency, optimal vibration (i.e., uniform surface motion) can be achieved by designing elements with very small width-to-thickness ratios. However, for optimal radiation impedance (i.e., highest radiated power), the width should be as large as possible. This leads to a contradiction that can be solved by subdicing wide elements. To systematically examine the effect of subdicing on the performance of a 1-D ultrasound transducer array, we applied finite-element simulations. We investigated the influence of subdicing on the radiation impedance, on the time and frequency response, and on the directivity of linear arrays with variable element widths. We also studied the effect of varying the depth of the subdicing cut. The results show that, for elements having a width greater than 0.6 times the wavelength, subdicing improves the performance compared with that of nonsubdiced elements: the emitted pressure may be increased up to a factor of three, the ringing time may be reduced by up to 50%, the bandwidth increased by up to 77%, and the sidelobes reduced by up to 13 dB. Moreover, this simulation study shows that all these improvements can already be achieved by subdicing the elements to a depth of 70% of the total element thickness. Thus, subdicing can improve important transducer parameters and, therefore, help in achieving images with improved signal-to-noise ratio and improved resolution. PMID:27164584

  17. Enhanced Sensitivity of Surface Acoustic Wave-Based Rate Sensors Incorporating Metallic Dot Arrays

    PubMed Central

    Wang, Wen; Shao, Xiuting; Liu, Xinlu; Liu, Jiuling; He, Shitang

    2014-01-01

    A new surface acoustic wave (SAW)-based rate sensor pattern incorporating metallic dot arrays was developed in this paper. Two parallel SAW delay lines with a reverse direction and an operation frequency of 80 MHz on a same X-112°Y LiTaO3 wafer are fabricated as the feedback of two SAW oscillators, and mixed oscillation frequency was used to characterize the external rotation. To enhance the Coriolis force effect acting on the SAW propagation, a copper (Cu) dot array was deposited along the SAW propagation path of the SAW devices. The approach of partial-wave analysis in layered media was referred to analyze the response mechanisms of the SAW based rate sensor, resulting in determination of the optimal design parameters. To improve the frequency stability of the oscillator, the single phase unidirectional transducers (SPUDTs) and combed transducer were used to form the SAW device to minimize the insertion loss and accomplish the single mode selection, respectively. Excellent long-term (measured in hours) frequency stability of 0.1 ppm/h was obtained. Using the rate table with high precision, the performance of the developed SAW rate sensor was evaluated experimentally; satisfactory detection sensitivity (16.7 Hz·deg·s−1) and good linearity were observed. PMID:24577520

  18. A High-Frequency Annular-Array Transducer Using an Interdigital Bonded 1-3 Composite

    PubMed Central

    Chabok, Hamid Reza; Cannata, Jonathan M.; Kim, Hyung Ham; Williams, Jay A.; Park, Jinhyoung; Shung, K. Kirk

    2011-01-01

    This paper reports the design, fabrication, and characterization of a 1–3 composite annular-array transducer. An interdigital bonded (IB) 1–3 composite was prepared using two IB operations on a fine-grain piezoelectric ceramic. The final composite had 19-μm-wide posts separated by 6-μm-wide polymer kerfs. A novel method to remove metal electrodes from polymer portions of the 1–3 composite was established to eliminate the need for patterning and aligning the electrode on the composite to the electrodes on a flexible circuit. Unloaded epoxy was used for both the matching and backing layers and a flexible circuit was used for interconnect. A prototype array was successfully fabricated and tested. The results were in reasonable agreement with those predicted by a circuit-analogous model. The average center frequency estimated from the measured pulse-echo responses of array elements was 33.5 MHz and the −6-dB fractional bandwidth was 57%. The average insertion loss recorded was 14.3 dB, and the maximum crosstalk between the nearest-neighbor elements was less than −37 dB. Images of a wire phantom and excised porcine eye were obtained to show the capabilities of the array for high-frequency ultrasound imaging. PMID:21244988

  19. Pipe wall damage detection by electromagnetic acoustic transducer generated guided waves in absence of defect signals.

    PubMed

    Vasiljevic, Milos; Kundu, Tribikram; Grill, Wolfgang; Twerdowski, Evgeny

    2008-05-01

    Most investigators emphasize the importance of detecting the reflected signal from the defect to determine if the pipe wall has any damage and to predict the damage location. However, often the small signal from the defect is hidden behind the other arriving wave modes and signal noise. To overcome the difficulties associated with the identification of the small defect signal in the time history plots, in this paper the time history is analyzed well after the arrival of the first defect signal, and after different wave modes have propagated multiple times through the pipe. It is shown that the defective pipe can be clearly identified by analyzing these late arriving diffuse ultrasonic signals. Multiple reflections and scattering of the propagating wave modes by the defect and pipe ends do not hamper the defect detection capability; on the contrary, it apparently stabilizes the signal and makes it easier to distinguish the defective pipe from the defect-free pipe. This paper also highlights difficulties associated with the interpretation of the recorded time histories due to mode conversion by the defect. The design of electro-magnetic acoustic transducers used to generate and receive the guided waves in the pipe is briefly described in the paper.

  20. A New Method to Evaluate Surface Defects with an Electromagnetic Acoustic Transducer.

    PubMed

    Zhang, Kang; Yi, Pengxing; Li, Yahui; Hui, Bing; Zhang, Xuming

    2015-01-01

    Characterizing a surface defect is very crucial in non-destructive testing (NDT). We employ an electromagnetic acoustic transducer (EMAT) to detect the surface defect of a nonmagnetic material. An appropriate feature that can avoid the interference of the human factor is vital for evaluating the crack quantitatively. Moreover, it can also reduce the influence of other factors, such as the lift-off, during the testing. In this paper, we conduct experiments at various depths of surface cracks in an aluminum plate, and a new feature, lift-off slope (LOS), is put forward for the theoretical and experimental analyses of the lift-off effect on the receiving signals. Besides, by changing the lift-off between the receiving probe and the sample for testing, a new method is adopted to evaluate surface defects with the EMAT. Compared with other features, the theoretical and experimental results show that the feature lift-off slope has many advantages prior to the other features for evaluating the surface defect with the EMAT. This can reduce the lift-off effect of one probe. Meanwhile, it is not essential to measure the signal without defects. PMID:26193282

  1. A New Method to Evaluate Surface Defects with an Electromagnetic Acoustic Transducer

    PubMed Central

    Zhang, Kang; Yi, Pengxing; Li, Yahui; Hui, Bing; Zhang, Xuming

    2015-01-01

    Characterizing a surface defect is very crucial in non-destructive testing (NDT). We employ an electromagnetic acoustic transducer (EMAT) to detect the surface defect of a nonmagnetic material. An appropriate feature that can avoid the interference of the human factor is vital for evaluating the crack quantitatively. Moreover, it can also reduce the influence of other factors, such as the lift-off, during the testing. In this paper, we conduct experiments at various depths of surface cracks in an aluminum plate, and a new feature, lift-off slope (LOS), is put forward for the theoretical and experimental analyses of the lift-off effect on the receiving signals. Besides, by changing the lift-off between the receiving probe and the sample for testing, a new method is adopted to evaluate surface defects with the EMAT. Compared with other features, the theoretical and experimental results show that the feature lift-off slope has many advantages prior to the other features for evaluating the surface defect with the EMAT. This can reduce the lift-off effect of one probe. Meanwhile, it is not essential to measure the signal without defects. PMID:26193282

  2. Line-focusing electromagnetic acoustic transducers for the detection of slit defects.

    PubMed

    Ogi, H; Hirao, M; Ohtani, T

    1999-01-01

    This paper describes the design principles of a line-focusing electromagnetic acoustic transducer (LF-EMAT) and the results of a feasibility test for detecting slit-type defects in metals. The LF-EMAT excites shear vertical (SV) elastic waves and focuses them to a line in a metal body. It consists of a permanent magnet block and a meanderline coil, whose spacing is continuously varied so that the excited SV waves become coherent on a focal line after traveling oblique paths. The measured directivity of generation and reception show a sharp peak at the designed focal line. The LF-EMATs are then applied to detecting slit defects in the bottom surface of steel blocks, on which the focal lines are located. Portions of the scattered defect signals are received by the same EMAT. When operated at 4 MHz, the LF-EMATs are capable of detecting slits deeper than 0.05 mm. The sensitivity decreases with liftoff and the LF-EMATs are usable with liftoff up to 0.6 mm. PMID:18238430

  3. Development of a spherically focused phased array transducer for ultrasonic image-guided hyperthermia

    NASA Astrophysics Data System (ADS)

    Liu, Jingfei; Foiret, Josquin; Stephens, Douglas N.; Le Baron, Olivier; Ferrara, Katherine W.

    2016-07-01

    A 1.5 MHz prolate spheroidal therapeutic array with 128 circular elements was designed to accommodate standard imaging arrays for ultrasonic image-guided hyperthermia. The implementation of this dual-array system integrates real-time therapeutic and imaging functions with a single ultrasound system (Vantage 256, Verasonics). To facilitate applications involving small animal imaging and therapy the array was designed to have a beam depth of field smaller than 3.5 mm and to electronically steer over distances greater than 1 cm in both the axial and lateral directions. In order to achieve the required f number of 0.69, 1-3 piezocomposite modules were mated within the transducer housing. The performance of the prototype array was experimentally evaluated with excellent agreement with numerical simulation. A focal volume (2.70 mm (axial)  ×  0.65 mm (transverse)  ×  0.35 mm (transverse)) defined by the  -6 dB focal intensity was obtained to address the dimensions needed for small animal therapy. An electronic beam steering range defined by the  -3 dB focal peak intensity (17 mm (axial)  ×  14 mm (transverse)  ×  12 mm (transverse)) and  -8 dB lateral grating lobes (24 mm (axial)  ×  18 mm (transverse)  ×  16 mm (transverse)) was achieved. The combined testing of imaging and therapeutic functions confirmed well-controlled local heating generation and imaging in a tissue mimicking phantom. This dual-array implementation offers a practical means to achieve hyperthermia and ablation in small animal models and can be incorporated within protocols for ultrasound-mediated drug delivery.

  4. Development of a spherically focused phased array transducer for ultrasonic image-guided hyperthermia

    NASA Astrophysics Data System (ADS)

    Liu, Jingfei; Foiret, Josquin; Stephens, Douglas N.; Le Baron, Olivier; Ferrara, Katherine W.

    2016-07-01

    A 1.5 MHz prolate spheroidal therapeutic array with 128 circular elements was designed to accommodate standard imaging arrays for ultrasonic image-guided hyperthermia. The implementation of this dual-array system integrates real-time therapeutic and imaging functions with a single ultrasound system (Vantage 256, Verasonics). To facilitate applications involving small animal imaging and therapy the array was designed to have a beam depth of field smaller than 3.5 mm and to electronically steer over distances greater than 1 cm in both the axial and lateral directions. In order to achieve the required f number of 0.69, 1-3 piezocomposite modules were mated within the transducer housing. The performance of the prototype array was experimentally evaluated with excellent agreement with numerical simulation. A focal volume (2.70 mm (axial)  ×  0.65 mm (transverse)  ×  0.35 mm (transverse)) defined by the  ‑6 dB focal intensity was obtained to address the dimensions needed for small animal therapy. An electronic beam steering range defined by the  ‑3 dB focal peak intensity (17 mm (axial)  ×  14 mm (transverse)  ×  12 mm (transverse)) and  ‑8 dB lateral grating lobes (24 mm (axial)  ×  18 mm (transverse)  ×  16 mm (transverse)) was achieved. The combined testing of imaging and therapeutic functions confirmed well-controlled local heating generation and imaging in a tissue mimicking phantom. This dual-array implementation offers a practical means to achieve hyperthermia and ablation in small animal models and can be incorporated within protocols for ultrasound-mediated drug delivery.

  5. Development of a spherically focused phased array transducer for ultrasonic image-guided hyperthermia.

    PubMed

    Liu, Jingfei; Foiret, Josquin; Stephens, Douglas N; Le Baron, Olivier; Ferrara, Katherine W

    2016-07-21

    A 1.5 MHz prolate spheroidal therapeutic array with 128 circular elements was designed to accommodate standard imaging arrays for ultrasonic image-guided hyperthermia. The implementation of this dual-array system integrates real-time therapeutic and imaging functions with a single ultrasound system (Vantage 256, Verasonics). To facilitate applications involving small animal imaging and therapy the array was designed to have a beam depth of field smaller than 3.5 mm and to electronically steer over distances greater than 1 cm in both the axial and lateral directions. In order to achieve the required f number of 0.69, 1-3 piezocomposite modules were mated within the transducer housing. The performance of the prototype array was experimentally evaluated with excellent agreement with numerical simulation. A focal volume (2.70 mm (axial)  ×  0.65 mm (transverse)  ×  0.35 mm (transverse)) defined by the  -6 dB focal intensity was obtained to address the dimensions needed for small animal therapy. An electronic beam steering range defined by the  -3 dB focal peak intensity (17 mm (axial)  ×  14 mm (transverse)  ×  12 mm (transverse)) and  -8 dB lateral grating lobes (24 mm (axial)  ×  18 mm (transverse)  ×  16 mm (transverse)) was achieved. The combined testing of imaging and therapeutic functions confirmed well-controlled local heating generation and imaging in a tissue mimicking phantom. This dual-array implementation offers a practical means to achieve hyperthermia and ablation in small animal models and can be incorporated within protocols for ultrasound-mediated drug delivery.

  6. Characterization of Transducer Performance and Narrowband Transient Ultrasonic Fields in Metals by Rayleigh-Sommerfeld Backpropagation of Compression Acoustic Waves Measured with Double-Pulsed Tv Holography

    NASA Astrophysics Data System (ADS)

    Trillo, Cristina; Doval, Ángel F.; Fernández, José L.; Rodríguez-Gómez, Pablo; López-Vázquez, J. Carlos

    2014-10-01

    This article presents a method aimed at the characterization of the narrowband transient acoustic field radiated by an ultrasonic plane transducer into a homogeneous, isotropic and optically opaque prismatic solid, and the assessment of the performance of the acoustic source. The method relies on a previous technique based on the full-field optical measurement of an acoustic wavepacket at the surface of a solid and its subsequent numerical backpropagation within the material. The experimental results show that quantitative transversal and axial profiles of the complex amplitude of the beam can be obtained at any plane between the measurement and excitation surfaces. The reconstruction of the acoustic field at the transducer face, carried out on a defective transducer model, shows that the method could also be suitable for the nondestructive testing of the performance of ultrasonic sources. In all cases, the measurements were performed with the transducer working under realistic loading conditions.

  7. Three-Dimensional Mid-Air Acoustic Manipulation by Ultrasonic Phased Arrays

    PubMed Central

    Ochiai, Yoichi; Hoshi, Takayuki; Rekimoto, Jun

    2014-01-01

    The essence of levitation technology is the countervailing of gravity. It is known that an ultrasound standing wave is capable of suspending small particles at its sound pressure nodes. The acoustic axis of the ultrasound beam in conventional studies was parallel to the gravitational force, and the levitated objects were manipulated along the fixed axis (i.e. one-dimensionally) by controlling the phases or frequencies of bolted Langevin-type transducers. In the present study, we considered extended acoustic manipulation whereby millimetre-sized particles were levitated and moved three-dimensionally by localised ultrasonic standing waves, which were generated by ultrasonic phased arrays. Our manipulation system has two original features. One is the direction of the ultrasound beam, which is arbitrary because the force acting toward its centre is also utilised. The other is the manipulation principle by which a localised standing wave is generated at an arbitrary position and moved three-dimensionally by opposed and ultrasonic phased arrays. We experimentally confirmed that expanded-polystyrene particles of 0.6 mm, 1 mm, and 2 mm in diameter could be manipulated by our proposed method. PMID:24849371

  8. Three-dimensional mid-air acoustic manipulation by ultrasonic phased arrays.

    PubMed

    Ochiai, Yoichi; Hoshi, Takayuki; Rekimoto, Jun

    2014-01-01

    The essence of levitation technology is the countervailing of gravity. It is known that an ultrasound standing wave is capable of suspending small particles at its sound pressure nodes. The acoustic axis of the ultrasound beam in conventional studies was parallel to the gravitational force, and the levitated objects were manipulated along the fixed axis (i.e. one-dimensionally) by controlling the phases or frequencies of bolted Langevin-type transducers. In the present study, we considered extended acoustic manipulation whereby millimetre-sized particles were levitated and moved three-dimensionally by localised ultrasonic standing waves, which were generated by ultrasonic phased arrays. Our manipulation system has two original features. One is the direction of the ultrasound beam, which is arbitrary because the force acting toward its centre is also utilised. The other is the manipulation principle by which a localised standing wave is generated at an arbitrary position and moved three-dimensionally by opposed and ultrasonic phased arrays. We experimentally confirmed that expanded-polystyrene particles of 0.6 mm, 1 mm, and 2 mm in diameter could be manipulated by our proposed method.

  9. Three-dimensional mid-air acoustic manipulation by ultrasonic phased arrays.

    PubMed

    Ochiai, Yoichi; Hoshi, Takayuki; Rekimoto, Jun

    2014-01-01

    The essence of levitation technology is the countervailing of gravity. It is known that an ultrasound standing wave is capable of suspending small particles at its sound pressure nodes. The acoustic axis of the ultrasound beam in conventional studies was parallel to the gravitational force, and the levitated objects were manipulated along the fixed axis (i.e. one-dimensionally) by controlling the phases or frequencies of bolted Langevin-type transducers. In the present study, we considered extended acoustic manipulation whereby millimetre-sized particles were levitated and moved three-dimensionally by localised ultrasonic standing waves, which were generated by ultrasonic phased arrays. Our manipulation system has two original features. One is the direction of the ultrasound beam, which is arbitrary because the force acting toward its centre is also utilised. The other is the manipulation principle by which a localised standing wave is generated at an arbitrary position and moved three-dimensionally by opposed and ultrasonic phased arrays. We experimentally confirmed that expanded-polystyrene particles of 0.6 mm, 1 mm, and 2 mm in diameter could be manipulated by our proposed method. PMID:24849371

  10. Microfabrication of electrode patterns for high-frequency ultrasound transducer arrays.

    PubMed

    Bernassau, Anne L; García-Gancedo, Luis; Hutson, David; Démoré, Christine E M; McAneny, Jim J; Button, Tim W; Cochran, Sandy

    2012-08-01

    High-frequency ultrasound is needed for medical imaging with high spatial resolution. A key issue in the development of ultrasound imaging arrays to operate at high frequencies (≥30 MHz) is the need for photolithographic patterning of array electrodes. To achieve this directly on 1-3 piezocomposite, the material requires not only planar, parallel, and smooth surfaces, but also an epoxy composite filler that is resistant to chemicals, heat, and vacuum. This paper reports, first, on the surface finishing of 1-3 piezocomposite materials by lapping and polishing. Excellent surface flatness has been obtained, with an average surface roughness of materials as low as 3 nm and step heights between ceramic/polymer of ∼80 nm. Subsequently, high-frequency array elements were patterned directly on top of these surfaces using a photolithography process. A 30-MHz linear array electrode pattern with 50-μm element pitch has been patterned on the lapped and polished surface of a high-frequency 1-3 piezocomposite. Excellent electrode edge definition and electrical contact to the composite were obtained. The composite has been lapped to a final thickness of ∼55 μm. Good adhesion of electrodes on the piezocomposite has been achieved and electrical impedance measurements have demonstrated their basic functionality. The array was then packaged, and acoustic pulse-echo measurements were performed. These results demonstrate that direct patterning of electrodes by photolithography on 1-3 piezocomposite is feasible for fabrication of high-frequency ultrasound arrays. Furthermore, this method is more conducive to mass production than other reported array fabrication techniques. PMID:22899129

  11. Microfabrication of electrode patterns for high-frequency ultrasound transducer arrays.

    PubMed

    Bernassau, Anne L; García-Gancedo, Luis; Hutson, David; Démoré, Christine E M; McAneny, Jim J; Button, Tim W; Cochran, Sandy

    2012-08-01

    High-frequency ultrasound is needed for medical imaging with high spatial resolution. A key issue in the development of ultrasound imaging arrays to operate at high frequencies (≥30 MHz) is the need for photolithographic patterning of array electrodes. To achieve this directly on 1-3 piezocomposite, the material requires not only planar, parallel, and smooth surfaces, but also an epoxy composite filler that is resistant to chemicals, heat, and vacuum. This paper reports, first, on the surface finishing of 1-3 piezocomposite materials by lapping and polishing. Excellent surface flatness has been obtained, with an average surface roughness of materials as low as 3 nm and step heights between ceramic/polymer of ∼80 nm. Subsequently, high-frequency array elements were patterned directly on top of these surfaces using a photolithography process. A 30-MHz linear array electrode pattern with 50-μm element pitch has been patterned on the lapped and polished surface of a high-frequency 1-3 piezocomposite. Excellent electrode edge definition and electrical contact to the composite were obtained. The composite has been lapped to a final thickness of ∼55 μm. Good adhesion of electrodes on the piezocomposite has been achieved and electrical impedance measurements have demonstrated their basic functionality. The array was then packaged, and acoustic pulse-echo measurements were performed. These results demonstrate that direct patterning of electrodes by photolithography on 1-3 piezocomposite is feasible for fabrication of high-frequency ultrasound arrays. Furthermore, this method is more conducive to mass production than other reported array fabrication techniques.

  12. Estimation of guided wave scattering matrices from spatially distributed transducer arrays

    NASA Astrophysics Data System (ADS)

    Chen, Xin; Michaels, Jennifer E.; Michaels, Thomas E.

    2013-01-01

    Because of their ability to travel relatively long distances with low attenuation, guided waves are being considered as a tool for the detection of defects in plate-like structures for aerospace, civil, and petrochemical applications. When a guided wave encounters a defect, a scattered field related to the characteristics of the defect is generated. The far field scattering behavior can be described by a scattering matrix that quantifies the amplitude of the scattered signal as a function of incident and scattered angles. Because of the mode and frequency dependence of guided waves interacting with defects, the scattering matrix is typically defined for specific guided wave modes (incident and scattered) at a designated frequency. Prior work has utilized finite element modeling and full wavefield scanning to estimate scattering matrices, but these approaches may be impractical because of either computational requirements or experimental issues. Here, we propose a methodology for estimating a scattering matrix based upon limited experimental data recorded from a spatially distributed transducer array. After applying baseline subtraction to extract changes in received signals resulting from the introduction of a scatterer, we further process differenced signals to obtain a limited number of scattering matrix data points corresponding to the incident and scattered angles for each transducer pair. We perform radial basis function interpolation of these initial points to estimate the complete scattering matrix and evaluate the efficacy of the proposed method via experiments with a glued-on linear scatterer.

  13. In-flight measurement of ice growth on an airfoil using an array of ultrasonic transducers

    NASA Technical Reports Server (NTRS)

    Hansman, R. John, Jr.; Kirby, Mark S.; Mcknight, Robert C.; Humes, Robert L.

    1987-01-01

    Results from three research flights to obtain in-flight ultrasonic pulse-echo measurements of airfoil ice thickness as a function of time using an array of eight ultrasonic transducers mounted flush with the leading edge of the airfoil are presented. The accuracy of the thickness measurements is found to be within 0.5 mm of mechanical and stereophotograph measurements of the ice accretion. The ultrasonic measurements demonstrate that the ice growth rate typically varies during the flight, with variations in the ice growth rate for dry ice growth being primarily due to fluctuations in the cloud liquid water content. Discrepancies between experimental results and results predicted by an analytic icing code underline the need for a better understanding of the physics of wet ice growth.

  14. Quantitative 3-d diagnostic ultrasound imaging using a modified transducer array and an automated image tracking technique.

    PubMed

    Hossack, John A; Sumanaweera, Thilaka S; Napel, Sandy; Ha, Jun S

    2002-08-01

    An approach for acquiring dimensionally accurate three-dimensional (3-D) ultrasound data from multiple 2-D image planes is presented. This is based on the use of a modified linear-phased array comprising a central imaging array that acquires multiple, essentially parallel, 2-D slices as the transducer is translated over the tissue of interest. Small, perpendicularly oriented, tracking arrays are integrally mounted on each end of the imaging transducer. As the transducer is translated in an elevational direction with respect to the central imaging array, the images obtained by the tracking arrays remain largely coplanar. The motion between successive tracking images is determined using a minimum sum of absolute difference (MSAD) image matching technique with subpixel matching resolution. An initial phantom scanning-based test of a prototype 8 MHz array indicates that linear dimensional accuracy of 4.6% (2 sigma) is achievable. This result compares favorably with those obtained using an assumed average velocity [31.5% (2 sigma) accuracy] and using an approach based on measuring image-to-image decorrelation [8.4% (2 sigma) accuracy]. The prototype array and imaging system were also tested in a clinical environment, and early results suggest that the approach has the potential to enable a low cost, rapid, screening method for detecting carotid artery stenosis. The average time for performing a screening test for carotid stenosis was reduced from an average of 45 minutes using 2-D duplex Doppler to 12 minutes using the new 3-D scanning approach.

  15. A circular array transducer for photoacoustic imaging by using piezoelectric single crystal lead magnesium niobate-lead zirconate titanate

    NASA Astrophysics Data System (ADS)

    Cao, Yonggang; Ha, Kanglyeol; Kim, Moojoon; Kang, Hyunwook; Oh, Jung-Hwan; Kim, Jungsoon

    2015-07-01

    The ultrasound transducers of which center frequencies are lower than 10 MHz are commonly used in low frequency photoacoustic (PA) imaging systems. However, the improvement of their sensitivity is still needed to detect weak PA signals. In this study, a circular array transducer was constructed by using 120 needle hydrophones made of piezoelectric single crystal lead magnesium niobate-lead zirconate titanate (PMN-PZT). The needle hydrophone was designed to have high sensitivity and wide bandwidth through the Krimtholz-Leedom-Matthaei (KLM) simulation of receiving impulse response. The sensitivity of the fabricated PMN-PZT hydrophone was compared with a commercial poly(vinylidene fluoride) (PVDF) needle hydrophone. The usefulness of the circular array transducer was demonstrated by applying it to a PA system for obtaining images.

  16. Non-linear, adaptive array processing for acoustic interference suppression.

    PubMed

    Hoppe, Elizabeth; Roan, Michael

    2009-06-01

    A method is introduced where blind source separation of acoustical sources is combined with spatial processing to remove non-Gaussian, broadband interferers from space-time displays such as bearing track recorder displays. This differs from most standard techniques such as generalized sidelobe cancellers in that the separation of signals is not done spatially. The algorithm performance is compared to adaptive beamforming techniques such as minimum variance distortionless response beamforming. Simulations and experiments using two acoustic sources were used to verify the performance of the algorithm. Simulations were also used to determine the effectiveness of the algorithm under various signal to interference, signal to noise, and array geometry conditions. A voice activity detection algorithm was used to benchmark the performance of the source isolation.

  17. Acoustic Holographic Rendering with Two-dimensional Metamaterial-based Passive Phased Array

    PubMed Central

    Xie, Yangbo; Shen, Chen; Wang, Wenqi; Li, Junfei; Suo, Dingjie; Popa, Bogdan-Ioan; Jing, Yun; Cummer, Steven A.

    2016-01-01

    Acoustic holographic rendering in complete analogy with optical holography are useful for various applications, ranging from multi-focal lensing, multiplexed sensing and synthesizing three-dimensional complex sound fields. Conventional approaches rely on a large number of active transducers and phase shifting circuits. In this paper we show that by using passive metamaterials as subwavelength pixels, holographic rendering can be achieved without cumbersome circuitry and with only a single transducer, thus significantly reducing system complexity. Such metamaterial-based holograms can serve as versatile platforms for various advanced acoustic wave manipulation and signal modulation, leading to new possibilities in acoustic sensing, energy deposition and medical diagnostic imaging. PMID:27739472

  18. Acoustic Holographic Rendering with Two-dimensional Metamaterial-based Passive Phased Array

    NASA Astrophysics Data System (ADS)

    Xie, Yangbo; Shen, Chen; Wang, Wenqi; Li, Junfei; Suo, Dingjie; Popa, Bogdan-Ioan; Jing, Yun; Cummer, Steven A.

    2016-10-01

    Acoustic holographic rendering in complete analogy with optical holography are useful for various applications, ranging from multi-focal lensing, multiplexed sensing and synthesizing three-dimensional complex sound fields. Conventional approaches rely on a large number of active transducers and phase shifting circuits. In this paper we show that by using passive metamaterials as subwavelength pixels, holographic rendering can be achieved without cumbersome circuitry and with only a single transducer, thus significantly reducing system complexity. Such metamaterial-based holograms can serve as versatile platforms for various advanced acoustic wave manipulation and signal modulation, leading to new possibilities in acoustic sensing, energy deposition and medical diagnostic imaging.

  19. Handheld Thermoacoustic Scanning System Based on a Linear-array Transducer.

    PubMed

    Ji, Zhong; Ding, Wenzheng; Ye, Fanghao; Lou, Cunguang

    2016-07-01

    To receive the information necessary for imaging, traditional microwave-induced thermoacoustic imaging systems (MITISs) use a type of circular-scanning mode using single or arc detectors. However, the use of MITISs for body scanning is complicated by restrictions in space and imaging time. A linear-array detector, the most widely used transducer in medical ultrasound imaging systems for body scanning, is a possible alternative to MITISs for scanning biological tissues, such as from the breast or limbs. In this paper, a handheld MITIS, based on a linear-array detector and a multiple data acquisition system, is described, and the capacity of the system is explored experimentally. First, the vertical and lateral resolution of the system is discussed. Next, real-time imaging of a moving object, obtained with an image capture rate of 20 frame/s, is described. Finally, a phantom experiment is detailed, investigating the overall imaging capability. The results show that this system achieves rapid scanning with a large field of view. The system has the obvious advantages of being handheld, not using coupled fluids, and achieving real-time imaging with a large field of view, which make this MITIS more suitable for clinical applications.

  20. Handheld Thermoacoustic Scanning System Based on a Linear-array Transducer.

    PubMed

    Ji, Zhong; Ding, Wenzheng; Ye, Fanghao; Lou, Cunguang

    2016-07-01

    To receive the information necessary for imaging, traditional microwave-induced thermoacoustic imaging systems (MITISs) use a type of circular-scanning mode using single or arc detectors. However, the use of MITISs for body scanning is complicated by restrictions in space and imaging time. A linear-array detector, the most widely used transducer in medical ultrasound imaging systems for body scanning, is a possible alternative to MITISs for scanning biological tissues, such as from the breast or limbs. In this paper, a handheld MITIS, based on a linear-array detector and a multiple data acquisition system, is described, and the capacity of the system is explored experimentally. First, the vertical and lateral resolution of the system is discussed. Next, real-time imaging of a moving object, obtained with an image capture rate of 20 frame/s, is described. Finally, a phantom experiment is detailed, investigating the overall imaging capability. The results show that this system achieves rapid scanning with a large field of view. The system has the obvious advantages of being handheld, not using coupled fluids, and achieving real-time imaging with a large field of view, which make this MITIS more suitable for clinical applications. PMID:26294659

  1. Optimization of a phased-array transducer for multiple harmonic imaging in medical applications: frequency and topology.

    PubMed

    Matte, Guillaume M; Van Neer, Paul L M J; Danilouchkine, Mike G; Huijssen, Jacob; Verweij, Martin D; de Jong, Nico

    2011-03-01

    Second-harmonic imaging is currently one of the standards in commercial echographic systems for diagnosis, because of its high spatial resolution and low sensitivity to clutter and near-field artifacts. The use of nonlinear phenomena mirrors is a great set of solutions to improve echographic image resolution. To further enhance the resolution and image quality, the combination of the 3rd to 5th harmonics--dubbed the superharmonics--could be used. However, this requires a bandwidth exceeding that of conventional transducers. A promising solution features a phased-array design with interleaved low- and high-frequency elements for transmission and reception, respectively. Because the amplitude of the backscattered higher harmonics at the transducer surface is relatively low, it is highly desirable to increase the sensitivity in reception. Therefore, we investigated the optimization of the number of elements in the receiving aperture as well as their arrangement (topology). A variety of configurations was considered, including one transmit element for each receive element (1/2) up to one transmit for 7 receive elements (1/8). The topologies are assessed based on the ratio of the harmonic peak pressures in the main and grating lobes. Further, the higher harmonic level is maximized by optimization of the center frequency of the transmitted pulse. The achievable SNR for a specific application is a compromise between the frequency-dependent attenuation and nonlinearity at a required penetration depth. To calculate the SNR of the complete imaging chain, we use an approach analogous to the sonar equation used in underwater acoustics. The generated harmonic pressure fields caused by nonlinear wave propagation were modeled with the iterative nonlinear contrast source (INCS) method, the KZK, or the Burger's equation. The optimal topology for superharmonic imaging was an interleaved design with 1 transmit element per 6 receive elements. It improves the SNR by ~5 dB compared with

  2. Acoustic contrast control in an arc-shaped area using a linear loudspeaker array.

    PubMed

    Zhao, Sipei; Qiu, Xiaojun; Burnett, Ian

    2015-02-01

    This paper proposes a method of creating acoustic contrast control in an arc-shaped area using a linear loudspeaker array. The boundary of the arc-shaped area is treated as the envelope of the tangent lines that can be formed by manipulating the phase profile of the loudspeakers in the array. When compared with the existing acoustic contrast control method, the proposed method is able to generate sound field inside an arc-shaped area and achieve a trade-off between acoustic uniformity and acoustic contrast. The acoustic contrast created by the proposed method increases while the acoustic uniformity decreases with frequency.

  3. Acousto-optic Bragg diffraction in paratellurite by the sidelobes of the spatial radiation spectrum of an acoustic transducer

    NASA Astrophysics Data System (ADS)

    Kotov, V. M.

    2016-09-01

    Acousto-optic Bragg diffraction in paratellurite is investigated within the two first diffraction orders for the case of diffraction by the sidelobes of the spatial radiation spectrum of an acoustic transducer. One of the diffraction orders is due to anisotropic diffraction, and the other, to isotropic diffraction. Such a diffraction regime is achieved when the diffraction plane is inclined toward the optical axis of the crystal. For light with a wavelength of 0.63 × 10-4 cm diffracted by a "slow" sound wave with a frequency of 26 MHz, the effect manifests itself when the angle between the acousto-optic diffraction plane and the optical axis of paratellurite is ~3°. The effect is experimentally verified. The diffraction efficiency is 20% for each of the diffraction orders for a microwave signal of 8 V at the transducer.

  4. Monitoring of high-intensity focused ultrasound treatment by shear wave elastography induced by two-dimensional-array therapeutic transducer

    NASA Astrophysics Data System (ADS)

    Iwasaki, Ryosuke; Takagi, Ryo; Nagaoka, Ryo; Jimbo, Hayato; Yoshizawa, Shin; Saijo, Yoshifumi; Umemura, Shin-ichiro

    2016-07-01

    Shear wave elastography (SWE) is expected to be a noninvasive monitoring method of high-intensity focused ultrasound (HIFU) treatment. However, conventional SWE techniques encounter difficulty in inducing shear waves with adequate displacements in deep tissue. To observe tissue coagulation at the HIFU focal depth via SWE, in this study, we propose using a two-dimensional-array therapeutic transducer for not only HIFU exposure but also creating shear sources. The results show that the reconstructed shear wave velocity maps detected the coagulated regions as the area of increased propagation velocity even in deep tissue. This suggests that “HIFU-push” shear elastography is a promising solution for the purpose of coagulation monitoring in deep tissue, because push beams irradiated by the HIFU transducer can naturally reach as deep as the tissue to be coagulated by the same transducer.

  5. Handheld probe integrating laser diode and ultrasound transducer array for ultrasound/photoacoustic dual modality imaging.

    PubMed

    Daoudi, K; van den Berg, P J; Rabot, O; Kohl, A; Tisserand, S; Brands, P; Steenbergen, W

    2014-10-20

    Ultrasound and photoacoustics can be utilized as complementary imaging techniques to improve clinical diagnoses. Photoacoustics provides optical contrast and functional information while ultrasound provides structural and anatomical information. As of yet, photoacoustic imaging uses large and expensive systems, which limits their clinical application and makes the combination costly and impracticable. In this work we present and evaluate a compact and ergonomically designed handheld probe, connected to a portable ultrasound system for inexpensive, real-time dual-modality ultrasound/photoacoustic imaging. The probe integrates an ultrasound transducer array and a highly efficient diode stack laser emitting 130 ns pulses at 805 nm wavelength and a pulse energy of 0.56 mJ, with a high pulse repetition frequency of up to 10 kHz. The diodes are driven by a customized laser driver, which can be triggered externally with a high temporal stability necessary to synchronize the ultrasound detection and laser pulsing. The emitted beam is collimated with cylindrical micro-lenses and shaped using a diffractive optical element, delivering a homogenized rectangular light intensity distribution. The system performance was tested in vitro and in vivo by imaging a human finger joint.

  6. Double aperture focusing transducer for controlling microparticle motions in trapezoidal microchannels with surface acoustic waves

    NASA Astrophysics Data System (ADS)

    Tan, Ming K.; Tjeung, Ricky; Ervin, Hannah; Yeo, Leslie Y.; Friend, James

    2009-09-01

    We present a method for controlling the motion of microparticles suspended in an aqueous solution, which fills in a microchannel fabricated into a piezoelectric substrate, using propagating surface acoustic waves. The cross-sectional shape of this microchannel is trapezoidal, preventing the formation of acoustic standing waves across the channel width and therefore allowing the steering of microparticles. The induced acoustic streaming transports these particles to eliminate the use of external pumps for fluid actuation.

  7. Acoustical standards in engineering acoustics

    NASA Astrophysics Data System (ADS)

    Burkhard, Mahlon D.

    2001-05-01

    The Engineering Acoustics Technical Committee is concerned with the evolution and improvement of acoustical techniques and apparatus, and with the promotion of new applications of acoustics. As cited in the Membership Directory and Handbook (2002), the interest areas include transducers and arrays; underwater acoustic systems; acoustical instrumentation and monitoring; applied sonics, promotion of useful effects, information gathering and transmission; audio engineering; acoustic holography and acoustic imaging; acoustic signal processing (equipment and techniques); and ultrasound and infrasound. Evident connections between engineering and standards are needs for calibration, consistent terminology, uniform presentation of data, reference levels, or design targets for product development. Thus for the acoustical engineer standards are both a tool for practices, for communication, and for comparison of his efforts with those of others. Development of many standards depends on knowledge of the way products are put together for the market place and acoustical engineers provide important input to the development of standards. Acoustical engineers and members of the Engineering Acoustics arm of the Society both benefit from and contribute to the Acoustical Standards of the Acoustical Society.

  8. Tunable arrayed waveguide grating driven by surface acoustic waves

    NASA Astrophysics Data System (ADS)

    Crespo-Poveda, Antonio; Hernández-Mínguez, Alberto; Biermann, Klaus; Tahraoui, Abbes; Gargallo, Bernardo; Muñoz, Pascual; Santos, Paulo V.; Cantarero, Andrés.; de Lima, Maurício M.

    2016-03-01

    We present a design approach for compact reconfigurable phased-array wavelength-division multiplexing (WDM) devices with N access waveguides (WGs) based on multimode interference (MMI) couplers. The proposed devices comprise two MMI couplers which are employed as power splitters and combiners, respectively, linked by an array of N single-mode WGs. First, passive devices are explored. Taking advantage of the transfer phases between the access ports of the MMI couplers, we derive very simple phase relations between the arms that provide wavelength dispersion at the output plane of the devices. When the effective refractive index of the WGs is modulated with the proper relative optical phase difference, each wavelength component can switch paths between the preset output channel and the remaining output WGs. Moreover, very simple phase relations between the modulated WGs that enable the reconfiguration of the output channel distribution when the appropriated coupling lengths of the MMI couplers are chosen are also derived. In this way, a very compact expression to calculate the channel assignment of the devices as a function of the applied phase shift is derived for the general case of N access WGs. Finally, the experimental results corresponding to an acoustically driven phased-array WDM device with five access WGs fabricated on (Al,Ga)As are shown.

  9. Fabrication and Evaluation of Fully-Sampled, Two-Dimensional Transducer Array for “Sonic Window” Imaging System

    PubMed Central

    Eames, Matthew D.C.; Hossack, John A.

    2008-01-01

    A low-cost, fully-sampled, 3600 element 2D transducer array operating at 5 MHz and designed for use in a hand-held ultrasound system is described here. Four array configurations are presented – 1. array with both matching and pedestal backing layers, 2. array with a matching layer but no backing pedestal, 3. array with a backing pedestal but no matching layer, and 4. array with neither matching layer nor backing pedestal. Each array was characterized in terms of impedance measurements, pulse-echo response, and experimental beamprofile. Comparative finite element analysis simulations are also presented. Average estimated active element yield for the four arrays was 94%. The array with pedestal layer proved the most promising, providing a 26 % bandwidth and a 1.7 dB improvement in sensitivity with respect to the array with neither pedestal nor matching layer. Although this bandwidth is acceptable for our specific application (C-scan imaging), reverberations within the substrate material remain a potential challenge. We are currently working to fabricate a custom PCB material to address this concern, and may also consider using a pre-compensated transmit waveform or matched digital filter approach to further reduce the effects of such reverberations. PMID:18490042

  10. Model of a Piezoelectric Transducer

    NASA Technical Reports Server (NTRS)

    Goodenow, Debra

    2004-01-01

    It's difficult to control liquid and gas in propellant tanks in zero gravity. A possible a design would utilize acoustic liquid manipulation (ALM) technology which uses ultrasonic beams conducted through a liquid and solid media, to push gas bubbles in the liquid to desirable locations. We can propel and control the bubble with acoustic radiation pressure by aiming the acoustic waves on the bubble s surface. This allows us to design a so called smart tank in which the ALM devices transfer the gas to the outer wall of the tank and isolating the liquid in the center. Because the heat transfer rate of a gas is lower of that of the liquid it would substantially decrease boil off and provide of for a longer storage life. The ALM beam is composed of little wavelets which are individual waves that constructively interfere with each other to produce a single, combined acoustic wave front. This is accomplished by using a set of synchronized ultrasound transducers arranged in an array. A slight phase offset of these elements allows us to focus and steer the beam. The device that we are using to produce the acoustic beam is called the piezoelectric transducer. This device converts electrical energy to mechanical energy, which appears in the form of acoustic energy. Therefore the behavior of the device is dependent on both the mechanical characteristics, such as its density, cross-sectional area, and its electrical characteristics, such as, electric flux permittivity and coupling factor. These devices can also be set up in a number of modes which are determined by the way the piezoelectric device is arranged, and the shape of the transducer. For this application we are using the longitudinal or thickness mode for our operation. The transducer also vibrates in the lateral mode, and one of the goals of my project is to decrease the amount of energy lost to the lateral mode. To model the behavior of the transducers I will be using Pspice, electric circuit modeling tool, to

  11. In vivo mouse brain tomography by fast dual-scanning photoacoustic imaging system based on array transducer

    NASA Astrophysics Data System (ADS)

    Yang, Sihua; Xing, Da

    2008-12-01

    A full-view photoacoustic tomography system with dual-scanning using a linear transducer array for fast imaging of complicated blood network was developed. In this system, a 128-element linear transducer array was used to detect photoacoustic signals by combined scanning of electronic scan and mechanical scan. An improved limited-field filtered back projection algorithm with directivity factors was applied to reconstruct the distribution of the absorbed optical energy deposit. An in vivo experiment on a mouse brain was performed to evaluate the ability of this composite system. A clear view of the cerebrovascular network on the brain cortex was acquired successfully. Furthermore, the reconstruct images with different number of scanning positions were also investigated and analyzed to induce a compromised proposal between scanning time and scanning number. The experimental results demonstrate the multi-element photoacoustic imaging system has the potential to acquire the time-resolved functional information for fundamental research of small animal brain imaging.

  12. Linear-array-based photoacoustic imaging of human microcirculation with a range of high frequency transducer probes

    NASA Astrophysics Data System (ADS)

    Zafar, Haroon; Breathnach, Aedán; Subhash, Hrebesh M.; Leahy, Martin J.

    2015-05-01

    Photoacoustic imaging (PAI) with a linear-array-based probe can provide a convenient means of imaging the human microcirculation within its native structural context and adds functional information. PAI using a multielement linear transducer array combined with multichannel collecting system was used for in vivo volumetric imaging of the blood microcirculation, the total concentration of hemoglobin (HbT), and the hemoglobin oxygen saturation (sO2) within human tissue. Three-dimensional (3-D) PA and ultrasound (US) volumetric scans were acquired from the forearm skin by linearly translating the transducer with a stepper motor over a region of interest, while capturing two-dimensional images using 15, 21, and 40 MHz frequency transducer probes. For the microvasculature imaging, PA images were acquired at 800- and 1064-nm wavelengths. For the HbT and sO2 estimates, PA images were collected at 750- and 850-nm wavelengths. 3-D microcirculation, HbT, and sO2 maps of the forearm skin were obtained from normal subjects. The linear-array-based PAI has been found promising in terms of resolution, imaging depth, and imaging speed for in vivo microcirculation imaging within human skin. We believe that a reflection type probe, similar to existing clinical US probes, is most likely to succeed in real clinical applications. Its advantages include ease of use, speed, and familiarity for radiographers and clinicians.

  13. Determination of acoustic impedances of multi matching layers for narrowband ultrasonic airborne transducers at frequencies <2.5 MHz - Application of a genetic algorithm.

    PubMed

    Saffar, Saber; Abdullah, Amir

    2012-01-01

    The effective ultrasonic energy radiation into the air of piezoelectric transducers requires using multilayer matching systems with accurately selected acoustic impedances and the thickness of particular layers. One major problem of ultrasonic transducers, radiating acoustic energy into air, is to find the proper acoustic impedances of one or more matching layers. This work aims at developing an original solution to the acoustic impedance mismatch between transducer and air. If the acoustic impedance defences between transducer and air be more, then finding best matching layer(s) is harder. Therefore we consider PZT (lead zirconate titanate piezo electric) transducer and air that has huge acoustic impedance deference. The vibration source energy (PZT), which is used to generate the incident wave, consumes a part of the mechanical energy and converts it to an electrical one in theoretical calculation. After calculating matching layers, we consider the energy source as layer to design a transducer. However, this part of the mechanical energy will be neglected during the mathematical work. This approximation is correct only if the transducer is open-circuit. Since the possibilities of choosing material with required acoustic impedance are limited (the counted values cannot always be realized and applied in practice) it is necessary to correct the differences between theoretical values and the possibilities of practical application of given acoustic impedances. Such a correction can be done by manipulating other parameters of matching layers (e.g. by changing their thickness). The efficiency of the energy transmission from the piezoceramic transducer through different layers with different thickness and different attenuation enabling a compensation of non-ideal real values by changing their thickness was computer analyzed (base on genetic algorithm). Firstly, three theoretical solutions were investigated. Namely, Chebyshev, Desilets and Souquet theories. However, the

  14. Acoustic source localization in mixed field using spherical microphone arrays

    NASA Astrophysics Data System (ADS)

    Huang, Qinghua; Wang, Tong

    2014-12-01

    Spherical microphone arrays have been used for source localization in three-dimensional space recently. In this paper, a two-stage algorithm is developed to localize mixed far-field and near-field acoustic sources in free-field environment. In the first stage, an array signal model is constructed in the spherical harmonics domain. The recurrent relation of spherical harmonics is independent of far-field and near-field mode strengths. Therefore, it is used to develop spherical estimating signal parameter via rotational invariance technique (ESPRIT)-like approach to estimate directions of arrival (DOAs) for both far-field and near-field sources. In the second stage, based on the estimated DOAs, simple one-dimensional MUSIC spectrum is exploited to distinguish far-field and near-field sources and estimate the ranges of near-field sources. The proposed algorithm can avoid multidimensional search and parameter pairing. Simulation results demonstrate the good performance for localizing far-field sources, or near-field ones, or mixed field sources.

  15. A Flexible Ultrasound Transducer Array with Micro-Machined Bulk PZT

    PubMed Central

    Wang, Zhe; Xue, Qing-Tang; Chen, Yuan-Quan; Shu, Yi; Tian, He; Yang, Yi; Xie, Dan; Luo, Jian-Wen; Ren, Tian-Ling

    2015-01-01

    This paper proposes a novel flexible piezoelectric micro-machined ultrasound transducer, which is based on PZT and a polyimide substrate. The transducer is made on the polyimide substrate and packaged with medical polydimethylsiloxane. Instead of etching the PZT ceramic, this paper proposes a method of putting diced PZT blocks into holes on the polyimide which are pre-etched. The device works in d31 mode and the electromechanical coupling factor is 22.25%. Its flexibility, good conformal contacting with skin surfaces and proper resonant frequency make the device suitable for heart imaging. The flexible packaging ultrasound transducer also has a good waterproof performance after hundreds of ultrasonic electric tests in water. It is a promising ultrasound transducer and will be an effective supplementary ultrasound imaging method in the practical applications. PMID:25625905

  16. A flexible ultrasound transducer array with micro-machined bulk PZT.

    PubMed

    Wang, Zhe; Xue, Qing-Tang; Chen, Yuan-Quan; Shu, Yi; Tian, He; Yang, Yi; Xie, Dan; Luo, Jian-Wen; Ren, Tian-Ling

    2015-01-01

    This paper proposes a novel flexible piezoelectric micro-machined ultrasound transducer, which is based on PZT and a polyimide substrate. The transducer is made on the polyimide substrate and packaged with medical polydimethylsiloxane. Instead of etching the PZT ceramic, this paper proposes a method of putting diced PZT blocks into holes on the polyimide which are pre-etched. The device works in d31 mode and the electromechanical coupling factor is 22.25%. Its flexibility, good conformal contacting with skin surfaces and proper resonant frequency make the device suitable for heart imaging. The flexible packaging ultrasound transducer also has a good waterproof performance after hundreds of ultrasonic electric tests in water. It is a promising ultrasound transducer and will be an effective supplementary ultrasound imaging method in the practical applications. PMID:25625905

  17. Simulations and measurements of 3-D ultrasonic fields radiated by phased-array transducers using the westervelt equation.

    PubMed

    Doinikov, Alexander A; Novell, Anthony; Calmon, Pierre; Bouakaz, Ayache

    2014-09-01

    The purpose of this work is to validate, by comparing numerical and experimental results, the ability of the Westervelt equation to predict the behavior of ultrasound beams generated by phased-array transducers. To this end, the full Westervelt equation is solved numerically and the results obtained are compared with experimental measurements. The numerical implementation of the Westervelt equation is performed using the explicit finite-difference time-domain method on a three-dimensional Cartesian grid. The validation of the developed numerical code is first carried out by using experimental data obtained for two different focused circular transducers in the regimes of small-amplitude and finite-amplitude excitations. Then, the comparison of simulated and measured ultrasonic fields is extended to the case of a modified 32-element array transducer. It is shown that the developed code is capable of correctly predicting the behavior of the main lobe and the grating lobes in the cases of zero and nonzero steering angles for both the fundamental and the second-harmonic components.

  18. Acoustic power measurement of high-intensity focused ultrasound transducer using a pressure sensor.

    PubMed

    Zhou, Yufeng

    2015-03-01

    The acoustic power of high-intensity focused ultrasound (HIFU) is an important parameter that should be measured prior to each treatment to guarantee effective and safe outcomes. A new calibration technique was developed that involves estimating the pressure distribution, calculating the acoustic power using an underwater pressure blast sensor, and compensating the contribution of harmonics to the acoustic power. The output of a clinical extracorporeal HIFU system (center frequency of ~1 MHz, p+ = 2.5-57.2 MPa, p(-) = -1.8 to -13.9 MPa, I(SPPA) = 513-22,940 W/cm(2), -6 dB size of 1.6 × 10 mm: lateral × axial) was measured using this approach and then compared with that obtained using a radiation force balance. Similarities were found between each method at acoustic power ranging from 18.2 W to 912 W with an electrical-to-acoustic conversion efficiency of ~42%. The proposed method has advantages of low weight, smaller size, high sensitivity, quick response, high signal-to-noise ratio (especially at low power output), robust performance, and easy operation of HIFU exposimetry measurement.

  19. Acoustic power measurement of high-intensity focused ultrasound transducer using a pressure sensor.

    PubMed

    Zhou, Yufeng

    2015-03-01

    The acoustic power of high-intensity focused ultrasound (HIFU) is an important parameter that should be measured prior to each treatment to guarantee effective and safe outcomes. A new calibration technique was developed that involves estimating the pressure distribution, calculating the acoustic power using an underwater pressure blast sensor, and compensating the contribution of harmonics to the acoustic power. The output of a clinical extracorporeal HIFU system (center frequency of ~1 MHz, p+ = 2.5-57.2 MPa, p(-) = -1.8 to -13.9 MPa, I(SPPA) = 513-22,940 W/cm(2), -6 dB size of 1.6 × 10 mm: lateral × axial) was measured using this approach and then compared with that obtained using a radiation force balance. Similarities were found between each method at acoustic power ranging from 18.2 W to 912 W with an electrical-to-acoustic conversion efficiency of ~42%. The proposed method has advantages of low weight, smaller size, high sensitivity, quick response, high signal-to-noise ratio (especially at low power output), robust performance, and easy operation of HIFU exposimetry measurement. PMID:25659300

  20. Application of pulse compression signal processing techniques to electromagnetic acoustic transducers for noncontact thickness measurements and imaging

    SciTech Connect

    Ho, K.S.; Gan, T.H.; Billson, D.R.; Hutchins, D.A.

    2005-05-15

    A pair of noncontact Electromagnetic Acoustic Transducers (EMATs) has been used for thickness measurements and imaging of metallic plates. This was performed using wide bandwidth EMATs and pulse-compression signal processing techniques, using chirp excitation. This gives a greatly improved signal-to-noise ratio for air-coupled experiments, increasing the speed of data acquisition. A numerical simulation of the technique has confirmed the performance. Experimental results indicate that it is possible to perform noncontact ultrasonic imaging and thickness gauging in a wide range of metal plates. An accuracy of up to 99% has been obtained for aluminum, brass, and copper samples. The resolution of the image obtained using the pulse compression approach was also improved compared to a transient pulse signal from conventional pulser(receiver). It is thus suggested that the combination of EMATs and pulse compression can lead to a wide range of online applications where fast time acquisition is required.

  1. Real-time observation of coherent acoustic phonons generated by an acoustically mismatched optoacoustic transducer using x-ray diffraction

    SciTech Connect

    Persson, A. I. H.; Andreasson, B. P.; Enquist, H.; Jurgilaitis, A.; Larsson, J.

    2015-11-14

    The spectrum of laser-generated acoustic phonons in indium antimonide coated with a thin nickel film has been studied using time-resolved x-ray diffraction. Strain pulses that can be considered to be built up from coherent phonons were generated in the nickel film by absorption of short laser pulses. Acoustic reflections at the Ni–InSb interface leads to interference that strongly modifies the resulting phonon spectrum. The study was performed with high momentum transfer resolution together with high time resolution. This was achieved by using a third-generation synchrotron radiation source that provided a high-brightness beam and an ultrafast x-ray streak camera to obtain a temporal resolution of 10 ps. We also carried out simulations, using commercial finite element software packages and on-line dynamic diffraction tools. Using these tools, it is possible to calculate the time-resolved x-ray reflectivity from these complicated strain shapes. The acoustic pulses have a peak strain amplitude close to 1%, and we investigated the possibility to use this device as an x-ray switch. At a bright source optimized for hard x-ray generation, the low reflectivity may be an acceptable trade-off to obtain a pulse duration that is more than an order of magnitude shorter.

  2. Angular spectrum method and ray algorithm for the acoustic field of a focusing transducer in an anisotropic solid.

    PubMed

    Every, Arthur G; Amulele, George M

    2002-03-01

    The angular spectrum method is applied to calculating the acoustic field of a liquid-coupled focusing transducer in an anisotropic slab-shaped solid with surfaces normal to the axis of the transducer. The stationary phase approximation (SPA) is used to determine the dominant contributions to this field and calculate the echo signals produced by waves that have been reflected off the rear surface of the solid. The dominant features of this field and of the echoes are reproduced well by a hybrid ray method devised to simulate the finite point-spread function of the lens. Both approaches in the paraxial approximation yield a split focus for each wave polarization branch for a general direction of the surface normal. Echo arrival times and amplitudes calculated by the two methods are in good agreement. The hybrid ray method is shown to be particularly suited to handling multiple stationary phase points within the angular spectrum of the incident field and stationary phase points not associated with the normally incident ray, and should be useful for dealing with scattering from cracks and other defects. Pulse echo calculations for different crystallographic directions in a nickel-based superalloy are shown to be in good agreement with measurements carried out on single crystal specimens of the alloy. PMID:12322879

  3. Angular spectrum method and ray algorithm for the acoustic field of a focusing transducer in an anisotropic solid.

    PubMed

    Every, Arthur G; Amulele, George M

    2002-03-01

    The angular spectrum method is applied to calculating the acoustic field of a liquid-coupled focusing transducer in an anisotropic slab-shaped solid with surfaces normal to the axis of the transducer. The stationary phase approximation (SPA) is used to determine the dominant contributions to this field and calculate the echo signals produced by waves that have been reflected off the rear surface of the solid. The dominant features of this field and of the echoes are reproduced well by a hybrid ray method devised to simulate the finite point-spread function of the lens. Both approaches in the paraxial approximation yield a split focus for each wave polarization branch for a general direction of the surface normal. Echo arrival times and amplitudes calculated by the two methods are in good agreement. The hybrid ray method is shown to be particularly suited to handling multiple stationary phase points within the angular spectrum of the incident field and stationary phase points not associated with the normally incident ray, and should be useful for dealing with scattering from cracks and other defects. Pulse echo calculations for different crystallographic directions in a nickel-based superalloy are shown to be in good agreement with measurements carried out on single crystal specimens of the alloy.

  4. Endoscopic ultrasound examination of the upper gastrointestinal tract using a curved-array transducer. A preliminary report.

    PubMed

    Vilmann, P; Khattar, S; Hancke, S

    1991-01-01

    Endoscopic ultrasound examination (EUS) of the upper gastrointestinal (GI) tract for the assessment of mural and extramural pathology has attracted growing international interest in recent years. Since February 1989, EUS has been performed on selected patients in our institution using a new Picker-Pentax fiber-optic ultrasound (US) gastroscope. The instrument consists of a forward-view fiber-optic gastroscope with a 5-MHz curved-array linear US transducer mounted directly behind the lens. The scanning plane lies in the long axis of the scope. Based on in vitro US examinations and EUS of 118 patients over an 18-month period, our preliminary experience with the instrument is described. Using EUS, various lesions in the esophageal wall as well as in the gastric and duodenal walls can be visualized. Furthermore, organs and structures outside the GI tract can be seen, and lesions such as enlarged lymph nodes in the mediastinum and abdomen; solid and cystic masses in the liver, pancreas and retroperitoneum; arterial aneurysms; esophageal varices; and gall stones and calcifications can be demonstrated. The 5-MHz transducer does not provide very detailed information on the GI wall. The direction of the ultrasound scanning planes is difficult to define, as the transducer cannot be seen through the optic lens. The method demands great expertise in endoscopy and ultrasound. Indications for EUS have not been definitively established. Evaluation of the diagnostic accuracy of this technique requires further controlled studies. We believe that EUS using a curved-array linear transducer will provide significant diagnostic information of clinical relevance to gastroenterology. PMID:1948619

  5. Experiments with Ultrasonic Transducers.

    ERIC Educational Resources Information Center

    Greenslade, Thomas R., Jr.

    1994-01-01

    Discusses the use of 40 kHz ultrasonic transducers to study wave phenomena. Determines that the resulting wavelength of 9 mm allows acoustic experiments to be performed on a tabletop. Includes transducer characteristics and activities on speed of sound, reflection, double- and single-slit diffraction, standing waves, acoustical zone plate, and…

  6. Circuit-field coupled finite element analysis method for an electromagnetic acoustic transducer under pulsed voltage excitation

    NASA Astrophysics Data System (ADS)

    Hao, Kuan-Sheng; Huang, Song-Ling; Zhao, Wei; Wang, Shen

    2011-06-01

    This paper presents an analytical method for electromagnetic acoustic transducers (EMATs) under voltage excitation and considers the non-uniform distribution of the biased magnetic field. A complete model of EMATs including the non-uniform biased magnetic field, a pulsed eddy current field and the acoustic field is built up. The pulsed voltage excitation is transformed to the frequency domain by fast Fourier transformation (FFT). In terms of the time harmonic field equations of the EMAT system, the impedances of the coils under different frequencies are calculated according to the circuit-field coupling method and Poynting's theorem. Then the currents under different frequencies are calculated according to Ohm's law and the pulsed current excitation is obtained by inverse fast Fourier transformation (IFFT). Lastly, the sequentially coupled finite element method (FEM) is used to calculate the Lorentz force in the EMATs under the current excitation. An actual EMAT with a two-layer two-bundle printed circuit board (PCB) coil, a rectangular permanent magnet and an aluminium specimen is analysed. The coil impedances and the pulsed current are calculated and compared with the experimental results. Their agreement verified the validity of the proposed method. Furthermore, the influences of lift-off distances and the non-uniform static magnetic field on the Lorentz force under pulsed voltage excitation are studied.

  7. Temperature and trapping characterization of an acoustic trap with miniaturized integrated transducers--towards in-trap temperature regulation.

    PubMed

    Johansson, Linda; Evander, Mikael; Lilliehorn, Tobias; Almqvist, Monica; Nilsson, Johan; Laurell, Thomas; Johansson, Stefan

    2013-07-01

    An acoustic trap with miniaturized integrated transducers (MITs) for applications in non-contact trapping of cells or particles in a microfluidic channel was characterized by measuring the temperature increase and trapping strength. The fluid temperature was measured by the fluorescent response of Rhodamine B in the microchannel. The trapping strength was measured by the area of a trapped particle cluster counter-balanced by the hydrodynamic force. One of the main objectives was to obtain quantitative values of the temperature in the fluidic channel to ensure safe handling of cells and proteins. Another objective was to evaluate the trapping-to-temperature efficiency for the trap as a function of drive frequency. Thirdly, trapping-to-temperature efficiency data enables identifying frequencies and voltage values to use for in-trap temperature regulation. It is envisioned that operation with only in-trap temperature regulation enables the realization of small, simple and fast temperature-controlled trap systems. The significance of potential gradients at the trap edges due to the finite size of the miniaturized transducers for the operation was emphasized and expressed analytically. The influence of the acoustic near field was evaluated in FEM-simulation and compared with a more ideal 1D standing wave. The working principle of the trap was examined by comparing measurements of impedance, temperature increase and trapping strength with impedance transfer calculations of fluid-reflector resonances and frequencies of high reflectance at the fluid-reflector boundary. The temperature increase was found to be moderate, 7°C for a high trapping strength, at a fluid flow of 0.5mms(-1) for the optimal driving frequency. A fast temperature response with a fall time of 8s and a rise time of 11s was observed. The results emphasize the importance of selecting the proper drive frequency for long term handling of cells, as opposed to the more pragmatic way of selecting the

  8. Thin-film sparse boundary array design for passive acoustic mapping during ultrasound therapy.

    PubMed

    Coviello, Christian M; Kozick, Richard J; Hurrell, Andrew; Smith, Penny Probert; Coussios, Constantin-C

    2012-10-01

    A new 2-D hydrophone array for ultrasound therapy monitoring is presented, along with a novel algorithm for passive acoustic mapping using a sparse weighted aperture. The array is constructed using existing polyvinylidene fluoride (PVDF) ultrasound sensor technology, and is utilized for its broadband characteristics and its high receive sensitivity. For most 2-D arrays, high-resolution imagery is desired, which requires a large aperture at the cost of a large number of elements. The proposed array's geometry is sparse, with elements only on the boundary of the rectangular aperture. The missing information from the interior is filled in using linear imaging techniques. After receiving acoustic emissions during ultrasound therapy, this algorithm applies an apodization to the sparse aperture to limit side lobes and then reconstructs acoustic activity with high spatiotemporal resolution. Experiments show verification of the theoretical point spread function, and cavitation maps in agar phantoms correspond closely to predicted areas, showing the validity of the array and methodology. PMID:23143581

  9. Extension of the crosstalk cancellation method in ultrasonic transducer arrays from the harmonic regime to the transient one.

    PubMed

    Bybi, A; Grondel, S; Assaad, J; Hladky-Hennion, A-C

    2014-02-01

    This paper describes a procedure to extend the crosstalk correction method presented in a previous paper [A. Bybi, S. Grondel, J. Assaad, A.-C. Hladky-Hennion, M. Rguiti, Reducing crosstalk in array structures by controlling the excitation voltage of individual elements: a feasibility study, Ultrasonics, 53 (6) (2013) 1135-1140] from the harmonic regime to the transient one. For this purpose a part of an ultrasonic transducer array radiating in water is modeled around the frequency 0.5 MHz using the finite element method. The study is carried out at low frequency in order to respect the same operating conditions than the previous paper. This choice facilitated the fabrication of the transducer arrays and the comparison of the numerical results with the experimental ones. The modeled array is composed of seventeen elements with the central element excited, while the others are grounded. The matching layers and the backing are not taken into account which limits the crosstalk only to the piezoelectric elements and fluid. This consideration reduces the structure density mesh and results in faster computation time (about 25 min for each configuration using a computer with a processor Intel Core i5-3210M, frequency 2.5 GHz and having 4 Go memory (RAM)). The novelty of this research work is to prove the efficiency of the crosstalk correction method in large frequency band as it is the case in medical imaging. The numerical results show the validity of the approach and demonstrate that crosstalk can be reduced by at least 13 dB in terms of displacement. Consequently, the directivity pattern of the individual element can be improved. PMID:24064509

  10. Use of Electromagnetic Acoustic Transducers (emats) for Cement Bond Logging of Gas Storage Wells

    NASA Astrophysics Data System (ADS)

    Bolshakov, A. O.; Domangue, E. J.; Barolak, J. G.; Patterson, D. J.

    2008-02-01

    According to the Department of Energy (DOE), there are approximately 110 operators maintaining more than 17,000 gas storage wells in over 415 underground storage facilities across the USA. In virtually every application, steel casing, cemented into place, serves to isolate the well from the underground formations. The process of cementing wellbore casing provides two major benefits: 1) cement prevents gas migration between the casing and formation; 2) cement transfers stress from the casing to the formation, increasing the effective strength and working pressure of the casing. Current cement evaluation techniques use an acoustic wave generated and received by a logging tool within the wellbore to detect cement placed outside the casing. These techniques rely on fluid in the casing to provide acoustic coupling between the logging tool and the casing and therefore are unable to operate in gas-filled boreholes. This paper details efforts to confirm the validity and applicability of the use of EMATs for evaluating cement in gas-filled boreholes. The methods and techniques proposed for the cement bond logging using EMATs are confirmed and validated based on the results obtained from the numerical modeling and experiments with physical cement models. Partial funding for this investigation was provided by the DOE and Gas Storage Technology Consortium.

  11. A hardware model of the auditory periphery to transduce acoustic signals into neural activity

    PubMed Central

    Tateno, Takashi; Nishikawa, Jun; Tsuchioka, Nobuyoshi; Shintaku, Hirofumi; Kawano, Satoyuki

    2013-01-01

    To improve the performance of cochlear implants, we have integrated a microdevice into a model of the auditory periphery with the goal of creating a microprocessor. We constructed an artificial peripheral auditory system using a hybrid model in which polyvinylidene difluoride was used as a piezoelectric sensor to convert mechanical stimuli into electric signals. To produce frequency selectivity, the slit on a stainless steel base plate was designed such that the local resonance frequency of the membrane over the slit reflected the transfer function. In the acoustic sensor, electric signals were generated based on the piezoelectric effect from local stress in the membrane. The electrodes on the resonating plate produced relatively large electric output signals. The signals were fed into a computer model that mimicked some functions of inner hair cells, inner hair cell–auditory nerve synapses, and auditory nerve fibers. In general, the responses of the model to pure-tone burst and complex stimuli accurately represented the discharge rates of high-spontaneous-rate auditory nerve fibers across a range of frequencies greater than 1 kHz and middle to high sound pressure levels. Thus, the model provides a tool to understand information processing in the peripheral auditory system and a basic design for connecting artificial acoustic sensors to the peripheral auditory nervous system. Finally, we discuss the need for stimulus control with an appropriate model of the auditory periphery based on auditory brainstem responses that were electrically evoked by different temporal pulse patterns with the same pulse number. PMID:24324432

  12. A hardware model of the auditory periphery to transduce acoustic signals into neural activity.

    PubMed

    Tateno, Takashi; Nishikawa, Jun; Tsuchioka, Nobuyoshi; Shintaku, Hirofumi; Kawano, Satoyuki

    2013-01-01

    To improve the performance of cochlear implants, we have integrated a microdevice into a model of the auditory periphery with the goal of creating a microprocessor. We constructed an artificial peripheral auditory system using a hybrid model in which polyvinylidene difluoride was used as a piezoelectric sensor to convert mechanical stimuli into electric signals. To produce frequency selectivity, the slit on a stainless steel base plate was designed such that the local resonance frequency of the membrane over the slit reflected the transfer function. In the acoustic sensor, electric signals were generated based on the piezoelectric effect from local stress in the membrane. The electrodes on the resonating plate produced relatively large electric output signals. The signals were fed into a computer model that mimicked some functions of inner hair cells, inner hair cell-auditory nerve synapses, and auditory nerve fibers. In general, the responses of the model to pure-tone burst and complex stimuli accurately represented the discharge rates of high-spontaneous-rate auditory nerve fibers across a range of frequencies greater than 1 kHz and middle to high sound pressure levels. Thus, the model provides a tool to understand information processing in the peripheral auditory system and a basic design for connecting artificial acoustic sensors to the peripheral auditory nervous system. Finally, we discuss the need for stimulus control with an appropriate model of the auditory periphery based on auditory brainstem responses that were electrically evoked by different temporal pulse patterns with the same pulse number. PMID:24324432

  13. Quantitative analysis of temperature dependent acoustic trapping characteristics by using concentric annular type dual element ultrasonic transducer.

    PubMed

    Chung, In-Young; Lee, Jungwoo

    2015-02-01

    This paper presents the temperature dependence of lateral acoustic trapping capability by probing the speed of sound in individual lipid droplets at a given temperature of water and measuring its corresponding displacement, a value for quantitatively evaluating a spring-like behavior of the acoustic trap with certain strength. A 20/40 MHz dual element LiNbO3 ultrasonic transducer is fabricated to simultaneously perform both transverse trapping and sound speed measurement for each droplet over a discrete temperature range from 20°C to 30°C. Time of flight method is employed for pulse tracking that determines the arrival time of an echo reflected back from either a trapped droplet or a mylar film. The estimated speeds of sound in water and droplets are 1484.8 m/s and 1431.6 m/s at 20°C, while 1506.0 m/s and 1400.6 m/s at 30°C, respectively. As the temperature rises, the sound speed in droplets decreases at an average rate of 3.1 m/s/°C, and the speed in water increases at 2.1 m/s/°C. The average displacement varies from 150.0 μm to 179.0 μm with an increasing rate of 2.9 μm/°C, and its standard deviation is obtained between 1.0 μm and 2.0 μm over the same temperature range. Reduced sound speed as a function of rising temperature results in increased displacement, indicating that the trapping strength is adjustable by regulating ambient temperature in water as well as by changing transducer excitation parameters. Therefore, the results suggest that the temperature dependence of this trapping technique can be exploited for developing a remote manipulation tool of micron-sized particles in a thermally fluctuating environment. It is also shown that any deviated trapping strength caused by thermal disturbance near the trap can be restored to its desired level by compensating either temperature difference or trapping system condition.

  14. A Deconvolution Approach for the Mapping of Acoustic Sources (DAMAS) Determined from Phased Microphone Arrays

    NASA Technical Reports Server (NTRS)

    Brooks, Thomas F.; Humphreys, William M.

    2006-01-01

    Current processing of acoustic array data is burdened with considerable uncertainty. This study reports an original methodology that serves to demystify array results, reduce misinterpretation, and accurately quantify position and strength of acoustic sources. Traditional array results represent noise sources that are convolved with array beamform response functions, which depend on array geometry, size (with respect to source position and distributions), and frequency. The Deconvolution Approach for the Mapping of Acoustic Sources (DAMAS) method removes beamforming characteristics from output presentations. A unique linear system of equations accounts for reciprocal influence at different locations over the array survey region. It makes no assumption beyond the traditional processing assumption of statistically independent noise sources. The full rank equations are solved with a new robust iterative method. DAMAS is quantitatively validated using archival data from a variety of prior high-lift airframe component noise studies, including flap edge/cove, trailing edge, leading edge, slat, and calibration sources. Presentations are explicit and straightforward, as the noise radiated from a region of interest is determined by simply summing the mean-squared values over that region. DAMAS can fully replace existing array processing and presentations methodology in most applications. It appears to dramatically increase the value of arrays to the field of experimental acoustics.

  15. A Deconvolution Approach for the Mapping of Acoustic Sources (DAMAS) Determined from Phased Microphone Arrays

    NASA Technical Reports Server (NTRS)

    Brooks, Thomas F.; Humphreys, William M., Jr.

    2004-01-01

    Current processing of acoustic array data is burdened with considerable uncertainty. This study reports an original methodology that serves to demystify array results, reduce misinterpretation, and accurately quantify position and strength of acoustic sources. Traditional array results represent noise sources that are convolved with array beamform response functions, which depend on array geometry, size (with respect to source position and distributions), and frequency. The Deconvolution Approach for the Mapping of Acoustic Sources (DAMAS) method removes beamforming characteristics from output presentations. A unique linear system of equations accounts for reciprocal influence at different locations over the array survey region. It makes no assumption beyond the traditional processing assumption of statistically independent noise sources. The full rank equations are solved with a new robust iterative method. DAMAS is quantitatively validated using archival data from a variety of prior high-lift airframe component noise studies, including flap edge/cove, trailing edge, leading edge, slat, and calibration sources. Presentations are explicit and straightforward, as the noise radiated from a region of interest is determined by simply summing the mean-squared values over that region. DAMAS can fully replace existing array processing and presentations methodology in most applications. It appears to dramatically increase the value of arrays to the field of experimental acoustics.

  16. Near field acoustic holography based on the equivalent source method and pressure-velocity transducers.

    PubMed

    Zhang, Yong-Bin; Jacobsen, Finn; Bi, Chuan-Xing; Chen, Xin-Zhao

    2009-09-01

    The advantage of using the normal component of the particle velocity rather than the sound pressure in the hologram plane as the input of conventional spatial Fourier transform based near field acoustic holography (NAH) and also as the input of the statistically optimized variant of NAH has recently been demonstrated. This paper examines whether there might be a similar advantage in using the particle velocity as the input of NAH based on the equivalent source method (ESM). Error sensitivity considerations indicate that ESM-based NAH is less sensitive to measurement errors when it is based on particle velocity input data than when it is based on measurements of sound pressure data, and this is confirmed by a simulation study and by experimental results. A method that combines pressure- and particle velocity-based reconstructions in order to distinguish between contributions to the sound field generated by sources on the two sides of the hologram plane is also examined.

  17. Gating of Acoustic Transducer Channels Is Shaped by Biomechanical Filter Processes.

    PubMed

    Hummel, Jennifer; Schöneich, Stefan; Kössl, Manfred; Scherberich, Jan; Hedwig, Berthold; Prinz, Simone; Nowotny, Manuela

    2016-02-24

    Mechanoelectrical transduction of acoustic signals is the fundamental process for hearing in all ears across the animal kingdom. Here, we performed in vivo laser-vibrometric and electrophysiological measurements at the transduction site in an insect ear (Mecopoda elongata) to relate the biomechanical tonotopy along the hearing organ to the frequency tuning of the corresponding sensory cells. Our mechanical and electrophysiological map revealed a biomechanical filter process that considerably sharpens the neuronal response. We demonstrate that the channel gating, which acts on chordotonal stretch receptor neurons, is based on a mechanical directionality of the sound-induced motion. Further, anatomical studies of the transduction site support our finding of a stimulus-relevant tilt. In conclusion, we were able to show, in an insect ear, that directionality of channel gating considerably sharpens the neuronal frequency selectivity at the peripheral level and have identified a mechanism that enhances frequency discrimination in tonotopically organized ears.

  18. The design, characterization, and comparison of MEMS comb-drive acoustic emission transducers with the principles of area-change and gap-change

    NASA Astrophysics Data System (ADS)

    Kabir, Minoo; Saboonchi, Hossain; Ozevin, Didem

    2015-04-01

    Comb-drive transducers are made of interdigitized fingers formed by the stationary part known as stator and the moving part known as rotor, and based on the transduction principle of capacitance change. They can be designed as area-change or gap-change mechanism to convert the mechanical signal at in-plane direction into electrical output. The comb-drive transducers can be utilized to differentiate the wave motion in orthogonal directions when they are utilized with the outof- plane transducers. However, their sensitivity is weak to detect the wave motion released by newly formed damage surfaces. In this study, Micro-Electro-Mechanical System (MEMS) comb-drive Acoustic Emission (AE) transducer designs with two different mechanisms are designed, characterized and compared for sensing high frequency wave propagation. The MEMS AE transducers are manufactured using MetalMUMPs (Metal Multi-User MEMS Processes), which use electroplating technique for highly elevated microstructure geometries. Each type of the transducers is numerically modeled using COMSOL Multiphysics program in order to determine the sensitivity based on the applied load. The transducers are experimentally characterized and compared to the numerical models. The experiments include laser excitation to control the direction of the wave generation, and actual crack growth monitoring of aluminum 7075 specimens loaded under fatigue. Behavior and responses of the transducers are compared based on the parameters such as waveform signature, peak frequency, damping, sensitivity, and signal to noise ratio. The comparisons between the measured parameters are scaled according to the respective capacitance of each sensor in order to determine the most sensitive design geometry.

  19. Direct measurement of solids: High temperature sensing Final report Experimental development and testing of high temperature pulsed EMATs (electromagnetic acoustic transducer):

    SciTech Connect

    Boyd, D.M.; Spanner, G.E.; Sperline, P.D.

    1988-04-01

    A pulsed laser/pulsed EMAT (electromagnetic acoustic transducer) receiver system has been demonstrated for measuring the time of flight of acoustic signals in hot steel samples. Attenuation and signal-to-noise ratio are important parameters to be monitored. A continuous contact EMAT application was not achieved; thermal analysis found that contact times of 5 seconds with cooling times of 45 seconds are required at 1300/degree/C. The equipment requires field hardening and improved packaging before system reliability can be assessed. 22 refs., 35 figs. (DLC)

  20. Performance of an underwater acoustic volume array using time-reversal focusing.

    PubMed

    Root, Joseph A; Rogers, Peter H

    2002-11-01

    Time reversal permits acoustic focusing and beam forming in inhomogeneous and/or high-scattering environments. A volumetric array geometry can suppress back lobes and can fit a large, powerful array of elements into small spaces, like the free-water spaces on submarines. This research investigates applying the time-reversal method to an underwater acoustic volume array. The experiments evaluate the focusing performance of a 27-element volume array when different scattering structures are present within the volume of the array. The array is arranged in a 3x3x3 cubic matrix configuration with 18.75-cm vertical and horizontal element spacing. The system utilizes second-derivative Gaussian pulses to focus on a point 30 cm from the array. Results include a comparison between time-reversal focusing and standard focusing, an evaluation of the volume array's ability to suppress back lobes, and an analysis of how different scattering environments affect focal region size. Potential underwater applications for a volume array using time reversal include acoustic imaging, naval mine hunting, sonar, and underwater communications.

  1. Improvement of Power Efficiency for Underwater Acoustic Communication Using Orthogonal Signal Division Multiplexing over Multiple Transducers

    NASA Astrophysics Data System (ADS)

    Ebihara, Tadashi

    2013-07-01

    In underwater acoustic (UWA) communication, power efficiency is one of the important characteristics. This paper is about multistream transmission using orthogonal signal division multiplexing (OSDM) as a technique to increase power efficiency. In this work, the performance of multistream transmission using OSDM is evaluated both experimentally in a test tank and by numerical simulation. Through this study, it is confirmed that the multistream transmission scheme is effective in enhancing the power efficiency compared with the single-stream transmission using higher order modulation. Moreover, the performance of multistream transmission using OSDM is compared with the existing scheme, multistream transmission using orthogonal frequency division multiplexing (OFDM). The obtained results suggest that multistream transmission using OSDM is attractive because it can achieve the same bit-error rate (BER) and the same data rate with less power of the signal, compared with the reference. Although the calculation cost of OSDM in the receiver remains as an issue, multistream transmission using OSDM may contribute to high-speed UWA communication because of its excellent power efficiency.

  2. Tripling the detection view of high-frequency linear-array-based photoacoustic computed tomography by using two planar acoustic reflectors

    PubMed Central

    Li, Guo; Xia, Jun; Wang, Kun; Maslov, Konstantin; Anastasio, Mark A.

    2015-01-01

    Background Linear-array-based photoacoustic computed tomography (PACT) suffers from a limited view. Circular scanning does increase the detection view angle but is time-consuming. Therefore, it is desirable to increase the detection view angle of linear-array-based PACT without sacrificing imaging speed. Methods Two planar acoustic reflectors placed at 120 degrees to each other were added to a linear-array-based PACT system. Each reflector redirects originally undetectable photoacoustic waves back to the transducer array elements, and together they triple the original detection view angle of the PACT system. Results Adding two reflectors increased the detection view angle from 80 to 240 degrees. As a comparison, a single-reflector PACT has a detection view angle of only 160 degrees. A leaf skeleton phantom with a rich vascular network was imaged with the double-reflector PACT, and most of its features were recovered. Conclusions The two acoustic reflectors triple the detection view angle of a linear-array-based PACT without compromising the original imaging speed. This nearly full-view detection capability produces higher-quality images than single-reflector PACT or conventional PACT without reflectors. PMID:25694954

  3. A robust roughness quantification technique using a standard imaging array transducer

    NASA Astrophysics Data System (ADS)

    Samuel, Stanley; Adler, Ronald; Meyer, Charles

    2002-05-01

    Our goal is to measure cartilage roughness using intra-articular ultrasound imaging, thus providing a useful diagnostic tool for the early detection of osteoarthritis. Measuring the effectiveness of possible chondroprotective pharmacological or mechanical interventions depends on the availability of such a device. We have developed an empirical model of roughness using sandpaper for angles ranging from 20 degrees to 60 degrees at distances ranging from 25 mm to 80 mm. Roughness quantification is achieved using a scattering replacement normalization technique. An ultrasound imaging system employing a broadband 7 MHz multi-element transducer was used for insonifying the flat sandpaper surface. Dynamic focusing was performed at all distances and angles. The broadband transducer facilitates the selection of select bandwidths during analysis, which is beneficial for studying surfaces of varying roughness scales. Sandpaper of 150-, 400-, and 600-grit were examined for this study. The normalized average backscattered power (normalized with 150-grit) for 7-8 MHz frequency band provides well-behaved roughness characteristics. The students t test showed that the backscattering results for the 150- and 400-grit are significantly different with 0.025

  4. An intelligent sensor array distributed system for vibration analysis and acoustic noise characterization of a linear switched reluctance actuator.

    PubMed

    Salvado, José; Espírito-Santo, António; Calado, Maria

    2012-01-01

    This paper proposes a distributed system for analysis and monitoring (DSAM) of vibrations and acoustic noise, which consists of an array of intelligent modules, sensor modules, communication bus and a host PC acting as data center. The main advantages of the DSAM are its modularity, scalability, and flexibility for use of different type of sensors/transducers, with analog or digital outputs, and for signals of different nature. Its final cost is also significantly lower than other available commercial solutions. The system is reconfigurable, can operate either with synchronous or asynchronous modes, with programmable sampling frequencies, 8-bit or 12-bit resolution and a memory buffer of 15 kbyte. It allows real-time data-acquisition for signals of different nature, in applications that require a large number of sensors, thus it is suited for monitoring of vibrations in Linear Switched Reluctance Actuators (LSRAs). The acquired data allows the full characterization of the LSRA in terms of its response to vibrations of structural origins, and the vibrations and acoustic noise emitted under normal operation. The DSAM can also be used for electrical machine condition monitoring, machine fault diagnosis, structural characterization and monitoring, among other applications.

  5. An Intelligent Sensor Array Distributed System for Vibration Analysis and Acoustic Noise Characterization of a Linear Switched Reluctance Actuator

    PubMed Central

    Salvado, José; Espírito-Santo, António; Calado, Maria

    2012-01-01

    This paper proposes a distributed system for analysis and monitoring (DSAM) of vibrations and acoustic noise, which consists of an array of intelligent modules, sensor modules, communication bus and a host PC acting as data center. The main advantages of the DSAM are its modularity, scalability, and flexibility for use of different type of sensors/transducers, with analog or digital outputs, and for signals of different nature. Its final cost is also significantly lower than other available commercial solutions. The system is reconfigurable, can operate either with synchronous or asynchronous modes, with programmable sampling frequencies, 8-bit or 12-bit resolution and a memory buffer of 15 kbyte. It allows real-time data-acquisition for signals of different nature, in applications that require a large number of sensors, thus it is suited for monitoring of vibrations in Linear Switched Reluctance Actuators (LSRAs). The acquired data allows the full characterization of the LSRA in terms of its response to vibrations of structural origins, and the vibrations and acoustic noise emitted under normal operation. The DSAM can also be used for electrical machine condition monitoring, machine fault diagnosis, structural characterization and monitoring, among other applications. PMID:22969364

  6. Fast contactless vibrating structure characterization using real time field programmable gate array-based digital signal processing: demonstrations with a passive wireless acoustic delay line probe and vision.

    PubMed

    Goavec-Mérou, G; Chrétien, N; Friedt, J-M; Sandoz, P; Martin, G; Lenczner, M; Ballandras, S

    2014-01-01

    Vibrating mechanical structure characterization is demonstrated using contactless techniques best suited for mobile and rotating equipments. Fast measurement rates are achieved using Field Programmable Gate Array (FPGA) devices as real-time digital signal processors. Two kinds of algorithms are implemented on FPGA and experimentally validated in the case of the vibrating tuning fork. A first application concerns in-plane displacement detection by vision with sampling rates above 10 kHz, thus reaching frequency ranges above the audio range. A second demonstration concerns pulsed-RADAR cooperative target phase detection and is applied to radiofrequency acoustic transducers used as passive wireless strain gauges. In this case, the 250 ksamples/s refresh rate achieved is only limited by the acoustic sensor design but not by the detection bandwidth. These realizations illustrate the efficiency, interest, and potentialities of FPGA-based real-time digital signal processing for the contactless interrogation of passive embedded probes with high refresh rates. PMID:24517814

  7. Fast contactless vibrating structure characterization using real time field programmable gate array-based digital signal processing: Demonstrations with a passive wireless acoustic delay line probe and vision

    NASA Astrophysics Data System (ADS)

    Goavec-Mérou, G.; Chrétien, N.; Friedt, J.-M.; Sandoz, P.; Martin, G.; Lenczner, M.; Ballandras, S.

    2014-01-01

    Vibrating mechanical structure characterization is demonstrated using contactless techniques best suited for mobile and rotating equipments. Fast measurement rates are achieved using Field Programmable Gate Array (FPGA) devices as real-time digital signal processors. Two kinds of algorithms are implemented on FPGA and experimentally validated in the case of the vibrating tuning fork. A first application concerns in-plane displacement detection by vision with sampling rates above 10 kHz, thus reaching frequency ranges above the audio range. A second demonstration concerns pulsed-RADAR cooperative target phase detection and is applied to radiofrequency acoustic transducers used as passive wireless strain gauges. In this case, the 250 ksamples/s refresh rate achieved is only limited by the acoustic sensor design but not by the detection bandwidth. These realizations illustrate the efficiency, interest, and potentialities of FPGA-based real-time digital signal processing for the contactless interrogation of passive embedded probes with high refresh rates.

  8. Tracking sperm whale (Physeter macrocephalus) dive profiles using a towed passive acoustic array

    NASA Astrophysics Data System (ADS)

    Thode, Aaron

    2004-07-01

    A passive acoustic method is presented for tracking sperm whale dive profiles, using two or three hydrophones deployed as either a vertical or large-aperture towed array. The relative arrival times between the direct and surface-reflected acoustic paths are used to obtain the ranges and depths of animals with respect to the array, provided that the hydrophone depths are independently measured. Besides reducing the number of hydrophones required, exploiting surface reflections simplifies automation of the data processing. Experimental results are shown from 2002 and 2003 cruises in the Gulf of Mexico for two different towed array deployments. The 2002 deployment consisted of two short-aperture towed arrays separated by 170 m, while the 2003 deployment placed an autonomous acoustic recorder in tandem with a short-aperture towed array, and used ship noise to time-align the acoustic data. The resulting dive profiles were independently checked using single-hydrophone localizations, whenever multipath reflections from the ocean bottom could be exploited to effectively create a large-aperture vertical array. This technique may have applications for basic research and for real-time mitigation for seismic airgun surveys.

  9. 21 CFR 892.1570 - Diagnostic ultrasonic transducer.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... that converts electrical signals into acoustic signals and acoustic signals into electrical signals and... include transmission media for acoustically coupling the transducer to the body surface, such as...

  10. 21 CFR 892.1570 - Diagnostic ultrasonic transducer.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... that converts electrical signals into acoustic signals and acoustic signals into electrical signals and... include transmission media for acoustically coupling the transducer to the body surface, such as...

  11. 21 CFR 892.1570 - Diagnostic ultrasonic transducer.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... that converts electrical signals into acoustic signals and acoustic signals into electrical signals and... include transmission media for acoustically coupling the transducer to the body surface, such as...

  12. Stability of Programmable Shunt Valve Settings with Simultaneous Use of the Optune Transducer Array: A Case Report.

    PubMed

    Chan, Andrew K; Birk, Harjus S; Winkler, Ethan A; Viner, Jennifer A; Taylor, Jennie W; McDermott, Michael W

    2016-07-07

    The Optune® transducer array (Novocure Ltd., Haifa, Israel) is an FDA-approved noninvasive regional therapy that aims to inhibit the growth of glioblastoma multiforme (GBM) cells via utilization of alternating electric fields. Some patients with GBM may develop hydrocephalus and benefit from subsequent shunt placement, but special attention must be paid to patients in whom programmable valves are utilized, given the potential effect of the magnetic fields on valve settings. We present the first case report illustrating the stability of programmable shunt valve settings in a neurosurgical patient undergoing therapy with the Optune device. In this study, shunt valve settings were stable over a period of five days despite Optune therapy. This is reassuring for patients with GBM who require simultaneous treatment with both the Optune device and a programmable shunt system.

  13. Reflection at a liquid-solid interface of a transient ultrasonic field radiated by a linear phased array transducer.

    PubMed

    Maghlaoui, Nadir; Belgroune, Djema; Ourak, Mohamed; Djelouah, Hakim

    2016-09-01

    In order to put in evidence the specular reflection and the non-specular reflection in the transient case, we have used a model for the study of the transient ultrasonic waves radiated by a linear phased array transducer in a liquid and reflected by a solid plane interface. This method is an extension of the angular spectrum method to the transient case where the reflection at the plane interface is taken into account by using the reflection coefficient for harmonic plane waves. The results obtained highlighted the different components of the ultrasonic field: the direct and edge waves as well as the longitudinal head waves or leaky Rayleigh waves. The transient representation of these waves have been carefully analyzed and discussed by the rays model. Instantaneous cartographies allowed a clear description of all the waves which appear at the liquid-solid interface. The obtained results have been compared to those obtained with a finite element method package.

  14. Stability of Programmable Shunt Valve Settings with Simultaneous Use of the Optune Transducer Array: A Case Report.

    PubMed

    Chan, Andrew K; Birk, Harjus S; Winkler, Ethan A; Viner, Jennifer A; Taylor, Jennie W; McDermott, Michael W

    2016-01-01

    The Optune® transducer array (Novocure Ltd., Haifa, Israel) is an FDA-approved noninvasive regional therapy that aims to inhibit the growth of glioblastoma multiforme (GBM) cells via utilization of alternating electric fields. Some patients with GBM may develop hydrocephalus and benefit from subsequent shunt placement, but special attention must be paid to patients in whom programmable valves are utilized, given the potential effect of the magnetic fields on valve settings. We present the first case report illustrating the stability of programmable shunt valve settings in a neurosurgical patient undergoing therapy with the Optune device. In this study, shunt valve settings were stable over a period of five days despite Optune therapy. This is reassuring for patients with GBM who require simultaneous treatment with both the Optune device and a programmable shunt system. PMID:27551653

  15. Stability of Programmable Shunt Valve Settings with Simultaneous Use of the Optune Transducer Array: A Case Report

    PubMed Central

    Chan, Andrew K; Winkler, Ethan A; Viner, Jennifer A; Taylor, Jennie W; McDermott, Michael W.

    2016-01-01

    The Optune® transducer array (Novocure Ltd., Haifa, Israel) is an FDA-approved noninvasive regional therapy that aims to inhibit the growth of glioblastoma multiforme (GBM) cells via utilization of alternating electric fields. Some patients with GBM may develop hydrocephalus and benefit from subsequent shunt placement, but special attention must be paid to patients in whom programmable valves are utilized, given the potential effect of the magnetic fields on valve settings. We present the first case report illustrating the stability of programmable shunt valve settings in a neurosurgical patient undergoing therapy with the Optune device. In this study, shunt valve settings were stable over a period of five days despite Optune therapy. This is reassuring for patients with GBM who require simultaneous treatment with both the Optune device and a programmable shunt system. PMID:27551653

  16. Reflection at a liquid-solid interface of a transient ultrasonic field radiated by a linear phased array transducer.

    PubMed

    Maghlaoui, Nadir; Belgroune, Djema; Ourak, Mohamed; Djelouah, Hakim

    2016-09-01

    In order to put in evidence the specular reflection and the non-specular reflection in the transient case, we have used a model for the study of the transient ultrasonic waves radiated by a linear phased array transducer in a liquid and reflected by a solid plane interface. This method is an extension of the angular spectrum method to the transient case where the reflection at the plane interface is taken into account by using the reflection coefficient for harmonic plane waves. The results obtained highlighted the different components of the ultrasonic field: the direct and edge waves as well as the longitudinal head waves or leaky Rayleigh waves. The transient representation of these waves have been carefully analyzed and discussed by the rays model. Instantaneous cartographies allowed a clear description of all the waves which appear at the liquid-solid interface. The obtained results have been compared to those obtained with a finite element method package. PMID:27290651

  17. Flat HIFU transducer with a sawtooth-shaped ultrasound radiation face

    NASA Astrophysics Data System (ADS)

    Son, Keon-Ho; Cho, Young-Ki; Kim, Dae-Seung; Kim, Myung-Deok; Kang, Kook-Jin

    2013-10-01

    High-intensity focused ultrasound (HIFU) transducers are spherically-curved in order to obtain a high intensity gain of the converged ultrasound energy at the geometrical focus. Ultrasound imaging devices monitor the procedure of HIFU treatment in ultrasound-guided HIFU systems where the image probe is positioned at the apex of the HIFU transducer, which has a spherical surface. However, the remote image probe's location yields a poor image quality compared to that obtained using conventional ultrasound imaging where the image probe is in direct contact with the surface. A phased array HIFU transducer with a new structure is suggested to overcome this limitation. The centers of the array elements are distributed over the flat surface of the transducer. However, the elements are tilted to form a geometrical focus, like a transducer with a spherically-curved surface, to obtain a high focal gain. The cross-section of the ultrasound radiation face of the transducer resembles the teeth of a saw. The acoustic field emitted from this transducer was simulated in order to design and produce the transducer. The simulation was compared with the measured sound field to verify that the transducer was correctly manufactured and designed; subsequently, the acoustic power was measured, and ultrasound images were obtained through the installation of an image probe on the transducer, which confirmed the application of this transducer to HIFU treatment.

  18. Coherence-Weighted Synthetic Focusing Applied to Photoacoustic Imaging Using a High-Frequency Annular-Array Transducer

    PubMed Central

    Chitnis, Parag V.; Aristizábal, Orlando; Filoux, Erwan; Sampathkumar, Ashwin; Mamou, Jonathan; Ketterling, Jeffrey A.

    2016-01-01

    This paper presents an adaptive synthetic-focusing scheme that, when applied to photoacoustic (PA) data acquired using an annular array, improves focusing across a greater imaging depth and enhances spatial resolution. The imaging system was based on a 40-MHz, 5-element, annular-array transducer with a focal length of 12 mm and an 800-μm diameter hole through its central element to facilitate coaxial delivery of 532-nm laser. The transducer was raster-scanned to facilitate 3D acquisition of co-registered ultrasound and PA image data. Three synthetic-focusing schemes were compared for obtaining PA A-lines for each scan location: delay-and-sum (DAS), DAS weighted with a coherence factor (DAS + CF), and DAS weighted with a sign-coherence factor (DAS + SCF). Bench-top experiments that used an 80-μm hair were performed to assess the enhancement provided by the two coherence-based schemes. Both coherence-based schemes increased the signal-to-noise ratio by approximately 10 dB. When processed using the DAS-only scheme, the lateral dimension of the hair in a PA image with 20 dB dynamic range was between 300 μm and 1 mm for imaging depth ranging from 8 to 20 mm. In comparison, the DAS + CF scheme resulted in a lateral dimension of 200 to 450 μm over the same range. The DAS + SCF synthetic focusing further improved the smallest-resolvable dimension, which was between 150 and 400 μm over the same range of imaging depth. When used on PA data obtained from a 12-day-old mouse embryo, the DAS + SCF processing improved visualization of neurovasculature. PMID:25925675

  19. Coherence-Weighted Synthetic Focusing Applied to Photoacoustic Imaging Using a High-Frequency Annular-Array Transducer.

    PubMed

    Chitnis, Parag V; Aristizábal, Orlando; Filoux, Erwan; Sampathkumar, Ashwin; Mamou, Jonathan; Ketterling, Jeffrey A

    2016-01-01

    This paper presents an adaptive synthetic-focusing scheme that, when applied to photoacoustic (PA) data acquired using an annular array, improves focusing across a greater imaging depth and enhances spatial resolution. The imaging system was based on a 40-MHz, 5-element, annular-array transducer with a focal length of 12 mm and an 800-µm diameter hole through its central element to facilitate coaxial delivery of 532-nm laser. The transducer was raster-scanned to facilitate 3D acquisition of co-registered ultrasound and PA image data. Three synthetic-focusing schemes were compared for obtaining PA A-lines for each scan location: delay-and-sum (DAS), DAS weighted with a coherence factor (DAS + CF), and DAS weighted with a sign-coherence factor (DAS + SCF). Bench-top experiments that used an 80-µm hair were performed to assess the enhancement provided by the two coherence-based schemes. Both coherence-based schemes increased the signal-to-noise ratio by approximately 10 dB. When processed using the DAS-only scheme, the lateral dimension of the hair in a PA image with 20 dB dynamic range was between 300 µm and 1 mm for imaging depth ranging from 8 to 20 mm. In comparison, the DAS + CF scheme resulted in a lateral dimension of 200 to 450 µm over the same range. The DAS + SCF synthetic focusing further improved the smallest-resolvable dimension, which was between 150 and 400 µm over the same range of imaging depth. When used on PA data obtained from a 12-day-old mouse embryo, the DAS + SCF processing improved visualization of neurovasculature. PMID:25925675

  20. Assessment of Microphone Phased Array for Measuring Launch Vehicle Lift-off Acoustics

    NASA Technical Reports Server (NTRS)

    Garcia, Roberto

    2012-01-01

    The specific purpose of the present work was to demonstrate the suitability of a microphone phased array for launch acoustics applications via participation in selected firings of the Ares I Scale Model Acoustics Test. The Ares I Scale Model Acoustics Test is a part of the discontinued Constellation Program Ares I Project, but the basic understanding gained from this test is expected to help development of the Space Launch System vehicles. Correct identification of sources not only improves the predictive ability, but provides guidance for a quieter design of the launch pad and optimization of the water suppression system. This document contains the results of the NASA Engineering and Safety Center assessment.

  1. Acoustic performance of a large-aperture, seabed, fiber-optic hydrophone array

    NASA Astrophysics Data System (ADS)

    Cranch, G. A.; Crickmore, R.; Kirkendall, C. K.; Bautista, A.; Daley, K.; Motley, S.; Salzano, J.; Latchem, J.; Nash, P. J.

    2004-06-01

    A large-aperture, seabed mounted, fiber-optic hydrophone array has been constructed and characterized. The system is designed for use as a large area surveillance array for deployment in shallow water regions. The underwater portion comprises two arrays of 48 hydrophones separated by a 3 km fiber-optic link, which are connected to a shore station by 40 km of single-mode optical fiber. The hydrophone is based on a fiber-optic Michelson interferometer and the acoustic transduction mechanism is a fiber-wrapped mandrel design. No electrical power is required in the underwater portion. The performance of the system is described, characterized during laboratory measurements and during a recent sea trial. Specifically, measurements of the acoustic resolution, array shape, beam patterns, array gain, and target tracking capability of this array. The system demonstrates self-noise levels up to 20 dB (typically 10 dB) lower than the ambient acoustic noise experienced in the sea trial and array gains close to the theoretical maximum. The system telemetry and electronics have been designed to be expandable to accommodate several hundred hydrophones.

  2. Design and characterization of a laterally mounted phased-array transducer breast-specific MRgHIFU device with integrated 11-channel receiver array

    PubMed Central

    Payne, A.; Merrill, R.; Minalga, E.; Vyas, U.; Bever, J. de; Todd, N.; Hadley, R.; Dumont, E.; Neumayer, L.; Christensen, D.; Roemer, R.; Parker, D.

    2012-01-01

    Purpose: This work presents the design and preliminary evaluation of a new laterally mounted phased-array MRI-guided high-intensity focused ultrasound (MRgHIFU) system with an integrated 11-channel phased-array radio frequency (RF) coil intended for breast cancer treatment. The design goals for the system included the ability to treat the majority of tumor locations, to increase the MR image’s signal-to-noise ratio (SNR) throughout the treatment volume and to provide adequate comfort for the patient. Methods: In order to treat the majority of the breast volume, the device was designed such that the treated breast is suspended in a 17-cm diameter treatment cylinder. A laterally shooting 1-MHz, 256-element phased-array ultrasound transducer with flexible positioning is mounted outside the treatment cylinder. This configuration achieves a reduced water volume to minimize RF coil loading effects, to position the coils closer to the breast for increased signal sensitivity, and to reduce the MR image noise associated with using water as the coupling fluid. This design uses an 11-channel phased-array RF coil that is placed on the outer surface of the cylinder surrounding the breast. Mechanical positioning of the transducer and electronic steering of the focal spot enable placement of the ultrasound focus at arbitrary locations throughout the suspended breast. The treatment platform allows the patient to lie prone in a face-down position. The system was tested for comfort with 18 normal volunteers and SNR capabilities in one normal volunteer and for heating accuracy and stability in homogeneous phantom and inhomogeneous ex vivo porcine tissue. Results: There was a 61% increase in mean relative SNR achieved in a homogeneous phantom using the 11-channel RF coil when compared to using only a single-loop coil around the chest wall. The repeatability of the system’s energy delivery in a single location was excellent, with less than 3% variability between repeated

  3. Design of broadband linear micromachined ultrasonic transducer arrays by means of boundary element method coupled with normal mode theory.

    PubMed

    Boulmé, Audren; Certon, Dominique

    2015-09-01

    In view of the maturity of fabrication processes for capacitive micromachined ultrasonic transducers (cMUTs), engineers and researchers now need efficient and accurate modeling tools to design linear arrays according to a set of technological specifications, such as sensitivity, bandwidth, and directivity pattern. A simplified modeling tool was developed to meet this requirement. It consists of modeling one element as a set of cMUT columns, each being a 1-D periodic array of cMUTs. Model description and assessment of simulation results are given in the first part of the paper. The approach is based on the theory of linear systems so the output data are linked to input data through a large matrix, known as an admittance matrix. In the second part of the paper, we propose reorganization of matrix equations by applying the normal mode theory. From the modal decomposition, two categories of eigenmodes are highlighted, one for which all cMUTs vibrate in phase (the fundamental mode) and the others, which correspond to localized subwavelength resonances, known as baffle modes. The last part of the paper focuses mainly on the fundamental mode and gives several design strategies to optimize the frequency response of an element.

  4. Photoacoustic imaging for deep targets in the breast using a multichannel 2D array transducer

    NASA Astrophysics Data System (ADS)

    Xie, Zhixing; Wang, Xueding; Morris, Richard F.; Padilla, Frederic R.; Lecarpentier, Gerald L.; Carson, Paul L.

    2011-03-01

    A photoacoustic (PA) imaging system was developed to achieve high sensitivity for the detection and characterization of vascular anomalies in the breast in the mammographic geometry. Signal detection from deep in the breast was achieved by a broadband 2D PVDF planar array that has a round shape with one side trimmed straight to improve fit near the chest wall. This array has 572 active elements and a -6dB bandwidth of 0.6-1.7 MHz. The low frequency enhances imaging depth and increases the size of vascular collections displayed without edge enhancement. The PA signals from all the elements go through low noise preamplifiers in the probe that are very close to the array elements for optimized noise control. Driven by 20 independent on-probe signal processing channels, imaging with both high sensitivity and good speed was achieved. To evaluate the imaging depth and the spatial resolution of this system,2.38mm I.D. artificial vessels embedded deeply in ex vivo breasts harvested from fresh cadavers and a 3mm I.D. tube in breast mimicking phantoms made of pork loin and fat tissues were imaged. Using near-infrared laser light with incident energy density within the ANSI safety limit, imaging depths of up to 49 mm in human breasts and 52 mm in phantoms were achieved. With a high power tunable laser working on multiple wavelengths, this system might contribute to 3D noninvasive imaging of morphological and physiological tissue features throughout the breast.

  5. Fabrication of broadband poly(vinylidene difluoride-trifluroethylene) line-focus ultrasonic transducers for surface acoustic wave measurements of anisotropy of a (100) silicon wafer.

    PubMed

    Lu, Yan; He, Cunfu; Song, Guorong; Wu, Bin; Chung, Cheng-Hsien; Lee, Yung-Chun

    2014-01-01

    This paper investigates a new method for fabrication of broadband line-focus ultrasonic transducers by sol-gel spin-coating the poly(vinylidene difluoride-trifluroethylene) [P(VDF-TrFE)] copolymer film on a concave fine-polished beryllium copper backing. The ferroelectric hysteresis loops of the P(VDF-TrFE) films spin-coated from different molar ratios of VDF/TrFE, 77/23 and 55/45, were measured to select the better mixture. Owing to the better acoustic matching to water, compared with lead zirconate titanate (PZT), the fabricated transducers show relatively wide bandwidth of approximately 50 MHz with high central frequency of 60 MHz obtained at the focal plane when a fused-quartz acts as a reflecting target. Each one of the two finished transducers has a focal length of 5mm and a full aperture angle of 90°. After applying the specially developed digital signal processing algorithm to the defocusing experiment data, which is called V(f,z) analysis method based on two-dimensional fast Fourier transform (2-D FFT), the operating frequency can extend from several MHz to over 90 MHz. Surface acoustic wave (SAW) velocities of a typical (100) silicon wafer was measured along various directions between [100] and [010] to represent the anisotropic features.

  6. Unique gel-coupled acoustic sensor array monitors human voice and physiology

    NASA Astrophysics Data System (ADS)

    Scanlon, Michael

    2002-11-01

    The health and performance of soldiers, firefighters, and other first responders in strenuous and hazardous environments can be continuously and remotely monitored with body-worn acoustic sensors. The Army Research Laboratory's gel-coupled acoustic physiological monitoring sensor has acoustic impedance properties similar to the skin that facilitate the transmission of body sounds into the sensor pad, yet significantly repel ambient airborne noises due to an impedance mismatch. Acoustic signal processing detects physiological events such as heartbeats, breaths, wheezes, coughs, blood pressure, activity, motion, and voice for communication and automatic speech recognition. Acoustic sensors can be in a helmet or in a strap around the neck, chest, and wrist. Although the physiological sounds have high SNR, the acoustic sensor also responds to motion-induced artifacts that sometimes obscure meaningful physiology. A noise-canceling sensor array configuration helps remove motion noise by using two acoustic sensors on the front sides of the neck and 2 additional acoustic sensors on each wrist. The motion noise detected on all 4 sensors will be dissimilar and out of phase, yet the physiology on all 4 sensors is covariant. Pulse wave transit time between neck and wrist will indicate systolic blood pressure. Data from a firefighter experiment will be presented.

  7. Acoustic phonon spectrum and thermal transport in nanoporous alumina arrays

    SciTech Connect

    Kargar, Fariborz; Ramirez, Sylvester; Debnath, Bishwajit; Malekpour, Hoda; Lake, Roger; Balandin, Alexander A.

    2015-10-28

    We report results of a combined investigation of thermal conductivity and acoustic phonon spectra in nanoporous alumina membranes with the pore diameter decreasing from D=180 nm to 25 nm. The samples with the hexagonally arranged pores were selected to have the same porosity Ø ≈13%. The Brillouin-Mandelstam spectroscopy measurements revealed bulk-like phonon spectrum in the samples with D = 180 nm pores and spectral features, which were attributed to spatial confinement, in the samples with 25 nm and 40 nm pores. The velocity of the longitudinal acoustic phonons was reduced in the samples with smaller pores. As a result, analysis of the experimental data and calculated phonon dispersion suggests that both phonon-boundary scattering and phonon spatial confinement affect heat conduction in membranes with the feature sizes D < 40 nm.

  8. Acoustic phonon spectrum and thermal transport in nanoporous alumina arrays

    SciTech Connect

    Kargar, Fariborz; Ramirez, Sylvester; Debnath, Bishwajit; Malekpour, Hoda; Lake, Roger; Balandin, Alexander A.

    2015-10-28

    We report results of a combined investigation of thermal conductivity and acoustic phonon spectra in nanoporous alumina membranes with the pore diameter decreasing from D=180 nm to 25 nm. The samples with the hexagonally arranged pores were selected to have the same porosity Ø ≈13%. The Brillouin-Mandelstam spectroscopy measurements revealed bulk-like phonon spectrum in the samples with D=180-nm pores and spectral features, which were attributed to spatial confinement, in the samples with 25-nm and 40-nm pores. The velocity of the longitudinal acoustic phonons was reduced in the samples with smaller pores. As a result, analysis of the experimental data and calculated phonon dispersion suggests that both phonon-boundary scattering and phonon spatial confinement affect heat conduction in membranes with the feature sizes D<40 nm.

  9. Acoustic phonon spectrum and thermal transport in nanoporous alumina arrays

    DOE PAGES

    Kargar, Fariborz; Ramirez, Sylvester; Debnath, Bishwajit; Malekpour, Hoda; Lake, Roger; Balandin, Alexander A.

    2015-10-28

    We report results of a combined investigation of thermal conductivity and acoustic phonon spectra in nanoporous alumina membranes with the pore diameter decreasing from D=180 nm to 25 nm. The samples with the hexagonally arranged pores were selected to have the same porosity Ø ≈13%. The Brillouin-Mandelstam spectroscopy measurements revealed bulk-like phonon spectrum in the samples with D = 180 nm pores and spectral features, which were attributed to spatial confinement, in the samples with 25 nm and 40 nm pores. The velocity of the longitudinal acoustic phonons was reduced in the samples with smaller pores. As a result, analysismore » of the experimental data and calculated phonon dispersion suggests that both phonon-boundary scattering and phonon spatial confinement affect heat conduction in membranes with the feature sizes D < 40 nm.« less

  10. Inferring the acoustic dead-zone volume by split-beam echo sounder with narrow-beam transducer on a noninertial platform.

    PubMed

    Patel, Ruben; Pedersen, Geir; Ona, Egil

    2009-02-01

    Acoustic measurement of near-bottom fish with a directional transducer is generally problematical because the powerful bottom echo interferes with weaker echoes from fish within the main lobe but at greater ranges than that of the bottom. The volume that is obscured is called the dead zone. This has already been estimated for the special case of a flat horizontal bottom when observed by an echo sounder with a stable vertical transducer beam [Ona, E., and Mitson, R. B. (1996). ICES J. Mar. Sci. 53, 677-690]. The more general case of observation by a split-beam echo sounder with a transducer mounted on a noninertial platform is addressed here. This exploits the capability of a split-beam echo sounder to measure the bottom slope relative to the beam axis and thence to allow the dead-zone volume over a flat but sloping bottom to be estimated analytically. The method is established for the Simrad EK60 scientific echo sounder, with split-beam transducers operating at 18, 38, 70, 120, and 200 kHz. It is validated by comparing their estimates of seafloor slope near the Lofoten Islands, N67-70, with simultaneous measurements made by two hydrographic multibeam sonars, the Simrad EM100295 kHz and EM30030 kHz systems working in tandem.

  11. Inferring the acoustic dead-zone volume by split-beam echo sounder with narrow-beam transducer on a noninertial platform.

    PubMed

    Patel, Ruben; Pedersen, Geir; Ona, Egil

    2009-02-01

    Acoustic measurement of near-bottom fish with a directional transducer is generally problematical because the powerful bottom echo interferes with weaker echoes from fish within the main lobe but at greater ranges than that of the bottom. The volume that is obscured is called the dead zone. This has already been estimated for the special case of a flat horizontal bottom when observed by an echo sounder with a stable vertical transducer beam [Ona, E., and Mitson, R. B. (1996). ICES J. Mar. Sci. 53, 677-690]. The more general case of observation by a split-beam echo sounder with a transducer mounted on a noninertial platform is addressed here. This exploits the capability of a split-beam echo sounder to measure the bottom slope relative to the beam axis and thence to allow the dead-zone volume over a flat but sloping bottom to be estimated analytically. The method is established for the Simrad EK60 scientific echo sounder, with split-beam transducers operating at 18, 38, 70, 120, and 200 kHz. It is validated by comparing their estimates of seafloor slope near the Lofoten Islands, N67-70, with simultaneous measurements made by two hydrographic multibeam sonars, the Simrad EM100295 kHz and EM30030 kHz systems working in tandem. PMID:19206847

  12. A methodology for analyzing an acoustic scene in sensor arrays

    NASA Astrophysics Data System (ADS)

    Man, Hong; Hohil, Myron E.; Desai, Sachi

    2007-10-01

    Presented here is a novel clustering method for Hidden Markov Models (HMMs) and its application in acoustic scene analysis. In this method, HMMs are clustered based on a similarity measure for stochastic models defined as the generalized probability product kernel (GPPK), which can be efficiently evaluated according to a fast algorithm introduced by Chen and Man (2005) [1]. Acoustic signals from various sources are partitioned into small frames. Frequency features are extracted from each of the frames to form observation vectors. These frames are further grouped into segments, and an HMM is trained from each of such segments. An unknown segment is categorized with a known event if its HMM has the closest similarity with the HMM from the corresponding labeled segment. Experiments are conducted on an underwater acoustic dataset from Steven Maritime Security Laboratory, Data set contains a swimmer signature, a noise signature from the Hudson River, and a test sequence with a swimmer in the Hudson River. Experimental results show that the proposed method can successfully associate the test sequence with the swimmer signature at very high confidence, despite their different time behaviors.

  13. Spontaneous assembly of chemically encoded two-dimensional coacervate droplet arrays by acoustic wave patterning

    PubMed Central

    Tian, Liangfei; Martin, Nicolas; Bassindale, Philip G.; Patil, Avinash J.; Li, Mei; Barnes, Adrian; Drinkwater, Bruce W.; Mann, Stephen

    2016-01-01

    The spontaneous assembly of chemically encoded, molecularly crowded, water-rich micro-droplets into periodic defect-free two-dimensional arrays is achieved in aqueous media by a combination of an acoustic standing wave pressure field and in situ complex coacervation. Acoustically mediated coalescence of primary droplets generates single-droplet per node micro-arrays that exhibit variable surface-attachment properties, spontaneously uptake dyes, enzymes and particles, and display spatial and time-dependent fluorescence outputs when exposed to a reactant diffusion gradient. In addition, coacervate droplet arrays exhibiting dynamical behaviour and exchange of matter are prepared by inhibiting coalescence to produce acoustically trapped lattices of droplet clusters that display fast and reversible changes in shape and spatial configuration in direct response to modulations in the acoustic frequencies and fields. Our results offer a novel route to the design and construction of ‘water-in-water' micro-droplet arrays with controllable spatial organization, programmable signalling pathways and higher order collective behaviour. PMID:27708286

  14. Spontaneous assembly of chemically encoded two-dimensional coacervate droplet arrays by acoustic wave patterning

    NASA Astrophysics Data System (ADS)

    Tian, Liangfei; Martin, Nicolas; Bassindale, Philip G.; Patil, Avinash J.; Li, Mei; Barnes, Adrian; Drinkwater, Bruce W.; Mann, Stephen

    2016-10-01

    The spontaneous assembly of chemically encoded, molecularly crowded, water-rich micro-droplets into periodic defect-free two-dimensional arrays is achieved in aqueous media by a combination of an acoustic standing wave pressure field and in situ complex coacervation. Acoustically mediated coalescence of primary droplets generates single-droplet per node micro-arrays that exhibit variable surface-attachment properties, spontaneously uptake dyes, enzymes and particles, and display spatial and time-dependent fluorescence outputs when exposed to a reactant diffusion gradient. In addition, coacervate droplet arrays exhibiting dynamical behaviour and exchange of matter are prepared by inhibiting coalescence to produce acoustically trapped lattices of droplet clusters that display fast and reversible changes in shape and spatial configuration in direct response to modulations in the acoustic frequencies and fields. Our results offer a novel route to the design and construction of `water-in-water' micro-droplet arrays with controllable spatial organization, programmable signalling pathways and higher order collective behaviour.

  15. Seismo-acoustic Signals Recorded at KSIAR, the Infrasound Array Installed at PS31

    NASA Astrophysics Data System (ADS)

    Kim, T. S.; Che, I. Y.; Jeon, J. S.; Chi, H. C.; Kang, I. B.

    2014-12-01

    One of International Monitoring System (IMS)'s primary seismic stations, PS31, called Korea Seismic Research Station (KSRS), was installed around Wonju, Korea in 1970s. It has been operated by US Air Force Technical Applications Center (AFTAC) for more than 40 years. KSRS is composed of 26 seismic sensors including 19 short period, 6 long period and 1 broad band seismometers. The 19 short period sensors were used to build an array with a 10-km aperture while the 6 long period sensors were used for a relatively long period array with a 40-km aperture. After KSRS was certified as an IMS station in 2006 by Comprehensive Nuclear Test Ban Treaty Organization (CTBTO), Korea Institute of Geoscience and Mineral Resources (KIGAM) which is the Korea National Data Center started to take over responsibilities on the operation and maintenance of KSRS from AFTAC. In April of 2014, KIGAM installed an infrasound array, KSIAR, on the existing four short period seismic stations of KSRS, the sites KS05, KS06, KS07 and KS16. The collocated KSIAR changed KSRS from a seismic array into a seismo-acoustic array. The aperture of KSIAR is 3.3 km. KSIAR also has a 100-m small aperture infrasound array at KS07. The infrasound data from KSIAR except that from the site KS06 is being transmitted in real time to KIGAM with VPN and internet line. An initial analysis on seismo-acoustic signals originated from local and regional distance ranges has been performed since May 2014. The analysis with the utilization of an array process called Progressive Multi-Channel Correlation (PMCC) detected seismo-acoustic signals caused by various sources including small explosions in relation to constructing local tunnels and roads. Some of them were not found in the list of automatic bulletin of KIGAM. The seismo-acoustic signals recorded by KSIAR are supplying a useful information for discriminating local and regional man-made events from natural events.

  16. Hydrogen gas sensor fabricated from polyanisidine nanofibers deposited on 36° YX LiTaO 3 layered surface acoustic wave transducer

    NASA Astrophysics Data System (ADS)

    Al-Mashat, Laith; Tran, Henry D.; Wlodarski, Wojtek; Kaner, Richard B.; Kalantar-zadeh, Kourosh

    2007-12-01

    Polyanisidine nanofibers gas sensor based on a ZnO/36° YX LiTaO 3 surface acoustic wave (SAW) transducer was developed and tested at different concentrations of hydrogen gas in synthetic air. Nanofibrous mats of polyanisidine were synthesized without the need for templates or functional dopants by simply introducing an initiator into the reaction mixture of a rapidly mixed reaction between the monomer (anisidine) and the oxidant. The polyanisidine nanofibers are characterized using scanning electron microscopy (SEM) and Ultraviolet-Visible Spectroscopy (UV-vis). Polyanisidine nanofibers were deposited onto the SAW transducer and exposed to different concentrations of hydrogen gas. The frequency shift due to the sensor response was 294 kHz towards 1% of H II. All tests were conducted at room temperature and the sensor performance was assessed for a two day period with a high degree of reproducibility obtained.

  17. Acoustic and vibration performance evaluations of a velocity sensing hull array

    NASA Astrophysics Data System (ADS)

    Cray, Benjamin A.; Christman, Russell A.

    1996-04-01

    Acoustic and vibration measurements were conducted at the Naval Undersea Warfare Center's Seneca Lake Facility to investigate the in situ signal response of a linear array of velocity sensors (sensors that measure either acoustic particle acceleration, velocity, or displacement have generically been denoted as velocity sensors) on a coating. The coating used at Seneca Lake consisted of air-voided elastomeric tiles with an overall coating thickness of approximately 3 inches. The accelerometer array and coating were mounted on the Seneca Lake Hull Fixture, which measures 33 feet lengthwise with an arc length of 20 feet. The fixture weighs approximately 30 tons. Specifically, measurements of in situ sensitivity, velocity reduction, reflection gain, array beam response, and equivalent planewave self-noise levels are presented.

  18. Comparison of vector velocity imaging using directional beamforming and transverse oscillation for a convex array transducer

    NASA Astrophysics Data System (ADS)

    Jensen, Jørgen Arendt

    2014-03-01

    Vector velocity imaging can reveal both the magnitude and direction of the blood velocity. Several techniques have been suggested for estimating the velocity, and this paper compares the performance for directional beam-forming and transverse oscillation (TO) vector flow imaging (VFI). Data have been acquired using the SARUS experimental ultrasound scanner connected to a BK 8820e (BK Medical, Herlev, Denmark) convex array probe with 192 active elements. A duplex sequence with 129 B-mode emissions interleaved with 129 flow emissions has been made. The flow was generated in a recirculating flow rig with a stationary, laminar flow, and the volume flow was measured by a MAG 3000 (Danfos, Sønderbog, Denmark) magnetic flow meter for reference. Data were beamformed with an optimized transverse oscillation scheme for the TO VFI, and standard fourth-order estimators were employed for the velocity estimation. Directional RF lines were beamformed along the flow direction and cross-correlation employed to estimate the velocity magnitude. The velocities were determined for beam-to-flow angles of 60, 75 and 90 degrees. Using 32 emissions the standard deviation relative to the peak velocity for TO estimation was 7.0% at a beam-to-flow angle of 75° . This was 3.8% for directional beamforming and at 60° it was 2.2%. The general improvement, however, comes at an increase by a factor of roughly 11 in the number of calculations for the directional beamformation compared to the TO method.

  19. Acoustic contrast, planarity and robustness of sound zone methods using a circular loudspeaker array.

    PubMed

    Coleman, Philip; Jackson, Philip J B; Olik, Marek; Møller, Martin; Olsen, Martin; Abildgaard Pedersen, Jan

    2014-04-01

    Since the mid 1990s, acoustics research has been undertaken relating to the sound zone problem-using loudspeakers to deliver a region of high sound pressure while simultaneously creating an area where the sound is suppressed-in order to facilitate independent listening within the same acoustic enclosure. The published solutions to the sound zone problem are derived from areas such as wave field synthesis and beamforming. However, the properties of such methods differ and performance tends to be compared against similar approaches. In this study, the suitability of energy focusing, energy cancelation, and synthesis approaches for sound zone reproduction is investigated. Anechoic simulations based on two zones surrounded by a circular array show each of the methods to have a characteristic performance, quantified in terms of acoustic contrast, array control effort and target sound field planarity. Regularization is shown to have a significant effect on the array effort and achieved acoustic contrast, particularly when mismatched conditions are considered between calculation of the source weights and their application to the system.

  20. Single-shot measurements of the acoustic field of an electrohydraulic lithotripter using a hydrophone array

    PubMed Central

    Alibakhshi, Mohammad A.; Kracht, Jonathan M.; Cleveland, Robin O.; Filoux, Erwan; Ketterling, Jeffrey A.

    2013-01-01

    Piezopolymer-based hydrophone arrays consisting of 20 elements were fabricated and tested for use in measuring the acoustic field from a shock-wave lithotripter. The arrays were fabricated from piezopolymer films and were mounted in a housing to allow submersion into water. The motivation was to use the array to determine how the shot-to-shot variability of the spark discharge in an electrohydraulic lithotripter affects the resulting focused acoustic field. It was found that the dominant effect of shot-to-shot variability was to laterally shift the location of the focus by up to 5 mm from the nominal acoustic axis of the lithotripter. The effect was more pronounced when the spark discharge was initiated with higher voltages. The lateral beamwidth of individual, instantaneous shock waves were observed to range from 1.5 mm to 24 mm. Due to the spatial variation of the acoustic field, the average of instantaneous beamwidths were observed to be 1 to 2 mm narrower than beamwidths determined from traditional single-point measurements that average the pressure measured at each location before computing beamwidth. PMID:23654419

  1. An acoustic-array based structural health monitoring technique for wind turbine blades

    NASA Astrophysics Data System (ADS)

    Aizawa, Kai; Poozesh, Peyman; Niezrecki, Christopher; Baqersad, Javad; Inalpolat, Murat; Heilmann, Gunnar

    2015-04-01

    This paper proposes a non-contact measurement technique for health monitoring of wind turbine blades using acoustic beamforming techniques. The technique works by mounting an audio speaker inside a wind turbine blade and observing the sound radiated from the blade to identify damage within the structure. The main hypothesis for the structural damage detection is that the structural damage (cracks, edge splits, holes etc.) on the surface of a composite wind turbine blade results in changes in the sound radiation characteristics of the structure. Preliminary measurements were carried out on two separate test specimens, namely a composite box and a section of a wind turbine blade to validate the methodology. The rectangular shaped composite box and the turbine blade contained holes with different dimensions and line cracks. An acoustic microphone array with 62 microphones was used to measure the sound radiation from both structures when the speaker was located inside the box and also inside the blade segment. A phased array beamforming technique and CLEAN-based subtraction of point spread function from a reference (CLSPR) were employed to locate the different damage types on both the composite box and the wind turbine blade. The same experiment was repeated by using a commercially available 48-channel acoustic ring array to compare the test results. It was shown that both the acoustic beamforming and the CLSPR techniques can be used to identify the damage in the test structures with sufficiently high fidelity.

  2. Acoustic contrast, planarity and robustness of sound zone methods using a circular loudspeaker array.

    PubMed

    Coleman, Philip; Jackson, Philip J B; Olik, Marek; Møller, Martin; Olsen, Martin; Abildgaard Pedersen, Jan

    2014-04-01

    Since the mid 1990s, acoustics research has been undertaken relating to the sound zone problem-using loudspeakers to deliver a region of high sound pressure while simultaneously creating an area where the sound is suppressed-in order to facilitate independent listening within the same acoustic enclosure. The published solutions to the sound zone problem are derived from areas such as wave field synthesis and beamforming. However, the properties of such methods differ and performance tends to be compared against similar approaches. In this study, the suitability of energy focusing, energy cancelation, and synthesis approaches for sound zone reproduction is investigated. Anechoic simulations based on two zones surrounded by a circular array show each of the methods to have a characteristic performance, quantified in terms of acoustic contrast, array control effort and target sound field planarity. Regularization is shown to have a significant effect on the array effort and achieved acoustic contrast, particularly when mismatched conditions are considered between calculation of the source weights and their application to the system. PMID:25234991

  3. Customization of the acoustic field produced by a piezoelectric array through interelement delays

    PubMed Central

    Chitnis, Parag V.; Barbone, Paul E.; Cleveland, Robin O.

    2008-01-01

    A method for producing a prescribed acoustic pressure field from a piezoelectric array was investigated. The array consisted of 170 elements placed on the inner surface of a 15 cm radius spherical cap. Each element was independently driven by using individual pulsers each capable of generating 1.2 kV. Acoustic field customization was achieved by independently controlling the time when each element was excited. The set of time delays necessary to produce a particular acoustic field was determined by using an optimization scheme. The acoustic field at the focal plane was simulated by using the angular spectrum method, and the optimization searched for the time delays that minimized the least squared difference between the magnitudes of the simulated and desired pressure fields. The acoustic field was shaped in two different ways: the −6 dB focal width was increased to different desired widths and the ring-shaped pressure distributions of various prescribed diameters were produced. For both cases, the set of delays resulting from the respective optimization schemes were confirmed to yield the desired pressure distributions by using simulations and measurements. The simulations, however, predicted peak positive pressures roughly half those obtained from the measurements, which was attributed to the exclusion of nonlinearity in the simulations. PMID:18537369

  4. Design of acoustic logging signal source of imitation based on field programmable gate array

    NASA Astrophysics Data System (ADS)

    Zhang, K.; Ju, X. D.; Lu, J. Q.; Men, B. Y.

    2014-08-01

    An acoustic logging signal source of imitation is designed and realized, based on the Field Programmable Gate Array (FPGA), to improve the efficiency of examining and repairing acoustic logging tools during research and field application, and to inspect and verify acoustic receiving circuits and corresponding algorithms. The design of this signal source contains hardware design and software design,and the hardware design uses an FPGA as the control core. Four signals are made first by reading the Random Access Memory (RAM) data which are inside the FPGA, then dealing with the data by digital to analog conversion, amplification, smoothing and so on. Software design uses VHDL, a kind of hardware description language, to program the FPGA. Experiments illustrate that the ratio of signal to noise for the signal source is high, the waveforms are stable, and also its functions of amplitude adjustment, frequency adjustment and delay adjustment are in accord with the characteristics of real acoustic logging waveforms. These adjustments can be used to imitate influences on sonic logging received waveforms caused by many kinds of factors such as spacing and span of acoustic tools, sonic speeds of different layers and fluids, and acoustic attenuations of different cementation planes.

  5. Crack orientation and depth estimation in a low-pressure turbine disc using a phased array ultrasonic transducer and an artificial neural network.

    PubMed

    Yang, Xiaoxia; Chen, Shili; Jin, Shijiu; Chang, Wenshuang

    2013-01-01

    Stress corrosion cracks (SCC) in low-pressure steam turbine discs are serious hidden dangers to production safety in the power plants, and knowing the orientation and depth of the initial cracks is essential for the evaluation of the crack growth rate, propagation direction and working life of the turbine disc. In this paper, a method based on phased array ultrasonic transducer and artificial neural network (ANN), is proposed to estimate both the depth and orientation of initial cracks in the turbine discs. Echo signals from cracks with different depths and orientations were collected by a phased array ultrasonic transducer, and the feature vectors were extracted by wavelet packet, fractal technology and peak amplitude methods. The radial basis function (RBF) neural network was investigated and used in this application. The final results demonstrated that the method presented was efficient in crack estimation tasks. PMID:24064602

  6. Crack Orientation and Depth Estimation in a Low-Pressure Turbine Disc Using a Phased Array Ultrasonic Transducer and an Artificial Neural Network

    PubMed Central

    Yang, Xiaoxia; Chen, Shili; Jin, Shijiu; Chang, Wenshuang

    2013-01-01

    Stress corrosion cracks (SCC) in low-pressure steam turbine discs are serious hidden dangers to production safety in the power plants, and knowing the orientation and depth of the initial cracks is essential for the evaluation of the crack growth rate, propagation direction and working life of the turbine disc. In this paper, a method based on phased array ultrasonic transducer and artificial neural network (ANN), is proposed to estimate both the depth and orientation of initial cracks in the turbine discs. Echo signals from cracks with different depths and orientations were collected by a phased array ultrasonic transducer, and the feature vectors were extracted by wavelet packet, fractal technology and peak amplitude methods. The radial basis function (RBF) neural network was investigated and used in this application. The final results demonstrated that the method presented was efficient in crack estimation tasks. PMID:24064602

  7. Crack orientation and depth estimation in a low-pressure turbine disc using a phased array ultrasonic transducer and an artificial neural network.

    PubMed

    Yang, Xiaoxia; Chen, Shili; Jin, Shijiu; Chang, Wenshuang

    2013-09-13

    Stress corrosion cracks (SCC) in low-pressure steam turbine discs are serious hidden dangers to production safety in the power plants, and knowing the orientation and depth of the initial cracks is essential for the evaluation of the crack growth rate, propagation direction and working life of the turbine disc. In this paper, a method based on phased array ultrasonic transducer and artificial neural network (ANN), is proposed to estimate both the depth and orientation of initial cracks in the turbine discs. Echo signals from cracks with different depths and orientations were collected by a phased array ultrasonic transducer, and the feature vectors were extracted by wavelet packet, fractal technology and peak amplitude methods. The radial basis function (RBF) neural network was investigated and used in this application. The final results demonstrated that the method presented was efficient in crack estimation tasks.

  8. Source Localization with Acoustic Sensor Arrays Using Generative Model Based Fitting with Sparse Constraints

    PubMed Central

    Velasco, Jose; Pizarro, Daniel; Macias-Guarasa, Javier

    2012-01-01

    This paper presents a novel approach for indoor acoustic source localization using sensor arrays. The proposed solution starts by defining a generative model, designed to explain the acoustic power maps obtained by Steered Response Power (SRP) strategies. An optimization approach is then proposed to fit the model to real input SRP data and estimate the position of the acoustic source. Adequately fitting the model to real SRP data, where noise and other unmodelled effects distort the ideal signal, is the core contribution of the paper. Two basic strategies in the optimization are proposed. First, sparse constraints in the parameters of the model are included, enforcing the number of simultaneous active sources to be limited. Second, subspace analysis is used to filter out portions of the input signal that cannot be explained by the model. Experimental results on a realistic speech database show statistically significant localization error reductions of up to 30% when compared with the SRP-PHAT strategies. PMID:23202021

  9. Estimation of low-altitude moving target trajectory using single acoustic array.

    PubMed

    Tong, Jianfei; Xie, Wei; Hu, Yu-Hen; Bao, Ming; Li, Xiaodong; He, Wei

    2016-04-01

    An acoustic-signature based method of estimating the flight trajectory of low-altitude flying aircraft that only requires a stationary microphone array is proposed. This method leverages the Doppler shifts of engine sound to estimate the closest point of approach distance, time, and speed. It also leverages the acoustic phase shift over the microphone array to estimate the direction of arrival of the target. Combining these parameters, this algorithm provides a total least square estimate of the target trajectory under the assumption of constant target height, direction, and speed. Analytical bounds of potential performance degradation due to noise are derived and the estimation error caused by signal propagation delay is analyzed, and both are verified with extensive simulation. The proposed algorithm is also validated by processing the data collected in field experiments. PMID:27106332

  10. System gain function calculation for acoustic arrays using ray optical methods

    NASA Astrophysics Data System (ADS)

    Schmid, O.; Vonwinterfeld, C.

    1980-11-01

    The gain function of an acoustic antenna array is calculated with respect to waves, propagating from a point source into an homogeneous medium (water) with a sinusoidally varying surface of known phase statistics, treating antenna and environment as one system. An asymptotic solution (high frequency approximation) is developed. For distances of several wavelengths between the array and the surface of the medium, the propagation mechanism is described by a geometrical theory of diffraction applied to scalar waves. The gain function of the antenna together with the reflecting surface is obtained from the cross correlations of the resulting sound fields of each antenna element.

  11. Helmet-mounted acoustic array for hostile fire detection and localization in an urban environment

    NASA Astrophysics Data System (ADS)

    Scanlon, Michael V.

    2008-04-01

    The detection and localization of hostile weapons firing has been demonstrated successfully with acoustic sensor arrays on unattended ground sensors (UGS), ground-vehicles, and unmanned aerial vehicles (UAVs). Some of the more mature systems have demonstrated significant capabilities and provide direct support to ongoing counter-sniper operations. The Army Research Laboratory (ARL) is conducting research and development for a helmet-mounted system to acoustically detect and localize small arms firing, or other events such as RPG, mortars, and explosions, as well as other non-transient signatures. Since today's soldier is quickly being asked to take on more and more reconnaissance, surveillance, & target acquisition (RSTA) functions, sensor augmentation enables him to become a mobile and networked sensor node on the complex and dynamic battlefield. Having a body-worn threat detection and localization capability for events that pose an immediate danger to the soldiers around him can significantly enhance their survivability and lethality, as well as enable him to provide and use situational awareness clues on the networked battlefield. This paper addresses some of the difficulties encountered by an acoustic system in an urban environment. Complex reverberation, multipath, diffraction, and signature masking by building structures makes this a very harsh environment for robust detection and classification of shockwaves and muzzle blasts. Multifunctional acoustic detection arrays can provide persistent surveillance and enhanced situational awareness for every soldier.

  12. Modal content based damage indicators and phased array transducers for structural health monitoring of aircraft structures using ultrasonic guided waves

    NASA Astrophysics Data System (ADS)

    Ren, Baiyang

    Composite materials, especially carbon fiber reinforced polymers (CFRP), have been widely used in the aircraft industry because of their high specific strength and stiffness, resistance to corrosion and good fatigue life. Due to their highly anisotropic material properties and laminated structures, joining methods like bolting and riveting are no longer appropriate for joining CFRP since they initiate defects during the assembly and severely compromise the integrity of the structure; thus new techniques for joining CFRP are highly demanded. Adhesive bonding is a promising method because it relieves stress concentration, reduces weight and provides smooth surfaces. Additionally, it is a low-cost alternative to the co-cured method which is currently used to manufacture components of aircraft fuselage. Adhesive defects, disbonds at the interface between adherend and adhesive layer, are focused on in this thesis because they can be initialized by either poor surface preparation during the manufacturing or fatigue loads during service. Aircraft need structural health monitoring (SHM) systems to increase safety and reduce loss, and adhesive bonds usually represent the hotspots of the assembled structure. There are many nondestructive evaluation (NDE) methods for bond inspection. However, these methods cannot be readily integrated into an SHM system because of the bulk size and weight of the equipment and requirement of accessibility to one side of the bonded joint. The first objective of this work is to develop instruments, actuators, sensors and a data acquisition system for SHM of bond lines using ultrasonic guided waves which are well known to be able to cover large volume of the structure and inaccessible regions. Different from widely used guided wave sensors like PZT disks, the new actuators, piezoelectric fiber composite (PFC) phased array transducers0 (PAT), can control the modal content of the excited waves and the new sensors, polyvinylidene fluoride (PVDF

  13. Objective Assessment and Design Improvement of a Staring, Sparse Transducer Array by the Spatial Crosstalk Matrix for 3D Photoacoustic Tomography

    PubMed Central

    Kosik, Ivan; Raess, Avery

    2015-01-01

    Accurate reconstruction of 3D photoacoustic (PA) images requires detection of photoacoustic signals from many angles. Several groups have adopted staring ultrasound arrays, but assessment of array performance has been limited. We previously reported on a method to calibrate a 3D PA tomography (PAT) staring array system and analyze system performance using singular value decomposition (SVD). The developed SVD metric, however, was impractical for large system matrices, which are typical of 3D PAT problems. The present study consisted of two main objectives. The first objective aimed to introduce the crosstalk matrix concept to the field of PAT for system design. Figures-of-merit utilized in this study were root mean square error, peak signal-to-noise ratio, mean absolute error, and a three dimensional structural similarity index, which were derived between the normalized spatial crosstalk matrix and the identity matrix. The applicability of this approach for 3D PAT was validated by observing the response of the figures-of-merit in relation to well-understood PAT sampling characteristics (i.e. spatial and temporal sampling rate). The second objective aimed to utilize the figures-of-merit to characterize and improve the performance of a near-spherical staring array design. Transducer arrangement, array radius, and array angular coverage were the design parameters examined. We observed that the performance of a 129-element staring transducer array for 3D PAT could be improved by selection of optimal values of the design parameters. The results suggested that this formulation could be used to objectively characterize 3D PAT system performance and would enable the development of efficient strategies for system design optimization. PMID:25875177

  14. Robotic vehicle uses acoustic array for detection and localization in urban environments

    NASA Astrophysics Data System (ADS)

    Young, Stuart H.; Scanlon, Michael V.

    2001-09-01

    Sophisticated robotic platforms with diverse sensor suites are quickly replacing the eyes and ears of soldiers on the complex battlefield. The Army Research Laboratory (ARL) in Adelphi, Maryland has developed a robot-based acoustic detection system that will detect an impulsive noise event, such as a sniper's weapon firing or door slam, and activate a pan-tilt to orient a visible and infrared camera toward the detected sound. Once the cameras are cued to the target, onboard image processing can then track the target and/or transmit the imagery to a remote operator for navigation, situational awareness, and target detection. Such a vehicle can provide reconnaissance, surveillance, and target acquisition for soldiers, law enforcement, and rescue personnel, and remove these people from hazardous environments. ARL's primary robotic platforms contain 16-in. diameter, eight-element acoustic arrays. Additionally, a 9- in. array is being developed in support of DARPA's Tactical Mobile Robot program. The robots have been tested in both urban and open terrain. The current acoustic processing algorithm has been optimized to detect the muzzle blast from a sniper's weapon, and reject many interfering noise sources such as wind gusts, generators, and self-noise. However, other detection algorithms for speech and vehicle detection/tracking are being developed for implementation on this and smaller robotic platforms. The collaboration between two robots, both with known positions and orientations, can provide useful triangulation information for more precise localization of the acoustic events. These robots can be mobile sensor nodes in a larger, more expansive, sensor network that may include stationary ground sensors, UAVs, and other command and control assets. This report will document the performance of the robot's acoustic localization, describe the algorithm, and outline future work.

  15. Preliminary in vivo breast vibro-acoustography results with a quasi 2-dimensional array transducer: a step forward towards clinical applications

    PubMed Central

    Mehrmohammadi, Mohammad; Fazzio, Robert T.; Whaley, Dana H.; Pruthi, Sandhya; Kinnick, Randall R.; Fatemi, Mostafa; Alizad, Azra

    2014-01-01

    We have previously investigated the application of a novel imaging modality, vibro-acoustography (VA) using an annular confocal transducer (confocal VA), integrated into a clinical prone stereotactic mammography system to detect various breast abnormalities. To shorten the scanning time and provide improved coverage of the breast, we have evolved our imaging system by implementing VA on a clinical ultrasound scanner equipped with a “quasi-2-dimensional” array transducer. We call this technique “quasi-2D vibro-acoustography” (Q2DVA). A clinical ultrasound scanner (GE Vivid 7) was modified to perform both ultrasound (US) imaging and VA using an array transducer consisting of a matrix of 12 rows by 70 columns of ultrasound elements. The newly designed system was used to perform VA on patients with either benign or cancerous lesions. Our results indicate that benign and malignant solid breast lesions were easily detected using our newly modified VA system. It was also possible to detect micro-calcifications within the breast. Our results suggest that with further development, Q2DVA could provide high-resolution diagnostic information in the clinical setting and may be used either as a stand-alone or as a complementary tool in support of other clinical imaging modalities. PMID:25438862

  16. Efficient Array Design for Sonotherapy

    PubMed Central

    Stephens, Douglas N.; Kruse, Dustin E.; Ergun, Arif S.; Barnes, Stephen; Ming Lu, X.; Ferrara, Katherine

    2008-01-01

    New linear multi-row, multi-frequency arrays have been designed, constructed and tested as fully operational ultrasound probes to produce confocal imaging and therapeutic acoustic intensities with a standard commercial ultrasound imaging system. The triple-array probes and imaging system produce high quality B-mode images with a center row imaging array at 5.3 MHz, and sufficient acoustic power with dual therapeutic arrays to produce mild hyperthermia at 1.54 MHz. The therapeutic array pair in the first probe design (termed G3) utilizes a high bandwidth and peak pressure, suitable for mechanical therapies. The second multi-array design (termed G4) has a redesigned therapeutic array pair which is optimized for high time-averaged power output suitable for mild hyperthermia applications. The “thermal therapy” design produces more than 4 Watts of acoustic power from the low frequency arrays with only a 10.5 °C internal rise in temperature after 100 seconds of continuous use with an unmodified conventional imaging system, or substantially longer operation at lower acoustic power. The low frequency arrays in both probe designs were examined and contrasted for real power transfer efficiency with a KLM model which includes all lossy contributions in the power delivery path from system transmitters to tissue load. Laboratory verification was successfully performed for the KLM derived estimates of transducer parallel model acoustic resistance and dissipation resistance, which are the critical design factors for acoustic power output and undesired internal heating respectively. PMID:18591737

  17. Origami acoustics: using principles of folding structural acoustics for simple and large focusing of sound energy

    NASA Astrophysics Data System (ADS)

    Harne, Ryan L.; Lynd, Danielle T.

    2016-08-01

    Fixed in spatial distribution, arrays of planar, electromechanical acoustic transducers cannot adapt their wave energy focusing abilities unless each transducer is externally controlled, creating challenges for the implementation and portability of such beamforming systems. Recently, planar, origami-based structural tessellations are found to facilitate great versatility in system function and properties through kinematic folding. In this research we bridge the physics of acoustics and origami-based design to discover that the simple topological reconfigurations of a Miura-ori-based acoustic array yield many orders of magnitude worth of reversible change in wave energy focusing: a potential for acoustic field morphing easily obtained through deployable, tessellated architectures. Our experimental and theoretical studies directly translate the roles of folding the tessellated array to the adaptations in spectral and spatial wave propagation sensitivities for far field energy transmission. It is shown that kinematic folding rules and flat-foldable tessellated arrays collectively provide novel solutions to the long-standing challenges of conventional, electronically-steered acoustic beamformers. While our examples consider sound radiation from the foldable array in air, linear acoustic reciprocity dictates that the findings may inspire new innovations for acoustic receivers, e.g. adaptive sound absorbers and microphone arrays, as well as concepts that include water-borne waves.

  18. Acoustic-emission linear-pulse holography

    SciTech Connect

    Collins, H.D.; Lemon, D.K.; Busse, L.J.

    1982-06-01

    This paper describes Acoustic Emission Linear Pulse Holography which combines the advantages of linear imaging and acoustic emission into a single NDE inspection system. This unique system produces a chronological linear holographic image of a flaw by utilizing the acoustic energy emitted during crack growth. Conventional linear holographic imaging uses an ultrasonic transducer to transmit energy into the volume being imaged. When the crack or defect reflects that energy, the crack acts as a new source of acoustic waves. To formulate an image of that source, a receiving transducer is scanned over the volume of interest and the phase of the received signals is measured at successive points on the scan. The innovation proposed here is the utilization of the crack generated acoustic emission as the acoustic source and generation of a line image of the crack as it grows. A thirty-two point sampling array is used to construct phase-only linear holograms of simulated acoustic emission sources on large metal plates. The phases are calculated using the pulse time-of-flight (TOF) times from the reference transducer to the array of receivers. Computer reconstruction of the image is accomplished using a one-dimensional FFT algorithm (i.e., backward wave). Experimental results are shown which graphically illustrate the unique acoustic emission images of a single point and a linear crack in a 100 mm x 1220 mm x 1220 mm aluminum plate.

  19. Modeling the acoustic receptions at the NPAL array from the Kauai source

    NASA Astrophysics Data System (ADS)

    Vera, Michael D.; Dzieciuch, Matthew A.

    2003-04-01

    Acoustic transmissions from a 75-Hz source near Kauai to a vertical line array near California were recorded as part of the North Pacific Acoustic Laboratory (NPAL) experiment. Extensive environmental measurements were also performed as part of the experiment and were intended to ensure correspondence between numerical simulations and the data. Despite the availability of this information, the process of identifying the recorded arrivals with predictions has not been a simple one. Since the source is near the seafloor at about 800 m depth, and the depth at the receiver is approximately 1800 m, acoustic interaction with the bathymetry has been explored as a possible complication. Ray simulations that allow for specular reflection from the bottom indicate that fully-refracted and bottom-interacting paths can reach the receiver range (about 3900 km) at similar travel times. The simultaneous presence of both kinds of acoustic energy could contribute to the identification difficulties. A series of parabolic-equation simulations have been performed for different geoacoustic parameters in an attempt to correspond more closely to the data. The sensitivity of the predictions to the method used to extract and interpolate the sound speeds has also been investigated. [Work supported by ONR.] a)J. A. Colosi, B. D. Cornuelle, B. D. Dushaw, M. A. Dzieciuch, B. M. Howe, J. A. Mercer, R. C. Spindel, and P. F. Worcester.

  20. Low acoustic attenuation silicone rubber lens for medical ultrasonic array probe.

    PubMed

    Itsumi, Kazuhiro; Hosono, Yasuharu; Yamamoto, Noriko; Yamashita, Yohachi John

    2009-04-01

    Effects of heavy density (rho = 9.2 x 10(3) kg/m(3)) Yb(2)O(3) fine dopant (16 nm in diameter) on the acoustic properties of a high-temperature-vulcanization (HTV) silicone rubber have been investigated, to develop a new acoustic lens material with a low acoustic attenuation (alpha) for the medical array probe application. The HTV silicone rubber has advantages in that it shows a lower alpha than that of a room-temperature-vulcanization (RTV) silicone rubber and it can be mixed by applying shear stress, using roll-milling equipment. Roll-milling time dependence of the HTV silicone rubber indicates that the alpha is closely affected by the dispersion of nanopowders in the rubber matrix. The 8 vol% Yb(2)O(3)-doped HTV silicone rubber mixed for 30 min showed the lowest alpha of 0.73 dB/mm MHz with an acoustic impedance [AI = sound speed (c) x density (rho)] of 1.43 x 10(6) kg/m(2)s at 37 degrees C. Moreover, simulation results reveal that a 5 MHz linear probe using the HTV silicone rubber doped with Yb(2)O(3) powder showed relative sensitivity around 2.6 to 3.0 dB higher than a probe using RTV silicone rubber doped with Yb(2)O(3) powder or SiO2-doped conventional silicone rubber for the ultrasonic medical application. PMID:19406717

  1. Acoustic emission linear pulse holography

    SciTech Connect

    Collins, H. D.; Busse, L. J.; Lemon, D. K.

    1985-07-30

    Defects in a structure are imaged as they propagate, using their emitted acoustic energy as a monitored source. Short bursts of acoustic energy propagate through the structure to a discrete element receiver array. A reference timing transducer located between the array and the inspection zone initiates a series of time-of-flight measurements. A resulting series of time-of-flight measurements are then treated as aperture data and are transferred to a computer for reconstruction of a synthetic linear holographic image. The images can be displayed and stored as a record of defect growth.

  2. Acoustic emission linear pulse holography

    SciTech Connect

    Collins, H. Dale; Busse, Lawrence J.; Lemon, Douglas K.

    1985-01-01

    Defects in a structure are imaged as they propagate, using their emitted acoustic energy as a monitored source. Short bursts of acoustic energy propagate through the structure to a discrete element receiver array. A reference timing transducer located between the array and the inspection zone initiates a series of time-of-flight measurements. A resulting series of time-of-flight measurements are then treated as aperture data and are transferred to a computer for reconstruction of a synthetic linear holographic image. The images can be displayed and stored as a record of defect growth.

  3. On the precision of time-of-flight shear wave speed estimation in homogeneous soft solids: initial results using a matrix array transducer.

    PubMed

    Wang, Michael; Byram, Brett; Palmeri, Mark; Rouze, Ned; Nightingale, Kathryn

    2013-04-01

    A system capable of tracking radiation-force-induced shear wave propagation in a 3-D volume using ultrasound is presented. In contrast to existing systems, which use 1-D array transducers, a 2-D matrix array is used for tracking shear wave displacements. A separate single-element transducer is used for radiation force excitation. This system allows shear wave propagation in all directions away from the push to be observed. It is shown that for a limit of 64 tracking beams, by placing the beams at the edges of the measurement region of interest (ROI) at multiple directions from the push, time-of- flight (TOF) shear wave speed (SWS) measurement uncertainty can theoretically be reduced by 40% compared with equally spacing the tracking beams within the ROI along a single plane, as is typical when using a 1-D array for tracking. This was verified by simulation, and a reduction of 30% was experimentally observed on a homogeneous phantom. Analytical expressions are presented for the relationship between TOF SWS measurement uncertainty and various shear wave imaging parameters. It is shown that TOF SWS uncertainty is inversely proportional to ROI size, and inversely proportional to the square root of the number of tracking locations for a given distribution of beam locations relative to the push. TOF SWS uncertainty is shown to increase with the square of the SWS, indicating that TOF SWS measurements are intrinsically less precise for stiffer materials.

  4. Acoustic investigation of wall jet over a backward-facing step using a microphone phased array

    NASA Astrophysics Data System (ADS)

    Perschke, Raimund F.; Ramachandran, Rakesh C.; Raman, Ganesh

    2015-02-01

    The acoustic properties of a wall jet over a hard-walled backward-facing step of aspect ratios 6, 3, 2, and 1.5 are studied using a 24-channel microphone phased array at Mach numbers up to M=0.6. The Reynolds number based on inflow velocity and step height assumes values from Reh = 3.0 ×104 to 7.2 ×105. Flow without and with side walls is considered. The experimental setup is open in the wall-normal direction and the expansion ratio is effectively 1. In case of flow through a duct, symmetry of the flow in the spanwise direction is lost downstream of separation at all but the largest aspect ratio as revealed by oil paint flow visualization. Hydrodynamic scattering of turbulence from the trailing edge of the step contributes significantly to the radiated sound. Reflection of acoustic waves from the bottom plate results in a modulation of power spectral densities. Acoustic source localization has been conducted using a 24-channel microphone phased array. Convective mean-flow effects on the apparent source origin have been assessed by placing a loudspeaker underneath a perforated flat plate and evaluating the displacement of the beamforming peak with inflow Mach number. Two source mechanisms are found near the step. One is due to interaction of the turbulent wall jet with the convex edge of the step. Free-stream turbulence sound is found to be peaked downstream of the step. Presence of the side walls increases free-stream sound. Results of the flow visualization are correlated with acoustic source maps. Trailing-edge sound and free-stream turbulence sound can be discriminated using source localization.

  5. Microfluidic device for acoustic cell lysis

    SciTech Connect

    Branch, Darren W.; Cooley, Erika Jane; Smith, Gennifer Tanabe; James, Conrad D.; McClain, Jaime L.

    2015-08-04

    A microfluidic acoustic-based cell lysing device that can be integrated with on-chip nucleic acid extraction. Using a bulk acoustic wave (BAW) transducer array, acoustic waves can be coupled into microfluidic cartridges resulting in the lysis of cells contained therein by localized acoustic pressure. Cellular materials can then be extracted from the lysed cells. For example, nucleic acids can be extracted from the lysate using silica-based sol-gel filled microchannels, nucleic acid binding magnetic beads, or Nafion-coated electrodes. Integration of cell lysis and nucleic acid extraction on-chip enables a small, portable system that allows for rapid analysis in the field.

  6. Shallow water acoustic backscatter and reverberation measurements using a 68-kHz cylindrical array

    NASA Astrophysics Data System (ADS)

    Gallaudet, Timothy Cole

    2001-10-01

    The characterization of high frequency, shallow water acoustic backscatter and reverberation is important because acoustic systems are used in many scientific, commercial, and military applications. The approach taken is to use data collected by the Toroidal Volume Search Sonar (TVSS), a 68 kHz multibeam sonar capable of 360° imaging in a vertical plane perpendicular to its direction of travel. With this unique capability, acoustic backscatter imagery of the seafloor, sea surface, and horizontal and vertical planes in the volume are constructed from data obtained in 200m deep waters in the Northeastern Gulf of Mexico when the TVSS was towed 78m below the surface, 735m astern of a towship. The processed imagery provide a quasi-synoptic characterization of the spatial and temporal structure of boundary and volume acoustic backscatter and reverberation. Diffraction, element patterns, and high sidelobe levels are shown to be the most serious problems affecting cylindrical arrays such as the TVSS, and an amplitude shading method is presented for reducing the peak sidelobe levels of irregular-line and non-coplanar arrays. Errors in the towfish's attitude and motion sensor, and irregularities in the TVSS's transmitted beampattern produce artifacts in the TVSS-derived bathymetry and seafloor acoustic backscatter imagery. Correction strategies for these problems are described, which are unique in that they use environmental information extracted from both ocean boundaries. Sea surface and volume acoustic backscatter imagery are used to explore and characterize the structure of near-surface bubble clouds, schooling fish, and zooplankton. The simultaneous horizontal and vertical coverage provided by the TVSS is shown to be a primary advantage, motivating further use of multibeam sonars in these applications. Whereas boundary backscatter fluctuations are well described by Weibull, K, and Rayleigh mixture probability distributions, those corresponding to volume backscatter are

  7. Standoff photoacoustic detections with high-sensitivity microphones and acoustic arrays

    NASA Astrophysics Data System (ADS)

    Choa, Fow-Sen; Wang, Chen-Chia; Khurgin, Jacob; Samuels, Alan; Trivedi, Sudhir; Gupta, Deepa

    2016-05-01

    Standoff detection of dangerous chemicals like explosives, nerve gases, and harmful aerosols has continuously been an important subject due to the serious concern about terrorist threats to both overseas and homeland lives and facility. Compared with other currently available standoff optical detection techniques, like Raman, photo-thermal, laser induced breakdown spectroscopy,...etc., photoacoustic (PA) sensing has the advantages of background free and very high detection sensitivity, no need of back reflection surfaces, and 1/R instead of 1/R2 signal decay distance dependence. Furthermore, there is still a great room for PA sensitivity improvement by using different PA techniques, including lockin amplifier, employing new microphones, and microphone array techniques. Recently, we have demonstrated standoff PA detection of isopropanol vapor, solid phase TNT and RDX at a standoff distance. To further calibrate the detection sensitivity, we use nerve gas simulants that were generated and calibrated by a commercial vapor generator. For field operations, array of microphones and microphone-reflector pairs can be utilized to achieve noise rejection and signal enhancement. We have experimentally demonstrated signal enhancement and noise reduction using an array of 4 microphone/4 reflector system as well as an array of 16-microphone/1 reflector. In this work we will review and compare different standoff techniques and discuss the advantages of using different photoacoustic techniques. We will also discuss new advancement of using new types of microphone and the performance comparison of using different structure of microphone arrays and combining lock-in amplifier with acoustic arrays. Demonstration of out-door real-time operations with high power mid-IR laser and microphone array will be presented.

  8. A preliminary engineering design of intravascular dual-frequency transducers for contrast-enhanced acoustic angiography and molecular imaging.

    PubMed

    Ma, Jianguo; Martin, K; Dayton, Paul A; Jiang, Xiaoning

    2014-05-01

    Current intravascular ultrasound (IVUS) probes are not optimized for contrast detection because of their design for high-frequency fundamental-mode imaging. However, data from transcutaneous contrast imaging suggests the possibility of utilizing contrast ultrasound for molecular imaging or vasa vasorum assessment to further elucidate atherosclerotic plaque deposition. This paper presents the design, fabrication, and characterization of a small-aperture (0.6 × 3 mm) IVUS probe optimized for high-frequency contrast imaging. The design utilizes a dual-frequency (6.5 MHz/30 MHz) transducer arrangement for exciting microbubbles at low frequencies (near their resonance) and detecting their broadband harmonics at high frequencies, minimizing detected tissue backscatter. The prototype probe is able to generate nonlinear microbubble response with more than 1.2 MPa of rarefractional pressure (mechanical index: 0.48) at 6.5 MHz, and is also able to detect microbubble response with a broadband receiving element (center frequency: 30 MHz, -6-dB fractional bandwidth: 58.6%). Nonlinear super-harmonics from microbubbles flowing through a 200-μm-diameter micro-tube were clearly detected with a signal-to-noise ratio higher than 12 dB. Preliminary phantom imaging at the fundamental frequency (30 MHz) and dual-frequency super-harmonic imaging results suggest the promise of small aperture, dual-frequency IVUS transducers for contrast-enhanced IVUS imaging. PMID:24801226

  9. A Preliminary Engineering Design of Intravascular Dual-Frequency Transducers for Contrast-Enhanced Acoustic Angiography and Molecular Imaging

    PubMed Central

    Ma, Jianguo; Martin, K. Heath; Dayton, Paul A.; Jiang, Xiaoning

    2014-01-01

    Current intravascular ultrasound (IVUS) probes are not optimized for contrast detection because of their design for high-frequency fundamental-mode imaging. However, data from transcutaneous contrast imaging suggests the possibility of utilizing contrast ultrasound for molecular imaging or vasa vasorum assessment to further elucidate atherosclerotic plaque deposition. This paper presents the design, fabrication, and characterization of a small-aperture (0.6 × 3 mm) IVUS probe optimized for high-frequency contrast imaging. The design utilizes a dual-frequency (6.5 MHz/30 MHz) transducer arrangement for exciting microbubbles at low frequencies (near their resonance) and detecting their broadband harmonics at high frequencies, minimizing detected tissue backscatter. The prototype probe is able to generate nonlinear microbubble response with more than 1.2 MPa of rarefractional pressure (mechanical index: 0.48) at 6.5 MHz, and is also able to detect microbubble response with a broadband receiving element (center frequency: 30 MHz, −6-dB fractional bandwidth: 58.6%). Nonlinear super-harmonics from microbubbles flowing through a 200-μm-diameter micro-tube were clearly detected with a signal-to-noise ratio higher than 12 dB. Preliminary phantom imaging at the fundamental frequency (30 MHz) and dual-frequency super-harmonic imaging results suggest the promise of small aperture, dual-frequency IVUS transducers for contrast-enhanced IVUS imaging. PMID:24801226

  10. Deconvolution methods and systems for the mapping of acoustic sources from phased microphone arrays

    NASA Technical Reports Server (NTRS)

    Brooks, Thomas F. (Inventor); Humphreys, Jr., William M. (Inventor)

    2010-01-01

    A method and system for mapping acoustic sources determined from a phased microphone array. A plurality of microphones are arranged in an optimized grid pattern including a plurality of grid locations thereof. A linear configuration of N equations and N unknowns can be formed by accounting for a reciprocal influence of one or more beamforming characteristics thereof at varying grid locations among the plurality of grid locations. A full-rank equation derived from the linear configuration of N equations and N unknowns can then be iteratively determined. A full-rank can be attained by the solution requirement of the positivity constraint equivalent to the physical assumption of statically independent noise sources at each N location. An optimized noise source distribution is then generated over an identified aeroacoustic source region associated with the phased microphone array in order to compile an output presentation thereof, thereby removing the beamforming characteristics from the resulting output presentation.

  11. Deconvolution Methods and Systems for the Mapping of Acoustic Sources from Phased Microphone Arrays

    NASA Technical Reports Server (NTRS)

    Brooks, Thomas F. (Inventor); Humphreys, Jr., William M. (Inventor)

    2012-01-01

    Mapping coherent/incoherent acoustic sources as determined from a phased microphone array. A linear configuration of equations and unknowns are formed by accounting for a reciprocal influence of one or more cross-beamforming characteristics thereof at varying grid locations among the plurality of grid locations. An equation derived from the linear configuration of equations and unknowns can then be iteratively determined. The equation can be attained by the solution requirement of a constraint equivalent to the physical assumption that the coherent sources have only in phase coherence. The size of the problem may then be reduced using zoning methods. An optimized noise source distribution is then generated over an identified aeroacoustic source region associated with a phased microphone array (microphones arranged in an optimized grid pattern including a plurality of grid locations) in order to compile an output presentation thereof, thereby removing beamforming characteristics from the resulting output presentation.

  12. Phased Acoustic Array Measurements of a 5.75 Percent Hybrid Wing Body Aircraft

    NASA Technical Reports Server (NTRS)

    Burnside, Nathan J.; Horne, William C.; Elmer, Kevin R.; Cheng, Rui; Brusniak, Leon

    2016-01-01

    Detailed acoustic measurements of the noise from the leading-edge Krueger flap of a 5.75 percent Hybrid Wing Body (HWB) aircraft model were recently acquired with a traversing phased microphone array in the AEDC NFAC (Arnold Engineering Development Complex, National Full Scale Aerodynamics Complex) 40- by 80-Foot Wind Tunnel at NASA Ames Research Center. The spatial resolution of the array was sufficient to distinguish between individual support brackets over the full-scale frequency range of 100 to 2875 Hertz. For conditions representative of landing and take-off configuration, the noise from the brackets dominated other sources near the leading edge. Inclusion of flight-like brackets for select conditions highlights the importance of including the correct number of leading-edge high-lift device brackets with sufficient scale and fidelity. These measurements will support the development of new predictive models.

  13. Can you hear me now? Range-testing a submerged passive acoustic receiver array in a Caribbean coral reef habitat.

    PubMed

    Selby, Thomas H; Hart, Kristen M; Fujisaki, Ikuko; Smith, Brian J; Pollock, Clayton J; Hillis-Starr, Zandy; Lundgren, Ian; Oli, Madan K

    2016-07-01

    Submerged passive acoustic technology allows researchers to investigate spatial and temporal movement patterns of many marine and freshwater species. The technology uses receivers to detect and record acoustic transmissions emitted from tags attached to an individual. Acoustic signal strength naturally attenuates over distance, but numerous environmental variables also affect the probability a tag is detected. Knowledge of receiver range is crucial for designing acoustic arrays and analyzing telemetry data. Here, we present a method for testing a relatively large-scale receiver array in a dynamic Caribbean coastal environment intended for long-term monitoring of multiple species. The U.S. Geological Survey and several academic institutions in collaboration with resource management at Buck Island Reef National Monument (BIRNM), off the coast of St. Croix, recently deployed a 52 passive acoustic receiver array. We targeted 19 array-representative receivers for range-testing by submersing fixed delay interval range-testing tags at various distance intervals in each cardinal direction from a receiver for a minimum of an hour. Using a generalized linear mixed model (GLMM), we estimated the probability of detection across the array and assessed the effect of water depth, habitat, wind, temperature, and time of day on the probability of detection. The predicted probability of detection across the entire array at 100 m distance from a receiver was 58.2% (95% CI: 44.0-73.0%) and dropped to 26.0% (95% CI: 11.4-39.3%) 200 m from a receiver indicating a somewhat constrained effective detection range. Detection probability varied across habitat classes with the greatest effective detection range occurring in homogenous sand substrate and the smallest in high rugosity reef. Predicted probability of detection across BIRNM highlights potential gaps in coverage using the current array as well as limitations of passive acoustic technology within a complex coral reef environment

  14. Can you hear me now? Range-testing a submerged passive acoustic receiver array in a Caribbean coral reef habitat

    USGS Publications Warehouse

    Selby, Thomas H.; Hart, Kristen M.; Fujisaki, Ikuko; Smith, Brian J.; Pollock, Clayton J; Hillis-Star, Zandy M; Lundgren, Ian; Oli, Madan K.

    2016-01-01

    Submerged passive acoustic technology allows researchers to investigate spatial and temporal movement patterns of many marine and freshwater species. The technology uses receivers to detect and record acoustic transmissions emitted from tags attached to an individual. Acoustic signal strength naturally attenuates over distance, but numerous environmental variables also affect the probability a tag is detected. Knowledge of receiver range is crucial for designing acoustic arrays and analyzing telemetry data. Here, we present a method for testing a relatively large-scale receiver array in a dynamic Caribbean coastal environment intended for long-term monitoring of multiple species. The U.S. Geological Survey and several academic institutions in collaboration with resource management at Buck Island Reef National Monument (BIRNM), off the coast of St. Croix, recently deployed a 52 passive acoustic receiver array. We targeted 19 array-representative receivers for range-testing by submersing fixed delay interval range-testing tags at various distance intervals in each cardinal direction from a receiver for a minimum of an hour. Using a generalized linear mixed model (GLMM), we estimated the probability of detection across the array and assessed the effect of water depth, habitat, wind, temperature, and time of day on the probability of detection. The predicted probability of detection across the entire array at 100 m distance from a receiver was 58.2% (95% CI: 44.0–73.0%) and dropped to 26.0% (95% CI: 11.4–39.3%) 200 m from a receiver indicating a somewhat constrained effective detection range. Detection probability varied across habitat classes with the greatest effective detection range occurring in homogenous sand substrate and the smallest in high rugosity reef. Predicted probability of detection across BIRNM highlights potential gaps in coverage using the current array as well as limitations of passive acoustic technology within a complex coral reef

  15. THE BARYON ACOUSTIC OSCILLATION BROADBAND AND BROAD-BEAM ARRAY: DESIGN OVERVIEW AND SENSITIVITY FORECASTS

    SciTech Connect

    Pober, Jonathan C.; Parsons, Aaron R.; McQuinn, Matthew; Ali, Zaki; DeBoer, David R.; McDonald, Patrick; Aguirre, James E.; Bradley, Richard F.; Chang, Tzu-Ching; Morales, Miguel F.

    2013-03-15

    This work describes a new instrument optimized for a detection of the neutral hydrogen 21 cm power spectrum between redshifts of 0.5 and 1.5: the Baryon Acoustic Oscillation Broadband and Broad-beam (BAOBAB) array. BAOBAB will build on the efforts of a first generation of 21 cm experiments that are targeting a detection of the signal from the Epoch of Reionization at z {approx} 10. At z {approx} 1, the emission from neutral hydrogen in self-shielded overdense halos also presents an accessible signal, since the dominant, synchrotron foreground emission is considerably fainter than at redshift 10. The principle science driver for these observations are baryon acoustic oscillations in the matter power spectrum which have the potential to act as a standard ruler and constrain the nature of dark energy. BAOBAB will fully correlate dual-polarization antenna tiles over the 600-900 MHz band with a frequency resolution of 300 kHz and a system temperature of 50 K. The number of antennas will grow in staged deployments, and reconfigurations of the array will allow for both traditional imaging and high power spectrum sensitivity operations. We present calculations of the power spectrum sensitivity for various array sizes, with a 35 element array measuring the cosmic neutral hydrogen fraction as a function of redshift, and a 132 element system detecting the BAO features in the power spectrum, yielding a 1.8% error on the z {approx} 1 distance scale, and, in turn, significant improvements to constraints on the dark energy equation of state over an unprecedented range of redshifts from {approx}0.5 to 1.5.

  16. Improved Piezoelectric Loudspeakers And Transducers

    NASA Technical Reports Server (NTRS)

    Regan, Curtis Randall; Jalink, Antony; Hellbaum, Richard F.; Rohrbach, Wayne W.

    1995-01-01

    Loudspeakers and related acoustic transducers of improved type feature both light weight and energy efficiency of piezoelectric transducers and mechanical coupling efficiency. Active component of transducer made from wafer of "rainbow" piezoelectric material, ceramic piezoelectric material chemically reduced on one face. Chemical treatment forms wafer into dishlike shallow section of sphere. Both faces then coated with electrically conductive surface layers serving as electrodes. Applications include high-fidelity loudspeakers, and underwater echo ranging devices.

  17. Acoustic Tooth Cleaner

    NASA Technical Reports Server (NTRS)

    Heyman, J. S.

    1984-01-01

    Acoustically-energized water jet aids in plaque breakdown. Acoustic Wand includes acoustic transducer 1/4 wave plate, and tapered cone. Together elements energize solution of water containing mild abrasive injected into mouth to help prevent calculous buildup.

  18. A new sparse design method on phased array-based acoustic emission sensor for partial discharge detection

    NASA Astrophysics Data System (ADS)

    Xie, Qing; Cheng, Shuyi; Lü, Fangcheng; Li, Yanqing

    2014-03-01

    The acoustic detecting performance of a partial discharge (PD) ultrasonic sensor array can be improved by increasing the number of array elements. However, it will increase the complexity and cost of the PD detection system. Therefore, a sparse sensor with an optimization design can be chosen to ensure good acoustic performance. In this paper, first, a quantitative method is proposed for evaluating the acoustic performance of a square PD ultrasonic array sensor. Second, a method of sparse design is presented to combine the evaluation method with the chaotic monkey algorithm. Third, an optimal sparse structure of a 3 × 3 square PD ultrasonic array sensor is deduced. It is found that, under different sparseness and sparse structure, the main beam width of the directivity function shows a small variation, while the sidelobe amplitude shows a bigger variation. For a specific sparseness, the acoustic performance under the optimal sparse structure is close to that using a full array. Finally, some simulations based on the above method show that, for certain sparseness, the sensor with the optimal sparse structure exhibits superior positioning accuracy compared to that with a stochastic one. The sensor array structure may be chosen according to the actual requirements for an actual engineering application.

  19. Gigahertz Acoustic Vibrations of Elastically Anisotropic Indium-Tin-Oxide Nanorod Arrays.

    PubMed

    Guo, Peijun; Schaller, Richard D; Ocola, Leonidas E; Ketterson, John B; Chang, Robert P H

    2016-09-14

    Active control of light is important for photonic integrated circuits, optical switches, and telecommunications. Coupling light with acoustic vibrations in nanoscale optical resonators offers optical modulation capabilities with high bandwidth and small footprint. Instead of using noble metals, here we introduce indium-tin-oxide nanorod arrays (ITO-NRAs) as the operating media and demonstrate optical modulation covering the visible spectral range (from 360 to 700 nm) with ∼20 GHz bandwidth through the excitation of coherent acoustic vibrations in ITO-NRAs. This broadband modulation results from the collective optical diffraction by the dielectric ITO-NRAs, and a high differential transmission modulation up to 10% is achieved through efficient near-infrared, on-plasmon-resonance pumping. By combining the frequency signatures of the vibrational modes with finite-element simulations, we further determine the anisotropic elastic constants for single-crystalline ITO, which are not known for the bulk phase. This technique to determine elastic constants using coherent acoustic vibrations of uniform nanostructures can be generalized to the study of other inorganic materials.

  20. Gigahertz Acoustic Vibrations of Elastically Anisotropic Indium-Tin-Oxide Nanorod Arrays.

    PubMed

    Guo, Peijun; Schaller, Richard D; Ocola, Leonidas E; Ketterson, John B; Chang, Robert P H

    2016-09-14

    Active control of light is important for photonic integrated circuits, optical switches, and telecommunications. Coupling light with acoustic vibrations in nanoscale optical resonators offers optical modulation capabilities with high bandwidth and small footprint. Instead of using noble metals, here we introduce indium-tin-oxide nanorod arrays (ITO-NRAs) as the operating media and demonstrate optical modulation covering the visible spectral range (from 360 to 700 nm) with ∼20 GHz bandwidth through the excitation of coherent acoustic vibrations in ITO-NRAs. This broadband modulation results from the collective optical diffraction by the dielectric ITO-NRAs, and a high differential transmission modulation up to 10% is achieved through efficient near-infrared, on-plasmon-resonance pumping. By combining the frequency signatures of the vibrational modes with finite-element simulations, we further determine the anisotropic elastic constants for single-crystalline ITO, which are not known for the bulk phase. This technique to determine elastic constants using coherent acoustic vibrations of uniform nanostructures can be generalized to the study of other inorganic materials. PMID:27526053

  1. Indirect calibration of a large microphone array for in-duct acoustic measurements

    NASA Astrophysics Data System (ADS)

    Leclère, Q.; Pereira, A.; Finez, A.; Souchotte, P.

    2016-08-01

    This paper addresses the problem of in situ calibration of a pin hole-mounted microphone array for in-duct acoustic measurements. One approach is to individually measure the frequency response of each microphone, by submitting the probe to be calibrated and a reference microphone to the same pressure field. Although simple, this task may be very time consuming for large microphone arrays and eventually suffer from lack of access to microphones once they are installed on the test bench. An alternative global calibration procedure is thus proposed in this paper. The approach is based on the fact that the acoustic pressure can be expanded onto an analytically known spatial basis. A projection operator is defined allowing the projection of measurements onto the duct modal basis. The main assumption of the method is that the residual resulting from the difference between actual and projected measurements is mainly dominated by calibration errors. An iterative procedure to estimate the calibration factors of each microphone is proposed and validated through an experimental set-up. In addition, it is shown that the proposed scheme allows an optimization of physical parameters such as the sound speed and parameters associated to the test bench itself, such as the duct radius or the termination reflection coefficient.

  2. Modelling of the acoustic field of a multi-element HIFU array scattered by human ribs

    NASA Astrophysics Data System (ADS)

    Gélat, Pierre; ter Haar, Gail; Saffari, Nader

    2011-09-01

    The efficacy of high-intensity focused ultrasound (HIFU) for the treatment of a range of different cancers, including those of the liver, prostate and breast, has been demonstrated. As a non-invasive focused therapy, HIFU offers considerable advantages over techniques such as chemotherapy and surgical resection in terms of reduced risk of harmful side effects. Despite this, there are a number of significant challenges which currently hinder its widespread clinical application. One of these challenges is the need to transmit sufficient energy through the rib cage to induce tissue necrosis in the required volume whilst minimizing the formation of side lobes. Multi-element random-phased arrays are currently showing great promise in overcoming the limitations of single-element transducers. Nevertheless, successful treatment of a patient with liver tumours requires a thorough understanding of the way in which the ultrasonic pressure field from a HIFU array is scattered by the rib cage. In order to address this, a boundary element approach based on a generalized minimal residual (GMRES) implementation of the Burton-Miller formulation was used in conjunction with phase conjugation techniques to focus the field of a 256-element random HIFU array behind human ribs at locations requiring intercostal and transcostal treatment. Simulations were carried out on a 3D mesh of quadratic pressure patches generated using CT scan anatomical data for adult ribs 9-12 on the right side. The methodology was validated on spherical and cylindrical scatterers. Field calculations were also carried out for idealized ribs, consisting of arrays of strip-like scatterers, demonstrating effects of splitting at the focus. This method has the advantage of fully accounting for the effect of scattering and diffraction in 3D under continuous wave excitation.

  3. Modelling of the acoustic field of a multi-element HIFU array scattered by human ribs.

    PubMed

    Gélat, Pierre; Ter Haar, Gail; Saffari, Nader

    2011-09-01

    The efficacy of high-intensity focused ultrasound (HIFU) for the treatment of a range of different cancers, including those of the liver, prostate and breast, has been demonstrated. As a non-invasive focused therapy, HIFU offers considerable advantages over techniques such as chemotherapy and surgical resection in terms of reduced risk of harmful side effects. Despite this, there are a number of significant challenges which currently hinder its widespread clinical application. One of these challenges is the need to transmit sufficient energy through the rib cage to induce tissue necrosis in the required volume whilst minimizing the formation of side lobes. Multi-element random-phased arrays are currently showing great promise in overcoming the limitations of single-element transducers. Nevertheless, successful treatment of a patient with liver tumours requires a thorough understanding of the way in which the ultrasonic pressure field from a HIFU array is scattered by the rib cage. In order to address this, a boundary element approach based on a generalized minimal residual (GMRES) implementation of the Burton-Miller formulation was used in conjunction with phase conjugation techniques to focus the field of a 256-element random HIFU array behind human ribs at locations requiring intercostal and transcostal treatment. Simulations were carried out on a 3D mesh of quadratic pressure patches generated using CT scan anatomical data for adult ribs 9-12 on the right side. The methodology was validated on spherical and cylindrical scatterers. Field calculations were also carried out for idealized ribs, consisting of arrays of strip-like scatterers, demonstrating effects of splitting at the focus. This method has the advantage of fully accounting for the effect of scattering and diffraction in 3D under continuous wave excitation.

  4. An Air-Coupled Multiple Moving Membrane Micromachined Ultrasonic Transducer With Inverse Biasing Functionality.

    PubMed

    Emadi, Arezoo; Buchanan, Douglas A

    2016-08-01

    A novel air-coupled multiple moving membrane-capacitive micromachined ultrasonic transducer ( [Formula: see text]-CMUT) with individually biased deflectable plates has been developed. Unlike the conventional capacitive micromachined ultrasonic transducer, this device cell structure includes an additional deflectable plate that is suspended underneath the transducer top plate. This added flexible plate contributes to the device signal transmission and reception. It is demonstrated that due to the presence of this added moving plate, the transducer is capable of operating under inverse bias condition, where the driving voltage is sandwiched between two grounded electrodes. COMSOL electromechanical simulations were conducted to investigate the influence of the transducer additional moving plate. A set of three individuals and an array of [Formula: see text]-CMUT transducers were fabricated using a sacrificial technique and with resonant frequencies ranging from 0.8 to 2.1 MHz. Electrical, optical, and pitch-catch acoustic measurements were performed to characterize the transducers properties under inverse bias condition. The experimental results are shown to be in good agreement with the simulation results for all of the fabricated transducers. It is shown that these transducers are fully functional under both normal and inverse bias conditions without any degradation in the transducer performance. PMID:27254861

  5. Transcranial passive acoustic mapping with hemispherical sparse arrays using CT-based skull-specific aberration corrections: a simulation study.

    PubMed

    Jones, Ryan M; O'Reilly, Meaghan A; Hynynen, Kullervo

    2013-07-21

    The feasibility of transcranial passive acoustic mapping with hemispherical sparse arrays (30 cm diameter, 16 to 1372 elements, 2.48 mm receiver diameter) using CT-based aberration corrections was investigated via numerical simulations. A multi-layered ray acoustic transcranial ultrasound propagation model based on CT-derived skull morphology was developed. By incorporating skull-specific aberration corrections into a conventional passive beamforming algorithm (Norton and Won 2000 IEEE Trans. Geosci. Remote Sens. 38 1337-43), simulated acoustic source fields representing the emissions from acoustically-stimulated microbubbles were spatially mapped through three digitized human skulls, with the transskull reconstructions closely matching the water-path control images. Image quality was quantified based on main lobe beamwidths, peak sidelobe ratio, and image signal-to-noise ratio. The effects on the resulting image quality of the source's emission frequency and location within the skull cavity, the array sparsity and element configuration, the receiver element sensitivity, and the specific skull morphology were all investigated. The system's resolution capabilities were also estimated for various degrees of array sparsity. Passive imaging of acoustic sources through an intact skull was shown possible with sparse hemispherical imaging arrays. This technique may be useful for the monitoring and control of transcranial focused ultrasound (FUS) treatments, particularly non-thermal, cavitation-mediated applications such as FUS-induced blood-brain barrier disruption or sonothrombolysis, for which no real-time monitoring techniques currently exist.

  6. Transcranial passive acoustic mapping with hemispherical sparse arrays using CT-based skull-specific aberration corrections: a simulation study

    PubMed Central

    Jones, Ryan M.; O’Reilly, Meaghan A.; Hynynen, Kullervo

    2013-01-01

    The feasibility of transcranial passive acoustic mapping with hemispherical sparse arrays (30 cm diameter, 16 to 1372 elements, 2.48 mm receiver diameter) using CT-based aberration corrections was investigated via numerical simulations. A multi-layered ray acoustic transcranial ultrasound propagation model based on CT-derived skull morphology was developed. By incorporating skull-specific aberration corrections into a conventional passive beamforming algorithm (Norton and Won 2000 IEEE Trans. Geosci. Remote Sens. 38 1337–43), simulated acoustic source fields representing the emissions from acoustically-stimulated microbubbles were spatially mapped through three digitized human skulls, with the transskull reconstructions closely matching the water-path control images. Image quality was quantified based on main lobe beamwidths, peak sidelobe ratio, and image signal-to-noise ratio. The effects on the resulting image quality of the source’s emission frequency and location within the skull cavity, the array sparsity and element configuration, the receiver element sensitivity, and the specific skull morphology were all investigated. The system’s resolution capabilities were also estimated for various degrees of array sparsity. Passive imaging of acoustic sources through an intact skull was shown possible with sparse hemispherical imaging arrays. This technique may be useful for the monitoring and control of transcranial focused ultrasound (FUS) treatments, particularly non-thermal, cavitation-mediated applications such as FUS-induced blood-brain barrier disruption or sonothrombolysis, for which no real-time monitoring technique currently exists. PMID:23807573

  7. Transcranial passive acoustic mapping with hemispherical sparse arrays using CT-based skull-specific aberration corrections: a simulation study

    NASA Astrophysics Data System (ADS)

    Jones, Ryan M.; O'Reilly, Meaghan A.; Hynynen, Kullervo

    2013-07-01

    The feasibility of transcranial passive acoustic mapping with hemispherical sparse arrays (30 cm diameter, 16 to 1372 elements, 2.48 mm receiver diameter) using CT-based aberration corrections was investigated via numerical simulations. A multi-layered ray acoustic transcranial ultrasound propagation model based on CT-derived skull morphology was developed. By incorporating skull-specific aberration corrections into a conventional passive beamforming algorithm (Norton and Won 2000 IEEE Trans. Geosci. Remote Sens. 38 1337-43), simulated acoustic source fields representing the emissions from acoustically-stimulated microbubbles were spatially mapped through three digitized human skulls, with the transskull reconstructions closely matching the water-path control images. Image quality was quantified based on main lobe beamwidths, peak sidelobe ratio, and image signal-to-noise ratio. The effects on the resulting image quality of the source’s emission frequency and location within the skull cavity, the array sparsity and element configuration, the receiver element sensitivity, and the specific skull morphology were all investigated. The system’s resolution capabilities were also estimated for various degrees of array sparsity. Passive imaging of acoustic sources through an intact skull was shown possible with sparse hemispherical imaging arrays. This technique may be useful for the monitoring and control of transcranial focused ultrasound (FUS) treatments, particularly non-thermal, cavitation-mediated applications such as FUS-induced blood-brain barrier disruption or sonothrombolysis, for which no real-time monitoring techniques currently exist.

  8. Real-time monitoring of focused ultrasound blood-brain barrier opening via subharmonic acoustic emission detection: implementation of confocal dual-frequency piezoelectric transducers

    NASA Astrophysics Data System (ADS)

    Tsai, Chih-Hung; Zhang, Jia-Wei; Liao, Yi-Yi; Liu, Hao-Li

    2016-04-01

    Burst-tone focused ultrasound exposure in the presence of microbubbles has been demonstrated to be effective at inducing temporal and local opening of the blood-brain barrier (BBB), which promises significant clinical potential to deliver therapeutic molecules into the central nervous system (CNS). Traditional contrast-enhanced imaging confirmation after focused ultrasound (FUS) exposure serves as a post-operative indicator of the effectiveness of FUS-BBB opening, however, an indicator that can concurrently report the BBB status and BBB-opening effectiveness is required to provide effective feedback to implement this treatment clinically. In this study, we demonstrate the use of subharmonic acoustic emission detection with implementation on a confocal dual-frequency piezoelectric ceramic structure to perform real-time monitoring of FUS-BBB opening. A confocal dual-frequency (0.55 MHz/1.1 MHz) focused ultrasound transducer was designed. The 1.1 MHz spherically-curved ceramic was employed to deliver FUS exposure to induce BBB-opening, whereas the outer-ring 0.55 MHz ceramic was employed to detect the subharmonic acoustic emissions originating from the target position. In stage-1 experiments, we employed spectral analysis and performed an energy spectrum density (ESD) calculation. An optimized 0.55 MHz ESD level change was shown to effectively discriminate the occurrence of BBB-opening. Wideband acoustic emissions received from 0.55 MHz ceramics were also analyzed to evaluate its correlations with erythrocyte extravasations. In stage-2 real-time monitoring experiments, we applied the predetermined ESD change as a detection threshold in PC-controlled algorithm to predict the FUS exposure intra-operatively. In stage-1 experiment, we showed that subharmonic ESD presents distinguishable dynamics between intact BBB and opened BBB, and therefore a threshold ESD change level (5.5 dB) can be identified for BBB-opening prediction. Using this ESD change threshold detection as a

  9. Real-time monitoring of focused ultrasound blood-brain barrier opening via subharmonic acoustic emission detection: implementation of confocal dual-frequency piezoelectric transducers.

    PubMed

    Tsai, Chih-Hung; Zhang, Jia-Wei; Liao, Yi-Yi; Liu, Hao-Li

    2016-04-01

    Burst-tone focused ultrasound exposure in the presence of microbubbles has been demonstrated to be effective at inducing temporal and local opening of the blood-brain barrier (BBB), which promises significant clinical potential to deliver therapeutic molecules into the central nervous system (CNS). Traditional contrast-enhanced imaging confirmation after focused ultrasound (FUS) exposure serves as a post-operative indicator of the effectiveness of FUS-BBB opening, however, an indicator that can concurrently report the BBB status and BBB-opening effectiveness is required to provide effective feedback to implement this treatment clinically. In this study, we demonstrate the use of subharmonic acoustic emission detection with implementation on a confocal dual-frequency piezoelectric ceramic structure to perform real-time monitoring of FUS-BBB opening. A confocal dual-frequency (0.55 MHz/1.1 MHz) focused ultrasound transducer was designed. The 1.1 MHz spherically-curved ceramic was employed to deliver FUS exposure to induce BBB-opening, whereas the outer-ring 0.55 MHz ceramic was employed to detect the subharmonic acoustic emissions originating from the target position. In stage-1 experiments, we employed spectral analysis and performed an energy spectrum density (ESD) calculation. An optimized 0.55 MHz ESD level change was shown to effectively discriminate the occurrence of BBB-opening. Wideband acoustic emissions received from 0.55 MHz ceramics were also analyzed to evaluate its correlations with erythrocyte extravasations. In stage-2 real-time monitoring experiments, we applied the predetermined ESD change as a detection threshold in PC-controlled algorithm to predict the FUS exposure intra-operatively. In stage-1 experiment, we showed that subharmonic ESD presents distinguishable dynamics between intact BBB and opened BBB, and therefore a threshold ESD change level (5.5 dB) can be identified for BBB-opening prediction. Using this ESD change threshold detection as a

  10. Statistical analysis of storm electrical discharges reconstituted from a lightning mapping system, a lightning location system, and an acoustic array

    NASA Astrophysics Data System (ADS)

    Gallin, Louis-Jonardan; Farges, Thomas; Marchiano, Régis; Coulouvrat, François; Defer, Eric; Rison, William; Schulz, Wolfgang; Nuret, Mathieu

    2016-04-01

    In the framework of the European Hydrological Cycle in the Mediterranean Experiment project, a field campaign devoted to the study of electrical activity during storms took place in the south of France in 2012. An acoustic station composed of four microphones and four microbarometers was deployed within the coverage of a Lightning Mapping Array network. On the 26 October 2012, a thunderstorm passed just over the acoustic station. Fifty-six natural thunder events, due to cloud-to-ground and intracloud flashes, were recorded. This paper studies the acoustic reconstruction, in the low frequency range from 1 to 40 Hz, of the recorded flashes and their comparison with detections from electromagnetic networks. Concurrent detections from the European Cooperation for Lightning Detection lightning location system were also used. Some case studies show clearly that acoustic signal from thunder comes from the return stroke but also from the horizontal discharges which occur inside the clouds. The huge amount of observation data leads to a statistical analysis of lightning discharges acoustically recorded. Especially, the distributions of altitudes of reconstructed acoustic detections are explored in detail. The impact of the distance to the source on these distributions is established. The capacity of the acoustic method to describe precisely the lower part of nearby cloud-to-ground discharges, where the Lightning Mapping Array network is not effective, is also highlighted.

  11. Analysis of binary mixtures of aqueous aromatic hydrocarbons with low-phase-noise shear-horizontal surface acoustic wave sensors using multielectrode transducer designs.

    PubMed

    Bender, Florian; Mohler, Rachel E; Ricco, Antonio J; Josse, Fabien

    2014-11-18

    The present work investigates a compact sensor system that provides rapid, real-time, in situ measurements of the identities and concentrations of aromatic hydrocarbons at parts-per-billion concentrations in water through the combined use of kinetic and thermodynamic response parameters. The system uses shear-horizontal surface acoustic wave (SH-SAW) sensors operating directly in the liquid phase. The 103 MHz SAW sensors are coated with thin sorbent polymer films to provide the appropriate limits of detection as well as partial selectivity for the analytes of interest, the BTEX compounds (benzene, toluene, ethylbenzene, and xylenes), which are common indicators of fuel and oil accidental releases in groundwater. Particular emphasis is placed on benzene, a known carcinogen and the most challenging BTEX analyte with regard to both regulated levels and its solubility properties. To demonstrate the identification and quantification of individual compounds in multicomponent aqueous samples, responses to binary mixtures of benzene with toluene as well as ethylbenzene were characterized at concentrations below 1 ppm (1 mg/L). The use of both thermodynamic and kinetic (i.e., steady-state and transient) responses from a single polymer-coated SH-SAW sensor enabled identification and quantification of the two BTEX compounds in binary mixtures in aqueous solution. The signal-to-noise ratio was improved, resulting in lower limits of detection and improved identification at low concentrations, by designing and implementing a type of multielectrode transducer pattern, not previously reported for chemical sensor applications. The design significantly reduces signal distortion and root-mean-square (RMS) phase noise by minimizing acoustic wave reflections from electrode edges, thus enabling limits of detection for BTEX analytes of 9-83 ppb (calculated from RMS noise); concentrations of benzene in water as low as ~100 ppb were measured directly. Reliable quantification of BTEX

  12. Transducer characterization

    SciTech Connect

    Cross, B. T.; Eoff, J. M.; Schuetz, L. J.; Cunningham, K. R.

    1980-07-02

    This report has been prepared specifically for ultrasonic transducer users within the Nondestructive Testing Evaluation (NDE) community of the weapons complex. The purpose of the report is to establish an initial set of uniform procedures for measuring and recording transducer performance data, and to establish a common foundation on which more comprehensive transducer performance evaluations may be added as future transducer performance criteria expands. Transducer parameters and the problems with measuring them are discussed and procedures for measuring transducer performance are recommended with special precautionary notes regarding critical aspects of each measurement. An important consideration regarding the recommended procedures is the cost of implementation. There are two distinct needs for transducer performance characterization in the complex. Production oriented users need a quick, reliable means to check a transducer to ascertain its suitability for continued service. Development groups and the Transducer Center need a comprehensive characterization means to collect adequate data to evaluate theoretical concepts or to build exact replacement transducers. The instrumentation, equipment, and procedures recommended for monitoring production transducers are utilitarian and provide only that information needed to determine transducer condition.

  13. Improving Plating by Use of Intense Acoustic Beams

    NASA Technical Reports Server (NTRS)

    Oeftering, Richard C.; Denofrio, Charles

    2003-01-01

    An improved method of selective plating of metals and possibly other materials involves the use of directed high-intensity acoustic beams. The beams, typically in the ultrasonic frequency range, can be generated by fixed-focus transducers (see figure) or by phased arrays of transducers excited, variously, by continuous waves, tone bursts, or single pulses. The nonlinear effects produced by these beams are used to alter plating processes in ways that are advantageous.

  14. Feasibility of vibro-acoustography with a quasi-2D ultrasound array transducer for detection and localizing of permanent prostate brachytherapy seeds: A pilot ex vivo study

    SciTech Connect

    Mehrmohammadi, Mohammad; Kinnick, Randall R.; Fatemi, Mostafa; Alizad, Azra; Davis, Brian J.

    2014-09-15

    Purpose: Effective permanent prostate brachytherapy (PPB) requires precise placement of radioactive seeds in and around the prostate. The impetus for this research is to examine a new ultrasound-based imaging modality, vibro-acoustography (VA), which may serve to provide a high rate of PPB seed detection while also effecting enhanced prostate imaging. The authors investigate the ability of VA, implemented on a clinical ultrasound (US) scanner and equipped with a quasi-2D (Q2D) array US transducer, to detect and localize PPB seeds in excised prostate specimens. Methods: Nonradioactive brachytherapy seeds were implanted into four excised cadaver prostates. A clinical US scanner equipped with a Q2D array US transducer was customized to acquire both US and C-scan VA images at various depths. The VA images were then used to detect and localize the implanted seeds in prostate tissue. To validate the VA results, computed tomography (CT) images of the same tissue samples were obtained to serve as the reference by which to evaluate the performance of VA in PPB seed detection. Results: The results indicate that VA is capable of accurately identifying the presence and distribution of PPB seeds with a high imaging contrast. Moreover, a large ratio of the PPB seeds implanted into prostate tissue samples could be detected through acquired VA images. Using CT-based seed identification as the standard, VA was capable of detecting 74%–92% of the implanted seeds. Additionally, the angular independency of VA in detecting PPB seeds was demonstrated through a well-controlled phantom experiment. Conclusions: Q2DVA detected a substantial portion of the seeds by using a 2D array US transducer in excised prostate tissue specimens. While VA has inherent advantages associated with conventional US imaging, it has the additional advantage of permitting detection of PPB seeds independent of their orientation. These results suggest the potential of VA as a method for PPB imaging that

  15. Inter-costal Liver Ablation Under Real Time MR-Thermometry With Partial Activation Of A HIFU Phased Array Transducer

    NASA Astrophysics Data System (ADS)

    Quesson, Bruno; Merle, Mathilde; Köhler, Max; Mougenot, Charles; Roujol, Sebastien; de Senneville, Baudouin Denis; Moonen, Chrit

    2010-03-01

    HIFU ablation of tumours located inside the liver is hampered by the rib cage, which partially obstructs the beam path and may create adverse effects such as skin burns. This study presents a method for selectively deactivating the transducer elements causing undesired temperature increases near the bones. A manual segmentation of the bones visualized on 3D anatomical MR images acquired prior to sonication was performed to identify the beam obstruction. The resulting mask was projected (ray tracing starting from the focal point) on the transducer and elements with more than 50% obstruction of their active surface were deactivated. The effectiveness of the method for HIFU ablations is demonstrated ex vivo and in vivo in the liver of pigs with real-time MR thermometry, using the proton resonant frequency (PRF) method. For both ex vivo and in vivo experiments, the temperature increase near the bones was significantly reduced when the elements located in front of the ribs were deactivated. The temperature evolution at the focal point were similar, indicative of the absence of loss of heating efficacy when the elements were deactivated. This method is simple, rapid and reliable and allows to perform intercostal MRgHIFU ablation of the liver while sparing the ribs.

  16. Confined acoustic and optical plasmons in double-layered quantum-wire arrays with strong tunneling

    NASA Astrophysics Data System (ADS)

    Dethlefsen, A. F.; Heyn, Ch.; Heitmann, D.; Schüller, C.

    2006-05-01

    We investigate electronic excitations in GaAs-AlxGa1-xAs double-layered quantum wire arrays with strong tunneling coupling by resonant inelastic light scattering. By applying an external electric field, we can change the one-dimensional (1D) electron density and the symmetry of the double quantum-well (DQW) structure at the same time. We identify confined optical 1D intersubband plasmons (COP) and confined acoustic 1D intersubband plasmons (CAP). Due to the tunneling coupling, the energies of the CAP exhibit a minimum for a symmetric DQW potential, whereas the energies of the COP are dominated by the total carrier density, and are nearly insensitive to the symmetry of the potential.

  17. Acoustically based fetal heart rate monitor

    NASA Technical Reports Server (NTRS)

    Baker, Donald A.; Zuckerwar, Allan J.

    1991-01-01

    The acoustically based fetal heart rate monitor permits an expectant mother to perform the fetal Non-Stress Test in her home. The potential market would include the one million U.S. pregnancies per year requiring this type of prenatal surveillance. The monitor uses polyvinylidene fluoride (PVF2) piezoelectric polymer film for the acoustic sensors, which are mounted in a seven-element array on a cummerbund. Evaluation of the sensor ouput signals utilizes a digital signal processor, which performs a linear prediction routine in real time. Clinical tests reveal that the acoustically based monitor provides Non-Stress Test records which are comparable to those obtained with a commercial ultrasonic transducer.

  18. Self-adapting root-MUSIC algorithm and its real-valued formulation for acoustic vector sensor array

    NASA Astrophysics Data System (ADS)

    Wang, Peng; Zhang, Guo-jun; Xue, Chen-yang; Zhang, Wen-dong; Xiong, Ji-jun

    2012-12-01

    In this paper, based on the root-MUSIC algorithm for acoustic pressure sensor array, a new self-adapting root-MUSIC algorithm for acoustic vector sensor array is proposed by self-adaptive selecting the lead orientation vector, and its real-valued formulation by Forward-Backward(FB) smoothing and real-valued inverse covariance matrix is also proposed, which can reduce the computational complexity and distinguish the coherent signals. The simulation experiment results show the better performance of two new algorithm with low Signal-to-Noise (SNR) in direction of arrival (DOA) estimation than traditional MUSIC algorithm, and the experiment results using MEMS vector hydrophone array in lake trails show the engineering practicability of two new algorithms.

  19. Underwater Acoustics.

    ERIC Educational Resources Information Center

    Creasey, D. J.

    1981-01-01

    Summarizes the history of underwater acoustics and describes related research studies and teaching activities at the University of Birmingham (England). Also includes research studies on transducer design and mathematical techniques. (SK)

  20. Autonomous hydrophone array for long-term acoustic monitoring in the open ocean

    NASA Astrophysics Data System (ADS)

    D'Eu, J.-F.; Brachet, C.; Goslin, J.; Royer, J.-Y.; Ammann, J.

    2009-04-01

    We are developing an array of new autonomous hydrophones, benefiting from a long-lasting collaboration with the Pacific Marine Environmental Laboratory (NOAA and Oregon state University). The hydrophones are deployed on a mooring line anchored to the seafloor by an expendable anchor weight. The length of the line is adjusted so that the sensor (and buoy) lies in the middle of the SOFAR channel at about 1000m depth for mid-latitudes (depending on the speed-of-sound profile). The buoy at depth keeps the line under tension and prevents wave-motion noise from the sensor. The instrument continuously samples and records the acoustic signals at 240Hz for seismic studies, or 480Hz (or more) for marine mammal studies. The SOFAR channel acts as an acoustic wave-guide in the ocean so that acoustic waves can propagate with little attenuation over long distances. Autonomous hydrophones allow the detection and localization of the low-magnitude (Mw>2.5) seismic activity along oceanic ridges and in deformed intraplate areas, which remains generally undetected or poorly localized by land-based seismic networks. An array of hydrophones can monitor a much wider area (more than 1000 km across) than ocean-bottom seismometers, which suffer from the rapid attenuation of seismic waves in the crust and upper mantle. Arrays of autonomous hydrophones thus succeed in detecting and locating 30 to 50 times more earthquakes than those listed in the catalogs from land-based seismograph stations. Data are buffered on flash cards and then regularly stored on hard disks or on solid-state drives (e.g. 20Gb of data per year at 240Hz sampling rate). We use 24-bit sigma-delta converters with programmable gain amplifiers. As timing is a key issue for an accurate localisation of the seismic events, instruments are synchronized with GPS time and have a low-power, highly stable calibrated clock (10-8 drift). All electronics and batteries (Li or alcaline) are placed in titanium pressure cases for long

  1. Three-dimensional acoustic imaging with planar microphone arrays and compressive sensing

    NASA Astrophysics Data System (ADS)

    Ning, Fangli; Wei, Jingang; Qiu, Lianfang; Shi, Hongbing; Li, Xiaofan

    2016-10-01

    For obtaining super-resolution source maps, we extend compressive sensing (CS) to three-dimensional acoustic imaging. Source maps are simulated with a planar microphone array and a CS algorithm. Comparing the source maps of the CS algorithm with those of the conventional beamformer (CBF) and Tikhonov Regularization (TIKR), we find that the CS algorithm is computationally more effective and can obtain much higher resolution source maps than the CBF and TIKR. The effectiveness of the CS algorithm is analyzed. The CS algorithm can locate the sound sources exactly when the frequency is above 4000 Hz and the signal-to-noise ratio (SNR) is above 12 dB. The location error of the CS algorithm increases as the frequency drops below the threshold, and the errors in location and power increase as SNR decreases. The further from the array the source is, the larger the location error is. The lateral resolution of the CS algorithm is much better than the range resolution. Finally, experimental measurements are conducted in a semi-anechoic room. Two mobile phones are served as sound sources. The results show that the CS algorithm can reconstruct two sound sources near the bottom of the two mobile phones where the speakers are located. The feasibility of the CS algorithm is also validated with the experiment.

  2. Array model interpolation and subband iterative adaptive filters applied to beamforming-based acoustic echo cancellation.

    PubMed

    Bai, Mingsian R; Chi, Li-Wen; Liang, Li-Huang; Lo, Yi-Yang

    2016-02-01

    In this paper, an evolutionary exposition is given in regard to the enhancing strategies for acoustic echo cancellers (AECs). A fixed beamformer (FBF) is utilized to focus on the near-end speaker while suppressing the echo from the far end. In reality, the array steering vector could differ considerably from the ideal freefield plane wave model. Therefore, an experimental procedure is developed to interpolate a practical array model from the measured frequency responses. Subband (SB) filtering with polyphase implementation is exploited to accelerate the cancellation process. Generalized sidelobe canceller (GSC) composed of an FBF and an adaptive blocking module is combined with AEC to maximize cancellation performance. Another enhancement is an internal iteration (IIT) procedure that enables efficient convergence in the adaptive SB filters within a sample time. Objective tests in terms of echo return loss enhancement (ERLE), perceptual evaluation of speech quality (PESQ), word recognition rate for automatic speech recognition (ASR), and subjective listening tests are conducted to validate the proposed AEC approaches. The results show that the GSC-SB-AEC-IIT approach has attained the highest ERLE without speech quality degradation, even in double-talk scenarios. PMID:26936567

  3. Guided acoustic wave inspection system

    DOEpatents

    Chinn, Diane J.

    2004-10-05

    A system for inspecting a conduit for undesirable characteristics. A transducer system induces guided acoustic waves onto said conduit. The transducer system detects the undesirable characteristics of the conduit by receiving guided acoustic waves that contain information about the undesirable characteristics. The conduit has at least two sides and the transducer system utilizes flexural modes of propagation to provide inspection using access from only the one side of the conduit. Cracking is detected with pulse-echo testing using one transducer to both send and receive the guided acoustic waves. Thinning is detected in through-transmission testing where one transducer sends and another transducer receives the guided acoustic waves.

  4. Room acoustics analysis using circular arrays: an experimental study based on sound field plane-wave decomposition.

    PubMed

    Torres, Ana M; Lopez, Jose J; Pueo, Basilio; Cobos, Maximo

    2013-04-01

    Plane-wave decomposition (PWD) methods using microphone arrays have been shown to be a very useful tool within the applied acoustics community for their multiple applications in room acoustics analysis and synthesis. While many theoretical aspects of PWD have been previously addressed in the literature, the practical advantages of the PWD method to assess the acoustic behavior of real rooms have been barely explored so far. In this paper, the PWD method is employed to analyze the sound field inside a selected set of real rooms having a well-defined purpose. To this end, a circular microphone array is used to capture and process a number of impulse responses at different spatial positions, providing angle-dependent data for both direct and reflected wavefronts. The detection of reflected plane waves is performed by means of image processing techniques applied over the raw array response data and over the PWD data, showing the usefulness of image-processing-based methods for room acoustics analysis.

  5. Particle manipulation with acoustic vortex beam induced by a brass plate with spiral shape structure

    NASA Astrophysics Data System (ADS)

    Wang, Tian; Ke, Manzhu; Li, Weiping; Yang, Qian; Qiu, Chunyin; Liu, Zhengyou

    2016-09-01

    In this work, we give direct demonstration of acoustic radiation force and acoustic torque on particles exerted by an acoustic vortex beam, which is realized by an acoustic artificial structure plate instead of traditional transducer arrays. First, the first order acoustic vortex beam, which has the distinctive features of a linear and continuous phase variation from -π to π around its propagation axis and a magnitude null at its core, is obtained through one single acoustic source incident upon a structured brass plate with Archimedean spiral grating engraved on the back surface. Second, annular self-patterning of polystyrene particles with a radius of 90 μm is realized in the gradient field of this acoustic vortex beam. In addition, we further exhibit acoustic angular momentum transfer to an acoustic absorptive matter, which is verified by a millimeter-sized polylactic acid disk self-rotating in water in the acoustic field of the generated vortex beam.

  6. Transducers for ultrasonic limb plethysmography

    NASA Technical Reports Server (NTRS)

    Nickell, W. T.; Wu, V. C.; Bhagat, P. K.

    1983-01-01

    The design, construction, and performance characteristics of ultasonic transducers suitable for limb plethysmography are presented. Both 3-mm-diameter flat-plate and 12-mm-diameter hemispheric ceramic transducers operating at 2 MHz were fitted in 1-mm thick epoxy-resin lens/acoustic-coupling structures and mounted in exercie-EKG electrode housings for placement on the calf using adhesive collars. The effects of transducer directional characteristics on performance under off-axis rotation and the electrical impedances of the transducers were measured: The flat transducer was found to be sensitive to rotation and have an impedance of 800 ohms; the hemispheric transducer, to be unaffected by rotation and have an impedance of 80 ohms. The use of hemispheric transducers as both transmitter and receiver, or of a flat transducer as transmitter and a hemispheric transducer as receiver, was found to produce adequate dimensional measurements, with minimum care in transducer placement, in short-term physiological experiments and long-term (up to 7-day) attachment tests.

  7. Theory and investigation of acoustic multiple-input multiple-output systems based on spherical arrays in a room.

    PubMed

    Morgenstern, Hai; Rafaely, Boaz; Zotter, Franz

    2015-11-01

    Spatial attributes of room acoustics have been widely studied using microphone and loudspeaker arrays. However, systems that combine both arrays, referred to as multiple-input multiple-output (MIMO) systems, have only been studied to a limited degree in this context. These systems can potentially provide a powerful tool for room acoustics analysis due to the ability to simultaneously control both arrays. This paper offers a theoretical framework for the spatial analysis of enclosed sound fields using a MIMO system comprising spherical loudspeaker and microphone arrays. A system transfer function is formulated in matrix form for free-field conditions, and its properties are studied using tools from linear algebra. The system is shown to have unit-rank, regardless of the array types, and its singular vectors are related to the directions of arrival and radiation at the microphone and loudspeaker arrays, respectively. The formulation is then generalized to apply to rooms, using an image source method. In this case, the rank of the system is related to the number of significant reflections. The paper ends with simulation studies, which support the developed theory, and with an extensive reflection analysis of a room impulse response, using the platform of a MIMO system.

  8. Theory and investigation of acoustic multiple-input multiple-output systems based on spherical arrays in a room.

    PubMed

    Morgenstern, Hai; Rafaely, Boaz; Zotter, Franz

    2015-11-01

    Spatial attributes of room acoustics have been widely studied using microphone and loudspeaker arrays. However, systems that combine both arrays, referred to as multiple-input multiple-output (MIMO) systems, have only been studied to a limited degree in this context. These systems can potentially provide a powerful tool for room acoustics analysis due to the ability to simultaneously control both arrays. This paper offers a theoretical framework for the spatial analysis of enclosed sound fields using a MIMO system comprising spherical loudspeaker and microphone arrays. A system transfer function is formulated in matrix form for free-field conditions, and its properties are studied using tools from linear algebra. The system is shown to have unit-rank, regardless of the array types, and its singular vectors are related to the directions of arrival and radiation at the microphone and loudspeaker arrays, respectively. The formulation is then generalized to apply to rooms, using an image source method. In this case, the rank of the system is related to the number of significant reflections. The paper ends with simulation studies, which support the developed theory, and with an extensive reflection analysis of a room impulse response, using the platform of a MIMO system. PMID:26627773

  9. Evaluation of the resolution of a metamaterial acoustic leaky wave antenna.

    PubMed

    Naify, Christina J; Rogers, Jeffery S; Guild, Matthew D; Rohde, Charles A; Orris, Gregory J

    2016-06-01

    Acoustic antennas have long been utilized to directionally steer acoustic waves in both air and water. Typically, these antennas are comprised of arrays of active acoustic elements, which are electronically phased to steer the acoustic profile in the desired direction. A new technology, known as an acoustic leaky wave antenna (LWA), has recently been shown to achieve directional steering of acoustic waves using a single active transducer coupled to a transmission line passive aperture. The LWA steers acoustic energy by preferential coupling to an input frequency and can be designed to steer from backfire to endfire, including broadside. This paper provides an analysis of resolution as a function of both input frequency and antenna length. Additionally, the resolution is compared to that achieved using an array of active acoustic elements. PMID:27369149

  10. Means of manufacturing annular arrays

    DOEpatents

    Day, R.A.

    1985-10-10

    A method is described for manufacturing an annular acoustic transducer array from a plate of transducer material, which enables production of precision aligned arrays at low cost. The circular plate is sawed along at least two lines that are radial to the axis of the plate. At steps along each radial cut, the plate is rotated first in one direction and then in an opposite direction by a predetermined angle such as slightly less than 90/sup 0/. The cuts result in the forming of several largely ring-shaped lands, each largely ring-shaped land being joined to the other rings of different radii by thin portions of the plate, and each ring being cut into segments. The bridges that join different rings hold the transducer together until it can be mounted on a lens.

  11. Direct calculation of acoustic streaming including the boundary layer phenomena in an ultrasonic air pump

    NASA Astrophysics Data System (ADS)

    Wada, Yuji; Koyama, Daisuke; Nakamura, Kentaro

    2012-05-01

    Direct finite difference fluid simulation of acoustic streaming on the fine-meshed three-dimensiona model by graphics processing unit (GPU)-oriented calculation array is discussed. Airflows due to the acoustic traveling wave are induced when an intense sound field is generated in a gap between a bending transducer and a reflector. Calculation results showed good agreement with the measurements in the pressure distribution. In addition to that, several flow-vortices were observed near the boundary of the reflector and the transducer, which have been often discussed in acoustic tube near the boundary, and have never been observed in the calculation in the ultrasonic air pump of this type.

  12. Detection and localization using an acoustic array on a small robotic platform

    NASA Astrophysics Data System (ADS)

    Young, Stuart H.; Scanlon, Michael V.

    2003-09-01

    The future battlefield will require an unprecedented level of automation in which soldier-operated autonomous and semi-autonomous ground, air and sea platforms along with mounted and dismounted soldiers will function as a tightly coupled team. Sophisticated robotic platforms with diverse sensor suites will be an integral part of the Objective Force, and must be able to collaborate not only amongst themselves but also with their manned partners. The Army Research Laboratory has developed a robot-based acoustic detection system that will detect and localize on an impulsive noise event, such as a sniper's weapon firing. Additionally, acoustic sensor arrays worn on a soldier's helmet or equipment can enhance his situational awareness and RSTA capabilities. The Land Warrior or Objective Force Warrior body-worn computer can detect tactically significant impulsive signatures from bullets, mortars, artillery, and missiles or spectral signatures from tanks, helicopters, UAVs, and mobile robots. Time-difference-of-arrival techniques can determine a sound's direction of arrival, while head attitude sensors can instantly determine the helmet orientation at time of capture. With precision GPS location of the soldier, along with the locations of other soldiers, robots, or unattended ground sensors that heard the same event, triangulation techniques can produce an accurate location of the target. Data from C-4 explosions and 0.50-Caliber shots shows that both helmet and robot systems can localize on the same event. This provides an awesome capability - mobile robots and soldiers working together on an ever-changing battlespace to detect the enemy and improve the survivability, mobility, and lethality of our future warriors.

  13. Acoustic imaging in a water filled metallic pipe

    SciTech Connect

    Kolbe, W.F.; Turko, B.T.; Leskovar, B.

    1984-04-01

    A method is described for the imaging of the interior of a water filled metallic pipe using acoustical techniques. The apparatus consists of an array of 20 acoustic transducers mounted circumferentially around the pipe. Each transducer is pulsed in sequence, and the echos resulting from bubbles in the interior are digitized and processed by a computer to generate an image. The electronic control and digitizing system and the software processing of the echo signals are described. The performance of the apparatus is illustrated by the imaging of simulated bubbles consisting of thin walled glass spheres suspended in the pipe.

  14. Acoustic force mapping in a hybrid acoustic-optical micromanipulation device supporting high resolution optical imaging† †Electronic supplementary information (ESI) available: Additional information about 1D model calculations for a piezoelectric transducer. See DOI: 10.1039/c6lc00182c Click here for additional data file.

    PubMed Central

    McDougall, Craig; MacDonald, Michael Peter; Ritsch-Marte, Monika

    2016-01-01

    Many applications in the life-sciences demand non-contact manipulation tools for forceful but nevertheless delicate handling of various types of sample. Moreover, the system should support high-resolution optical imaging. Here we present a hybrid acoustic/optical manipulation system which utilizes a transparent transducer, making it compatible with high-NA imaging in a microfluidic environment. The powerful acoustic trapping within a layered resonator, which is suitable for highly parallel particle handling, is complemented by the flexibility and selectivity of holographic optical tweezers, with the specimens being under high quality optical monitoring at all times. The dual acoustic/optical nature of the system lends itself to optically measure the exact acoustic force map, by means of direct force measurements on an optically trapped particle. For applications with (ultra-)high demand on the precision of the force measurements, the position of the objective used for the high-NA imaging may have significant influence on the acoustic force map in the probe chamber. We have characterized this influence experimentally and the findings were confirmed by model simulations. We show that it is possible to design the chamber and to choose the operating point in such a way as to avoid perturbations due to the objective lens. Moreover, we found that measuring the electrical impedance of the transducer provides an easy indicator for the acoustic resonances. PMID:27025398

  15. Microinterferometer transducer

    DOEpatents

    Corey, III, Harry S.

    1979-01-01

    An air-bearing microinterferometer transducer is provided for increased accuracy, range and linearity over conventional displacement transducers. A microinterferometer system is housed within a small compartment of an air-bearing displacement transducer housing. A movable cube corner reflector of the interferometer is mounted to move with the displacement gauging probe of the transducer. The probe is disposed for axial displacement by means of an air-bearing. Light from a single frequency laser is directed into an interferometer system within the transducer housing by means of a self-focusing fiber optic cable to maintain light coherency. Separate fringe patterns are monitored by a pair of fiber optic cables which transmit the patterns to a detecting system. The detecting system includes a bidirectional counter which counts the light pattern fringes according to the direction of movement of the probe during a displacement gauging operation.

  16. Dual-frequency super harmonic imaging piezoelectric transducers for transrectal ultrasound

    NASA Astrophysics Data System (ADS)

    Kim, Jinwook; Li, Sibo; Kasoji, Sandeep; Dayton, Paul A.; Jiang, Xiaoning

    2015-03-01

    In this paper, a 2/14 MHz dual-frequency single-element transducer and a 2/22 MHz sub-array (16/48-elements linear array) transducer were developed for contrast enhanced super-harmonic ultrasound imaging of prostate cancer with the low frequency ultrasound transducer as a transmitter for contrast agent (microbubble) excitation and the high frequency transducer as a receiver for detection of nonlinear responses from microbubbles. The 1-3 piezoelectric composite was used as active materials of the single-element transducers due to its low acoustic impedance and high coupling factor. A high dielectric constant PZT ceramic was used for the sub-array transducer due to its high dielectric property induced relatively low electrical impedance. The possible resonance modes of the active elements were estimated using finite element analysis (FEA). The pulse-echo response, peak-negative pressure and bubble response were tested, followed by in vitro contrast imaging tests using a graphite-gelatin tissue-mimicking phantom. The single-element dual frequency transducer (8 × 4 × 2 mm3) showed a -6 dB fractional bandwidth of 56.5% for the transmitter, and 41.8% for the receiver. A 2 MHz-transmitter (730 μm pitch and 6.5 mm elevation aperture) and a 22 MHz-receiver (240 μm pitch and 1.5 mm aperture) of the sub-array transducer exhibited -6 dB fractional bandwidth of 51.0% and 40.2%, respectively. The peak negative pressure at the far field was about -1.3 MPa with 200 Vpp, 1-cycle 2 MHz burst, which is high enough to excite microbubbles for nonlinear responses. The 7th harmonic responses from micro bubbles were successfully detected in the phantom imaging test showing a contrast-to-tissue ratio (CTR) of 16 dB.

  17. Propagation of acoustic waves in a one-dimensional array of noncohesive cylinders.

    PubMed

    Huillard, Guillaume; Noblin, Xavier; Rajchenbach, Jean

    2011-07-01

    By means of a photoelastic method, we access the visualization of acoustic waves propagating in a one-dimensional array of noncohesive cylinders. As pointed by Nesterenko in the case of spherical grains [V. F. Nesterenko, J. Appl. Mech. Tech. Phys. 24, p. 567 (1983)], the nonlinearity of the contact law between the grains induces a dependence of the wave velocity both on its amplitude and on the confinement force. Our experimental method allows one to access the evolution in time of the internal state of stress of individual grains with excellent accuracy. We show that the velocity of the sound presents two regimes as a function of the confining force. For low forces, the dependence is strongly nonlinear, while it weakens for higher forces. By means of the direct visualization of the contact zone, we show that both micro- and macroscale imperfections of the surface of contact explain the low forces behavior. We test the consistency of our experimental findings results with both the theoretical expectations and with the experimental determination of the force-displacement dependence. We show, moreover, that the main damping process originates in solid friction. PMID:21867329

  18. Acoustic anechoic layers with singly periodic array of scatterers: Computational methods, absorption mechanisms, and optimal design

    NASA Astrophysics Data System (ADS)

    Yang, Hai-Bin; Li, Yue; Zhao, Hong-Gang; Wen, Ji-Hong; Wen, Xi-Sen

    2014-10-01

    The acoustic properties of anechoic layers with a singly periodic array of cylindrical scatterers are investigated. A method combined plane wave expansion and finite element analysis is extended for out-of-plane incidence. The reflection characteristics of the anechoic layers with cavities and locally resonant scatterers are discussed. The backing is a steel plate followed by an air half space. Under this approximate zero transmission backing condition, the reflection reduction is induced by the absorption enhancement. The absorption mechanism is explained by the scattering/absorption cross section of the isolated scatterer. Three types of resonant modes which can induce efficient absorption are revealed. Due to the fact that the frequencies of the resonant modes are related to the size of the scatterers, anechoic layers with scatterers of mixed size can broaden the absorption band. A genetic optimization algorithm is adopted to design the anechoic layer with scatterers of mixed size at a desired frequency band from 2 kHz to 10 kHz for normal incidence, and the influence of the incident angle is also discussed.

  19. Extraction of acoustic normal mode depth functions using vertical line array data

    NASA Astrophysics Data System (ADS)

    Neilsen, Tracianne B.; Westwood, Evan K.

    2002-02-01

    A method for extracting the normal modes of acoustic propagation in the shallow ocean from sound recorded on a vertical line array (VLA) of hydrophones as a source travels nearby is presented. The mode extraction is accomplished by performing a singular value decomposition (SVD) of individual frequency components of the signal's temporally averaged, spatial cross-spectral density matrix. The SVD produces a matrix containing a mutually orthogonal set of basis functions, which are proportional to the depth-dependent normal modes, and a diagonal matrix containing the singular values, which are proportional to the modal source excitations and mode eigenvalues. The conditions under which the method is expected to work are found to be (1) sufficient depth sampling of the propagating modes by the VLA receivers; (2) sufficient source-VLA range sampling, and (3) sufficient range interval traversed by the source. The mode extraction method is applied to data from the Area Characterization Test II, conducted in September 1993 in the Hudson Canyon Area off the New Jersey coast. Modes are successfully extracted from cw tones recorded while (1) the source traveled along a range-independent track with constant bathymetry and (2) the source traveled up-slope with gradual changes in bathymetry. In addition, modes are successfully extracted at multiple frequencies from ambient noise.

  20. Wall pressure fluctuations and acoustics in turbulent pipe flow

    NASA Astrophysics Data System (ADS)

    Daniels, M. A.; Lauchle, G. C.

    1986-09-01

    Measurements of the turbulent boundary layer (TBL) wall pressure spectrum and the facility's propagating acoustic field were conducted in the Boundary Layer Research Facility. Subminiature, piezoresistive-type pressure transducers were used. Detailed calibration of the pressure transducers was performed using a standing wave tube. Measured sensitivities of the transducers were within 0.5 dB of factory specifications and measured phase differences between individual transducers were insignificant. The TBL wall pressure spectrum was obtained using a novel signal-processing technique that allowed a minimization of both acoustic and vibration-induced noise. This technique uses pairs of transducer difference signals from an exisymmetric array of three flush-mounted pressure sensors and permits cancellation of the propagating acoustic and vibrationally induced pressure fields. A measurement involving the coherence function between these transducer signals was shown to validate the measured TBL wall pressure spectra and all assumptions used in developing the measurement technique. Non-dimensionalized spectra of the TBL fluctuating wall pressure measured in this investigation are compared to those measured previously. These comparisons substantiated a maximum, normalized transducer diameter for the complete resolution of the high-frequency part of the TBL wall pressure spectrum.

  1. Quantitative and qualitative analyses of under-balcony acoustics with real and simulated arrays of multiple sources

    NASA Astrophysics Data System (ADS)

    Kwon, Youngmin

    The objective of this study was to quantitatively and qualitatively identify the acoustics of the under-balcony areas in music performance halls under realistic conditions that are close to an orchestral performance in consideration of multiple music instrumental sources and their diverse sound propagation patterns. The study executed monaural and binaural impulse response measurements with an array of sixteen directional sources (loudspeakers) for acoustical assessments. Actual measurements in a performance hall as well as computer simulations were conducted for the quantitative assessments. Psycho-acoustical listening tests were conducted for the qualitative assessments using the music signals binaurally recorded in the hall with the same source array. The results obtained from the multiple directional source tests were analyzed by comparing them to those obtained from the tests performed with a single omni-directional source. These two sets of results obtained in the under-balcony area were also compared to those obtained in the main orchestra area. The quantitative results showed that the use of a single source conforming to conventional measurement protocol seems to be competent for measurements of the room acoustical parameters such as EDTmid, RTmid, C80500-2k, IACCE3 and IACCL3. These quantitative measures, however, did not always agree with the results of the qualitative assessments. The primary reason is that, in many other acoustical analysis respects, the acoustical phenomena shown from the multiple source measurements were not similar to those shown from the single source measurements. Remarkable differences were observed in time-domain impulse responses, frequency content, spectral distribution, directional distribution of the early reflections, and in sound energy density over time. Therefore, the room acoustical parameters alone should not be the acoustical representative characterizing a performance hall or a specific area such as the under

  2. 1-3 Piezocomposite transducers for AUV applications

    NASA Astrophysics Data System (ADS)

    Pazol, Brian; Lannaman, Ken; Doust, Barry

    2001-05-01

    Sonar systems on board AUVs present interesting challenges to the transducer designer because of their small size, low weight requirements, and limited available power. 1-3 piezocomposite transducers offer many performance characteristics which make them ideal for deployment in AUVs. Piezocomposite transducers are light weight, have broad bandwidth, have high efficiency, and can be conformed to fit the curvature of the vehicle. The broad bandwidths and low sidelobes made possible by piezocomposites result in sharper images with less distortion. The piezocomposite material is mechanically robust and can survive the rigors of normal operations as well as AUV deployment and retrieval. In addition, the conformal configuration substantially reduces hydrodynamic drag. As a conformal array, there is nothing to get knocked off during deployment and retrieval operations, or entangled with natural or man-made objects suspended in the water column. This contributes directly to improving the operational endurance of the AUV system, thereby enhancing overall system utility. MSI has produced and tested a variety of piezocomposite transducers for use in obstacle avoidance, mine hunting, and acoustic communications. An overview of piezocomposites and recent results of piezocomposite transducers will be presented.

  3. Twenty years of barrel-stave flextensional transducer technology in Canada

    NASA Astrophysics Data System (ADS)

    Jones, Dennis F.

    2005-04-01

    The barrel-stave flextensional transducer, a compact underwater sound source, was conceived at DRDC Atlantic in 1986 [G. W. McMahon and D. F. Jones, U.S. Patent No. 4,922,470 (1 May 1990); Canadian Patent No. 1,285,646 (2 July 1991)]. Over the years, five barrel-stave designs belonging to three flextensional classes were built and tested at DRDC Atlantic. Three Class I transducers with operating frequencies ranging from 800 to 1600 Hz were integrated into submarine communications buoys, low frequency active horizontal projector arrays, and a broadband sonar towbody. A high-power Class II and broadband (1-7 kHz) Class III transducer were deployed under the ice in the Lincoln Sea for research related to rapidly deployable surveillance systems. These barrel-stave flextensional transducers have also supported a variety of marine mammal studies including vocal mimicry in long-finned pilot whales, coda dialects in sperm whales, and the R&D of acoustic detection and tracking systems for endangered northern right whales. In August 2004 a barrel-stave transducer was used to lure a trapped juvenile humpback whale to the sluice gates of a tidal generating station on the Annapolis River in Nova Scotia by transmitting humpback whale calls underwater. The acoustic performance parameters for all 5 transducers will be presented.

  4. Seismic and Acoustic Studies from a Seafloor Array on the Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    McDonald, Mark Armstrong

    This dissertation consists of two related but separate studies, one a refraction seismic study of the oceanic crust and the other an acoustic study of whale behavior in the presence of noise, both using seafloor array data. The goal of the first study was to measure the lateral thickness variability in the extrusive volcanic layer on the Juan de Fuca Ridge. The Juan de Fuca Ridge is a medium rate (6 cm per year full rate), active spreading center, separating the Juan de Fuca and Pacific plates. It is a site of volcanic eruptions, associated with creation of new oceanic crust, and hydrothermal vents which are important in the chemical balance of the oceans. To better understand the mechanisms controlling hydrothermal venting and the creation of new crust, a seismic refraction survey was conducted over a 20 km by 30 km area of the ridge. This survey, conducted in August of 1990, used airguns as energy sources and ocean bottom seismometers as recorders. A 3-dimensional traveltime inversion was used to interpret extrusive volcanic layer thickness changes of 300 m, occurring over less than several kilometers laterally. These thickness changes are interpreted as lava accumulations on the low side of listric faults in an episodic spreading system. The traveltime inversion also reveals a large horizontal seismic velocity anisotropy which is confined to the upper 500 m of crust. Compressional velocities are 3.35 km/s in the ridge strike direction and 2.25 km/s across strike. This anisotropy is believed to be caused by oriented fractures within the extrusive layer. The second study involved the tracking and analysis of whale vocalizations which were recorded on the array 10 percent of the time. The goal was to determine if noises such as generated by the airguns, shipping or earthquakes affected the behavior of these fin and blue whales. The vocalization patterns allow analysis of swimming speed, direction, respiration cycle and call interaction. While no clear noise

  5. Surface acoustic wave (SAW) microsensor array for measuring VOCs in drinking water.

    PubMed

    Groves, W A; Grey, A B; O'Shaughnessy, P T

    2006-09-01

    Exposure to volatile organic chemicals (VOCs) in drinking water has been linked to a number of adverse health effects including cancer, liver, and kidney damage. However, the large number of potential contaminants and the cost and complexity of existing analytical methods limits the extent to which water quality is routinely characterized. This project focused on the laboratory development and evaluation of an instrument for field analysis of VOCs in drinking water. The instrument is based on an array of six polymer-coated surface-acoustic-wave microsensors. A test-set consisting of dichloromethane, chloroform, 1,1,1-trichloroethane, perchloroethylene, and m-xylene was used in a series of experiments designed to optimize the purge-trap preconcentration system, calibrate the instrument over the concentration range of 0.2-2 times the USEPA maximum contaminant levels (MCLs), and compare results to those of a reference laboratory. The primary goal was to develop a cost-effective alternative for on-site evaluation of VOCs in water. Calibration and evaluation test results for spiked water samples demonstrate adequate sensitivity for 19 of the 21 regulated VOCs considered using a ten minute sampling and analysis cycle. Monte Carlo simulations characterized the performance of trained artificial neural networks (ANNs) which had correct classification rates of 99%, 90%, and 80% for the five individual test-set vapors and their binary and ternary mixtures, respectively. These results demonstrate the excellent potential of this technology for addressing the need for improved VOC field-screening methods for water supplies.

  6. The Acoustic Signal of a Helicopter can be Used to Track it With Seismic Arrays

    NASA Astrophysics Data System (ADS)

    Eibl, Eva P. S.; Lokmer, Ivan; Bean, Christopher J.; Akerlie, Eggert

    2016-04-01

    We apply traditional frequency domain methods usually applied to volcanic tremor on seismic recordings of a helicopter. On a volcano the source can be repeating, closely spaced earthquakes whereas for a helicopter the source are repeating pressure pulses from the rotor blades that are converted through acoustic-to-seismic coupling. In both cases the seismic signal is referred to as tremor. As frequency gliding is in this case merely caused by the Doppler effect, not a change in the source, we can use its shape to deduce properties of the helicopter. We show in this analysis that the amount of rotor blades, rotor revolutions per minute (RPM), flight direction, height and location can be deduced. The signal was recorded by a seven station broadband array with an aperture of 1.6 km. Our spacing is close enough to record the signal at all stations and far enough to observe traveltime differences. We perform a detailed spectral and location analysis of the signal, and compare our results with the known information on the helicopter's speed, location, height, the frequency of the blades rotation and the amount of blades. This analysis is based on the characteristic shape of the curve i.e. speed of the gliding, minimum and maximum fundamental frequency, amplitudes at the inflection points at different stations and traveltimes deduced from the inflection points at different stations. The helicopter GPS track gives us a robust way of testing the method. This observation has an educative value, because the same principles can be applied to signals in different disciplines.

  7. Near-field/far-field array manifold of an acoustic vector-sensor near a reflecting boundary.

    PubMed

    Wu, Yue Ivan; Lau, Siu-Kit; Wong, Kainam Thomas

    2016-06-01

    The acoustic vector-sensor (a.k.a. the vector hydrophone) is a practical and versatile sound-measurement device, with applications in-room, open-air, or underwater. It consists of three identical uni-axial velocity-sensors in orthogonal orientations, plus a pressure-sensor-all in spatial collocation. Its far-field array manifold [Nehorai and Paldi (1994). IEEE Trans. Signal Process. 42, 2481-2491; Hawkes and Nehorai (2000). IEEE Trans. Signal Process. 48, 2981-2993] has been introduced into the technical field of signal processing about 2 decades ago, and many direction-finding algorithms have since been developed for this acoustic vector-sensor. The above array manifold is subsequently generalized for outside the far field in Wu, Wong, and Lau [(2010). IEEE Trans. Signal Process. 58, 3946-3951], but only if no reflection-boundary is to lie near the acoustic vector-sensor. As for the near-boundary array manifold for the general case of an emitter in the geometric near field, the far field, or anywhere in between-this paper derives and presents that array manifold in terms of signal-processing mathematics. Also derived here is the corresponding Cramér-Rao bound for azimuth-elevation-distance localization of an incident emitter, with the reflected wave shown to play a critical role on account of its constructive or destructive summation with the line-of-sight wave. The implications on source localization are explored, especially with respect to measurement model mismatch in maximum-likelihood direction finding and with regard to the spatial resolution between coexisting emitters. PMID:27369140

  8. Ultrasonic transducer

    SciTech Connect

    Csaszar, G.; Goldman, F.M.; Oehley, G.; Svoboda, E.J.

    1983-08-30

    An ultrasonic transducer is provided substantially at the hot spot in an engine manifold for vaporizing the fuel from the carburetor prior to entry of the fuel-air mixture into the cylinders. Transducer comprises a crystal adapted to be vibrated at a high frequency on the order of at least 1,000,000 Hz and a resonator tuned to the frequency of the crystal and operatively secured to the crystal, said transducer having an active surface adapted to be contacted by the fuel for finely vaporizing same. The fine vaporization or gasification of the fuel (gasoline, for example) prior to entry into the cylinders causes a more complete burning of the fuel. As a result, the engine delivers more power with less fuel, while carbon monoxide and hydrocarbon emissions are reduced. In operation, the ultrasonic transducer enhances cold weather startup and operation, eliminates engine flooding, smooths out engine idle, and improves pick up and acceleration by increasing power at low engine RPM. Engine power is boosted, while saving gasoline. The ultrasonic transducer can be installed into the intake manifold below the carburetor without modifying the structure of the carburetor or the intake manifold.

  9. Acoustics

    NASA Technical Reports Server (NTRS)

    Goodman, Jerry R.; Grosveld, Ferdinand

    2007-01-01

    The acoustics environment in space operations is important to maintain at manageable levels so that the crewperson can remain safe, functional, effective, and reasonably comfortable. High acoustic levels can produce temporary or permanent hearing loss, or cause other physiological symptoms such as auditory pain, headaches, discomfort, strain in the vocal cords, or fatigue. Noise is defined as undesirable sound. Excessive noise may result in psychological effects such as irritability, inability to concentrate, decrease in productivity, annoyance, errors in judgment, and distraction. A noisy environment can also result in the inability to sleep, or sleep well. Elevated noise levels can affect the ability to communicate, understand what is being said, hear what is going on in the environment, degrade crew performance and operations, and create habitability concerns. Superfluous noise emissions can also create the inability to hear alarms or other important auditory cues such as an equipment malfunctioning. Recent space flight experience, evaluations of the requirements in crew habitable areas, and lessons learned (Goodman 2003; Allen and Goodman 2003; Pilkinton 2003; Grosveld et al. 2003) show the importance of maintaining an acceptable acoustics environment. This is best accomplished by having a high-quality set of limits/requirements early in the program, the "designing in" of acoustics in the development of hardware and systems, and by monitoring, testing and verifying the levels to ensure that they are acceptable.

  10. Dynamic Calibration of Pressure Transducers

    NASA Technical Reports Server (NTRS)

    Hess, R. W.; Davis, W. T.; Davis, P. A.

    1985-01-01

    Sinusoidal calibration signal produced in 4- to 100-Hz range. Portable oscillating-pressure device measures dynamic characteristics of pressure transducers installed in models or aircraft at frequency and oscillating-pressure ranges encountered during unsteady-pressure-measurement tests. Calibration is over range of frequencies and amplitudes not available with commercial acoustic calibration devices.

  11. Sub-10 nm Ytterbium Oxide Nanopowder-doped Silicone Rubber Acoustic Lens Material for Medical Echo Array Probe

    NASA Astrophysics Data System (ADS)

    Yamashita, Yohachi (John); Hosono, Yasuharu; Itsumi, Kazuhiro

    2007-09-01

    The effects of 8-nm-Yb2O3-nanopowders dopant, on the physical and acoustical properties of high-temperature-vulcanization (HTV) silicone (Q) rubber have been investigated, to develop a low acoustic attenuation (α) lens material for medical array probes. A 35 wt % (6 vol %) Yb2O3-doped HTV Q rubber showed a sound velocity (c) = 867 m/s, an acoustic impedance (Z) = 1.36× 106 kg\\cdotm-2\\cdots-1, an acoustic attenuation α = 0.66 dB\\cdotmm-1\\cdotMHz-1, and an α-figure of merits (FOM) (α× c) = 574 at 37 °C. The α-FOM value with Z = 1.36× 106 kg\\cdotm-2\\cdots-1 for a Q rubber lens material is the lowest attenuation ever reported. Microstructure observation revealed that the low-α rubber showed a uniform Yb2O3 nanopowder distribution in the rubber matrix.

  12. Ultrasonic transducer

    DOEpatents

    Taylor, Steven C.; Kraft, Nancy C.

    2007-03-13

    An ultrasonic transducer having an effective center frequency of about 42 MHz; a bandwidth of greater than 85% at 6 dB; a spherical focus of at least 0.5 inches in water; an F4 lens; a resolution sufficient to be able to detect and separate a 0.005 inch flat-bottomed hole at 0.005 inches below surface; and a beam size of approximately 0.006–0.008 inches measured off a 11/2 mm ball in water at the transducer's focal point.

  13. Acoustic tracking of an unmanned underwater vehicle using a passive ultrashort baseline array and a single long baseline beacon

    NASA Astrophysics Data System (ADS)

    Seaton, Kyle L.

    This thesis discusses a new approach to tracking the REMUS 100 AUV using a modified version of the Florida Atlantic University (FAU) ultrashort baseline (USBL) acoustic positioning system (APS). The REMUS 100 is designed to utilize a long baseline (LBL) acoustic positioning system to obtain positioning data in mid-mission. If the placement of one of the transponders of the LBL field is known, then tracking the position of the REMUS 100 AUV using a passive USBL array is possible. As part of the research for this thesis, the FAU USBL system was used to find a relative range between the REMUS 100 ranger and a LBL transponder. This relative range was then combined with direction of arrival information and LBL field component position information to determine an absolute position of the REMUS 100 ranger. The outcome was the demonstration of a passive USBL based tracking system.

  14. Acoustic Beam Forming Array Using Feedback-Controlled Microphones for Tuning and Self-Matching of Frequency Response

    NASA Technical Reports Server (NTRS)

    Radcliffe, Eliott (Inventor); Naguib, Ahmed (Inventor); Humphreys, Jr., William M. (Inventor)

    2014-01-01

    A feedback-controlled microphone includes a microphone body and a membrane operatively connected to the body. The membrane is configured to be initially deflected by acoustic pressure such that the initial deflection is characterized by a frequency response. The microphone also includes a sensor configured to detect the frequency response of the initial deflection and generate an output voltage indicative thereof. The microphone additionally includes a compensator in electric communication with the sensor and configured to establish a regulated voltage in response to the output voltage. Furthermore, the microphone includes an actuator in electric communication with the compensator, wherein the actuator is configured to secondarily deflect the membrane in opposition to the initial deflection such that the frequency response is adjusted. An acoustic beam forming microphone array including a plurality of the above feedback-controlled microphones is also disclosed.

  15. Site–Specific Sonoporation of Human Melanoma Cells at the Cellular Level Using High Lateral–Resolution Ultrasonic Micro–Transducer Arrays

    PubMed Central

    Thein, Myo; Cheng, An; Khanna, Payal; Zhang, Chunfeng; Park, Eun–Joo; Ahmed, Daniel; Goodrich, Christopher J.; Asphahani, Fareid; Wu, Fengbing; Smith, Nadine B.; Dong, Cheng; Jiang, Xiaoning; Zhang, Miqin; Xu, Jian

    2011-01-01

    We developed a new instrumental method by which human melanoma cells (LU1205) are sonoporated via radiation pressures exerted by highly–confined ultrasonic waves produced by high lateral–resolution Ultrasonic Micro–Transducer Arrays (UMTAs). The method enables cellular–level site–specific sonoporation within the cell monolayer due to UMTAs and can be applicable in the delivery of drugs and gene products in cellular assays. In this method, cells are seeded on the biochip that employs UMTAs for high spatial resolution and specificity. UMTAs are driven by 30–MHz sinusoidal signals and the resulting radiation pressures induce sonoporation in the targeted cells. The sonoporation degree and the effective lateral resolution of UMTAs are determined by performing fluorescent microscopy and analysis of carboxylic–acid–derivatized CdSe/ZnS quantum dots passively transported into the cells. Models representing the transducer–generated ultrasound radiation pressure, the ultrasound–inflicted cell membrane wound, and the transmembrane transport through the wound are developed to determine the ultrasound–pressure–dependent wound size and enhanced cellular uptake of nanoparticles. Model–based calculations show that the effective wound size and cellular uptake of nanoparticles increase linearly with increasing ultrasound pressure (i.e., at applied radiation pressures of 0.21, 0.29, and 0.40 MPa, the ultrasound–induced initial effective wound radii are 150, 460, and 650 nm, respectively, and the post–sonoporation intracellular quantum–dot concentrations are 7.8, 22.8, and 29.9 nM, respectively) and the threshold pressure required to induce sonoporation in LU1205 cells is ~0.12 MPa. PMID:21783355

  16. Observation of Marine Animals Using Underwater Acoustic Camera

    NASA Astrophysics Data System (ADS)

    Iida, Kohji; Takahashi, Rika; Tang, Yong; Mukai, Tohru; Sato, Masanori

    2006-05-01

    An underwater acoustic camera enclosed in a pressure-resistant case was constructed to observe underwater marine animals. This enabled the measurement of the size, shape, and behavior of living marine animals in the detection range up to 240 cm. The transducer array of the acoustic camera was driven by 3.5 MHz ultrasonic signals, and B-mode acoustic images were obtained. Observations were conducted for captive animals in a water tank and for natural animals in a field. The captive animals, including fish, squid and jellyfish, were observed, and a three-dimensional internal structure of animals was reconstructed using multiple acoustical images. The most important contributors of acoustic scattering were the swimbladder and vertebra of bladdered fish, and the liver and reproductive organs of invertebrate animals. In a field experiment, the shape, size, and swimming behavior of wild animals were observed. The possibilities and limitations of the underwater acoustic camera for fishery applications were discussed.

  17. Annular array and method of manufacturing same

    DOEpatents

    Day, Robert A.

    1989-01-01

    A method for manufacturing an annular acoustic transducer array from a plate of transducer material, which enables production of precision aligned arrays at low cost. The circular plate is sawed along at least two lines that are radial to the axis of the plate. At steps along each radial cut, the plate is rotated first in one direction and then in an opposite direction by a predetermined angle such as slightly less than 90.degree.. The cuts result in the forming of several largely ring-shaped lands, each largely ring-shaped land being joined to the other rings of different radii by thin portions of the plate, and each ring being cut into segments. The bridges that join different rings, hold the transducer together until it can be mounted on a lens.

  18. Acoustic Levitator Maintains Resonance

    NASA Technical Reports Server (NTRS)

    Barmatz, M. B.; Gaspar, M. S.

    1986-01-01

    Transducer loading characteristics allow resonance tracked at high temperature. Acoustic-levitation chamber length automatically adjusted to maintain resonance at constant acoustic frequency as temperature changes. Developed for containerless processing of materials at high temperatures, system does not rely on microphones as resonance sensors, since microphones are difficult to fabricate for use at temperatures above 500 degrees C. Instead, system uses acoustic transducer itself as sensor.

  19. PRESSURE TRANSDUCER

    DOEpatents

    Sander, H.H.

    1959-10-01

    A pressure or mechanical force transducer particularly adaptable to miniature telemetering systems is described. Basically the device consists of a transistor located within a magnetic field adapted to change in response to mechanical force. The conduction characteristics of the transistor in turn vary proportionally with changes in the magnetic flux across the transistor such that the output (either frequency of amplitude) of the transistor circuit is proportional to mechanical force or pressure.

  20. Pressure transducer

    DOEpatents

    Anderson, T.T.; Roop, C.J.; Schmidt, K.J.; Gunchin, E.R.

    1987-02-13

    A pressure transducer suitable for use in high temperature environments includes two pairs of induction coils, each pair being bifilarly wound together, and each pair of coils connected as opposite arms of a four arm circuit; an electrically conductive target moveably positioned between the coil pairs and connected to a diaphragm such that deflection of the diaphragm causes axial movement of the target and an unbalance in the bridge output. 7 figs.

  1. Pressure transducer

    DOEpatents

    Anderson, Thomas T.; Roop, Conard J.; Schmidt, Kenneth J.; Gunchin, Elmer R.

    1989-01-01

    A pressure transducer suitable for use in high temperature environments includes two pairs of induction coils, each pair being bifilarly wound together, and each pair of coils connected as opposite arms of a four arm circuit; an electrically conductive target moveably positioned between the coil pairs and connected to a diaphragm such that deflection of the diaphragm causes axial movement of the target and an unbalance in the bridge output.

  2. Method and apparatus for generating acoustic energy

    DOEpatents

    Guerrero, Hector N.

    2002-01-01

    A method and apparatus for generating and emitting amplified coherent acoustic energy. A cylindrical transducer is mounted within a housing, the transducer having an acoustically open end and an acoustically closed end. The interior of the transducer is filled with an active medium which may include scattering nuclei. Excitation of the transducer produces radially directed acoustic energy in the active medium, which is converted by the dimensions of the transducer, the acoustically closed end thereof, and the scattering nuclei, to amplified coherent acoustic energy directed longitudinally within the transducer. The energy is emitted through the acoustically open end of the transducer. The emitted energy can be used for, among other things, effecting a chemical reaction or removing scale from the interior walls of containment vessels.

  3. Flight parameter estimation using instantaneous frequency and time delay measurements from a three-element planar acoustic array.

    PubMed

    Lo, Kam W

    2016-05-01

    The acoustic signal emitted by a turbo-prop aircraft consists of a strong narrowband tone superimposed on a broadband random component. A ground-based three-element planar acoustic array can be used to estimate the full set of flight parameters of a turbo-prop aircraft in transit by measuring the time delay (TD) between the signal received at the reference sensor and the signal received at each of the other two sensors of the array over a sufficiently long period of time. This paper studies the possibility of using instantaneous frequency (IF) measurements from the reference sensor to improve the precision of the flight parameter estimates. A simplified Cramer-Rao lower bound analysis shows that the standard deviations in the estimates of the aircraft velocity and altitude can be greatly reduced when IF measurements are used together with TD measurements. Two flight parameter estimation algorithms that utilize both IF and TD measurements are formulated and their performances are evaluated using both simulated and real data. PMID:27250134

  4. A spiral wave front beacon for underwater navigation: transducer prototypes and testing.

    PubMed

    Dzikowicz, Benjamin R; Hefner, Brian T

    2012-05-01

    Transducers for acoustic beacons which can produce outgoing signals with wave fronts whose horizontal cross sections are circular or spiral are studied experimentally. A remote hydrophone is used to determine its aspect relative to the transducers by comparing the phase of the circular signal to the phase of the spiral signal. The transducers for a "physical-spiral" beacon are made by forming a strip of 1-3 piezocomposite transducer material around either a circular or spiral backing. A "phased-spiral" beacon is made from an array of transducer elements which can be driven either in phase or staggered out of phase so as to produce signals with either a circular or spiral wave front. Measurements are made to study outgoing signals and their usefulness in determining aspect angle. Vertical beam width is also examined and phase corrections applied when the hydrophone is out of the horizontal plane of the beacon. While numerical simulations indicate that the discontinuity in the physical-spiral beacon introduces errors into the measured phase, damping observed at the ends of the piezocomposite material is a more significant source of error. This damping is also reflected in laser Doppler vibrometer measurements of the transducer's surface velocity.

  5. A directional microphone array for acoustic studies of wind tunnel models

    NASA Technical Reports Server (NTRS)

    Soderman, P. T.; Noble, S. C.

    1974-01-01

    An end-fire microphone array that utilizes a digital time delay system has been designed and evaluated for measuring noise in wind tunnels. The directional response of both a four- and eight-element linear array of microphones has enabled substantial rejection of background noise and reverberations in the NASA Ames 40- by 80-foot wind tunnel. In addition, it is estimated that four- and eight-element arrays reject 6 and 9 dB, respectively, of microphone wind noise, as compared with a conventional omnidirectional microphone with nose cone. Array response to two types of jet engine models in the wind tunnel is presented. Comparisons of array response to loudspeakers in the wind tunnel and in free field are made.

  6. Topological Acoustics

    NASA Astrophysics Data System (ADS)

    Yang, Zhaoju; Gao, Fei; Shi, Xihang; Lin, Xiao; Gao, Zhen; Chong, Yidong; Zhang, Baile

    2015-03-01

    The manipulation of acoustic wave propagation in fluids has numerous applications, including some in everyday life. Acoustic technologies frequently develop in tandem with optics, using shared concepts such as waveguiding and metamedia. It is thus noteworthy that an entirely novel class of electromagnetic waves, known as "topological edge states," has recently been demonstrated. These are inspired by the electronic edge states occurring in topological insulators, and possess a striking and technologically promising property: the ability to travel in a single direction along a surface without backscattering, regardless of the existence of defects or disorder. Here, we develop an analogous theory of topological fluid acoustics, and propose a scheme for realizing topological edge states in an acoustic structure containing circulating fluids. The phenomenon of disorder-free one-way sound propagation, which does not occur in ordinary acoustic devices, may have novel applications for acoustic isolators, modulators, and transducers.

  7. Topological acoustics.

    PubMed

    Yang, Zhaoju; Gao, Fei; Shi, Xihang; Lin, Xiao; Gao, Zhen; Chong, Yidong; Zhang, Baile

    2015-03-20

    The manipulation of acoustic wave propagation in fluids has numerous applications, including some in everyday life. Acoustic technologies frequently develop in tandem with optics, using shared concepts such as waveguiding and metamedia. It is thus noteworthy that an entirely novel class of electromagnetic waves, known as "topological edge states," has recently been demonstrated. These are inspired by the electronic edge states occurring in topological insulators, and possess a striking and technologically promising property: the ability to travel in a single direction along a surface without backscattering, regardless of the existence of defects or disorder. Here, we develop an analogous theory of topological fluid acoustics, and propose a scheme for realizing topological edge states in an acoustic structure containing circulating fluids. The phenomenon of disorder-free one-way sound propagation, which does not occur in ordinary acoustic devices, may have novel applications for acoustic isolators, modulators, and transducers.

  8. Acoustic tracking of sperm whales in the Gulf of Alaska using a two-element vertical array and tags.

    PubMed

    Mathias, Delphine; Thode, Aaron M; Straley, Jan; Andrews, Russel D

    2013-09-01

    Between 15 and 17 August 2010, a simple two-element vertical array was deployed off the continental slope of Southeast Alaska in 1200 m water depth. The array was attached to a vertical buoy line used to mark each end of a longline fishing set, at 300 m depth, close to the sound-speed minimum of the deep-water profile. The buoy line also served as a depredation decoy, attracting seven sperm whales to the area. One animal was tagged with both a LIMPET dive depth-transmitting satellite and bioacoustic "B-probe" tag. Both tag datasets were used as an independent check of various passive acoustic schemes for tracking the whale in depth and range, which exploited the elevation angles and relative arrival times of multiple ray paths recorded on the array. Analytical tracking formulas were viable up to 2 km range, but only numerical propagation models yielded accurate locations up to at least 35 km range at Beaufort sea state 3. Neither localization approach required knowledge of the local bottom bathymetry. The tracking system was successfully used to estimate the source level of an individual sperm whale's "clicks" and "creaks" and predict the maximum detection range of the signals as a function of sea state.

  9. High energy, low frequency, ultrasonic transducer

    SciTech Connect

    Brown, Albert E.

    2000-01-01

    A wide bandwidth, ultrasonic transducer to generate nondispersive, extensional, pulsed acoustic pressure waves into concrete reinforced rods and tendons. The wave propagation distance is limited to double the length of the rod. The transducer acoustic impedance is matched to the rod impedance for maximum transfer of acoustic energy. The efficiency of the transducer is approximately 60 percent, depending upon the type of active elements used in the transducer. The transducer input energy is, for example, approximately 1 mJ. Ultrasonic reflections will occur at points along the rod where there are changes of one percent of a wavelength in the rod diameter. A reduction in the rod diameter will reflect a phase reversed echo, as compared with the reflection from an incremental increase in diameter. Echo signal processing of the stored waveform permits a reconstruction of those echoes into an image of the rod. The ultrasonic transducer has use in the acoustic inspection of long (40+foot) architectural reinforcements and structural supporting members, such as in bridges and dams.

  10. Acoustic Translation of an Acoustically Levitated Sample

    NASA Technical Reports Server (NTRS)

    Barmatz, M. B.; Allen, J. L.

    1986-01-01

    Acoustic-levitation apparatus uses only one acoustic mode to move sample from one region of chamber to another. Sample heated and cooled quickly by translation between hot and cold regions of levitation chamber. Levitated sample is raised into furnace region by raising plunger. Frequency of sound produced by transducers adjusted by feedback system to maintain (102) resonant mode, which levitates sample midway between transducers and plunger regardless of plunger position.

  11. Multifunctional transducer

    NASA Technical Reports Server (NTRS)

    Feldstein, C.; Lewis, G. W.; Culler, V. H.; Merrbaum, S. (Inventor)

    1981-01-01

    Several parameters of a small region of a muscle tissue or other object, can be simultaneously measured using with minimal traumatizing or damage of the object, a trifunctional transducer which can determine the force applied by a muscle fiber, the displacement of the fiber, and the change in thickness of the fiber. The transducer has three legs with inner ends joined together and outer ends formed to piece the tissue and remain within it. Two of the legs are relatively stiff, to measure force applied by the tissue, and a third leg is relatively flexible to measure displacement of the tissue relative to one or both stiff legs, and with the three legs lying in a common plane so that the force and displacement measurements all relate to the same direction of muscle movements. A flexible loop is attached to one of the stiff legs to measure changes in muscle thickness, with the upper end of the loop fixed to the leg and the lower end of the loop bearing against the surface of the tissue and being free to slide on the leg.

  12. Acoustic backing in 3-D integration of CMUT with front-end electronics.

    PubMed

    Berg, Sigrid; Rønnekleiv, Arne

    2012-07-01

    Capacitive micromachined ultrasonic transducers (CMUTs) have shown promising qualities for medical imaging. However, there are still some problems to be investigated, and some challenges to overcome. Acoustic backing is necessary to prevent SAWs excited in the surface of the silicon substrate from affecting the transmit pattern from the array. In addition, echoes resulting from bulk waves in the substrate must be removed. There is growing interest in integrating electronic circuits to do some of the beamforming directly below the transducer array. This may be easier to achieve for CMUTs than for traditional piezoelectric transducers. We will present simulations showing that the thickness of the silicon substrate and thicknesses and acoustic properties of the bonding material must be considered, especially when designing highfrequency transducers. Through simulations, we compare the acoustic properties of 3-D stacks bonded with three different bonding techniques; solid-liquid interdiffusion (SLID) bonding, direct fusion bonding, and anisotropic conductive adhesives (ACA). We look at a CMUT array with a center frequency of 30 MHz and three silicon wafers underneath, having a total silicon thickness of 100 μm. We find that fusion bonding is most beneficial if we want to prevent surface waves from damaging the array response, but SLID and ACA are also promising if bonding layer thicknesses can be reduced.

  13. Method and means for measuring acoustic emissions

    DOEpatents

    Renken, Jr., Claus J.

    1976-01-06

    The detection of acoustic emissions emanating from an object is achieved with a capacitive transducer coupled to the object. The capacitive transducer is charged and then allowed to discharge with the rate of discharge being monitored. Oscillations in the rate of discharge about the normally exponential discharge curve for the capacitive transducer indicate the presence of acoustic emissions.

  14. Effects of time-reversing array deformation in an ocean wave guide

    NASA Astrophysics Data System (ADS)

    Sabra, Karim G.; Dowling, David R.

    2004-06-01

    Active acoustic time reversal is a technique for focusing sounds recorded in complex unknown environments back to their remote point(s) of origin. It can be accomplished with a transducer array-a time-reversing array (TRA)-that sends and receives sound. Nearly all prior work on TRA performance has involved stationary arrays. This letter describes how random array deformation influences TRA retrofocusing in shallow ocean environments. For harmonic signals, randomly drifting array elements degrade TRA performance by ~20% when the average horizontal wavenumber times the root-mean-square horizontal element displacement approaches 0.5. TRA focusing should be less sensitive to vertical element drift.

  15. Micromachined silicon acoustic delay line with 3D-printed micro linkers and tapered input for improved structural stability and acoustic directivity

    NASA Astrophysics Data System (ADS)

    Cho, Y.; Kumar, A.; Xu, S.; Zou, J.

    2016-10-01

    Recent studies have shown that micromachined silicon acoustic delay lines can provide a promising solution to achieve real-time photoacoustic tomography without the need for complex transducer arrays and data acquisition electronics. To achieve deeper imaging depth and wider field of view, a longer delay time and therefore delay length are required. However, as the length of the delay line increases, it becomes more vulnerable to structural instability due to reduced mechanical stiffness. In this paper, we report the design, fabrication, and testing of a new silicon acoustic delay line enhanced with 3D printed polymer micro linker structures. First, mechanical deformation of the silicon acoustic delay line (with and without linker structures) under gravity was simulated by using finite element method. Second, the acoustic crosstalk and acoustic attenuation caused by the polymer micro linker structures were evaluated with both numerical simulation and ultrasound transmission testing. The result shows that the use of the polymer micro linker structures significantly improves the structural stability of the silicon acoustic delay lines without creating additional acoustic attenuation and crosstalk. In addition, the improvement of the acoustic acceptance angle of the silicon acoustic delay lines was also investigated to better suppress the reception of unwanted ultrasound signals outside of the imaging plane. These two improvements are expected to provide an effective solution to eliminate current limitations on the achievable acoustic delay time and out-of-plane imaging resolution of micromachined silicon acoustic delay line arrays.

  16. Wide-range frequency selectivity in an acoustic sensor fabricated using a microbeam array with non-uniform thickness

    NASA Astrophysics Data System (ADS)

    Shintaku, Hirofumi; Kobayashi, Takayuki; Zusho, Kazuki; Kotera, Hidetoshi; Kawano, Satoyuki

    2013-11-01

    In this study, we have demonstrated the fabrication of a microbeam array (MBA) with various thicknesses and investigated the suitability it for an acoustic sensor with wide-range frequency selectivity. For this, an MBA composed of 64 beams, with thicknesses varying from 2.99-142 µm, was fabricated by using single gray-scale lithography and a thick negative photoresist. The vibration of the beams in air was measured using a laser Doppler vibrometer; the resonant frequencies of the beams were measured to be from 11.5 to 290 kHz. Lastly, the frequency range of the MBA with non-uniform thickness was 10.9 times that of the MBA with uniform thickness.

  17. Characterization of a Multi-element Clinical HIFU System Using Acoustic Holography and Nonlinear Modeling

    PubMed Central

    Kreider, Wayne; Yuldashev, Petr V.; Sapozhnikov, Oleg A.; Farr, Navid; Partanen, Ari; Bailey, Michael R.; Khokhlova, Vera A.

    2014-01-01

    High-intensity focused ultrasound (HIFU) is a treatment modality that relies on the delivery of acoustic energy to remote tissue sites to induce thermal and/or mechanical tissue ablation. To ensure the safety and efficacy of this medical technology, standard approaches are needed for accurately characterizing the acoustic pressures generated by clinical ultrasound sources under operating conditions. Characterization of HIFU fields is complicated by nonlinear wave propagation and the complexity of phased-array transducers. Previous work has described aspects of an approach that combines measurements and modeling, and here we demonstrate this approach for a clinical phased array transducer. First, low-amplitude hydrophone measurements were performed in water over a scan plane between the array and the focus. Second, these measurements were used to holographically reconstruct the surface vibrations of the transducer and to set a boundary condition for a 3-D acoustic propagation model. Finally, nonlinear simulations of the acoustic field were carried out over a range of source power levels. Simulation results were compared to pressure waveforms measured directly by hydrophone at both low and high power levels, demonstrating that details of the acoustic field including shock formation are quantitatively predicted. PMID:25004539

  18. Non-intrusive, high-resolution, real-time, two-dimensional imaging of multiphase materials using acoustic array sensors

    NASA Astrophysics Data System (ADS)

    Cassiède, M.; Shaw, J. M.

    2015-04-01

    Two parallel multi-element ultrasonic acoustic arrays combined with sets of focal laws for acoustic signal generation and a classical tomographic inversion algorithm are used to generate real-time two-dimensional micro seismic acoustic images of multiphase materials. Proof of concept and calibration measurements were performed for single phase and two phase liquids, uniform polyvinyl chloride (PVC) plates, and aluminum cylinders imbedded in PVC plates. Measurement artefacts, arising from the limited range of viewing angles, and the compromise between data acquisition rate and image quality are discussed. The angle range of scanning and the image resolution were varied, and the effects on the quality of the reproduction of the speed of sound profiles of model solids and liquids with known geometries and compositions were analysed in detail. The best image quality results were obtained for a scanning angle range of [-35°, 35°] at a step size of 2.5° post processed to generate images on a 40 μm square grid. The data acquisition time for high quality images with a 30 mm × 40 mm view field is 10 min. Representation of two-phase solids with large differences in speed of sound between phases and where one phase is dispersed in the form of macroscopic objects (greater than 1 mm in diameter) proved to be the most difficult to image accurately. Liquid-liquid and liquid-vapor phase boundaries, in micro porous solids by contrast, were more readily defined. Displacement of air by water and water by heptane in natural porous limestone provides illustrative kinetic examples. Measurement results with these realistic cases demonstrate the feasibility of the technique to monitor in real time and on the micrometer length scale local composition and flow of organic liquids in inorganic porous media, one of many envisioned engineering applications. Improvement of data acquisition rate is an area for future collaborative study.

  19. Non-intrusive, high-resolution, real-time, two-dimensional imaging of multiphase materials using acoustic array sensors.

    PubMed

    Cassiède, M; Shaw, J M

    2015-04-01

    Two parallel multi-element ultrasonic acoustic arrays combined with sets of focal laws for acoustic signal generation and a classical tomographic inversion algorithm are used to generate real-time two-dimensional micro seismic acoustic images of multiphase materials. Proof of concept and calibration measurements were performed for single phase and two phase liquids, uniform polyvinyl chloride (PVC) plates, and aluminum cylinders imbedded in PVC plates. Measurement artefacts, arising from the limited range of viewing angles, and the compromise between data acquisition rate and image quality are discussed. The angle range of scanning and the image resolution were varied, and the effects on the quality of the reproduction of the speed of sound profiles of model solids and liquids with known geometries and compositions were analysed in detail. The best image quality results were obtained for a scanning angle range of [-35°, 35°] at a step size of 2.5° post processed to generate images on a 40 μm square grid. The data acquisition time for high quality images with a 30 mm × 40 mm view field is 10 min. Representation of two-phase solids with large differences in speed of sound between phases and where one phase is dispersed in the form of macroscopic objects (greater than 1 mm in diameter) proved to be the most difficult to image accurately. Liquid-liquid and liquid-vapor phase boundaries, in micro porous solids by contrast, were more readily defined. Displacement of air by water and water by heptane in natural porous limestone provides illustrative kinetic examples. Measurement results with these realistic cases demonstrate the feasibility of the technique to monitor in real time and on the micrometer length scale local composition and flow of organic liquids in inorganic porous media, one of many envisioned engineering applications. Improvement of data acquisition rate is an area for future collaborative study. PMID:25933884

  20. Non-intrusive, high-resolution, real-time, two-dimensional imaging of multiphase materials using acoustic array sensors

    SciTech Connect

    Cassiède, M.; Shaw, J. M.

    2015-04-15

    Two parallel multi-element ultrasonic acoustic arrays combined with sets of focal laws for acoustic signal generation and a classical tomographic inversion algorithm are used to generate real-time two-dimensional micro seismic acoustic images of multiphase materials. Proof of concept and calibration measurements were performed for single phase and two phase liquids, uniform polyvinyl chloride (PVC) plates, and aluminum cylinders imbedded in PVC plates. Measurement artefacts, arising from the limited range of viewing angles, and the compromise between data acquisition rate and image quality are discussed. The angle range of scanning and the image resolution were varied, and the effects on the quality of the reproduction of the speed of sound profiles of model solids and liquids with known geometries and compositions were analysed in detail. The best image quality results were obtained for a scanning angle range of [−35°, 35°] at a step size of 2.5° post processed to generate images on a 40 μm square grid. The data acquisition time for high quality images with a 30 mm × 40 mm view field is 10 min. Representation of two-phase solids with large differences in speed of sound between phases and where one phase is dispersed in the form of macroscopic objects (greater than 1 mm in diameter) proved to be the most difficult to image accurately. Liquid-liquid and liquid-vapor phase boundaries, in micro porous solids by contrast, were more readily defined. Displacement of air by water and water by heptane in natural porous limestone provides illustrative kinetic examples. Measurement results with these realistic cases demonstrate the feasibility of the technique to monitor in real time and on the micrometer length scale local composition and flow of organic liquids in inorganic porous media, one of many envisioned engineering applications. Improvement of data acquisition rate is an area for future collaborative study.

  1. Embedded Acoustic Sensor Array for Engine Fan Noise Source Diagnostic Test: Feasibility of Noise Telemetry via Wireless Smart Sensors

    NASA Technical Reports Server (NTRS)

    Zaman, Afroz; Bauch, Matthew; Raible, Daniel

    2011-01-01

    Aircraft engines have evolved into a highly complex system to meet ever-increasing demands. The evolution of engine technologies has primarily been driven by fuel efficiency, reliability, as well as engine noise concerns. One of the sources of engine noise is pressure fluctuations that are induced on the stator vanes. These local pressure fluctuations, once produced, propagate and coalesce with the pressure waves originating elsewhere on the stator to form a spinning pressure pattern. Depending on the duct geometry, air flow, and frequency of fluctuations, these spinning pressure patterns are self-sustaining and result in noise which eventually radiate to the far-field from engine. To investigate the nature of vane pressure fluctuations and the resulting engine noise, unsteady pressure signatures from an array of embedded acoustic sensors are recorded as a part of vane noise source diagnostics. Output time signatures from these sensors are routed to a control and data processing station adding complexity to the system and cable loss to the measured signal. "Smart" wireless sensors have data processing capability at the sensor locations which further increases the potential of wireless sensors. Smart sensors can process measured data locally and transmit only the important information through wireless communication. The aim of this wireless noise telemetry task was to demonstrate a single acoustic sensor wireless link for unsteady pressure measurement, and thus, establish the feasibility of distributed smart sensors scheme for aircraft engine vane surface unsteady pressure data transmission and characterization.

  2. Measured and calculated acoustic attenuation rates of tuned resonator arrays for two surface impedance distribution models with flow

    NASA Technical Reports Server (NTRS)

    Parrott, Tony L.; Abrahamson, A. Louis; Jones, Michael G.

    1988-01-01

    An experiment was performed to validate two analytical models for predicting low frequency attenuation of duct liner configurations built from an array of seven resonators that could be individually tuned via adjustable cavity depths. These analytical models had previously been developed for high frequency aero-engine inlet duct liner design. In the low frequency application, the liner surface impedance distribution is unavoidably spatially varying by virtue of available fabrication techniques. The characteristic length of this spatial variation may be a significant fraction of the acoustic wavelength. Comparison of measured and predicted attenuation rates and transmission losses for both modal decomposition and finite element propagation models were in good to excellent agreement for a test frequency range that included the first and second cavity resonance frequencies. This was true for either of two surface impedance distribution modeling procedures used to simplify the impedance boundary conditions. In the presence of mean flow, measurements revealed a fine scale structure of acoustic hot spots in the attenuation and phase profiles. These details were accurately predicted by the finite element model. Since no impedance changes due to mean flow were assumed, it is concluded that this fine scale structure was due to convective effects of the mean flow interacting with the surface impedance nonuniformities.

  3. Passive acoustic monitoring using a towed hydrophone array results in identification of a previously unknown beaked whale habitat.

    PubMed

    Yack, Tina M; Barlow, Jay; Calambokidis, John; Southall, Brandon; Coates, Shannon

    2013-09-01

    Beaked whales are diverse and species rich taxa. They spend the vast majority of their time submerged, regularly diving to depths of hundreds to thousands of meters, typically occur in small groups, and behave inconspicuously at the surface. These factors make them extremely difficult to detect using standard visual survey methods. However, recent advancements in acoustic detection capabilities have made passive acoustic monitoring (PAM) a viable alternative. Beaked whales can be discriminated from other odontocetes by the unique characteristics of their echolocation clicks. In 2009 and 2010, PAM methods using towed hydrophone arrays were tested. These methods proved highly effective for real-time detection of beaked whales in the Southern California Bight (SCB) and were subsequently implemented in 2011 to successfully detect and track beaked whales during the ongoing Southern California Behavioral Response Study. The three year field effort has resulted in (1) the successful classification and tracking of Cuvier's (Ziphius cavirostris), Baird's (Berardius bairdii), and unidentified Mesoplodon beaked whale species and (2) the identification of areas of previously unknown beaked whale habitat use. Identification of habitat use areas will contribute to a better understanding of the complex relationship between beaked whale distribution, occurrence, and preferred habitat characteristics on a relatively small spatial scale. These findings will also provide information that can be used to promote more effective management and conservation of beaked whales in the SCB, a heavily used Naval operation and training region.

  4. Cuspidal caustic and focusing of acoustical waves generated by a parametric array onto a concave reflecting surface

    NASA Astrophysics Data System (ADS)

    Castagnède, Bernard; Sahraoui, Sohbi; Tournat, Vincent; Tahani, Najat

    2009-09-01

    The present Note is devoted to the study of the so-called cuspidal caustic at the surface of a hemi-cylindrical reflector illuminated with plane waves. In order to generate low frequency (e.g. in the range of 4 kHz) acoustical plane waves, a commercially available parametric array has been used. It produces powerful ultrasonic carrier waves at 40 kHz which can be electronically modulated between 200 Hz and 10 kHz. Further self-demodulation process during propagation in air generates an ultra-directive acoustical field (i.e. quasi-planar wavefronts) enabling to accurately study the focusing process occurring along the cuspidal caustic. The focusing coefficient can be computed locally by using two numerical tools, on one hand by computing the density of tangent rays to the caustic, and on the other hand by using some numerical results provided by a ray tracing algorithm. Some preliminary experimental data are then provided in order to validate the numerical predictions (spatial position of the caustic and focusing coefficient). To cite this article: B. Castagnède et al., C. R. Mecanique 337 (2009).

  5. A source array for generating higher order acoustic modes in circular ducts

    NASA Technical Reports Server (NTRS)

    Wyerman, B. R.; Reethof, G.

    1976-01-01

    A unique source array has been developed for the generation of both spinning and non-spinning higher order modes in a circular duct. The array consists of two concentric rings of sources. Through individual control of the response of each element, the array provided phase and amplitude control in the radial as well as circumferential directions. Radial modes shapes were measured in a 12-inch diameter anechoically-terminated hollow duct. These modes could be generated at their cut-off frequency and throughout a frequency range extending to the cut-off frequency for the next higher order radial mode. Comparisons are given between theory and experiment for the generation of specific modes. The radial dependence of the measured mode shapes was enhanced considerably by the design of this array. The results indicate a significant improvement over previous mode generation mechanisms. The contamination of the generated mode by additional spurious modes is also considered for variations between individual elements within the source array.

  6. Enhancing active and passive remote sensing in the ocean using broadband acoustic transmissions and coherent hydrophone arrays

    NASA Astrophysics Data System (ADS)

    Tran, Duong Duy

    The statistics of broadband acoustic signal transmissions in a random continental shelf waveguide are characterized for the fully saturated regime. The probability distribution of broadband signal energies after saturated multi-path propagation is derived using coherence theory. The frequency components obtained from Fourier decomposition of a broadband signal are each assumed to be fully saturated, where the energy spectral density obeys the exponential distribution with 5.6 dB standard deviation and unity scintillation index. When the signal bandwidth and measurement time are respectively larger than the correlation bandwidth and correlation time of its energy spectral density components, the broadband signal energy obtained by integrating the energy spectral density across the signal bandwidth then follows the Gamma distribution with standard deviation smaller than 5.6 dB and scintillation index less than unity. The theory is verified with broadband transmissions in the Gulf of Maine shallow water waveguide in the 300-1200 Hz frequency range. The standard deviations of received broadband signal energies range from 2.7 to 4.6 dB for effective bandwidths up to 42 Hz, while the standard deviations of individual energy spectral density components are roughly 5.6 dB. The energy spectral density correlation bandwidths of the received broadband signals are found to be larger for signals with higher center frequency. Sperm whales in the New England continental shelf and slope were passively localized, in both range and bearing using a single low-frequency (< 2500 Hz), densely sampled, towed horizontal coherent hydrophone array system. Whale bearings were estimated using time-domain beamforming that provided high coherent array gain in sperm whale click signal-to-noise ratio. Whale ranges from the receiver array center were estimated using the moving array triangulation technique from a sequence of whale bearing measurements. The dive profile was estimated for a sperm

  7. Seismo-acoustic analysis of the ocean swell sources observed with Romanian infrasound array and seismic stations

    NASA Astrophysics Data System (ADS)

    Ghica, Daniela; Grecu, Bogdan; Popa, Mihaela

    2015-04-01

    Romanian Plostina infrasound array (IPLOR) is deployed in the central part of the country, in Vrancea region. Presently, IPLOR array configuration includes 6 elements equipped with Chaparral Physics sensors and with aperture of about 2.5 km. For the purpose of assessing the IPLOR performance in observing various types of infrasound sources, over five years of data (since June 2009 to present) were processed. Signal interactive analysis was performed using WinPMCC software. The detection results show that the station response was gradually improved, as the number of array elements increased from three to six, and wind noise reduction conditions were enhanced. A larger number of detected signals and a better array resolution at lower frequency were noticed as well. Microbaroms - the interaction of ocean swell with the atmosphere - represent a relevant type of infrasonic source present in the IPLOR detection plots, for which the signal characterization has been enhanced with the array upgrading process. IPLOR detection capability related to this energetic long-period infrasound waves, which propagate over large distances, shows an alternating behavior, being strongly influenced by the upper atmospheric winds, i.e. seasonally dependent stratospheric winds. The ocean swell can be considered as a seismo-acoustic source, leaving an imprint on both seismic and infrasonic recordings. The interaction with the atmosphere generates infrasound (microbarom), while the interaction with the sea floor emits seismic signal (microseism). Microbaroms have a sinusoidal wave character with a dominant period of 5 s. Due to low damping at this period in stratospheric wave duct, microbaroms are observed over large distance ranges up to a few thousand kilometres. Microseisms occur as an increasing of seismic background noise between 2 and 20 s; in this range, primary and secondary peaks, at 5 and 14 s, are observed. Common broad-band seismic data, recorded with Romanian dense seismic

  8. New Methods and Transducer Designs for Ultrasonic Diagnostics and Therapy

    NASA Astrophysics Data System (ADS)

    Rybyanets, A. N.; Naumenko, A. A.; Sapozhnikov, O. A.; Khokhlova, V. A.

    Recent advances in the field of physical acoustics, imaging technologies, piezoelectric materials, and ultrasonic transducer design have led to emerging of novel methods and apparatus for ultrasonic diagnostics, therapy and body aesthetics. The paper presents the results on development and experimental study of different high intensity focused ultrasound (HIFU) transducers. Technological peculiarities of the HIFU transducer design as well as theoretical and numerical models of such transducers and the corresponding HIFU fields are discussed. Several HIFU transducers of different design have been fabricated using different advanced piezoelectric materials. Acoustic field measurements for those transducers have been performed using a calibrated fiber optic hydrophone and an ultrasonic measurement system (UMS). The results of ex vivo experiments with different tissues as well as in vivo experiments with blood vessels are presented that prove the efficacy, safety and selectivity of the developed HIFU transducers and methods.

  9. Concepts and Development of Bio-Inspired Distributed Embedded Wired/Wireless Sensor Array Architectures for Acoustic Wave Sensing in Integrated Aerospace Vehicles

    NASA Technical Reports Server (NTRS)

    Ghoshal, Anindya; Prosser, William H.; Kirikera, Goutham; Schulz, Mark J.; Hughes, Derke J.; Orisamolu, Wally

    2003-01-01

    This paper discusses the modeling of acoustic emissions in plate structures and their sensing by embedded or surface bonded piezoelectric sensor arrays. Three different modeling efforts for acoustic emission (AE) wave generation and propagation are discussed briefly along with their advantages and disadvantages. Continuous sensors placed at right angles on a plate are being discussed as a new approach to measure and locate the source of acoustic waves. Evolutionary novel signal processing algorithms and bio-inspired distributed sensor array systems are used on large structures and integrated aerospace vehicles for AE source localization and preliminary results are presented. These systems allow for a great reduction in the amount of data that needs to be processed and also reduce the chances of false alarms from ambient noises. It is envisioned that these biomimetic sensor arrays and signal processing techniques will be useful for both wireless and wired sensor arrays for real time health monitoring of large integrated aerospace vehicles and earth fixed civil structures. The sensor array architectures can also be used with other types of sensors and for other applications.

  10. Focused high frequency needle transducer for ultrasonic imaging and trapping

    NASA Astrophysics Data System (ADS)

    Hsu, Hsiu-Sheng; Zheng, Fan; Li, Ying; Lee, Changyang; Zhou, Qifa; Kirk Shung, K.

    2012-07-01

    A miniature focused needle transducer (<1 mm) was fabricated using the press-focusing technique. The measured pulse-echo waveform showed the transducer had center frequency of 57.5 MHz with 54% bandwidth and 14 dB insertion loss. To evaluate the performance of this type of transducer, invitro ultrasonic biomicroscopy imaging on the rabbit eye was obtained. Moreover, a single beam acoustic trapping experiment was performed using this transducer. Trapping of targeted particle size smaller than the ultrasonic wavelength was observed. Potential applications of these devices include minimally invasive measurements of retinal blood flow and single beam acoustic trapping of microparticles.

  11. Ultrasonic Transducer Irradiation Test Results

    SciTech Connect

    Daw, Joshua; Palmer, Joe; Ramuhalli, Pradeep; Keller, Paul; Montgomery, Robert; Chien, Hual-Te; Kohse, Gordon; Tittmann, Bernhard; Reinhardt, Brian; Rempe, Joy

    2015-02-01

    Ultrasonic technologies offer the potential for high-accuracy and -resolution in-pile measurement of a range of parameters, including geometry changes, temperature, crack initiation and growth, gas pressure and composition, and microstructural changes. Many Department of Energy-Office of Nuclear Energy (DOE-NE) programs are exploring the use of ultrasonic technologies to provide enhanced sensors for in-pile instrumentation during irradiation testing. For example, the ability of small diameter ultrasonic thermometers (UTs) to provide a temperature profile in candidate metallic and oxide fuel would provide much needed data for validating new fuel performance models. Other ongoing efforts include an ultrasonic technique to detect morphology changes (such as crack initiation and growth) and acoustic techniques to evaluate fission gas composition and pressure. These efforts are limited by the lack of identified ultrasonic transducer materials capable of long term performance under irradiation test conditions. For this reason, the Pennsylvania State University (PSU) was awarded an ATR NSUF project to evaluate the performance of promising magnetostrictive and piezoelectric transducers in the Massachusetts Institute of Technology Research Reactor (MITR) up to a fast fluence of at least 1021 n/cm2. The goal of this research is to characterize and demonstrate magnetostrictive and piezoelectric transducer operation during irradiation, enabling the development of novel radiation-tolerant ultrasonic sensors for use in Material Testing Reactors (MTRs). As such, this test is an instrumented lead test and real-time transducer performance data is collected along with temperature and neutron and gamma flux data. The current work bridges the gap between proven out-of-pile ultrasonic techniques and in-pile deployment of ultrasonic sensors by acquiring the data necessary to demonstrate the performance of ultrasonic transducers. To date, one piezoelectric

  12. Optimization of an acoustic telemetry array for detecting transmitter-implanted fish

    USGS Publications Warehouse

    Clements, S.; Jepsen, D.; Karnowski, M.; Schreck, C.B.

    2005-01-01

    The development of miniature acoustic transmitters and economical, robust automated receivers has enabled researchers to study the movement patterns and survival of teleosts in estuarine and ocean environments, including many species and age-classes that were previously considered too small for implantation. During 2001-2003, we optimized a receiver mooring system to minimize gear and data loss in areas where current action or wave action and acoustic noise are high. In addition, we conducted extensive tests to determine (1) the performance of a transmitter and receiver (Vemco, Ltd.) that are widely used, particularly in North America and Europe and (2) the optimal placement of receivers for recording the passage of fish past a point in a linear-flow environment. Our results suggest that in most locations the mooring system performs well with little loss of data; however, boat traffic remains a concern due to entanglement with the mooring system. We also found that the reception efficiency of the receivers depends largely on the method and location of deployment. In many cases, we observed a range of 0-100% reception efficiency (the percentage of known transmissions that are detected while the receiver is within range of the transmitter) when using a conventional method of mooring. The efficiency was improved by removal of the mounting bar and obstructions from the mooring line. ?? Copyright by the American Fisheries Society 2005.

  13. Acoustic interferometers based on two-dimensional arrays of rigid cylinders in air

    NASA Astrophysics Data System (ADS)

    Sanchis, Lorenzo; Håkansson, Andreas; Cervera, Francisco; Sánchez-Dehesa, José

    2003-01-01

    This work presents a comprehensive study of acoustic interferometers based on sonic crystals, such as the one reported by Cervera et al. in Phys. Rev. Lett. 88, 023902 (2002). This kind of interferometers consist of a slab of rigid cylinders in air put in a periodic configuration. Their performance as a function of thickness and symmetry configuration (square and hexagonal) is analyzed by our setup, which obtains the reflectance spectra using the standing wave ratio technique. Experimental observations are fairly well simulated by a self-consistent wave theory that incorporates all orders of multiple scattering. An homogenization procedure shows that sound propagation inside the hexagonal-based crystals is isotropic while it is biaxial inside the square-based crystals. A method able to extract the acoustic band structure from the reflectance spectra of the finite crystals under study is also described. Finally, the robustness of the interference effects is also studied as a function of positional disorder inside the unit cells in the lattice.

  14. Development of a Nonlinear Acoustic Phased Array and its Interaction with Thin Plates

    NASA Astrophysics Data System (ADS)

    Anzel, Paul; Donahue, Carly; Daraio, Chiara

    2015-03-01

    Numerous technologies are based on the principle of focusing acoustic energy. We propose a new device to focus sound waves which exploits highly nonlinear dynamics. The advantages of this device are the capability of generating very highly powerful acoustic pulses and potential operation in high-temperature environments where traditional piezoelectrics may fail. This device is composed of rows of ball bearings placed in contact with a medium of interest and with an actuator on the top. Elastic spherical particles have a contact force that grows with their relative displacement to the three-halves power (Hertzian contact). When several spheres are placed in a row, the particles support the propagation of ``solitary waves''--strong, compact stress-wave pulses whose tendency to disperse is counteracted by the nonlinearity of the sphere's contact force. We present results regarding the experimental operation of the device and its comparison to theory and numerical simulations. We will show how well this system is capable of focusing energy at various locations in the medium, and the limits imposed by pre-compression. Finally, the effects of timing error on energy focusing will be demonstrated. This research has been supported by a NASA Space Technology Research Fellowship.

  15. a Post-Processing Technique for Guided Wave Array Data for the Inspection of Plate Structures

    NASA Astrophysics Data System (ADS)

    Velichko, A.; Wilcox, P. D.

    2008-02-01

    The paper describes a general approach for processing data from a guided wave transducer array on a plate-like structure. It is shown that improvements in resolution are obtained at the expense of sensitivity to noise. A method of quantifying this sensitivity is presented. Experimental data obtained from a guided wave array containing electromagnetic acoustic transducers (EMAT) elements for exciting and detecting the S0 Lamb wave mode in a 5-mm thick aluminium plate are processed with different algorithms and the results are discussed. Generalization of the technique for the case of multimode media is suggested.

  16. Optimization of guided wave array for inspection of large plate structures

    NASA Astrophysics Data System (ADS)

    Velichko, Alexander

    2016-02-01

    The paper describes a general approach for processing data from a guided wave transducer array on a plate-like structure. The problem of finding optimal array element layout, which allows the number of elements and amount of measured data to be minimized without compromising array performance, is considered. It is shown that in the case of the far field imaging the image can be reconstructed using much fewer array elements than the classical Nyquist-Shannon sampling theorem requires. A new sampling criterion is derived and an optimised sparse array layout is proposed. The theory is validated experimentally using a guided wave array containing electromagnetic acoustic transducer elements for exciting and detecting the S0 Lamb wave mode in a 3-mm-thick aluminum plate.

  17. Measurement methods of ultrasonic transducer sensitivity.

    PubMed

    Xiao, Dingguo; Fan, Qiong; Xu, Chunguang; Zhang, Xiuhua

    2016-05-01

    Sensitivity is an important parameter to describe the electro-acoustic energy conversion efficiency of ultrasonic transducer. In this paper, the definition of sensitivity and reciprocity of ultrasonic transducer is studied. The frequency response function of a transducer is the spectrum of its sensitivity, which reflects the response sensitivity of the transducer for input signals at different frequencies. Four common methods which are used to measure the disc-vibrator transducer sensitivity are discussed in current investigation. The reciprocity method and the pulse-echo method are based on the reciprocity of the transducer. In the laser vibrometer method measurement, the normal velocity on the transducer radiating surface is directly measured by a laser vibrometer. In the measurement process of the hydrophone method, a calibrated hydrophone is used to measure the transmitted field. The validity of these methods is checked by experimental test. All of the four methods described are sufficiently accurate for transducer sensitivity measurement, while each method has its advantages and limitations. In practical applications, the appropriate method to measure transducer sensitivity should be selected based on actual conditions. PMID:26953638

  18. High-Frequency (>50 MHz) Medical Ultrasound Linear Arrays Fabricated From Micromachined Bulk PZT Materials

    PubMed Central

    Liu, Changgeng; Zhou, Qifa; Djuth, Frank T.; Shung, K. Kirk

    2012-01-01

    This paper describes the development and characterization of a high-frequency (65-MHz) ultrasound transducer linear array. The array was built from bulk PZT which was etched using an optimized chlorine-based plasma dry-etching process. The median etch rate of 8 μm/h yielded a good profile (wall) angle (>83°) and a reasonable processing time for etch depths up to 40 μm (which corresponds to a 50-MHz transducer). A backing layer with an acoustic impedance of 6 MRayl and a front-end polymer matching layer yielded a transducer bandwidth of 40%. The major parameters of the transducer have been characterized. The two-way insertion loss and crosstalk between adjacent channels at the center frequency are 26.5 and −25 dB, respectively. PMID:24626041

  19. Airborne ultrasonic phased arrays using ferroelectrets: a new fabrication approach.

    PubMed

    Ealo, Joao L; Camacho, Jorge J; Fritsch, Carlos

    2009-04-01

    In this work, a novel procedure that considerably simplifies the fabrication process of ferroelectret-based multielement array transducers is proposed and evaluated. Also, the potential of ferroelectrets being used as active material for air-coupled ultrasonic transducer design is demonstrated. The new construction method of multi-element transducers introduces 2 distinctive improvements. First, active ferroelectret material is not discretized into elements, and second, the need of structuring upper and/or lower electrodes in advance of the permanent polarization of the film is removed. The aperture discretization and the mechanical connection are achieved in one step using a through-thickness conductive tape. To validate the procedure, 2 linear array prototypes of 32 elements, with a pitch of 3.43 mm and a wide usable frequency range from 30 to 300 kHz, were built and evaluated using a commercial phased-array system. A low crosstalk among elements, below -30 dB, was measured by interferometry. Likewise, a homogeneous response of the array elements, with a maximum deviation of +/-1.8 dB, was obtained. Acoustic beam steering measurements were accomplished at different deflection angles using a calibrated microphone. The ultrasonic beam parameters, namely, lateral resolution, side lobe level, grating lobes, and focus depth, were congruent with theory. Acoustic images of a single reflector were obtained using one of the array elements as the receiver. Resulting images are also in accordance with numerical simulation, demonstrating the feasibility of using these arrays in pulse-echo mode. The proposed procedure simplifies the manufacturing of multidimensional arrays with arbitrary shape elements and not uniformly distributed. Furthermore, this concept can be extended to nonflat arrays as long as the transducer substrate conforms to a developable surface. PMID:19406714

  20. Glass-windowed ultrasound transducers.

    PubMed

    Yddal, Tostein; Gilja, Odd Helge; Cochran, Sandy; Postema, Michiel; Kotopoulis, Spiros

    2016-05-01

    In research and industrial processes, it is increasingly common practice to combine multiple measurement modalities. Nevertheless, experimental tools that allow the co-linear combination of optical and ultrasonic transmission have rarely been reported. The aim of this study was to develop and characterise a water-matched ultrasound transducer architecture using standard components, with a central optical window larger than 10 mm in diameter allowing for optical transmission. The window can be used to place illumination or imaging apparatus such as light guides, miniature cameras, or microscope objectives, simplifying experimental setups. Four design variations of a basic architecture were fabricated and characterised with the objective to assess whether the variations influence the acoustic output. The basic architecture consisted of a piezoelectric ring and a glass disc, with an aluminium casing. The designs differed in piezoelectric element dimensions: inner diameter, ID=10 mm, outer diameter, OD=25 mm, thickness, TH=4 mm or ID=20 mm, OD=40 mm, TH=5 mm; glass disc dimensions OD=20-50 mm, TH=2-4 mm; and details of assembly. The transducers' frequency responses were characterised using electrical impedance spectroscopy and pulse-echo measurements, the acoustic propagation pattern using acoustic pressure field scans, the acoustic power output using radiation force balance measurements, and the acoustic pressure using a needle hydrophone. Depending on the design and piezoelectric element dimensions, the resonance frequency was in the range 350-630 kHz, the -6 dB bandwidth was in the range 87-97%, acoustic output power exceeded 1 W, and acoustic pressure exceeded 1 MPa peak-to-peak. 3D stress simulations were performed to predict the isostatic pressure required to induce material failure and 4D acoustic simulations. The pressure simulations indicated that specific design variations could sustain isostatic pressures up to 4.8 MPa.The acoustic simulations were able to

  1. Glass-windowed ultrasound transducers.

    PubMed

    Yddal, Tostein; Gilja, Odd Helge; Cochran, Sandy; Postema, Michiel; Kotopoulis, Spiros

    2016-05-01

    In research and industrial processes, it is increasingly common practice to combine multiple measurement modalities. Nevertheless, experimental tools that allow the co-linear combination of optical and ultrasonic transmission have rarely been reported. The aim of this study was to develop and characterise a water-matched ultrasound transducer architecture using standard components, with a central optical window larger than 10 mm in diameter allowing for optical transmission. The window can be used to place illumination or imaging apparatus such as light guides, miniature cameras, or microscope objectives, simplifying experimental setups. Four design variations of a basic architecture were fabricated and characterised with the objective to assess whether the variations influence the acoustic output. The basic architecture consisted of a piezoelectric ring and a glass disc, with an aluminium casing. The designs differed in piezoelectric element dimensions: inner diameter, ID=10 mm, outer diameter, OD=25 mm, thickness, TH=4 mm or ID=20 mm, OD=40 mm, TH=5 mm; glass disc dimensions OD=20-50 mm, TH=2-4 mm; and details of assembly. The transducers' frequency responses were characterised using electrical impedance spectroscopy and pulse-echo measurements, the acoustic propagation pattern using acoustic pressure field scans, the acoustic power output using radiation force balance measurements, and the acoustic pressure using a needle hydrophone. Depending on the design and piezoelectric element dimensions, the resonance frequency was in the range 350-630 kHz, the -6 dB bandwidth was in the range 87-97%, acoustic output power exceeded 1 W, and acoustic pressure exceeded 1 MPa peak-to-peak. 3D stress simulations were performed to predict the isostatic pressure required to induce material failure and 4D acoustic simulations. The pressure simulations indicated that specific design variations could sustain isostatic pressures up to 4.8 MPa.The acoustic simulations were able to

  2. Methods for Room Acoustic Analysis and Synthesis using a Monopole-Dipole Microphone Array

    NASA Technical Reports Server (NTRS)

    Abel, J. S.; Begault, Durand R.; Null, Cynthia H. (Technical Monitor)

    1998-01-01

    In recent work, a microphone array consisting of an omnidirectional microphone and colocated dipole microphones having orthogonally aligned dipole axes was used to examine the directional nature of a room impulse response. The arrival of significant reflections was indicated by peaks in the power of the omnidirectional microphone response; reflection direction of arrival was revealed by comparing zero-lag crosscorrelations between the omnidirectional response and the dipole responses to the omnidirectional response power to estimate arrival direction cosines with respect to the dipole axes.

  3. Transducer-Mounting Fixture

    NASA Technical Reports Server (NTRS)

    Spiegel, Kirk W.

    1990-01-01

    Transducer-mounting fixture holds transducer securely against stud. Projects only slightly beyond stud after installation. Flanged transducer fits into fixture when hinged halves open. When halves reclosed, fixture tightened onto threaded stud until stud makes contact with transducer. Knurled area on fixture aids in tightening fixture on stud.

  4. Low-Loss Wide-Band Floating Electrode Type Unidirectional Transducer Filters and Ladder-Type Resonator Filters Using High-Temperature-Stable High Electromechanical Coupling Surface Acoustic Wave Substrates

    NASA Astrophysics Data System (ADS)

    Yamanouchi, Kazuhiko; Ishii, Toru

    2003-05-01

    The important properties required for surface acoustic wave (SAW) substrates are large electromechanical coupling coefficients (k2), small temperature coefficient of frequency (TCF), low propagation loss, among other. LiNbO3 is a good SAW substrate because of its good properties and large size. We developed SiO2/rotated Y-cut, X-propagating LiNbO3 leaky SAW substrates with a large k2 (over 0.2) and zero TCF at a small thickness of SiO2 of H/λ=0.2 (H: SiO2 film thickness, λ: SAW wave-length) compared to those of other substrates and zero propagation attenuation in the case of metalized surface. In this paper, the theoretical and experimental results for SAW filters, resonators and resonator filters are described. The low-loss filters using floating electrode type unidirectional transducer (FEUDT) showed an insertion loss of below 1 dB at a center frequency of 400 MHz and bandwidth of 20 MHz. Also, the resonator showed the wide-band characteristics and resonator filters showed a bandwidth of 80 MHz at a center frequency of 500 MHz.

  5. 21 CFR 892.1570 - Diagnostic ultrasonic transducer.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... intended for use in diagnostic ultrasonic medical devices. Accessories of this generic type of device may include transmission media for acoustically coupling the transducer to the body surface, such as...

  6. 21 CFR 892.1570 - Diagnostic ultrasonic transducer.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... intended for use in diagnostic ultrasonic medical devices. Accessories of this generic type of device may include transmission media for acoustically coupling the transducer to the body surface, such as...

  7. Localization of multiple acoustic sources with small arrays using a coherence test.

    PubMed

    Mohan, Satish; Lockwood, Michael E; Kramer, Michael L; Jones, Douglas L

    2008-04-01

    Direction finding of more sources than sensors is appealing in situations with small sensor arrays. Potential applications include surveillance, teleconferencing, and auditory scene analysis for hearing aids. A new technique for time-frequency-sparse sources, such as speech and vehicle sounds, uses a coherence test to identify low-rank time-frequency bins. These low-rank bins are processed in one of two ways: (1) narrowband spatial spectrum estimation at each bin followed by summation of directional spectra across time and frequency or (2) clustering low-rank covariance matrices, averaging covariance matrices within clusters, and narrowband spatial spectrum estimation of each cluster. Experimental results with omnidirectional microphones and colocated directional microphones demonstrate the algorithm's ability to localize 3-5 simultaneous speech sources over 4 s with 2-3 microphones to less than 1 degree of error, and the ability to localize simultaneously two moving military vehicles and small arms gunfire. PMID:18397021

  8. Electromechanical acoustic liner

    NASA Technical Reports Server (NTRS)

    Sheplak, Mark (Inventor); Cattafesta, III, Louis N. (Inventor); Nishida, Toshikazu (Inventor); Horowitz, Stephen Brian (Inventor)

    2007-01-01

    A multi-resonator-based system responsive to acoustic waves includes at least two resonators, each including a bottom plate, side walls secured to the bottom plate, and a top plate disposed on top of the side walls. The top plate includes an orifice so that a portion of an incident acoustical wave compresses gas in the resonators. The bottom plate or the side walls include at least one compliant portion. A reciprocal electromechanical transducer coupled to the compliant portion of each of the resonators forms a first and second transducer/compliant composite. An electrical network is disposed between the reciprocal electromechanical transducer of the first and second resonator.

  9. A smart sensor system for trace organic vapor detection using a temperature-controlled array of surface acoustic wave vapor sensors, automated preconcentrator tubes, and pattern recognition

    SciTech Connect

    Grate, J.W.; Rose-Pehrsson, S.L.; Klusty, M.; Wohltjen, H.

    1993-05-01

    A smart sensor system for the detection, of toxic organophosphorus and toxic organosulfur vapors at trace concentrations has been designed, fabricated, and tested against a wide variety of vapor challenges. The key features of the system are: An array of four surface acoustic wave (SAW) vapor sensors, temperature control of the vapor sensors, the use of pattern recognition to analyze the sensor data, and an automated sampling system including thermally-desorbed preconcentrator tubes (PCTs).

  10. Micro-stereolithography as a transducer design method.

    PubMed

    Ho, K S; Bradley, R J; Billson, D R; Hutchins, D A

    2008-03-01

    This paper investigates the use of micro-stereolithography, a rapid prototyping technique, in the manufacture of transducers. It is illustrated for the production of electromagnetic acoustic transducer (EMATs) coils in both meander-line and spiral configurations. A synthetic aperture focussing technique (SAFT) has been applied to the ultrasonic signals from these devices to reconstruct images in metallic objects.

  11. Resonant transducers for solid-state plasma density modulation

    NASA Astrophysics Data System (ADS)

    Hallock, Gary A.; Meier, Mark A.

    2016-04-01

    We have developed transducers capable of modulating the plasma density and plasma density gradients in indium antimonide. These transducers make use of piezoelectric drivers to excite acoustic pressure resonance at 3λ/2, generating large amplitude standing waves and plasma density modulations. The plasma density has been directly measured using a laser diagnostic. A layered media model shows good agreement with the experimental measurements.

  12. Post-processing of guided wave array data for high resolution pipe inspection.

    PubMed

    Velichko, Alexander; Wilcox, Paul D

    2009-12-01

    This paper describes a method for processing data from a guided wave transducer array on a pipe. The raw data set from such an array contains the full matrix of time-domain signals from each transmitter-receiver combination. It is shown that for certain configurations of an array, the total focusing method can be applied, which allows the array to be focused at every point on a pipe in both transmission and reception. The effect of array configuration parameters on the sensitivity of the proposed method to random and coherent noise is discussed. Experimental results are presented using electromagnetic acoustic transducers for exciting and detecting the S(0) Lamb wave mode in a 12-in. diameter steel pipe at 200 kHz excitation frequency. The results show that using the imaging algorithm, a 2-mm (0.08 wavelength) diameter half-thickness hole can be detected.

  13. All-Optical Ultrasound Transducers for High Resolution Imaging

    NASA Astrophysics Data System (ADS)

    Sheaff, Clay Smith

    High frequency ultrasound (HFUS) has increasingly been used within the past few decades to provide high resolution (< 200 mum) imaging in medical applications such as endoluminal imaging, intravascular imaging, ophthalmology, and dermatology. The optical detection and generation of HFUS using thin films offers numerous advantages over traditional piezoelectric technology. Circumvention of an electronic interface with the device head is one of the most significant given the RF noise, crosstalk, and reduced capacitance that encumbers small-scale electronic transducers. Thin film Fabry-Perot interferometers - also known as etalons - are well suited for HFUS receivers on account of their high sensitivity, wide bandwidth, and ease of fabrication. In addition, thin films can be used to generate HFUS when irradiated with optical pulses - a method referred to as Thermoelastic Ultrasound Generation (TUG). By integrating a polyimide (PI) film for TUG into an etalon receiver, we have created for the first time an all-optical ultrasound transducer that is both thermally stable and capable of forming fully sampled 2-D imaging arrays of arbitrary configuration. Here we report (1) the design and fabrication of PI-etalon transducers; (2) an evaluation of their optical and acoustic performance parameters; (3) the ability to conduct high-resolution imaging with synthetic 2-D arrays of PI-etalon elements; and (4) work towards a fiber optic PI-etalon for in vivo use. Successful development of a fiber optic imager would provide a unique field-of-view thereby exposing an abundance of prospects for minimally-invasive analysis, diagnosis, and treatment of disease.

  14. Spatial acoustic signal processing for immersive communication

    NASA Astrophysics Data System (ADS)

    Atkins, Joshua

    Computing is rapidly becoming ubiquitous as users expect devices that can augment and interact naturally with the world around them. In these systems it is necessary to have an acoustic front-end that is able to capture and reproduce natural human communication. Whether the end point is a speech recognizer or another human listener, the reduction of noise, reverberation, and acoustic echoes are all necessary and complex challenges. The focus of this dissertation is to provide a general method for approaching these problems using spherical microphone and loudspeaker arrays.. In this work, a theory of capturing and reproducing three-dimensional acoustic fields is introduced from a signal processing perspective. In particular, the decomposition of the spatial part of the acoustic field into an orthogonal basis of spherical harmonics provides not only a general framework for analysis, but also many processing advantages. The spatial sampling error limits the upper frequency range with which a sound field can be accurately captured or reproduced. In broadband arrays, the cost and complexity of using multiple transducers is an issue. This work provides a flexible optimization method for determining the location of array elements to minimize the spatial aliasing error. The low frequency array processing ability is also limited by the SNR, mismatch, and placement error of transducers. To address this, a robust processing method is introduced and used to design a reproduction system for rendering over arbitrary loudspeaker arrays or binaurally over headphones. In addition to the beamforming problem, the multichannel acoustic echo cancellation (MCAEC) issue is also addressed. A MCAEC must adaptively estimate and track the constantly changing loudspeaker-room-microphone response to remove the sound field presented over the loudspeakers from that captured by the microphones. In the multichannel case, the system is overdetermined and many adaptive schemes fail to converge to

  15. Estimation of Acoustic Particle Motion and Source Bearing Using a Drifting Hydrophone Array Near a River Current Turbine to Assess Disturbances to Fish

    NASA Astrophysics Data System (ADS)

    Murphy, Paul G.

    River hydrokinetic turbines may be an economical alternative to traditional energy sources for small communities on Alaskan rivers. However, there is concern that sound from these turbines could affect sockeye salmon (Oncorhynchus nerka), an important resource for small, subsistence based communities, commercial fisherman, and recreational anglers. The hearing sensitivity of sockeye salmon has not been quantified, but behavioral responses to sounds at frequencies less than a few hundred Hertz have been documented for Atlantic salmon (Salmo salar), and particle motion is thought to be the primary mode of stimulation. Methods of measuring acoustic particle motion are well-established, but have rarely been necessary in energetic areas, such as river and tidal current environments. In this study, the acoustic pressure in the vicinity of an operating river current turbine is measured using a freely drifting hydrophone array. Analysis of turbine sound reveals tones that vary in frequency and magnitude with turbine rotation rate, and that may sockeye salmon may sense. In addition to pressure, the vertical components of particle acceleration and velocity are estimated by calculating the finite difference of the pressure signals from the hydrophone array. A method of determining source bearing using an array of hydrophones is explored. The benefits and challenges of deploying drifting hydrophone arrays for marine renewable energy converter monitoring are discussed.

  16. Irradiation Testing of Ultrasonic Transducers

    SciTech Connect

    Daw, Joshua; Tittmann, Bernhard; Reinhardt, Brian; Kohse, Gordon E.; Ramuhalli, Pradeep; Montgomery, Robert O.; Chien, Hual-Te; Villard, Jean-Francois; Palmer, Joe; Rempe, Joy

    2014-07-30

    Ultrasonic technologies offer the potential for high accuracy and resolution in-pile measurement of a range of parameters, including geometry changes, temperature, crack initiation and growth, gas pressure and composition, and microstructural changes. Many Department of Energy-Office of Nuclear Energy (DOE-NE) programs are exploring the use of ultrasonic technologies to provide enhanced sensors for in-pile instrumentation during irradiation testing. For example, the ability of single, small diameter ultrasonic thermometers (UTs) to provide a temperature profile in candidate metallic and oxide fuel would provide much needed data for validating new fuel performance models. Other efforts include an ultrasonic technique to detect morphology changes (such as crack initiation and growth) and acoustic techniques to evaluate fission gas composition and pressure. These efforts are limited by the lack of existing knowledge of ultrasonic transducer material survivability under irradiation conditions. For this reason, the Pennsylvania State University (PSU) was awarded an Advanced Test Reactor National Scientific User Facility (ATR NSUF) project to evaluate promising magnetostrictive and piezoelectric transducer performance in the Massachusetts Institute of Technology Research Reactor (MITR) up to a fast fluence of at least 1021 n/cm2 (E> 0.1 MeV). The goal of this research is to characterize magnetostrictive and piezoelectric transducer survivability during irradiation, enabling the development of novel radiation tolerant ultrasonic sensors for use in Material and Test Reactors (MTRs). As such, this test will be an instrumented lead test and real-time transducer performance data will be collected along with temperature and neutron and gamma flux data. The current work bridges the gap between proven out-of-pile ultrasonic techniques and in-pile deployment of ultrasonic sensors by acquiring the data necessary to demonstrate the performance of ultrasonic transducers.

  17. Acoustic levitation of a large solid sphere

    NASA Astrophysics Data System (ADS)

    Andrade, Marco A. B.; Bernassau, Anne L.; Adamowski, Julio C.

    2016-07-01

    We demonstrate that acoustic levitation can levitate spherical objects much larger than the acoustic wavelength in air. The acoustic levitation of an expanded polystyrene sphere of 50 mm in diameter, corresponding to 3.6 times the wavelength, is achieved by using three 25 kHz ultrasonic transducers arranged in a tripod fashion. In this configuration, a standing wave is created between the transducers and the sphere. The axial acoustic radiation force generated by each transducer on the sphere was modeled numerically as a function of the distance between the sphere and the transducer. The theoretical acoustic radiation force was verified experimentally in a setup consisting of an electronic scale and an ultrasonic transducer mounted on a motorized linear stage. The comparison between the numerical and experimental acoustic radiation forces presents a good agreement.

  18. Nonlinear Effects in Ultrasound Fields of Diagnostic-type Transducers Used for Kidney Stone Propulsion: Characterization in Water

    PubMed Central

    Karzova, M.; Cunitz, B.; Yuldashev, P.; Andriyakhina, Y.; Kreider, W.; Sapozhnikov, O.; Bailey, M.; Khokhlova, V.

    2016-01-01

    Newer imaging and therapeutic ultrasound technologies require higher in situ pressure levels compared to conventional diagnostic values. One example is the recently developed use of focused ultrasonic radiation force to move kidney stones and residual fragments out of the urinary collecting system. A commercial diagnostic 2.3 MHz C5-2 array probe is used to deliver the acoustic pushing pulses. The probe comprises 128 elements equally spaced at the 55 mm long convex cylindrical surface with 38 mm radius of curvature. The efficacy of the treatment can be increased by using higher transducer output to provide stronger pushing force; however, nonlinear acoustic saturation effect can be a limiting factor. In this work nonlinear propagation effects were analyzed for the C5-2 transducer using a combined measurement and modeling approach. Simulations were based on the 3D Westervelt equation; the boundary condition was set to match low power pressure beam scans. Focal waveforms simulated for increased output power levels were compared with the fiber-optic hydrophone measurements and were found in good agreement. It was shown that saturation effects do limit the acoustic pressure in the focal region of the transducer. This work has application to standard diagnostic probes and imaging. PMID:27087711

  19. Properties of Noise Cross Correlation Functions Obtained from a Distributed Acoustic Sensing (DAS) Array at Garner Valley, California

    NASA Astrophysics Data System (ADS)

    Zeng, X.; Lancelle, C.; Thurber, C. H.; Fratta, D.; Wang, H. F.; Chalari, A.; Clarke, A.

    2015-12-01

    The field test of Distributed Acoustic Sensing (DAS) conducted at Garner Valley, California on September 11-12, 2013 provided a continuous overnight record of ambient noise. The DAS array recorded ground motions every one meter of optical cable that was arranged approximately in the shape of a rectangle with dimensions of 160 m by 80 m. The long dimension of the array was adjacent to a state highway. Three hours of record were used to compute noise cross-correlation functions (NCFs) in one-minute windows. The trace from each sensor channel was pre-processed by downsampling to 200 Hz, followed by normalization in the time-domain and bandpass filtering between 2 and 20 Hz (Bensen et al., 2007). The one-minute NCFs were then stacked using the time-frequency domain phase-weighted stacking method (Schimmel & Gallart, 2007). The NCFs between channels were asymmetrical reflecting the direction of traffic noise. The group velocities were found using the frequency-time analysis method. The energy was concentrated between 5 and 15 Hz, which falls into the typical traffic noise frequency band. The resulting velocities were between 100 and 300 m/s for frequencies between 10 and 20 Hz, which are in the same range as described in the results for surface-wave dispersion obtained using an active source for the same site (Lancelle et al., 2015). The group velocity starts to decrease for frequencies greater than ~10 Hz, which was expected on the basis of a previous shear-wave velocity model (Steidl et al., 1996). Then, the phase velocity was calculated using the multichannel analysis of surface wave technique (MASW - Park et al., 1999) with 114 NCFs spaced one meter apart. The resulting dispersion curve between 5 and 15 Hz gave phase velocities that ranged from approximately 170 m/s at 15 Hz to 250 m/s at 5 Hz. These results are consistent with other results of active-source DAS and seismometer records obtained at the Garner Valley site (e.g., Stokoe et al. 2004). This analysis is

  20. Modeling of functionally graded piezoelectric ultrasonic transducers.

    PubMed

    Rubio, Wilfredo Montealegre; Buiochi, Flávio; Adamowski, Julio Cezar; Silva, Emílio Carlos Nelli

    2009-05-01

    The application of functionally graded material (FGM) concept to piezoelectric transducers allows the design of composite transducers without interfaces, due to the continuous change of property values. Thus, large improvements can be achieved, as reduction of stress concentration, increasing of bonding strength, and bandwidth. This work proposes to design and to model FGM piezoelectric transducers and to compare their performance with non-FGM ones. Analytical and finite element (FE) modeling of FGM piezoelectric transducers radiating a plane pressure wave in fluid medium are developed and their results are compared. The ANSYS software is used for the FE modeling. The analytical model is based on FGM-equivalent acoustic transmission-line model, which is implemented using MATLAB software. Two cases are considered: (i) the transducer emits a pressure wave in water and it is composed of a graded piezoceramic disk, and backing and matching layers made of homogeneous materials; (ii) the transducer has no backing and matching layer; in this case, no external load is simulated. Time and frequency pressure responses are obtained through a transient analysis. The material properties are graded along thickness direction. Linear and exponential gradation functions are implemented to illustrate the influence of gradation on the transducer pressure response, electrical impedance, and resonance frequencies.

  1. Micro-Horn Arrays for Ultrasonic Impedance Matching

    NASA Technical Reports Server (NTRS)

    Rao, Shanti; Palmer, Dean

    2009-01-01

    Thin-layered structures containing arrays of micromachined horns, denoted solid micro-horn arrays (SMIHAs), have been conceived as improved means of matching acoustic impedances between ultrasonic transducers and the media with which the transducers are required to exchange acoustic energy. Typically, ultrasonic transducers (e.g., those used in medical imaging) are piezoelectric or similar devices, which produce small displacements at large stresses. However, larger displacements at smaller stresses are required in the target media (e.g., human tissues) with which acoustic energy is to be exchanged. Heretofore, efficiencies in transmission of acoustic energy between ultrasonic transducers and target media have been severely limited because substantial mismatches of acoustic impedances have remained, even when coupling material layers have been interposed between the transducers and the target media. In contrast, SMIHAs can, in principle, be designed to effect more nearly complete acoustic impedance matching, leading to power transmission efficiencies of 90 percent or even greater. The SMIHA concept is based on extension, into the higher-frequency/ lower-wavelength ultrasonic range, of the use of horns to match acoustic impedances in the audible and lower-frequency ultrasonic ranges. In matching acoustic impedance in transmission from a higher-impedance acoustic source (e.g., a piezoelectric transducer) and a lowerimpedance target medium (e.g., air or human tissue), a horn acts as a mechanical amplifier. The shape and size of the horn can be optimized for matching acoustic impedance in a specified frequency range. A typical SMIHA would consist of a base plate, a face plate, and an array of horns that would constitute pillars that connect the two plates (see figure). In use, the base plate would be connected to an ultrasonic transducer and the face plate would be placed in contact with the target medium. As at lower frequencies, the sizes and shapes of the pillars

  2. Circuit for echo and noise suppression of acoustic signals transmitted through a drill string

    DOEpatents

    Drumheller, D.S.; Scott, D.D.

    1993-12-28

    An electronic circuit for digitally processing analog electrical signals produced by at least one acoustic transducer is presented. In a preferred embodiment of the present invention, a novel digital time delay circuit is utilized which employs an array of First-in-First-out (FiFo) microchips. Also, a bandpass filter is used at the input to this circuit for isolating drill string noise and eliminating high frequency output. 20 figures.

  3. The effects of transducer geometry on artifacts common to diagnostic bone imaging with conventional medical ultrasound.

    PubMed

    Mauldin, F William; Owen, Kevin; Tiouririne, Mohamed; Hossack, John A

    2012-06-01

    The portability, low cost, and non-ionizing radiation associated with medical ultrasound suggest that it has potential as a superior alternative to X-ray for bone imaging. However, when conventional ultrasound imaging systems are used for bone imaging, clinical acceptance is frequently limited by artifacts derived from reflections occurring away from the main axis of the acoustic beam. In this paper, the physical source of off-axis artifacts and the effect of transducer geometry on these artifacts are investigated in simulation and experimental studies. In agreement with diffraction theory, the sampled linear-array geometry possessed increased off-axis energy compared with single-element piston geometry, and therefore, exhibited greater levels of artifact signal. Simulation and experimental results demonstrated that the linear-array geometry exhibited increased artifact signal when the center frequency increased, when energy off-axis to the main acoustic beam (i.e., grating lobes) was perpendicularly incident upon off-axis surfaces, and when off-axis surfaces were specular rather than diffusive. The simulation model used to simulate specular reflections was validated experimentally and a correlation coefficient of 0.97 between experimental and simulated peak reflection contrast was observed. In ex vivo experiments, the piston geometry yielded 4 and 6.2 dB average contrast improvement compared with the linear array when imaging the spinous process and interlaminar space of an animal spine, respectively. This work indicates that off-axis reflections are a major source of ultrasound image artifacts, particularly in environments comprising specular reflecting (i.e., bone or bone-like) objects. Transducer geometries with reduced sensitivity to off-axis surface reflections, such as a piston transducer geometry, yield significant reductions in image artifact.

  4. Transducer applications, a compilation

    NASA Technical Reports Server (NTRS)

    1972-01-01

    The characteristics and applications of transducers are discussed. Subjects presented are: (1) thermal measurements, (2) liquid level and fluid flow measurements, (3) pressure transducers, (4) stress-strain measurements, (5) acceleration and velocity measurements, (6) displacement and angular rotation, and (7) transducer test and calibration methods.

  5. Extremely high-frequency piezoelectroacoustic transducer based on BN-tube/SiC-whiskers rope

    NASA Astrophysics Data System (ADS)

    Pokropivny, V.; Pokropivny, A.; Lohmus, A.; Lohmus, R.; Kovrygin, S.; Sylenko, P.; Partch, R.; Prilutskii, E.

    2007-03-01

    Innovative idea of piezoelectric electroacoustic transducer in extremely high-frequency terahertz range on the basis of BN-tube/SiC-whiskers rope is suggested and substantiated. Unlike an acoustic spectrum of solid rectangular pins and films used so far in ultrasonic pulsers and receivers, in the acoustic spectrum of circular hollow nanotubes, the peculiar squash E2g and the subsequent Eng modes of starlike chain belonging to a gallery of whispering acoustic modes was shown by ab initio RHF/6-31G calculations to exist in the Raman spectra. Inherent important feature of these standing vibrations is their weak attenuation and high frequency, which, as depended on the nanotube diameter, fall in the range of about ∼1 GHz-1 THz. Hypersound was suggested to be excited by resonant microwaves using the piezoelectric properties of BN heteropolar nanotubes and then to transmit it into a sample by high modulus encapsulated SiC-whiskers. Such BN-tube/SiC-whiskers of 100-800 nm in diameter and with ∼20 aspect ratio were synthesized by carbothermal and CVD techniques. Cactus-like arrays of SiC nanowhiskers were synthesized by CVD technique. A sketch of the hypersound generator/detector, with the piezoelectroacoustical transducer on the basis of the BN-tube/SiC-whisker assembly serving as hypersonic antenna, was advanced.

  6. Acoustic detection of UHE neutrinos - the ACORNE project

    NASA Astrophysics Data System (ADS)

    Thompson, L. F.; Perkin, J. D.; ACORNE Collaboration

    2008-11-01

    An interesting new possibility of detection of ultra-high energy (UHE) neutrinos is that of acoustic detection whereby the acoustic pressure pulse generated as a UHE neutrino interacts in a suitable medium such as water or ice is detected by an array of acoustic sensors. Recent years have seen something of a renaissance of this field and there are currently a number of activities worldwide to assess the potential of this technique. The UK-based ACORNE collaboration is one of these activities; ACORNE has access to the QinetiQ underwater acoustic range off Rona, an island off the North-West coast of Scotland. The poster will summarise ACORNE's R&D work, including simulation of the thermoacoustic emission of neutrino-induced particle cascades, reconstruction of event vertices and the effects of refraction, potential neutrino flux sensitivities from large area hydrophone arrays, a study transducer based calibration techniques and an analysis of the first acoustic data recorded by the Rona hydrophone array.

  7. Frequency response calibration of recess-mounted pressure transducers

    NASA Technical Reports Server (NTRS)

    Marcolini, M. A.; Lorber, P. F.; Miller, W. T., Jr.; Covino, A. F., Jr.

    1991-01-01

    A technique is described for measuring the frequency response of pressure transducers mounted inside a model, where a narrow pipette leads to an orifice at the surface. An acoustic driver is mounted to a small chamber which has an opening at the opposite end with an O-ring seal to place over the orifice. A 3.18 mm (1/8 inch) reference microphone is mounted to one side of the chamber. The acoustic driver receives an input of white noise, and the transducer and reference microphone outputs are compared to obtain the frequency response of the pressure transducer. Selected results are presented in the form of power spectra for both the transducer and the reference, as well as the amplitude variation and phase shift between the two signals as a function of frequency. The effect of pipette length and the use of this technique for identifying both blocked orifices and faulty transducers are described.

  8. Evaluating the Feasibility of Acoustic Radiation Force Impulse Shear Wave Elasticity Imaging of the Uterine Cervix With an Intracavity Array: A Simulation Study

    PubMed Central

    Feltovich, Helen; Homyk, Andrew D.; Carlson, Lindsey C.; Hall, Timothy J.

    2015-01-01

    The uterine cervix softens, shortens, and dilates throughout pregnancy in response to progressive disorganization of its layered collagen microstructure. This process is an essential part of normal pregnancy, but premature changes are associated with preterm birth. Clinically, there are no reliable noninvasive methods to objectively measure cervical softening or assess cervical microstructure. The goal of these preliminary studies was to evaluate the feasibility of using an intracavity ultrasound array to generate acoustic radiation force impulse (ARFI) excitations in the uterine cervix through simulation, and to optimize the acoustic radiation force (ARF) excitation for shear wave elasticity imaging (SWEI) of the tissue stiffness. The cervix is a unique soft tissue target for SWEI because it has significantly greater acoustic attenuation (α = 1.3 to 2.0 dB·cm−1·MHz−1) than other soft tissues, and the pathology being studied tends to lead to an increase in tissue compliance, with healthy cervix being relatively stiff compared with other soft tissues (E ≈ 25 kPa). Additionally, the cervix can only be accessed in vivo using a transvaginal or catheter-based array, which places additional constraints on the excitation focal characteristics that can be used during SWEI. Finite element method (FEM) models of SWEI show that larger-aperture, catheter-based arrays can utilize excitation frequencies up to 7 MHz to generate adequate focal gain up to focal depths 10 to 15 mm deep, with higher frequencies suffering from excessive amounts of near-field acoustic attenuation. Using full-aperture excitations can yield ~40% increases in ARFI-induced displacements, but also restricts the depth of field of the excitation to ~0.5 mm, compared with 2 to 6 mm, which limits the range that can be used for shear wave characterization of the tissue. The center-frequency content of the shear wave particle velocity profiles ranges from 1.5 to 2.5 kHz, depending on the focal

  9. Broadband performance of a moving time reversing array

    NASA Astrophysics Data System (ADS)

    Sabra, Karim G.; Dowling, David R.

    2003-09-01

    Acoustic time reversal exploits reciprocity between sources and receivers to generate backward propagating waves that automatically focus at their point of origin. In underwater acoustics, an array of transducers that can both transmit and receive, referred to as a time reversing array (TRA) or time reversal mirror (TRM), generates the back-propagating waves. Such arrays have been shown to spatially and temporally focus sound in unknown complicated multipath environments, and are therefore of interest for active sonar and underwater communication applications. Although stationary vertical linear TRAs have been favored in prior studies, practical applications of acoustic time reversal in underwater environments are likely to involve towed, tilted, horizontal, or bottom-mounted arrays. In particular, array motion introduces Doppler effects and eliminates source-receiver reciprocity, two factors that potentially impact the automatic focusing capability of TRAs. This paper presents the results from a theoretical and computational investigation into how array motion and orientation influence TRA retrofocusing in the shallow ocean. Here, the TRA tow speed is assumed constant, and the array is assumed to be straight and linear (vertical, horizontal, or tilted). And, for simplicity, the TRA is assumed to respond to a stationary point source emitting a broadband pulse. When a TRA moves, the retrofocus is predicted to shift in the direction of array motion due to the translation of the array between its reception and broadcast times. In addition, the performance of a towed horizontal TRA is predicted to degrade more rapidly with towing speed than that of an equivalent (but clearly idealized) towed vertical array because of range-dependent Doppler phase differences that do not influence the vertical array. However, short tilted arrays may approach vertical array performance and appear to be a potentially versatile compromise for implementing TRA concepts in active sonar or

  10. Broadband performance of a moving time reversing array.

    PubMed

    Sabra, Karim G; Dowling, David R

    2003-09-01

    Acoustic time reversal exploits reciprocity between sources and receivers to generate backward propagating waves that automatically focus at their point of origin. In underwater acoustics, an array of transducers that can both transmit and receive, referred to as a time reversing array (TRA) or time reversal mirror (TRM), generates the back-propagating waves. Such arrays have been shown to spatially and temporally focus sound in unknown complicated multipath environments, and are therefore of interest for active sonar and underwater communication applications. Although stationary vertical linear TRAs have been favored in prior studies, practical applications of acoustic time reversal in underwater environments are likely to involve towed, tilted, horizontal, or bottom-mounted arrays. In particular, array motion introduces Doppler effects and eliminates source-receiver reciprocity, two factors that potentially impact the automatic focusing capability of TRAs. This paper presents the results from a theoretical and computational investigation into how array motion and orientation influence TRA retrofocusing in the shallow ocean. Here, the TRA tow speed is assumed constant, and the array is assumed to be straight and linear (vertical, horizontal, or tilted). And, for simplicity, the TRA is assumed to respond to a stationary point source emitting a broadband pulse. When a TRA moves, the retrofocus is predicted to shift in the direction of array motion due to the translation of the array between its reception and broadcast times. In addition, the performance of a towed horizontal TRA is predicted to degrade more rapidly with towing speed than that of an equivalent (but clearly idealized) towed vertical array because of range-dependent Doppler phase differences that do not influence the vertical array. However, short tilted arrays may approach vertical array performance and appear to be a potentially versatile compromise for implementing TRA concepts in active sonar or

  11. Transducer selection and application in magnetoacoustic tomography with magnetic induction

    NASA Astrophysics Data System (ADS)

    Zhou, Yuqi; Wang, Jiawei; Sun, Xiaodong; Ma, Qingyu; Zhang, Dong

    2016-03-01

    As an acoustic receiver, transducer plays a vital role in signal acquisition and image reconstruction for magnetoacoustic tomography with magnetic induction (MAT-MI). In order to optimize signal acquisition, the expressions of acoustic pressure detection and waveform collection are theoretically studied based on the radiation theory of acoustic dipole and the reception pattern of transducer. Pressure distributions are simulated for a cylindrical phantom model using a planar piston transducer with different radii and bandwidths. The proposed theory is also verified by the experimental measurements of acoustic waveform detection for an aluminum foil cylinder. It is proved that acoustic pressure with sharp and clear boundary peaks can be detected by the large-radius transducer with wide bandwidth, reflecting the differential of the induced Lorentz force accurately, which is helpful for precise conductivity reconstruction. To detect acoustic pressure with acceptable pressure amplitude, peak pressure ratio, amplitude ratio, and improved signal to noise ratio, the scanning radius of 5-10 times the radius of the object should be selected to improve the accuracy of image reconstruction. This study provides a theoretical and experimental basis for transducer selection and application in MAT-MI to obtain reconstructed images with improved resolution and definition.

  12. Anisotropic Swirling Surface Acoustic Waves from Inverse Filtering for On-Chip Generation of Acoustic Vortices

    NASA Astrophysics Data System (ADS)

    Riaud, Antoine; Thomas, Jean-Louis; Charron, Eric; Bussonnière, Adrien; Bou Matar, Olivier; Baudoin, Michael

    2015-09-01

    From radio-electronics signal analysis to biological sample actuation, surface acoustic waves (SAWs) are involved in a multitude of modern devices. However, only the most simple standing or progressive waves such as plane and focused waves have been explored so far. In this paper, we expand the SAW toolbox with a wave family named "swirling surface acoustic waves" which are the 2D anisotropic analogue of bulk acoustic vortices. Similarly to their 3D counterpart, they appear as concentric structures of bright rings with a phase singularity in their center resulting in a central dark spot. After the rigorous mathematical definition of these waves, we synthesize them experimentally through the inverse filtering technique revisited for surface waves. For this purpose, we design a setup combining arrays of interdigitated transducers and a multichannel electronic that enables one to synthesize any prescribed wave field compatible with the anisotropy of the substrate in a region called the "acoustic scene." This work opens prospects for the design of integrated acoustic vortex generators for on-chip selective acoustic tweezing.

  13. Design and fabrication of a flexible large area fabric transducer for bone healing application

    NASA Astrophysics Data System (ADS)

    Jadidian, Bahram

    The electromechanical transducers have found applications in their either passive or active modes. These applications include hydrophone, medical imaging, nondestructive evaluation, motors, sensors, actuators, civil and aerospace engineering. Other medical applications for ultrasonic transducers include therapeutics, osteosynthesis, lithotripsy, thrombolysis, and transdermal drug administration. During the past few decades, lead zirconate titanate (PZT), has been utilized in transducer applications in the form of a bulk piezoelectric ceramic and/or ceramic-polymer composites because of its high piezoelectric charge coefficient d33. The usage of piezoelectric ceramic/polymer composites allows designers to overcome some of the problems dealing with either monolithic piezoceramics or piezopolymers in transducer applications. In this work, a variety of composites with different connectivity patterns were formed. Composites with 1-3 connectivity were fabricated using bundling and collimating methods. Sized and unsized fibers were woven to form fabric. The fabric was used to form 3-3 composites and spiral structures. Square sheets of the fabric were laminated on top of each other, heat treated, and embedded in different types of polymer. The effect of applied pressure on the stack during heat treatment was studied. Plane fabric was formed in the spiral manner and used to construct piezocomposites. A piezoelectric transducer with high thickness coupling coefficient and its matching layer were exploited for bone healing application. One of the structures with the highest electromechanical properties, developed in this work, was chosen for the array fabrication. The spiral composite elements, with the best properties, were arranged in a 3 x 4 format embedded in a flexible polymer. The mechanical endurance of the elements and the array was studied. A large area flexible matching layer with low attenuation was developed. An extensive study was performed to determine the

  14. The Ultrasound Brain Helmet: New Transducers and Volume Registration for In Vivo Simultaneous Multi-Transducer 3-D Transcranial Imaging

    PubMed Central

    Lindsey, Brooks D.; Light, Edward D.; Nicoletto, Heather A.; Bennett, Ellen R.; Laskowitz, Daniel T.; Smith, Stephen W.

    2012-01-01

    Because stroke remains an important and time-sensitive health concern in developed nations, we present a system capable of fusing 3-D transcranial ultrasound volumes acquired from two sides of the head. This system uses custom sparse array transducers built on flexible multilayer circuits that can be positioned for simultaneous imaging through both temporal acoustic windows, allowing for potential registration of multiple real-time 3-D scans of cerebral vasculature. We examine hardware considerations for new matrix arrays—transducer design and interconnects—in this application. Specifically, it is proposed that SNR may be increased by reducing the length of probe cables. This claim is evaluated as part of the presented system through simulation, experimental data, and in vivo imaging. Ultimately, gains in SNR of 7 dB are realized by replacing a standard probe cable with a much shorter flex interconnect; higher gains may be possible using ribbon-based probe cables. In vivo images are presented, showing cerebral arteries with and without the use of microbubble contrast agent; they have been registered and fused using a simple algorithm which maximizes normalized cross-correlation. PMID:21693401

  15. Effects of fine metal oxide particle dopant on the acoustic properties of silicone rubber lens for medical array probe.

    PubMed

    Hosono, Yasuharu; Yamashita, Yohachi; Itsumi, Kazuhiro

    2007-08-01

    The effects of fine metal oxide particles, particularly those of high-density elements (7.7 to 9.7 x 10(3) kg/m3), on the acoustic properties of silicone rubber have been investigated in order to develop an acoustic lens with a low acoustic attenuation. Silicone rubber doped with Yb2O3 powder having nanoparticle size of 16 nm showed a lower acoustic attenuation than silicone rubber doped with powders of CeO2, Bi2O3, Lu2O3 and HfO2. The silicone rubber doped with Yb2O3 powder showed a sound speed of 0.88 km/s, an acoustic impedance of 1.35 x 10(6) kg/m2s, an acoustic attenuation of 0.93 dB/mmMHz, and a Shore A hardness of 55 at 37 degrees C. Although typical silicone rubber doped with SiO2 (2.6 x 10(3) kg/m3) shows a sound speed of about 1.00 km/s, heavy metal oxide particles decreased the sound velocities to lower than 0.93 km/s. Therefore, an acoustic lens of silicone rubber doped with Yb2O3 powder provides increased sensitivity because it realizes a thinner acoustic lens than is conventionally used due to its low sound speed. Moreover, it has an advantage in that a focus point is not changed when the acoustic lens is pressed to a human body due to its reasonable hardness.

  16. Apparatus for real-time acoustic imaging of Rayleigh-Benard convection.

    PubMed

    Kuehn, Kerry; Polfer, Jonathan; Furno, Joanna; Finke, Nathan

    2007-11-01

    We have designed and built an apparatus for real-time acoustic imaging of convective flow patterns in optically opaque fluids. This apparatus takes advantage of recent advances in two-dimensional ultrasound transducer array technology; it employs a modified version of a commercially available ultrasound camera, similar to those employed in nondestructive testing of solids. Images of convection patterns are generated by observing the lateral variation of the temperature dependent speed of sound via refraction of acoustic plane waves passing vertically through the fluid layer. The apparatus has been validated by observing convection rolls in both silicone oil and ferrofluid. PMID:18052477

  17. Absolute calibration technique for broadband ultrasonic transducers

    NASA Technical Reports Server (NTRS)

    Yost, William T. (Inventor); Cantrell, John H. (Inventor)

    1994-01-01

    Calibrating an ultrasonic transducer can be performed with a reduced number of calculations and testing. A wide-band pulser is connected to an ultrasonic transducer under test to generate ultrasonic waves in a liquid. A single frequency is transmitted to the electrostatic acoustic transducer (ESAT) and the voltage change produced is monitored. Then a broadband ultrasonic pulse is generated by the ultrasonic transducer and received by the ESAT. The output of the ESAT is amplified and input to a digitized oscilloscope for fast Fourier transform. The resulting plot is normalized with the monitored signal from the single frequency pulse. The plot is then corrected for characteristics of the membrane and diffraction effects. The transfer function of the final plot is determined. The transfer function gives the final sensitivity of the ultrasonic transducer as a function of frequency. The advantage of the system is the speed of calibrating the transducer by a reduced number of measurements and removal of the membrane and diffraction effects.

  18. A Prototype PZT Matrix Transducer With Low-Power Integrated Receive ASIC for 3-D Transesophageal Echocardiography.

    PubMed

    Chen, Chao; Raghunathan, Shreyas B; Yu, Zili; Shabanimotlagh, Maysam; Chen, Zhao; Chang, Zu-yao; Blaak, Sandra; Prins, Christian; Ponte, Jacco; Noothout, Emile; Vos, Hendrik J; Bosch, Johan G; Verweij, Martin D; de Jong, Nico; Pertijs, Michiel A P

    2016-01-01

    This paper presents the design, fabrication, and experimental evaluation of a prototype lead zirconium titanate (PZT) matrix transducer with an integrated receive ASIC, as a proof of concept for a miniature three-dimensional (3-D) transesophageal echocardiography (TEE) probe. It consists of an array of 9 ×12 piezoelectric elements mounted on the ASIC via an integration scheme that involves direct electrical connections between a bond-pad array on the ASIC and the transducer elements. The ASIC addresses the critical challenge of reducing cable count, and includes front-end amplifiers with adjustable gains and micro-beamformer circuits that locally process and combine echo signals received by the elements of each 3 ×3 subarray. Thus, an order-of-magnitude reduction in the number of receive channels is achieved. Dedicated circuit techniques are employed to meet the strict space and power constraints of TEE probes. The ASIC has been fabricated in a standard 0.18-μm CMOS process and consumes only 0.44 mW/channel. The prototype has been acoustically characterized in a water tank. The ASIC allows the array to be presteered across ±37° while achieving an overall dynamic range of 77 dB. Both the measured characteristics of the individual transducer elements and the performance of the ASIC are in good agreement with expectations, demonstrating the effectiveness of the proposed techniques.

  19. DeepFocus Acoustic Microscope Transducer

    SciTech Connect

    2011-01-01

    A new nondestructive testing device being used to analyse nuclear fuel could reduce costs for manufacturing and other industry. For more information about INL research projects, visit http://www.facebook.com/idahonationallaboratory.

  20. DeepFocus Acoustic Microscope Transducer

    ScienceCinema

    None

    2016-07-12

    A new nondestructive testing device being used to analyse nuclear fuel could reduce costs for manufacturing and other industry. For more information about INL research projects, visit http://www.facebook.com/idahonationallaboratory.

  1. Piezoelectric fibers for conformal acoustics.

    PubMed

    Chocat, Noémie; Lestoquoy, Guillaume; Wang, Zheng; Rodgers, Daniel M; Joannopoulos, John D; Fink, Yoel

    2012-10-01

    Ultrasound transducers have many important applications in medical, industrial, and environmental settings. Large-active-area piezoelectric fibers are presented here, which can be woven into extended and flexible ultrasound transducing fabrics. This work opens significant opportunities for large-area, flexible and adjustable acoustic emission and sensing for a variety of emerging applications.

  2. Volumetric Acoustic Vector Intensity Probe

    NASA Technical Reports Server (NTRS)

    Klos, Jacob

    2006-01-01

    A new measurement tool capable of imaging the acoustic intensity vector throughout a large volume is discussed. This tool consists of an array of fifty microphones that form a spherical surface of radius 0.2m. A simultaneous measurement of the pressure field across all the microphones provides time-domain near-field holograms. Near-field acoustical holography is used to convert the measured pressure into a volumetric vector intensity field as a function of frequency on a grid of points ranging from the center of the spherical surface to a radius of 0.4m. The volumetric intensity is displayed on three-dimensional plots that are used to locate noise sources outside the volume. There is no restriction on the type of noise source that can be studied. The sphere is mobile and can be moved from location to location to hunt for unidentified noise sources. An experiment inside a Boeing 757 aircraft in flight successfully tested the ability of the array to locate low-noise-excited sources on the fuselage. Reference transducers located on suspected noise source locations can also be used to increase the ability of this device to separate and identify multiple noise sources at a given frequency by using the theory of partial field decomposition. The frequency range of operation is 0 to 1400Hz. This device is ideal for the study of noise sources in commercial and military transportation vehicles in air, on land and underwater.

  3. Design of a bullet beam pattern of a micro ultrasound transducer (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Roh, Yongrae; Lee, Seongmin

    2016-04-01

    Ultrasonic imaging transducer is often required to compose a beam pattern of a low sidelobe level and a small beam width over a long focal region to achieve good image resolution. Normal ultrasound transducers have many channels along its azimuth, which allows easy formation of the sound beam into a desired shape. However, micro-array transducers have no control of the beam pattern along their elevation. In this work, a new method is proposed to manipulate the beam pattern by using an acoustic multifocal lens and a shaded electrode on top of the piezoelectric layer. The shading technique split an initial uniform electrode into several segments and combined those segments to compose a desired beam pattern. For a given elevation width and frequency, the optimal pattern of the split electrodes was determined by means of the OptQuest-Nonlinear Program (OQ-NLP) algorithm to achieve the lowest sidelobe level. The requirement to achieve a small beam width with a long focal region was satisfied by employing an acoustic lens of three multiple focuses. Optimal geometry of the multifocal lens such as the radius of curvature and aperture diameter for each focal point was also determined by the OQ-NLP algorithm. For the optimization, a new index was devised to evaluate the on-axis response: focal region ratio = focal region / minimum beam width. The larger was the focal region ratio, the better was the beam pattern. Validity of the design has been verified through fabricating and characterizing an experimental prototype of the transducer.

  4. Visualization and simulation of a linear explosive-induced pyroshock wave using Q-switched laser and phased array transducers in a space launcher composite structure

    NASA Astrophysics Data System (ADS)

    Lee, Jung-Ryul; Jang, Jae-Kyeong; Choi, Mijin; Kong, Cheol-Won

    2015-04-01

    During space flights, pyrotechnic devices are used for various purposes such as separation of boosters, satellites, fairings, and stages. In particular, the prediction of high shock structural response induced by linear explosives is important for safe operation of pyrotechnic devices. In general, repetitive explosive testing using distributed accelerometers is widely used, but multiple test structures are usually necessary because they are easily damaged and not reusable. This paper pertains to a nondestructive technology to replace the damage-causing, time-consuming, expensive, dangerous, and low-repeatability explosive test with a laser-induced shock test. The method proposed in this paper predicts nondestructively the linear explosive-induced pyroshock wave, visualizes its propagation, and allows the simulation of some detonation conditions. A ballistic test based on a linear explosive and noncontact laser Doppler vibrometer (LDV) as well as a nondestructive pyroshock test using laser-induced shock and PZT array sensors is performed in a 12.68-mm thick composite sandwich panel. The optimal laser-induced shock experimental conditions to predict real pyroshock response spectra (SRSs) are investigated by controlling the optical characteristics of the laser beam and adjusting the frequency bands in signal acquisition. The similarity of the SRS of the conditioned laser-induced shock to that of the real explosive pyroshock is evaluated with the mean acceleration difference. Next, the experimentally-determined optimal conditions are applied to arbitrary points in the laser-induced shock scanning area. Finally, it is shown that the proposed method will allow nondestructive and quantitative pyroshock testing, pyroshock wave propagation visualization showing the direction and magnitude of principal wave propagation, and detonation speed simulation depending on explosive type and detonation initiation point and direction.

  5. Acoustic emission intrusion detector

    DOEpatents

    Carver, Donald W.; Whittaker, Jerry W.

    1980-01-01

    An intrusion detector is provided for detecting a forcible entry into a secured structure while minimizing false alarms. The detector uses a piezoelectric crystal transducer to sense acoustic emissions. The transducer output is amplified by a selectable gain amplifier to control the sensitivity. The rectified output of the amplifier is applied to a Schmitt trigger circuit having a preselected threshold level to provide amplitude discrimination. Timing circuitry is provided which is activated by successive pulses from the Schmitt trigger which lie within a selected time frame for frequency discrimination. Detected signals having proper amplitude and frequency trigger an alarm within the first complete cycle time of a detected acoustical disturbance signal.

  6. Characterization of transducer cavities to oscillatory inputs

    SciTech Connect

    Rogers, J.D.; Hollingshead, J.R.

    1993-12-31

    The design and use of measurement systems must ensure that the data are not computed by the measurement system. A wide variety of sources can be responsible for compromising the integrity of test data. Among the sources of error are transducer calibration errors, signal conditioning problems, recording problems, and characteristics of the mechanical system which introduce errors. In this paper, the characteristics of an acoustic cavity are discussed as they apply to a pressure measurement problem.

  7. An IVUS Transducer for Microbubble Therapies

    PubMed Central

    Kilroy, Joseph P.; Patil, Abhay V.; Rychak, Joshua J.; Hossack, John A.

    2014-01-01

    There is interest in examining the potential of modified intravascular ultrasound (IVUS) catheters to facilitate dual diagnostic and therapeutic roles using ultrasound plus microbubbles for localized drug delivery to the vessel wall. The goal of this study was to design, prototype, and validate an IVUS transducer for microbubble-based drug delivery. A 1-D acoustic radiation force model and finite element analysis guided the design of a 1.5-MHz IVUS transducer. Using the IVUS transducer, biotinylated microbubbles were displaced in water and bovine whole blood to the streptavidin-coated wall of a flow phantom by a 1.5-MHz center frequency, peak negative pressure = 70 kPa pulse with varying pulse repetition frequency (PRF) while monitoring microbubble adhesion with ultrasound. A fit was applied to the RF data to extract a time constant (τ). As PRF was increased in water, the time constant decreased (τ = 32.6 s, 1 kHz vs. τ = 8.2 s, 6 kHz), whereas in bovine whole blood an adhesion–no adhesion transition was found for PRFs ≥ 8 kHz. Finally, a fluorophore was delivered to an ex vivo swine artery using microbubbles and the IVUS transducer, resulting in a 6.6-fold increase in fluorescence. These results indicate the importance of PRF (or duty factor) for IVUS acoustic radiation force microbubble displacement and the potential for IVUS and microbubbles to provide localized drug delivery. PMID:24569249

  8. Hybrid optical and acoustic force based sorting

    NASA Astrophysics Data System (ADS)

    O'Mahoney, Paul; Brodie, Graham W.; Wang, Han; Demore, Christine E. M.; Cochran, Sandy; Spalding, Gabriel C.; MacDonald, Michael P.

    2014-09-01

    We report the combined use of optical sorting and acoustic levitation to give particle sorting. Differing sizes of microparticles are sorted optically both with and without the aid of acoustic levitation, and the results compared to show that the use of acoustic trapping can increase sorting efficiency. The use of a transparent ultrasonic transducer is also shown to streamline the integration of optics and acoustics. We also demonstrate the balance of optical radiation pressure and acoustic levitation to achieve vertical sorting.

  9. Method and system for generating a beam of acoustic energy from a borehole, and applications thereof

    DOEpatents

    Johnson Paul A.; Ten Cate, James A.; Guyer, Robert; Le Bas, Pierre-Yves; Vu, Cung; Nihei, Kurt; Schmitt, Denis P.; Skelt, Christopher

    2012-02-14

    A compact array of transducers is employed as a downhole instrument for acoustic investigation of the surrounding rock formation. The array is operable to generate simultaneously a first acoustic beam signal at a first frequency and a second acoustic beam signal at a second frequency different than the first frequency. These two signals can be oriented through an azimuthal rotation of the array and an inclination rotation using control of the relative phases of the signals from the transmitter elements or electromechanical linkage. Due to the non-linearity of the formation, the first and the second acoustic beam signal mix into the rock formation where they combine into a collimated third signal that propagates in the formation along the same direction than the first and second signals and has a frequency equal to the difference of the first and the second acoustic signals. The third signal is received either within the same borehole, after reflection, or another borehole, after transmission, and analyzed to determine information about rock formation. Recording of the third signal generated along several azimuthal and inclination directions also provides 3D images of the formation, information about 3D distribution of rock formation and fluid properties and an indication of the dynamic acoustic non-linearity of the formation.

  10. Crossflow force transducer. [LMFBR

    SciTech Connect

    Mulcahy, T M

    1982-05-01

    A force transducer for measuring lift and drag coefficients for a circular cylinder in turbulent water flow is presented. In addition to describing the actual design and construction of the strain-gauged force- ring based transducer, requirements for obtained valid fluid force test data are discussed, and pertinent flow test experience is related.

  11. Search for acoustic signals from high energy cascades

    NASA Technical Reports Server (NTRS)

    Bell, R.; Bowen, T.

    1985-01-01

    High energy cosmic ray secondaries can be detected by means of the cascades they produce when they pass through matter. When the charged particles of these cascades ionize the matter they are traveling through, the heat produced and resulting thermal expansion causes a thermoacoustic wave. These sound waves travel at about one hundred-thousandth the speed of light, and should allow an array of acoustic transducers to resolve structure in the cascade to about 1 cm without high speed electronics or segmentation of the detector.

  12. Search for acoustic signals from high energy cascades

    NASA Astrophysics Data System (ADS)

    Bell, R.; Bowen, T.

    1985-08-01

    High energy cosmic ray secondaries can be detected by means of the cascades they produce when they pass through matter. When the charged particles of these cascades ionize the matter they are traveling through, the heat produced and resulting thermal expansion causes a thermoacoustic wave. These sound waves travel at about one hundred-thousandth the speed of light, and should allow an array of acoustic transducers to resolve structure in the cascade to about 1 cm without high speed electronics or segmentation of the detector.

  13. Intracavitary ultrasound phased arrays for thermal therapies

    NASA Astrophysics Data System (ADS)

    Hutchinson, Erin

    Currently, the success of hyperthermia and thermal surgery treatments is limited by the technology used in the design and fabrication of clinical heating devices and the completeness of the thermometry systems used for guidance. For both hyperthermia and thermal surgery, electrically focused ultrasound generated by phased arrays provides a means of controlling localized energy deposition in body tissues. Intracavitary applicators can be used to bring the energy source close to a target volume, such as the prostate, thereby minimizing normal tissue damage. The work performed in this study was aimed at improving noninvasive prostate thermal therapies and utilized three research approaches: (1) Acoustic, thermal and optimization simulations, (2) Design and fabrication of multiple phased arrays, (3) Ex vivo and in vivo experimental testing of the heating capabilities of the phased arrays. As part of this study, a novel aperiodic phased array design was developed which resulted in a 30- 45% reduction in grating lobe levels when compared to conventional phased arrays. Measured acoustic fields generated by the constructed aperiodic arrays agreed closely with the fields predicted by the theoretical simulations and covered anatomically appropriate ranges. The power capabilities of these arrays were demonstrated to be sufficient for the purposes of hyperthermia and thermal surgery. The advantage of using phased arrays in place of fixed focus transducers was shown by demonstrating the ability of electronic scanning to increase the size of the necrosed tissue volume while providing a more uniform thermal dose, which can ultimately reduce patient treatment times. A theoretical study on the feasibility of MRI (magnetic resonance imaging) thermometry for noninvasive temperature feedback control was investigated as a means to improve transient and steady state temperature distributions achieved in hyperthermia treatments. MRI guided ex vivo and in vivo experiments demonstrated

  14. High temperature, high power piezoelectric composite transducers.

    PubMed

    Lee, Hyeong Jae; Zhang, Shujun; Bar-Cohen, Yoseph; Sherrit, Stewart

    2014-08-08

    Piezoelectric composites are a class of functional materials consisting of piezoelectric active materials and non-piezoelectric passive polymers, mechanically attached together to form different connectivities. These composites have several advantages compared to conventional piezoelectric ceramics and polymers, including improved electromechanical properties, mechanical flexibility and the ability to tailor properties by using several different connectivity patterns. These advantages have led to the improvement of overall transducer performance, such as transducer sensitivity and bandwidth, resulting in rapid implementation of piezoelectric composites in medical imaging ultrasounds and other acoustic transducers. Recently, new piezoelectric composite transducers have been developed with optimized composite components that have improved thermal stability and mechanical quality factors, making them promising candidates for high temperature, high power transducer applications, such as therapeutic ultrasound, high power ultrasonic wirebonding, high temperature non-destructive testing, and downhole energy harvesting. This paper will present recent developments of piezoelectric composite technology for high temperature and high power applications. The concerns and limitations of using piezoelectric composites will also be discussed, and the expected future research directions will be outlined.

  15. High Temperature, High Power Piezoelectric Composite Transducers

    PubMed Central

    Lee, Hyeong Jae; Zhang, Shujun; Bar-Cohen, Yoseph; Sherrit, StewarT.

    2014-01-01

    Piezoelectric composites are a class of functional materials consisting of piezoelectric active materials and non-piezoelectric passive polymers, mechanically attached together to form different connectivities. These composites have several advantages compared to conventional piezoelectric ceramics and polymers, including improved electromechanical properties, mechanical flexibility and the ability to tailor properties by using several different connectivity patterns. These advantages have led to the improvement of overall transducer performance, such as transducer sensitivity and bandwidth, resulting in rapid implementation of piezoelectric composites in medical imaging ultrasounds and other acoustic transducers. Recently, new piezoelectric composite transducers have been developed with optimized composite components that have improved thermal stability and mechanical quality factors, making them promising candidates for high temperature, high power transducer applications, such as therapeutic ultrasound, high power ultrasonic wirebonding, high temperature non-destructive testing, and downhole energy harvesting. This paper will present recent developments of piezoelectric composite technology for high temperature and high power applications. The concerns and limitations of using piezoelectric composites will also be discussed, and the expected future research directions will be outlined. PMID:25111242

  16. High temperature, high power piezoelectric composite transducers.

    PubMed

    Lee, Hyeong Jae; Zhang, Shujun; Bar-Cohen, Yoseph; Sherrit, Stewart

    2014-01-01

    Piezoelectric composites are a class of functional materials consisting of piezoelectric active materials and non-piezoelectric passive polymers, mechanically attached together to form different connectivities. These composites have several advantages compared to conventional piezoelectric ceramics and polymers, including improved electromechanical properties, mechanical flexibility and the ability to tailor properties by using several different connectivity patterns. These advantages have led to the improvement of overall transducer performance, such as transducer sensitivity and bandwidth, resulting in rapid implementation of piezoelectric composites in medical imaging ultrasounds and other acoustic transducers. Recently, new piezoelectric composite transducers have been developed with optimized composite components that have improved thermal stability and mechanical quality factors, making them promising candidates for high temperature, high power transducer applications, such as therapeutic ultrasound, high power ultrasonic wirebonding, high temperature non-destructive testing, and downhole energy harvesting. This paper will present recent developments of piezoelectric composite technology for high temperature and high power applications. The concerns and limitations of using piezoelectric composites will also be discussed, and the expected future research directions will be outlined. PMID:25111242

  17. Fabrication of an optical lens array using ultraviolet light and ultrasonication.

    PubMed

    Taniguchi, Satoki; Koyama, Daisuke; Nakamura, Kentaro; Matsukawa, Mami

    2015-04-01

    A technique to form an optical lens array using an ultraviolet (UV)-curable resin and ultrasound was investigated. A UV-curable gel film was formed on a glass plate having four lead zirconate titanate (PZT) transducers. Excitation of the transducers generated a lattice flexural vibration mode on the glass plate. The acoustic radiation force acted to deform the surface of the gel film, so that a lens array could be fabricated on the gel film. The lens array was exposed to UV light under ultrasonication to cure the UV-curable film. The quality factor of the transducer resonance was decreased upon curing of the resin film because the cured resin dampened the vibration of the plate. The acoustic characteristics of the UV-curable gel film were measured by using an ultrasound pulse technique at the MHz range. The sound speed of the gel increased from 987 to 1006 m/s (increase of 1.9%) as the UV exposure time increased. The attenuation coefficient also increased and the larger attenuation of the resin caused the lens array to have a lower quality factor. PMID:25497498

  18. Fabrication of an optical lens array using ultraviolet light and ultrasonication.

    PubMed

    Taniguchi, Satoki; Koyama, Daisuke; Nakamura, Kentaro; Matsukawa, Mami

    2015-04-01

    A technique to form an optical lens array using an ultraviolet (UV)-curable resin and ultrasound was investigated. A UV-curable gel film was formed on a glass plate having four lead zirconate titanate (PZT) transducers. Excitation of the transducers generated a lattice flexural vibration mode on the glass plate. The acoustic radiation force acted to deform the surface of the gel film, so that a lens array could be fabricated on the gel film. The lens array was exposed to UV light under ultrasonication to cure the UV-curable film. The quality factor of the transducer resonance was decreased upon curing of the resin film because the cured resin dampened the vibration of the plate. The acoustic characteristics of the UV-curable gel film were measured by using an ultrasound pulse technique at the MHz range. The sound speed of the gel increased from 987 to 1006 m/s (increase of 1.9%) as the UV exposure time increased. The attenuation coefficient also increased and the larger attenuation of the resin caused the lens array to have a lower quality factor.

  19. Pressure transducer and system for cryogenic environments

    NASA Technical Reports Server (NTRS)

    Chapman, John J. (Inventor)

    1992-01-01

    A silicon pressure die is bonded to a borosilicate substrate above the pneumatic port. A Wheatstone bridge circuit is formed on the silicon pressure die and has bridge elements of silicon doped with boron to a deposit density level of approximately 1 x 10(exp 19)-10(exp 21) boron/cc. A current source is provided to excite the Wheatstone bridge circuit. In addition, a temperature sensor is provided to provide temperature readings. An array may be formed of the resulting pressure transducers. This unique solution of materials permits operation of a pressure transducer in cryogenic environments.

  20. Effects of Ytterbium Oxide Nanopowder Particle Size on the Acoustic Properties of Silicone Rubber Lens for Medical Echo Array Probe

    NASA Astrophysics Data System (ADS)

    Yohachi; Yamashita; Hosono, Yasuharu; Yamamoto, Noriko; Itsumi, Kazuhiro

    2008-05-01

    The effects of Yb2O3 powder particle size, namely, 2000, 16, and 8 nm, on the physical and acoustic properties of a high-temperature-vulcanization (HTV) silicone (Q) rubber have been investigated in order to develop an acoustic lens material with a low sound velocity (c) and acoustic attenuation coefficient (α). The Yb2O3-doped HTV Q rubber with the large particle size of 2000 nm showed a density (ρ) of 1.6×103 kg/m3, with c = 828 m/s, characteristic acoustic impedance (Z) = 1.32×106 kg·m-2·s-1, α= 1.32 dB·mm-1·MHz-1, and an α-figure of merit (FOM) (α×c) of 1090 at 5 MHz at 37 °C. For the Yb2O3-doped Q rubber with the small particle size of 8 nm, ρ= 1.57×103 kg/m3, c = 864 m/s, Z = 1.36×106 kg·m-2·s-1, α= 0.68 dB·mm-1·MHz-1, and α-FOM = 590. The 16 nm Yb2O3-doped Q rubber had intermediate values of α= 0.88 dB·mm-1·MHz-1 and α-FOM = 760. These results show that there is a clear dopant particle size dependence on the acoustic properties of Yb2O3-doped HTV Q rubbers. The 8-nm-doped HTV Q rubber also showed an excellent mechanical properties for practical application. Microstructure observation revealed that the low-α rubber shows a uniform Yb2O3 nanopowder distribution in the HTV Q rubber matrix.