Science.gov

Sample records for acoustic pressure measurements

  1. Measurement of the acoustic reflex without a pressure seal.

    PubMed

    Surr, R K; Schuchman, G I

    1976-03-01

    Obtaining a hermetic seal in the external auditory canal is often a major obstacle in impedance audiometry. In the present study, the acoustic reflex threshold was determined for three groups of subjects, first with and then without a pressure-tight seal. It was found that for subjects with normal hearing or sensorineural hearing loss and normal tympanograms, 96% of the measurements obtained without a pressure seal were within 5 dB of those obtained with a seal. Among the subjects who exhibited negative middle ear pressure, the acoustic reflex could be measured consistently at the point of maximum compliance, while no response was observed without a pressure seal.

  2. Ares I Scale Model Acoustic Tests Instrumentation for Acoustic and Pressure Measurements

    NASA Technical Reports Server (NTRS)

    Vargas, Magda B.; Counter, Douglas D.

    2011-01-01

    The Ares I Scale Model Acoustic Test (ASMAT) was a development test performed at the Marshall Space Flight Center (MSFC) East Test Area (ETA) Test Stand 116. The test article included a 5% scale Ares I vehicle model and tower mounted on the Mobile Launcher. Acoustic and pressure data were measured by approximately 200 instruments located throughout the test article. There were four primary ASMAT instrument suites: ignition overpressure (IOP), lift-off acoustics (LOA), ground acoustics (GA), and spatial correlation (SC). Each instrumentation suite incorporated different sensor models which were selected based upon measurement requirements. These requirements included the type of measurement, exposure to the environment, instrumentation check-outs and data acquisition. The sensors were attached to the test article using different mounts and brackets dependent upon the location of the sensor. This presentation addresses the observed effect of the sensors and mounts on the acoustic and pressure measurements.

  3. Acoustics and Surface Pressure Measurements from Tandem Cylinder Configurations

    NASA Technical Reports Server (NTRS)

    Hutcheson, Florence V.; Brooks, Thomas F.; Lockard, David P.; Choudhari, Meelan M.; Stead, Daniel J.

    2014-01-01

    Acoustic and unsteady surface pressure measurements from two cylinders in tandem configurations were acquired to study the effect of spacing, surface trip and freestream velocity on the radiated noise. The Reynolds number ranged from 1.15x10(exp 5) to 2.17x10(exp 5), and the cylinder spacing varied between 1.435 and 3.7 cylinder diameters. The acoustic and surface pressure spectral characteristics associated with the different flow regimes produced by the cylinders' wake interference were identified. The dependence of the Strouhal number, peak Sound Pressure Level and spanwise coherence on cylinder spacing and flow velocity was examined. Directivity measurements were performed to determine how well the dipole assumption for the radiation of vortex shedding noise holds for the largest and smallest cylinder spacing tested.

  4. Ares I Scale Model Acoustic Test Instrumentation for Acoustic and Pressure Measurements

    NASA Technical Reports Server (NTRS)

    Vargas, Magda B.; Counter, Douglas

    2011-01-01

    Ares I Scale Model Acoustic Test (ASMAT) is a 5% scale model test of the Ares I vehicle, launch pad and support structures conducted at MSFC to verify acoustic and ignition environments and evaluate water suppression systems Test design considerations 5% measurements must be scaled to full scale requiring high frequency measurements Users had different frequencies of interest Acoustics: 200 - 2,000 Hz full scale equals 4,000 - 40,000 Hz model scale Ignition Transient: 0 - 100 Hz full scale equals 0 - 2,000 Hz model scale Environment exposure Weather exposure: heat, humidity, thunderstorms, rain, cold and snow Test environments: Plume impingement heat and pressure, and water deluge impingement Several types of sensors were used to measure the environments Different instrument mounts were used according to the location and exposure to the environment This presentation addresses the observed effects of the selected sensors and mount design on the acoustic and pressure measurements

  5. Model helicopter rotor high-speed impulsive noise: Measured acoustics and blade pressures

    NASA Technical Reports Server (NTRS)

    Boxwell, D. A.; Schmitz, F. H.; Splettstoesser, W. R.; Schultz, K. J.

    1983-01-01

    A 1/17-scale research model of the AH-1 series helicopter main rotor was tested. Model-rotor acoustic and simultaneous blade pressure data were recorded at high speeds where full-scale helicopter high-speed impulsive noise levels are known to be dominant. Model-rotor measurements of the peak acoustic pressure levels, waveform shapes, and directively patterns are directly compared with full-scale investigations, using an equivalent in-flight technique. Model acoustic data are shown to scale remarkably well in shape and in amplitude with full-scale results. Model rotor-blade pressures are presented for rotor operating conditions both with and without shock-like discontinuities in the radiated acoustic waveform. Acoustically, both model and full-scale measurements support current evidence that above certain high subsonic advancing-tip Mach numbers, local shock waves that exist on the rotor blades ""delocalize'' and radiate to the acoustic far-field.

  6. Measured wavenumber: frequency spectrum associated with acoustic and aerodynamic wall pressure fluctuations.

    PubMed

    Arguillat, Blandine; Ricot, Denis; Bailly, Christophe; Robert, Gilles

    2010-10-01

    Direct measurements of the wavenumber-frequency spectrum of wall pressure fluctuations beneath a turbulent plane channel flow have been performed in an anechoic wind tunnel. A rotative array has been designed that allows the measurement of a complete map, 63×63 measuring points, of cross-power spectral densities over a large area. An original post-processing has been developed to separate the acoustic and the aerodynamic exciting loadings by transforming space-frequency data into wavenumber-frequency spectra. The acoustic part has also been estimated from a simple Corcos-like model including the contribution of a diffuse sound field. The measured acoustic contribution to the surface pressure fluctuations is 5% of the measured aerodynamic surface pressure fluctuations for a velocity and boundary layer thickness relevant for automotive interior noise applications. This shows that for aerodynamically induced car interior noise, both contributions to the surface pressure fluctuations on car windows have to be taken into account.

  7. Optimization of Acoustic Pressure Measurements for Impedance Eduction

    NASA Technical Reports Server (NTRS)

    Jones, M. G.; Watson, W. R.; Nark, D. M.

    2007-01-01

    As noise constraints become increasingly stringent, there is continued emphasis on the development of improved acoustic liner concepts to reduce the amount of fan noise radiated to communities surrounding airports. As a result, multiple analytical prediction tools and experimental rigs have been developed by industry and academia to support liner evaluation. NASA Langley has also placed considerable effort in this area over the last three decades. More recently, a finite element code (Q3D) based on a quasi-3D implementation of the convected Helmholtz equation has been combined with measured data acquired in the Langley Grazing Incidence Tube (GIT) to reduce liner impedance in the presence of grazing flow. A new Curved Duct Test Rig (CDTR) has also been developed to allow evaluation of liners in the presence of grazing flow and controlled, higher-order modes, with straight and curved waveguides. Upgraded versions of each of these two test rigs are expected to begin operation by early 2008. The Grazing Flow Impedance Tube (GFIT) will replace the GIT, and additional capabilities will be incorporated into the CDTR. The current investigation uses the Q3D finite element code to evaluate some of the key capabilities of these two test rigs. First, the Q3D code is used to evaluate the microphone distribution designed for the GFIT. Liners ranging in length from 51 to 610 mm are investigated to determine whether acceptable impedance eduction can be achieved with microphones placed on the wall opposite the liner. This analysis indicates the best results are achieved for liner lengths of at least 203 mm. Next, the effects of moving this GFIT microphone array to the wall adjacent to the liner are evaluated, and acceptable results are achieved if the microphones are placed off the centerline. Finally, the code is used to investigate potential microphone placements in the CDTR rigid wall adjacent to the wall containing an acoustic liner, to determine if sufficient fidelity can be

  8. Correlation of combustor acoustic power levels inferred from internal fluctuating pressure measurements

    NASA Technical Reports Server (NTRS)

    Vonglahn, U. H.

    1978-01-01

    Combustion chamber acoustic power levels inferred from internal fluctuating pressure measurements are correlated with operating conditions and chamber geometries over a wide range. The variables include considerations of chamber design (can, annular, and reverse-flow annular) and size, number of fuel nozzles, burner staging and fuel split, airflow and heat release rates, and chamber inlet pressure and temperature levels. The correlated data include those obtained with combustion component development rigs as well as engines.

  9. 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.

  10. Pressure transducer for measuring acoustic radiation force based on a magnetic sensor

    NASA Astrophysics Data System (ADS)

    Kamimura, H. A. S.; Pavan, T. Z.; Almeida, T. W. J.; Pádua, M. L. A.; Baggio, A. L.; Fatemi, M.; Carneiro, A. A. O.

    2011-01-01

    This work presents a pressure transducer based on a magnetic sensor to measure acoustic radiation force (ARF) and small displacements. The methodology presented in this paper allowed this transducer to be calibrated for use as an acoustic pressure and intensity meter. It can control the acoustic intensity emitted by ultrasound used, for example, in ARF impulse imaging, vibro-acoustography and high-intensity focused ultrasound techniques. The device comprises a magnet, a membrane, a magnetoresistive sensor and a coil to cancel the external magnetic field. When ARF is applied to the membrane, the magnetic field on the sensor changes due to the magnetic target displacement. The variation of the output signal from the magnetic transducer is proportional to the acoustic pressure applied to the membrane. A focused ultrasound transducer with a central frequency of 3 MHz was used to apply a continuous ARF. The sensitivities of the magnetic transducer as an acoustic pressure and intensity meter, evaluated in water, were respectively 0.597 µV MPa-1 and 0.073 µV (W cm-2)-1/2, while those of the needle hydrophone (Onda model HNP-0400) used in the magnetic transducer calibration were respectively, 0.5024 mV MPa-1 and 6.153 mV (W cm-2)-1/2. The transducer resolution to displacement is 5 nm and 6 dB of signal attenuation occurs for 7° of misalignment. The transducer responded well to acoustic pressure in water above 200 kPa.

  11. Measurements of underwater acoustic pressure fields using a scanning laser Doppler vibrometer

    NASA Astrophysics Data System (ADS)

    Carroll, Gerard P.

    2004-05-01

    Laser Doppler vibrometers (LDV) are designed to measure structural vibration velocity by sensing the phase shift in the laser signal reflected from a vibrating source. It is known that index of refraction modulations resulting from acoustic pressure distributions along a laser light path will also cause a phase shift. Simpson et al. [J. Acoust. Soc. Am. 99(4), 2521(A) (1996)] have investigated this acousto-optic phase modulation as a possible contaminating effect for underwater LDV vibration measurements. This paper will investigate acousto-optic phase modulations measured by a scanning LDV as a method for measuring pressure radiating from underwater vibrating surfaces. This is done by passing the laser beam through the radiating pressure field and measuring the backscattered laser signal which is reflected off a rigid and retroreflective surface (outside the pressure field). It is shown experimentally, using the average pressure measured with an LDV over a plane in the vicinity of a vibrating structure, that the pressure at a far-field location normal to the plane can be determined.

  12. Pressure Measurement in Supersonic Air Flow by Differential Absorptive Laser-Induced Thermal Acoustics

    NASA Technical Reports Server (NTRS)

    Hart, Roger C.; Herring, Gregory C.; Balla, Robert J.

    2007-01-01

    Nonintrusive, off-body flow barometry in Mach-2 airflow has been demonstrated in a large-scale supersonic wind tunnel using seedless laser-induced thermal acoustics (LITA). The static pressure of the gas flow is determined with a novel differential absorption measurement of the ultrasonic sound produced by the LITA pump process. Simultaneously, stream-wise velocity and static gas temperature of the same spatially-resolved sample volume were measured with this nonresonant time-averaged LITA technique. Mach number, temperature and pressure have 0.2%, 0.4%, and 4% rms agreement, respectively, in comparison with known free-stream conditions.

  13. Pressure measurement in supersonic air flow by differential absorptive laser-induced thermal acoustics.

    PubMed

    Hart, Roger C; Herring, G C; Balla, R Jeffrey

    2007-06-15

    Nonintrusive, off-body flow barometry in Mach 2 airflow has been demonstrated in a large-scale supersonic wind tunnel using seedless laser-induced thermal acoustics (LITA). The static pressure of the gas flow is determined with a novel differential absorption measurement of the ultrasonic sound produced by the LITA pump process. Simultaneously, the streamwise velocity and static gas temperature of the same spatially resolved sample volume were measured with this nonresonant time-averaged LITA technique. Mach number, temperature, and pressure have 0.2%, 0.4%, and 4% rms agreement, respectively, in comparison with known free-stream conditions.

  14. Method for Estimating the Acoustic Pressure in Tissues Using Low-Amplitude Measurements in Water.

    PubMed

    Keravnou, Christina P; Izamis, Maria-Louisa; Averkiou, Michalakis A

    2015-11-01

    The aim of this study was to evaluate a simple, reliable and reproducible method for accuracy in estimating the acoustic pressure delivered in tissue exposed to ultrasound. Such a method would be useful for therapeutic applications of ultrasound with microbubbles, for example, sonoporation. The method is based on (i) low-amplitude water measurements that are easily made and do not suffer from non-linear propagation effects, and (ii) the attenuation coefficient of the tissue of interest. The range of validity of the extrapolation method for different attenuation and pressure values was evaluated with a non-linear propagation theoretical model. Depending on the specific tissue attenuation, the method produces good estimates of pressures in excess of 10 MPa. Ex vivo machine-perfused pig liver tissue was used to validate the method for source pressures up to 3.5 MPa. The method can be used to estimate the delivered pressure in vivo in diagnostic and therapeutic applications of ultrasound.

  15. Acoustic predictions using measured pressures from a model rotor in the DNW

    NASA Technical Reports Server (NTRS)

    Visintainer, Joseph A.; Burley, Casey L.; Marcolini, Michael A.; Liu, Sandy R.

    1991-01-01

    A contemporary design, 4-bladed United Technologies model rotor with pressure-instrumented blades was tested in the Duits-Nederslandse Windtunnel. Simultaneous acoustic and pressure measurements were made for a wide range of operating conditions. Microphones were optimally positioned at a number of locations in the flow forward of the rotor to measure rotor thickness noise, high-speed impulsive noise (both in the rotor plane), and blade-vortex interaction noise (forward and 25 deg below the rotor plane). The blade surface pressure data are used as aerodynamic input to WOPWOP, which is a state-of-the-art rotor noise prediction program that predicts rotor thickness and loading noise. The predicted results using WOPWOP are compared to the measured noise levels for cases where either thickness noise, blade-vortex interaction noise, or high-speed impulsive noise is the dominant noise mechanism. The comparisons show regions of good agreement, as well as areas where further improvement is necessary.

  16. Liquid mercury sound velocity measurements under high pressure and high temperature by picosecond acoustics in a diamond anvils cell.

    PubMed

    Decremps, F; Belliard, L; Couzinet, B; Vincent, S; Munsch, P; Le Marchand, G; Perrin, B

    2009-07-01

    Recent improvements to measure ultrasonic sound velocities of liquids under extreme conditions are described. Principle and feasibility of picosecond acoustics in liquids embedded in a diamond anvils cell are given. To illustrate the capability of these advances in the sound velocity measurement technique, original high pressure and high temperature results on the sound velocity of liquid mercury up to 5 GPa and 575 K are given. This high pressure technique will certainly be useful in several fundamental and applied problems in physics and many other fields such as geophysics, nonlinear acoustics, underwater sound, petrology or physical acoustics.

  17. Application of SH surface acoustic waves for measuring the viscosity of liquids in function of pressure and temperature.

    PubMed

    Kiełczyński, P; Szalewski, M; Balcerzak, A; Rostocki, A J; Tefelski, D B

    2011-12-01

    Viscosity measurements were carried out on triolein at pressures from atmospheric up to 650 MPa and in the temperature range from 10°C to 40°C using ultrasonic measuring setup. Bleustein-Gulyaev SH surface acoustic waves waveguides were used as viscosity sensors. Additionally, pressure changes occurring during phase transition have been measured over the same temperature range. Application of ultrasonic SH surface acoustic waves in the liquid viscosity measurements at high pressure has many advantages. It enables viscosity measurement during phase transitions and in the high-pressure range where the classical viscosity measurement methods cannot operate. Measurements of phase transition kinetics and viscosity of liquids at high pressures and various temperatures (isotherms) is a novelty. The knowledge of changes in viscosity in function of pressure and temperature can help to obtain a deeper insight into thermodynamic properties of liquids.

  18. Quantitative measurement of ultrasound pressure field by optical phase contrast method and acoustic holography

    NASA Astrophysics Data System (ADS)

    Oyama, Seiji; Yasuda, Jun; Hanayama, Hiroki; Yoshizawa, Shin; Umemura, Shin-ichiro

    2016-07-01

    A fast and accurate measurement of an ultrasound field with various exposure sequences is necessary to ensure the efficacy and safety of various ultrasound applications in medicine. The most common method used to measure an ultrasound pressure field, that is, hydrophone scanning, requires a long scanning time and potentially disturbs the field. This may limit the efficiency of developing applications of ultrasound. In this study, an optical phase contrast method enabling fast and noninterfering measurements is proposed. In this method, the modulated phase of light caused by the focused ultrasound pressure field is measured. Then, a computed tomography (CT) algorithm used to quantitatively reconstruct a three-dimensional (3D) pressure field is applied. For a high-intensity focused ultrasound field, a new approach that combines the optical phase contrast method and acoustic holography was attempted. First, the optical measurement of focused ultrasound was rapidly performed over the field near a transducer. Second, the nonlinear propagation of the measured ultrasound was simulated. The result of the new approach agreed well with that of the measurement using a hydrophone and was improved from that of the phase contrast method alone with phase unwrapping.

  19. Picosecond acoustics method for measuring the thermodynamical properties of solids and liquids at high pressure and high temperature.

    PubMed

    Decremps, F; Gauthier, M; Ayrinhac, S; Bove, L; Belliard, L; Perrin, B; Morand, M; Le Marchand, G; Bergame, F; Philippe, J

    2015-02-01

    Based on the original combination of picosecond acoustics and diamond anvils cell, recent improvements to accurately measure hypersonic sound velocities of liquids and solids under extreme conditions are described. To illustrate the capability of this technique, results are given on the pressure and temperature dependence of acoustic properties for three prototypical cases: polycrystal (iron), single-crystal (silicon) and liquid (mercury) samples. It is shown that such technique also enables the determination of the density as a function of pressure for liquids, of the complete set of elastic constants for single crystals, and of the melting curve for any kind of material. High pressure ultrafast acoustic spectroscopy technique clearly opens opportunities to measure thermodynamical properties under previously unattainable extreme conditions. Beyond physics, this state-of-the-art experiment would thus be useful in many other fields such as nonlinear acoustics, oceanography, petrology, in of view. A brief description of new developments and future directions of works conclude the article.

  20. DIASCoPE: Directly integrated acoustic system combined with pressure experiments—A new method for fast acoustic velocity measurements at high pressure

    NASA Astrophysics Data System (ADS)

    Whitaker, Matthew L.; Baldwin, Kenneth J.; Huebsch, William R.

    2017-03-01

    A new experimental system to measure elastic wave velocities in samples in situ under extreme conditions of pressure and temperature in a multi-anvil apparatus has been installed at Beamline 6-BM-B of the Advanced Photon Source at Argonne National Laboratory. This system allows for measurement of acoustic velocities via ultrasonic interferometry, and makes use of the synchrotron beam to measure sample densities via X-ray diffraction and sample lengths using X-radiographic imaging. This system is fully integrated into the automated software controls of the beamline and is capable of collecting robust data on elastic wave travel times in less than 1 s, which is an improvement of more than one to two orders of magnitude over existing systems. Moreover, this fast data collection time has been shown to have no effect on the obtained travel time results. This allows for more careful study of time-dependent phenomena with tighter snapshots in time of processes that would otherwise be lost or averaged out in other acoustic measurement systems.

  1. A Fabry-Perot fiber-optic ultrasonic hydrophone for the simultaneous measurement of temperature and acoustic pressure.

    PubMed

    Morris, Paul; Hurrell, Andrew; Shaw, Adam; Zhang, Edward; Beard, Paul

    2009-06-01

    A dual sensing fiber-optic hydrophone that can make simultaneous measurements of acoustic pressure and temperature at the same location has been developed for characterizing ultrasound fields and ultrasound-induced heating. The transduction mechanism is based on the detection of acoustically- and thermally-induced thickness changes in a polymer film Fabry-Perot interferometer deposited at the tip of a single mode optical fiber. The sensor provides a peak noise-equivalent pressure of 15 kPa (at 5 MHz, over a 20 MHz measurement bandwidth), an acoustic bandwidth of 50 MHz, and an optically defined element size of 10 microm. As well as measuring acoustic pressure, temperature changes up to 70 degrees C can be measured, with a resolution of 0.34 degrees C. To evaluate the thermal measurement capability of the sensor, measurements were made at the focus of a high-intensity focused ultrasound (HIFU) field in a tissue mimicking phantom. These showed that the sensor is not susceptible to viscous heating, is able to withstand high intensity fields, and can simultaneously acquire acoustic waveforms while monitoring induced temperature rises. These attributes, along with flexibility, small physical size (OD approximately 150 microm), immunity to Electro-Magnetic Interference (EMI), and low sensor cost, suggest that this type of hydrophone may provide a practical alternative to piezoelectric based hydrophones.

  2. Acoustic pressure-vector sensor array

    NASA Astrophysics Data System (ADS)

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

    2004-05-01

    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.

  3. Simultaneous measurement of temperature, hydrostatic pressure and acoustic signal using a single distributed Bragg reflector fiber laser

    NASA Astrophysics Data System (ADS)

    Tan, Yan-Nan; Zhang, Yang; Guan, Bai-Ou

    2011-05-01

    A fiber-optic sensor based on a dual polarization fiber grating laser for simultaneous measurement of temperature, hydrostatic pressure and acoustic signal is proposed and experimentally demonstrated. The acoustic wave induces a frequency modulation (FM) of the carrier in radio frequency (RF) range generated by the fiber laser and can be easily extracted by using the FM demodulation technique. The temperature can be determined by the laser wavelength. The hydrostatic pressure can be determined by monitoring the static shift of the carrier frequency and deducting the effect of the temperature.

  4. Fundamentals of Acoustics. Psychoacoustics and Hearing. Acoustical Measurements

    NASA Technical Reports Server (NTRS)

    Begault, Durand R.; Ahumada, Al (Technical Monitor)

    1997-01-01

    These are 3 chapters that will appear in a book titled "Building Acoustical Design", edited by Charles Salter. They are designed to introduce the reader to fundamental concepts of acoustics, particularly as they relate to the built environment. "Fundamentals of Acoustics" reviews basic concepts of sound waveform frequency, pressure, and phase. "Psychoacoustics and Hearing" discusses the human interpretation sound pressure as loudness, particularly as a function of frequency. "Acoustic Measurements" gives a simple overview of the time and frequency weightings for sound pressure measurements that are used in acoustical work.

  5. Wireless Acoustic Measurement System

    NASA Technical Reports Server (NTRS)

    Anderson, Paul D.; Dorland, Wade D.

    2005-01-01

    A prototype wireless acoustic measurement system (WAMS) is one of two main subsystems of the Acoustic Prediction/Measurement Tool, which comprises software, acoustic instrumentation, and electronic hardware combined to afford integrated capabilities for predicting and measuring noise emitted by rocket and jet engines. The other main subsystem is described in "Predicting Rocket or Jet Noise in Real Time" (SSC-00215-1), which appears elsewhere in this issue of NASA Tech Briefs. The WAMS includes analog acoustic measurement instrumentation and analog and digital electronic circuitry combined with computer wireless local-area networking to enable (1) measurement of sound-pressure levels at multiple locations in the sound field of an engine under test and (2) recording and processing of the measurement data. At each field location, the measurements are taken by a portable unit, denoted a field station. There are ten field stations, each of which can take two channels of measurements. Each field station is equipped with two instrumentation microphones, a micro-ATX computer, a wireless network adapter, an environmental enclosure, a directional radio antenna, and a battery power supply. The environmental enclosure shields the computer from weather and from extreme acoustically induced vibrations. The power supply is based on a marine-service lead-acid storage battery that has enough capacity to support operation for as long as 10 hours. A desktop computer serves as a control server for the WAMS. The server is connected to a wireless router for communication with the field stations via a wireless local-area network that complies with wireless-network standard 802.11b of the Institute of Electrical and Electronics Engineers. The router and the wireless network adapters are controlled by use of Linux-compatible driver software. The server runs custom Linux software for synchronizing the recording of measurement data in the field stations. The software includes a module that

  6. Wireless Acoustic Measurement System

    NASA Technical Reports Server (NTRS)

    Anderson, Paul D.; Dorland, Wade D.; Jolly, Ronald L.

    2007-01-01

    A prototype wireless acoustic measurement system (WAMS) is one of two main subsystems of the Acoustic Prediction/ Measurement Tool, which comprises software, acoustic instrumentation, and electronic hardware combined to afford integrated capabilities for predicting and measuring noise emitted by rocket and jet engines. The other main subsystem is described in the article on page 8. The WAMS includes analog acoustic measurement instrumentation and analog and digital electronic circuitry combined with computer wireless local-area networking to enable (1) measurement of sound-pressure levels at multiple locations in the sound field of an engine under test and (2) recording and processing of the measurement data. At each field location, the measurements are taken by a portable unit, denoted a field station. There are ten field stations, each of which can take two channels of measurements. Each field station is equipped with two instrumentation microphones, a micro- ATX computer, a wireless network adapter, an environmental enclosure, a directional radio antenna, and a battery power supply. The environmental enclosure shields the computer from weather and from extreme acoustically induced vibrations. The power supply is based on a marine-service lead-acid storage battery that has enough capacity to support operation for as long as 10 hours. A desktop computer serves as a control server for the WAMS. The server is connected to a wireless router for communication with the field stations via a wireless local-area network that complies with wireless-network standard 802.11b of the Institute of Electrical and Electronics Engineers. The router and the wireless network adapters are controlled by use of Linux-compatible driver software. The server runs custom Linux software for synchronizing the recording of measurement data in the field stations. The software includes a module that provides an intuitive graphical user interface through which an operator at the control server

  7. Effect of Turbulent Boundary Layer Flow on Measurement of Acoustic Pressure and Intensity. Revised.

    DTIC Science & Technology

    1984-05-18

    variation is identical to that in the k 3R domain. The measured response 77 -17- 18 May 1984 GCL: Ihz function shown in Figure 2 is by Farabee and Geib ...I1hz 14. Farabee, T. M. and F. E. Geib , Jr., OfLsurme nt , Boundarv Lav,,r Pressure Fields with an Array of Pressure Transducers in a Subsonic Flow...Research & Development Center (Copy No. 34) Department of the Navy Bethesda, MD 20084 Commanding Officer Attn: F. E. Geib Naval Ocean Systems Center Code

  8. Study of noise sources in a subsonic fan using measured blade pressures and acoustic theory

    NASA Technical Reports Server (NTRS)

    Hanson, D. B.

    1975-01-01

    Sources of noise in a 1.4 m (4.6 ft) diameter subsonic tip speed propulsive fan running statically outdoors are studied using a combination of techniques. Signals measured with pressure transducers on a rotor blade are plotted in a format showing the space-time history of inlet distortion. Study of these plots visually and with statistical correlation analysis confirms that the inlet flow contains long, thin eddies of turbulence. Turbulence generated in the boundary layer of the shroud upstream of the rotor tips was not found to be an important noise source. Fan noise is diagnosed by computing narrowband spectra of rotor and stator sound power and comparing these with measured sound power spectra. Rotor noise is computed from spectra of the measured blade pressures and stator noise is computed using the author's stator noise theory. It is concluded that the rotor and stator sources contribute about equally at frequencies in the vicinity of the first three harmonics of blade passing frequency. At higher frequencies, the stator contribution diminishes rapidly and the rotor/inlet turbulence mechanism dominates. Two parametric studies are performed by using the rotor noise calculation procedure which was correlated with test. In the first study, the effects on noise spectrum and directivity are calculated for changes in turbulence properties, rotational Mach number, number of blades, and stagger angle. In the second study the influences of design tip speed and blade number on noise are evaluated.

  9. Method specificity of non-invasive blood pressure measurement: oscillometry and finger pulse pressure vs acoustic methods.

    PubMed Central

    De Mey, C; Schroeter, V; Butzer, R; Roll, S; Belz, G G

    1995-01-01

    1. The agreement of blood pressure measurements by stethoscope auscultation (SBPa, DBPa-IV and DBPa-V), oscillometry (Dinamap; SBPo, and DBPo) and digital photoplethysmography (Finapres; SBPf, and DBPf) with the graphical analysis of the analogue microphone signals of vascular wall motion sound (SBPg and DBPg) was evaluated in eight healthy subjects in the presence of responses to the intravenous infusion of 1 microgram min-1 isoprenaline. 2. In general, there was good agreement between the SBP/DBP-measurements based on auscultatory Korotkoff-I- and IV-criteria and the reference method; the average method difference in estimating the isoprenaline responses for SBPa-SBPg was: -1.1, 95% CI: -5.4 to 3.1 mm Hg with a within-subject between-method repeatability coefficient (REP) of 11.6 mm Hg and for DBPa-IV-DBPg: 3.5, 95% CI: -0.5 to 6.5 mm Hg, REP: 11.5 mm Hg. The ausculatation of Korotkoff-V substantially overestimated the isoprenaline induced reduction of DBP: method difference DBPa-V-DBPg: -11.3, 95% CI: -17.8 to -4.7 mm Hg, REP: 31.8 mm Hg. 3. Oscillometry yielded good approximations for the SBP response to isoprenaline (average method difference SBPo-SBPg: -2.9, 95% CI: -9.0 to 3.3 mm Hg, REP: 17.6 mm Hg) but was poorly sensitive with regard to the DBP responses: method difference DBPo-DBPg: 6.5, 95% CI: -1.3 to 14.3 mm Hg, REP: 25.7 mm Hg. 4. Whilst the finger pulse pressure agreed well with regard to DBP (method difference for the DBP responses to isoprenaline: DBPf-DBPg: 1.8, 95% CI: -5.1 to 8.6 mm Hg, REP: 18.5 mm Hg) it was rather unsatisfactory with regard to SBP (method difference SBPf-SBPg: -14.1, 95% CI: -28.2 to -0.1 mm Hg, REP: 49.9 mm Hg).(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8554929

  10. Measuring acoustic habitats.

    PubMed

    Merchant, Nathan D; Fristrup, Kurt M; Johnson, Mark P; Tyack, Peter L; Witt, Matthew J; Blondel, Philippe; Parks, Susan E

    2015-03-01

    1. Many organisms depend on sound for communication, predator/prey detection and navigation. The acoustic environment can therefore play an important role in ecosystem dynamics and evolution. A growing number of studies are documenting acoustic habitats and their influences on animal development, behaviour, physiology and spatial ecology, which has led to increasing demand for passive acoustic monitoring (PAM) expertise in the life sciences. However, as yet, there has been no synthesis of data processing methods for acoustic habitat monitoring, which presents an unnecessary obstacle to would-be PAM analysts. 2. Here, we review the signal processing techniques needed to produce calibrated measurements of terrestrial and aquatic acoustic habitats. We include a supplemental tutorial and template computer codes in matlab and r, which give detailed guidance on how to produce calibrated spectrograms and statistical analyses of sound levels. Key metrics and terminology for the characterisation of biotic, abiotic and anthropogenic sound are covered, and their application to relevant monitoring scenarios is illustrated through example data sets. To inform study design and hardware selection, we also include an up-to-date overview of terrestrial and aquatic PAM instruments. 3. Monitoring of acoustic habitats at large spatiotemporal scales is becoming possible through recent advances in PAM technology. This will enhance our understanding of the role of sound in the spatial ecology of acoustically sensitive species and inform spatial planning to mitigate the rising influence of anthropogenic noise in these ecosystems. As we demonstrate in this work, progress in these areas will depend upon the application of consistent and appropriate PAM methodologies.

  11. Measuring acoustic habitats

    PubMed Central

    Merchant, Nathan D; Fristrup, Kurt M; Johnson, Mark P; Tyack, Peter L; Witt, Matthew J; Blondel, Philippe; Parks, Susan E

    2015-01-01

    1. Many organisms depend on sound for communication, predator/prey detection and navigation. The acoustic environment can therefore play an important role in ecosystem dynamics and evolution. A growing number of studies are documenting acoustic habitats and their influences on animal development, behaviour, physiology and spatial ecology, which has led to increasing demand for passive acoustic monitoring (PAM) expertise in the life sciences. However, as yet, there has been no synthesis of data processing methods for acoustic habitat monitoring, which presents an unnecessary obstacle to would-be PAM analysts. 2. Here, we review the signal processing techniques needed to produce calibrated measurements of terrestrial and aquatic acoustic habitats. We include a supplemental tutorial and template computer codes in matlab and r, which give detailed guidance on how to produce calibrated spectrograms and statistical analyses of sound levels. Key metrics and terminology for the characterisation of biotic, abiotic and anthropogenic sound are covered, and their application to relevant monitoring scenarios is illustrated through example data sets. To inform study design and hardware selection, we also include an up-to-date overview of terrestrial and aquatic PAM instruments. 3. Monitoring of acoustic habitats at large spatiotemporal scales is becoming possible through recent advances in PAM technology. This will enhance our understanding of the role of sound in the spatial ecology of acoustically sensitive species and inform spatial planning to mitigate the rising influence of anthropogenic noise in these ecosystems. As we demonstrate in this work, progress in these areas will depend upon the application of consistent and appropriate PAM methodologies. PMID:25954500

  12. Towards direct realisation of the SI unit of sound pressure in the audible hearing range based on optical free-field acoustic particle measurements

    NASA Astrophysics Data System (ADS)

    Koukoulas, Triantafillos; Piper, Ben

    2015-04-01

    Since the introduction of the International System of Units (the SI system) in 1960, weights, measures, standardised approaches, procedures, and protocols have been introduced, adapted, and extensively used. A major international effort and activity concentrate on the definition and traceability of the seven base SI units in terms of fundamental constants, and consequently those units that are derived from the base units. In airborne acoustical metrology and for the audible range of frequencies up to 20 kHz, the SI unit of sound pressure, the pascal, is realised indirectly and without any knowledge or measurement of the sound field. Though the principle of reciprocity was originally formulated by Lord Rayleigh nearly two centuries ago, it was devised in the 1940s and eventually became a calibration standard in the 1960s; however, it can only accommodate a limited number of acoustic sensors of specific types and dimensions. International standards determine the device sensitivity either through coupler or through free-field reciprocity but rely on the continuous availability of specific acoustical artefacts. Here, we show an optical method based on gated photon correlation spectroscopy that can measure sound pressures directly and absolutely in fully anechoic conditions, remotely, and without disturbing the propagating sound field. It neither relies on the availability or performance of any measurement artefact nor makes any assumptions of the device geometry and sound field characteristics. Most importantly, the required units of sound pressure and microphone sensitivity may now be experimentally realised, thus providing direct traceability to SI base units.

  13. Towards direct realisation of the SI unit of sound pressure in the audible hearing range based on optical free-field acoustic particle measurements

    SciTech Connect

    Koukoulas, Triantafillos Piper, Ben

    2015-04-20

    Since the introduction of the International System of Units (the SI system) in 1960, weights, measures, standardised approaches, procedures, and protocols have been introduced, adapted, and extensively used. A major international effort and activity concentrate on the definition and traceability of the seven base SI units in terms of fundamental constants, and consequently those units that are derived from the base units. In airborne acoustical metrology and for the audible range of frequencies up to 20 kHz, the SI unit of sound pressure, the pascal, is realised indirectly and without any knowledge or measurement of the sound field. Though the principle of reciprocity was originally formulated by Lord Rayleigh nearly two centuries ago, it was devised in the 1940s and eventually became a calibration standard in the 1960s; however, it can only accommodate a limited number of acoustic sensors of specific types and dimensions. International standards determine the device sensitivity either through coupler or through free-field reciprocity but rely on the continuous availability of specific acoustical artefacts. Here, we show an optical method based on gated photon correlation spectroscopy that can measure sound pressures directly and absolutely in fully anechoic conditions, remotely, and without disturbing the propagating sound field. It neither relies on the availability or performance of any measurement artefact nor makes any assumptions of the device geometry and sound field characteristics. Most importantly, the required units of sound pressure and microphone sensitivity may now be experimentally realised, thus providing direct traceability to SI base units.

  14. Acoustics of the piezo-electric pressure probe

    NASA Technical Reports Server (NTRS)

    Dutt, G. S.

    1974-01-01

    Acoustical properties of a piezoelectric device are reported for measuring the pressure in the plasma flow from an MPD arc. A description and analysis of the acoustical behavior in a piezoelectric probe is presented for impedance matching and damping. The experimental results are presented in a set of oscillographic records.

  15. Laser-Induced Thermal Acoustic Measurements in a Highly Back-Pressured Scramjet Isolator Model: A Research Plan

    NASA Technical Reports Server (NTRS)

    Middleton, Troy F.; Balla, Robert J.; Baurle, Robert A.; Wilson, Lloyd G.

    2008-01-01

    Under the Propulsion Discipline of NASA s Fundamental Aeronautics Program s Hypersonics Project, a test apparatus, for testing a scramjet isolator model, is being constructed at NASA's Langley Research Center. The test apparatus will incorporate a 1-inch by 2-inch by 15-inch-long scramjet isolator model supplied with 2.1 lbm/sec of unheated dry air through a Mach 2.5 converging-diverging nozzle. The planned research will incorporate progressively more challenging measurement techniques to characterize the flow field within the isolator, concluding with the application of the Laser-Induced Thermal Acoustic (LITA) measurement technique. The primary goal of this research is to use the data acquired to validate Computational Fluid Dynamics (CFD) models employed to characterize the complex flow field of a scramjet isolator. This paper describes the test apparatus being constructed, pre-test CFD simulations, and the LITA measurement technique.

  16. Blood pressure measurement

    MedlinePlus

    ... reading; Measuring blood pressure; Hypertension - blood pressure measurement; High blood pressure - blood pressure measurement ... High blood pressure has no symptoms so you may not know if you have this problem. High blood pressure ...

  17. Acoustic Impedance Measurement for Underground Surfaces.

    NASA Astrophysics Data System (ADS)

    Cockcroft, Paul William

    Available from UMI in association with The British Library. Requires signed TDF. This thesis investigates the measurement of acoustic impedance for surfaces likely to be found in underground coal mines. By introducing the concepts of industrial noise, the effects of noise on the ear and relevant legislation the need for the protection of workers can be appreciated. Representative acoustic impedance values are vital as input for existing computer models that predict sound levels in various underground environments. These enable the mining engineer to predict the noise level at any point within a mine in the vicinity of noisy machinery. The concepts of acoustic intensity and acoustic impedance are investigated and different acoustic impedance measurement techniques are detailed. The possible use of either an impedance tube or an intensity meter for these kinds of measurements are suggested. The problems with acoustic intensity and acoustic impedance measurements are discussed with reference to the restraints that an underground environment imposes on any measurement technique. The impedance tube method for work in an acoustics laboratory is shown and the theory explained, accompanied by a few representative results. The use of a Metravib intensity meter in a soundproof chamber to gain impedance values is explained in detail. The accompanying software for the analysis of the two measured pressure signals is shown as well as the actual results for a variety of test surfaces. The use of a Nagra IV-SJ tape recorder is investigated to determine the effect of recording on the measurement and subsequent analysis of the input signals, particularly with reference to the phase difference introduced between the two simultaneous pressure signals. The subsequent use of a Norwegian Electronic intensity meter, including a proposal for underground work, is shown along with results for tests completed with this piece of equipment. Finally, recommendations are made on how to link up

  18. Pressure-Coupled Acoustic-Transducer Assembly

    NASA Technical Reports Server (NTRS)

    Parker, F. Raymond

    1993-01-01

    Improved acoustic-transducer assembly easy to assemble, relocatable, and used at high temperatures. In assembly, piezoelectric acoustic transducer pressure-coupled to delay line or fixture through soft metal like aluminum, copper or gold. Transducer subassembly includes layered structure of coupling material, transducer, thin disk of coupling material acting as cushion for transducer, electrode disk with coaxial cable lead attached, insulation/damping material, and pressure plate. Pressure coupling precludes problem of matching coefficients of thermal expansion of transducer, coupling material, and delay line.

  19. Acoustic wave propagation in high-pressure system.

    PubMed

    Foldyna, Josef; Sitek, Libor; Habán, Vladimír

    2006-12-22

    Recently, substantial attention is paid to the development of methods of generation of pulsations in high-pressure systems to produce pulsating high-speed water jets. The reason is that the introduction of pulsations into the water jets enables to increase their cutting efficiency due to the fact that the impact pressure (so-called water-hammer pressure) generated by an impact of slug of water on the target material is considerably higher than the stagnation pressure generated by corresponding continuous jet. Special method of pulsating jet generation was developed and tested extensively under the laboratory conditions at the Institute of Geonics in Ostrava. The method is based on the action of acoustic transducer on the pressure liquid and transmission of generated acoustic waves via pressure system to the nozzle. The purpose of the paper is to present results obtained during the research oriented at the determination of acoustic wave propagation in high-pressure system. The final objective of the research is to solve the problem of transmission of acoustic waves through high-pressure water to generate pulsating jet effectively even at larger distances from the acoustic source. In order to be able to simulate numerically acoustic wave propagation in the system, it is necessary among others to determine dependence of the sound speed and second kinematical viscosity on operating pressure. Method of determination of the second kinematical viscosity and speed of sound in liquid using modal analysis of response of the tube filled with liquid to the impact was developed. The response was measured by pressure sensors placed at both ends of the tube. Results obtained and presented in the paper indicate good agreement between experimental data and values of speed of sound calculated from so-called "UNESCO equation". They also show that the value of the second kinematical viscosity of water depends on the pressure.

  20. Acoustic oscillatory pressure control for ramjet

    SciTech Connect

    Brown, R.S.; Dunlap, R.

    1988-08-02

    A method for controlling the acoustic oscillatory pressures generated by gas flow at the combustor inlet to a ramjet engine, the inlet including a sudden geometry expansion is described characterized by; restricting the inlet at the sudden expansion geometry such that the gas flow separates upstream and has a vena contracta downstream of the restricted inlet.

  1. Acoustic impedance measurements of pulse tube refrigerators

    NASA Astrophysics Data System (ADS)

    Iwase, Takashi; Biwa, Tetsushi; Yazaki, Taichi

    2010-02-01

    Complex acoustic impedance is determined in a prototype refrigerator that can mimic orifice-type, inertance-type, and double inlet-type pulse tube refrigerators from simultaneous measurements of pressure and velocity oscillations at the cold end. The impedance measurements revealed the means by which the oscillatory flow condition in the basic pulse tube refrigerator is improved by additional components such as a valve and a tank. The working mechanism of pulse tube refrigerators is explained based on an electrical circuit analogy.

  2. Nucleation pressure threshold in acoustic droplet vaporization

    NASA Astrophysics Data System (ADS)

    Miles, Christopher; Doering, Charles; Kripfgans, Oliver

    2016-11-01

    We combine classical nucleation theory with superharmonic focusing to predict necessary pressures to induce nucleation in acoustic droplet vaporization. We show that linear acoustics is a valid approximation to leading order when particle displacements in the sound field are small relative the radius of the droplet. This is done by perturbation analysis of an axisymmetric compressible inviscid flow about a droplet with small surface perturbations relative to the mean radius subjected to an incoming ultrasonic wave. The necessary nucleation pressure threshold inside the droplet is calculated to be - 9 . 33 +/- 0 . 30 MPa for typical experimental parameters by employing results from classical homogeneous nucleation theory. As a result we are able to predict if a given incident pressure waveform will induce nucleation. This research was supported by the Rackham Merit Fellowship, the University of Michigan Physics department, the University of Michigan's MCubed program, and NSF awards PHY-1205219 and DMS-1515161.

  3. Measurements of acoustic sources in motion

    NASA Technical Reports Server (NTRS)

    Maestrello, L.; Norum, T. D.

    1978-01-01

    Results of the far-field pressures measured from three different types of moving sources are presented. These acoustic sources consist of a point monopole, a small model jet, and an aircraft. Results for the pressure time history produced by the point source show good agreement with those predicted analytically. Both actual and simulated forward motion of the model jet show reductions in noise levels with forward speed at all angles between the source and observer. Measurement with the aircraft over both an anechoic floor and over the ground yields a method for evaluating the transfer function for ground reflections at various angles between the moving aircraft and measurement position.

  4. The acoustic field scattered from some approximate pressure release materials

    NASA Astrophysics Data System (ADS)

    Caille, Gary W.

    1988-03-01

    The objective was to determine if a pressure release boundary condition can be achieved by coating an elastic shell with a visco-elastic material. One necessary condition is that the coating must acoustically decouple the shell from the scattering problem. Two closed cell rubbers and two cork-rubber composites (nitrile and neoprene based) were investigated. The dynamic viscoelastic constants of the materials were determined by wave propagation techniques. The far field scattering form functions for an infinite cylindrical shell coated with the viscoelastic material were calculated using the complete elastic equations of motion. The form functions were experimentally measured for the different materials at different thicknesses as verification of the theory. A thick finite right cylindrical shell was coated with .25 inches of closed cell neoprene and the normalized scattered pressure measured. The pressure release normalized scattered pressure was determined for the end on incident plane wave case using the acoustic radiation Simplified Helmholtz Integral Program (SHIP).

  5. Tongue-Palate Contact Pressure, Oral Air Pressure, and Acoustics of Clear Speech

    ERIC Educational Resources Information Center

    Searl, Jeff; Evitts, Paul M.

    2013-01-01

    Purpose: The authors compared articulatory contact pressure (ACP), oral air pressure (Po), and speech acoustics for conversational versus clear speech. They also assessed the relationship of these measures to listener perception. Method: Twelve adults with normal speech produced monosyllables in a phrase using conversational and clear speech.…

  6. Response of space shuttle insulation panels to acoustic noise pressure

    NASA Technical Reports Server (NTRS)

    Vaicaitis, R.

    1976-01-01

    The response of reusable space shuttle insulation panels to random acoustic pressure fields are studied. The basic analytical approach in formulating the governing equations of motion uses a Rayleigh-Ritz technique. The input pressure field is modeled as a stationary Gaussian random process for which the cross-spectral density function is known empirically from experimental measurements. The response calculations are performed in both frequency and time domain.

  7. Acoustical Measurement Of Furnace Temperatures

    NASA Technical Reports Server (NTRS)

    Parthasarathy, Shakkottai; Venkateshan, Shakkottai P.

    1989-01-01

    Simple probes withstand severe conditions, yet give spatially-resolved temperature readings. Prototype acoustical system developed to measure temperatures from ambient to 1,800 degree F in such structures as large industrial lime kilns and recovery-boiler furnaces. Pulses of sound reflected from obstructions in sensing tube. Speed of sound and temperature in each segment deduced from travel times of pulses.

  8. Evaluation of the sensitivity of electro-acoustic measurements for process monitoring and control of an atmospheric pressure plasma jet system

    NASA Astrophysics Data System (ADS)

    Law, V. J.; O'Neill, F. T.; Dowling, D. P.

    2011-06-01

    The development of non-invasive process diagnostic techniques for the control of atmospheric plasmas is a critical issue for the wider adoption of this technology. This paper evaluates the use of a frequency-domain deconvolution of an electro-acoustic emission as a means to monitor and control the plasma formed using an atmospheric pressure plasma jet (APPJ) system. The air plasma system investigated was formed using a PlasmaTreat™ OpenAir applicator. Change was observed in the electro-acoustic signal with changes in substrate type (ceramic, steel, polymer). APPJ nozzle to substrate distance and substrate feature size were monitored. The decoding of the electro-acoustic emission yields three subdatasets that are described by three separate emission mechanisms. The three emissions are associated with the power supply fundamental drive frequency and its harmonics, the APPJ nozzle longitudinal mode acoustic emission and its odd overtones, and the acoustic surface reflection that is produced by the impedance mismatch between the discharge and the surface. Incorporating this knowledge into a LabVIEW program facilitated the continuous deconvolution of the electro-acoustic data. This enabled the use of specific frequency band test limits to control the APPJ treatment process which is sensitive to both plasma processing conditions and substrate type and features.

  9. Scale Model Thruster Acoustic Measurement Results

    NASA Technical Reports Server (NTRS)

    Kenny, R. Jeremy; Vargas, Magda B.

    2013-01-01

    Subscale rocket acoustic data is used to predict acoustic environments for full scale rockets. Over the last several years acoustic data has been collected during horizontal tests of solid rocket motors. Space Launch System (SLS) Scale Model Acoustic Test (SMAT) was designed to evaluate the acoustics of the SLS vehicle including the liquid engines and solid rocket boosters. SMAT is comprised of liquid thrusters scalable to the Space Shuttle Main engines (SSME) and Rocket Assisted Take Off (RATO) motors scalable to the 5-segment Reusable Solid Rocket Motor (RSTMV). Horizontal testing of the liquid thrusters provided an opportunity to collect acoustic data from liquid thrusters to characterize the acoustic environments. Acoustic data was collected during the horizontal firings of a single thruster and a 4-thruster (Quad) configuration. Presentation scope. Discuss the results of the single and 4-thruster acoustic measurements. Compare the measured acoustic levels of the liquid thrusters to the Solid Rocket Test Motor V - Nozzle 2 (SRTMV-N2).

  10. Combining COMSOL modeling with acoustic pressure maps to design sono-reactors.

    PubMed

    Wei, Zongsu; Weavers, Linda K

    2016-07-01

    Scaled-up and economically viable sonochemical systems are critical for increased use of ultrasound in environmental and chemical processing applications. In this study, computational simulations and acoustic pressure maps were used to design a larger-scale sono-reactor containing a multi-stepped ultrasonic horn. Simulations in COMSOL Multiphysics showed ultrasonic waves emitted from the horn neck and tip, generating multiple regions of high acoustic pressure. The volume of these regions surrounding the horn neck were larger compared with those below the horn tip. The simulated acoustic field was verified by acoustic pressure contour maps generated from hydrophone measurements in a plexiglass box filled with water. These acoustic pressure contour maps revealed an asymmetric and discrete distribution of acoustic pressure due to acoustic cavitation, wave interaction, and water movement by ultrasonic irradiation. The acoustic pressure contour maps were consistent with simulation results in terms of the effective scale of cavitation zones (∼ 10 cm and <5 cm above and below horn tip, respectively). With the mapped acoustic field and identified cavitation location, a cylindrically-shaped sono-reactor with a conical bottom was designed to evaluate the treatment capacity (∼ 5 L) for the multi-stepped horn using COMSOL simulations. In this study, verification of simulation results with experiments demonstrates that coupling of COMSOL simulations with hydrophone measurements is a simple, effective and reliable scientific method to evaluate reactor designs of ultrasonic systems.

  11. Ionic association and solvation of the ionic liquid 1-hexyl-3-methylimidazolium chloride in molecular solvents revealed by vapor pressure osmometry, conductometry, volumetry, and acoustic measurements.

    PubMed

    Sadeghi, Rahmat; Ebrahimi, Nosaibah

    2011-11-17

    A systematic study of osmotic coefficient, conductivity, volumetric and acoustic properties of solutions of ionic liquid 1-hexyl-3-methylimidazolium chloride ([C(6)mim][Cl]) in various molecular solvents has been made at different temperatures in order to study of ionic association and solvation behavior of [C(6)mim][Cl] in different solutions. Precise measurements on electrical conductances of solutions of [C(6)mim][Cl] in water, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and acetonitrile at 293.15, 298.15, and 303.15 K are reported and analyzed with Barthel's low-concentration chemical model (lcCM) to obtain the limiting molar conductivities and association constants of this ionic liquid in the investigated solvents. Strong ion pairing was found for the ionic liquid in 2-propanol, 1-butanol, and 1-propanol, whereas ion association in acetonitrile, methanol and ethanol is rather weak and in water the ionic liquid is fully dissociated. In the second part of this work, the apparent molar volumes and isentropic compressibilities of [C(6)mim][Cl] in water, methanol, ethanol, acetonitrile, 1-propanol, 2-propanol, and 1-butanol are obtained at the 288.15-313.15 K temperature range at 5 K intervals at atmospheric pressure from the precise measurements of density and sound velocity. The infinite dilution apparent molar volume and isentropic compressibility values of the free ions and ion pairs of [C(6)mim][Cl] in the investigated solvents as well as the excess molar volume of the investigated solutions are determined and their variations with temperature and type of solvents are also studied. Finally, the experimental measurements of osmotic coefficient at 318.15 K for binary solutions of [C(6)mim][Cl] in water, methanol, ethanol, 2-propanol, and acetonitrile are taken using the vapor pressure osmometry (VPO) method and from which the values of the solvent activity, vapor pressure, activity coefficients, and Gibbs free energies are calculated. The results are

  12. MRI acoustic noise: sound pressure and frequency analysis.

    PubMed

    Counter, S A; Olofsson, A; Grahn, H F; Borg, E

    1997-01-01

    The large gradient coils used in MRI generate, simultaneously with the pulsed radiofrequency (RF) wave, acoustic noise of high intensity that has raised concern regarding hearing safety. The sound pressure levels (SPLs) and power spectra of MRI acoustic noise were measured at the position of the human head in the isocenter of five MRI systems and with 10 different pulse sequences used in clinical MR scanning. Each protocol, including magnetization-prepared rapid gradient echo (MP-RAGE; 113 dB SPL linear), fast gradient echo turbo (114 dB SPL linear), and spin echo T1/2 mm (117 dB SPL linear), was found to have the high SPLs, rapid pulse rates, amplitude-modulated pulse envelopes, and multipeaked spectra. Since thickness and SPL were inversely related, the T1-weighted images generated more intense acoustic noise than the proton-dense T2-weighted measures. The unfiltered linear peak values provided more accurate measurements of the SPL and spectral content of the MRI acoustic noise than the commonly used dB A-weighted scale, which filters out the predominant low frequency components. Fourier analysis revealed predominantly low frequency energy peaks ranging from .05 to approximately 1 kHz, with a steep high frequency cutoff for each pulse sequence. Ear protectors of known attenuation ratings are recommended for all patients during MRI testing.

  13. Acoustic measurements of articulator motions.

    PubMed

    Schroeder, M R; Strube, H W

    1979-01-01

    Methods for estimating articulatory data from acoustic measurements are reviewed. First, relations between the vocal-tract area function and formant or impedance data are pointed out. Then the possibility of determining a (discretized) area function from the speech signal itself is considered. Finally, we look at the estimation of certain articulatory parameters rather than the area function. By using a regression method, such parameters can even be estimated independently of any vocal-tract model. Results for real-speech data are given.

  14. Dual mode acoustic wave sensor for precise pressure reading

    NASA Astrophysics Data System (ADS)

    Mu, Xiaojing; Kropelnicki, Piotr; Wang, Yong; Randles, Andrew Benson; Chuan Chai, Kevin Tshun; Cai, Hong; Gu, Yuan Dong

    2014-09-01

    In this letter, a Microelectromechanical system acoustic wave sensor, which has a dual mode (lateral field exited Lamb wave mode and surface acoustic wave (SAW) mode) behavior, is presented for precious pressure change read out. Comb-like interdigital structured electrodes on top of piezoelectric material aluminium nitride (AlN) are used to generate the wave modes. The sensor membrane consists of single crystalline silicon formed by backside-etching of the bulk material of a silicon on insulator wafer having variable device thickness layer (5 μm-50 μm). With this principle, a pressure sensor has been fabricated and mounted on a pressure test package with pressure applied to the backside of the membrane within a range of 0 psi to 300 psi. The temperature coefficient of frequency was experimentally measured in the temperature range of -50 °C to 300 °C. This idea demonstrates a piezoelectric based sensor having two modes SAW/Lamb wave for direct physical parameter—pressure readout and temperature cancellation which can operate in harsh environment such as oil and gas exploration, automobile and aeronautic applications using the dual mode behavior of the sensor and differential readout at the same time.

  15. Acoustic Wave Propagation in Pressure Sense Lines

    NASA Technical Reports Server (NTRS)

    Vitarius, Patrick; Gregory, Don A.; Wiley, John; Korman, Valentin

    2003-01-01

    Sense lines are used in pressure measurements to passively transmit information from hostile environments to areas where transducers can be used. The transfer function of a sense line can be used to obtain information about the measured environment from the protected sensor. Several properties of this transfer function are examined, including frequency dependence, Helmholtz resonance, and time of flight delay.

  16. System for Manipulating Drops and Bubbles Using Acoustic Radiation Pressure

    NASA Technical Reports Server (NTRS)

    Oeftering, Richard C. (Inventor)

    1999-01-01

    The manipulation and control of drops of liquid and gas bubbles is achieved using high intensity acoustics in the form of and/or acoustic radiation pressure and acoustic streaming. generated by a controlled wave emission from a transducer. Acoustic radiation pressure is used to deploy or dispense drops into a liquid or a gas or bubbles into a liquid at zero or near zero velocity from the discharge end of a needle such as a syringe needle. Acoustic streaming is useful in manipulating the drop or bubble during or after deployment. Deployment and discharge is achieved by focusing the acoustic radiation pressure on the discharge end of the needle, and passing the acoustic waves through the fluid in the needle. through the needle will itself, or coaxially through the fluid medium surrounding the needle. Alternatively, the acoustic waves can be counter-deployed by focusing on the discharge end of the needle from a transducer axially aligned with the needle, but at a position opposite the needle, to prevent premature deployment of the drop or bubble. The acoustic radiation pressure can also be used for detecting the presence or absence of a drop or a bubble at the tip of a needle or for sensing various physical characteristics of the drop or bubble such as size or density.

  17. Nonlinear Bubble Interactions in Acoustic Pressure Fields

    NASA Technical Reports Server (NTRS)

    Barbat, Tiberiu; Ashgriz, Nasser; Liu, Ching-Shi

    1996-01-01

    The systems consisting of a two-phase mixture, as clouds of bubbles or drops, have shown many common features in their responses to different external force fields. One of particular interest is the effect of an unsteady pressure field applied to these systems, case in which the coupling of the vibrations induced in two neighboring components (two drops or two bubbles) may result in an interaction force between them. This behavior was explained by Bjerknes by postulating that every body that is moving in an accelerating fluid is subjected to a 'kinetic buoyancy' equal with the product of the acceleration of the fluid multiplied by the mass of the fluid displaced by the body. The external sound wave applied to a system of drops/bubbles triggers secondary sound waves from each component of the system. These secondary pressure fields integrated over the surface of the neighboring drop/bubble may result in a force additional to the effect of the primary sound wave on each component of the system. In certain conditions, the magnitude of these secondary forces may result in significant changes in the dynamics of each component, thus in the behavior of the entire system. In a system containing bubbles, the sound wave radiated by one bubble at the location of a neighboring one is dominated by the volume oscillation mode and its effects can be important for a large range of frequencies. The interaction forces in a system consisting of drops are much smaller than those consisting of bubbles. Therefore, as a first step towards the understanding of the drop-drop interaction subject to external pressure fluctuations, it is more convenient to study the bubble interactions. This paper presents experimental results and theoretical predictions concerning the interaction and the motion of two levitated air bubbles in water in the presence of an acoustic field at high frequencies (22-23 KHz).

  18. Acoustic temperature measurement in a rocket noise field.

    PubMed

    Giraud, Jarom H; Gee, Kent L; Ellsworth, John E

    2010-05-01

    A 1 μm diameter platinum wire resistance thermometer has been used to measure temperature fluctuations generated during a static GEM-60 rocket motor test. Exact and small-signal relationships between acoustic pressure and acoustic temperature are derived in order to compare the temperature probe output with that of a 3.18 mm diameter condenser microphone. After preliminary plane wave tests yielded good agreement between the transducers within the temperature probe's ∼2 kHz bandwidth, comparison between the temperature probe and microphone data during the motor firing show that the ±∼3 K acoustic temperature fluctuations are a significant contributor to the total temperature variations.

  19. Measurement of endolymphatic pressure.

    PubMed

    Mom, T; Pavier, Y; Giraudet, F; Gilain, L; Avan, P

    2015-04-01

    Endolymphatic pressure measurement is of interest both to researchers in the physiology and pathophysiology of hearing and ENT physicians dealing with Menière's disease or similar conditions. It is generally agreed that endolymphatic hydrops is associated with Menière's disease and is accompanied by increased hydrostatic pressure. Endolymphatic pressure, however, cannot be measured precisely without endangering hearing, making the association between hydrops and increased endolymphatic pressure difficult to demonstrate. Several integrated in vivo models have been developed since the 1960s, but only a few allow measurement of endolymphatic hydrostatic pressure. Models associating measurement of hydrostatic pressure and endolymphatic potential and assessment of cochlear function are of value to elucidate the pathophysiology of endolymphatic hydrops. The present article presents the main types of models and discusses their respective interest.

  20. Relation between near field and far field acoustic measurements

    NASA Technical Reports Server (NTRS)

    Bies, D. A.; Scharton, T. D.

    1974-01-01

    Several approaches to the problem of determining the far field directivity of an acoustic source located in a reverberant environment, such as a wind tunnel, are investigated analytically and experimentally. The decrease of sound pressure level with distance is illustrated; and the spatial extent of the hydrodynamic and geometric near fields, the far field, and the reverberant field are described. A previously-prosposed analytical technique for predicting the far field directivity of the acoustic source on the basis of near field data is investigated. Experiments are conducted with small acoustic sources and an analysis is performed to determine the variation with distance from the source of the directionality of the sound field. A novel experiment is conducted in which the sound pressure measured at various distances from an acoustic driver located in the NASA Ames 40 x 80 ft wind tunnel is crosscorrelated with the driver excitation voltage.

  1. Acoustic Measurements of Small Solid Rocket Motor

    NASA Technical Reports Server (NTRS)

    Vargas, Magda B.; Kenny, R. Jeremy

    2010-01-01

    Rocket acoustic noise can induce loads and vibration on the vehicle as well as the surrounding structures. Models have been developed to predict these acoustic loads based on scaling existing solid rocket motor data. The NASA Marshall Space Flight Center acoustics team has measured several small solid rocket motors (thrust below 150,000 lbf) to anchor prediction models. This data will provide NASA the capability to predict the acoustic environments and consequent vibro-acoustic response of larger rockets (thrust above 1,000,000 lbf) such as those planned for the NASA Constellation program. This paper presents the methods used to measure acoustic data during the static firing of small solid rocket motors and the trends found in the data.

  2. Measurement of the Q value of an acoustic resonator.

    PubMed

    Biwa, Tetsushi; Ueda, Yuki; Nomura, Hiroshi; Mizutani, Uichiro; Yazaki, Taichi

    2005-08-01

    A cylindrical acoustic resonator was externally driven at the first resonance frequency by a compression driver. The acoustic energy stored in the resonator and the power dissipated per unit time were evaluated through the simultaneous measurements of acoustic pressure and velocity, in order to determine the Q value of the resonator. The resulting Q value, being employed as a measure of the damping in a resonator, was obtained as 36. However, the Q value determined from a frequency response curve known as a conventional technique turned out to be 25, which is 30% less than that obtained in the present method. By further applying these two methods in the case of a resonator having an acoustic load inside, we present an accurate measurement of the Q value of the resonator by making full use of its definition.

  3. Blade pressure measurements

    NASA Astrophysics Data System (ADS)

    Chivers, J. W. H.

    Three measurement techniques which enable rotating pressures to be measured during the normal operation of a gas turbine or a component test rig are described. The first technique was developed specifically to provide steady and transient blade surface pressure data to aid both fan flutter research and general fan performance development. This technique involves the insertion of miniature high frequency response pressure transducers into the fan blades of a large civil gas turbine. The other two techniques were developed to measure steady rotating pressures inside and on the surface of engine or rig turbine blades and also rotating pressures in cooling feed systems. These two low frequency response systems are known as the "pressure pineapple' (a name which resulted from the shape of the original prototype) and the rotating scanivalve.

  4. Acoustic waves in gases with strong pressure gradients

    NASA Technical Reports Server (NTRS)

    Zorumski, William E.

    1989-01-01

    The effect of strong pressure gradients on the acoustic modes (standing waves) of a rectangular cavity is investigated analytically. When the cavity response is represented by a sum of modes, each mode is found to have two resonant frequencies. The lower frequency is near the Viaesaela-Brundt frequency, which characterizes the buoyant effect, and the higher frequency is above the ordinary acoustic resonance frequency. This finding shows that the propagation velocity of the acoustic waves is increased due to the pressure gradient effect.

  5. [Measuring blood pressure].

    PubMed

    Estrada Reventos, Dolors; Pujol Navarro, Ester

    2008-09-01

    High blood pressure is one of the main factors which lead to cardiovascular cerebral-vascular and kidney diseases; therefore, nursing professionals should have enough basic knowledge to enable them to carry out a precocious diagnosis and correct follow-up procedures. Although students in nursing schools are taught how to correctly measure blood pressure, often this teaching does not meet the recommendations provided by different national and international guidelines. Thus it is important to know how to use the correct methodology to measure blood pressure.

  6. Acoustic Liner Drag: Measurements on Novel Facesheet Perforate Geometries

    NASA Technical Reports Server (NTRS)

    Howerton, Brian M.; Jones, Michael G.

    2016-01-01

    Interest in characterization of the aerodynamic drag of acoustic liners has increased in the past several years. This paper details experiments in the NASA Langley Grazing Flow Impedance Tube to quantify the relative drag of several perforate-over-honeycomb liner configurations at flow speeds of centerline flow Mach number equals 0.3 and 0.5. Various perforate geometries and orientations are investigated to determine their resistance factors using a static pressure drop approach. Comparison of these resistance factors gives a relative measurement of liner drag. For these same flow conditions, acoustic measurements are performed with tonal excitation from 400 to 3000 hertz at source sound pressure levels of 140 and 150 decibels. Educed impedance and attenuation spectra are used to determine the impact of variations in perforate geometry on acoustic performance.

  7. Programmable auditory stimulus generator and electro-acoustic transducers--measurements of sound pressure in an artificial ear and human ear canal.

    PubMed

    Maurer, K; Schröder, K; Schäfer, E

    1984-07-01

    The measurement of sound pressure wave forms of different headphones resulted in considerable differences in an artificial ear and in the external auditory canal in man. This concerns, in particular, the pattern of stimuli used to elicit the auditory nerve and brain-stem auditory evoked potentials. By varying the electrical input to the headphones by means of a programmable stimulus generator, it can be shown that the sound pressure wave form can be influenced considerably.

  8. Droplet actuation by surface acoustic waves: an interplay between acoustic streaming and radiation pressure

    NASA Astrophysics Data System (ADS)

    Brunet, Philippe; Baudoin, Michael; Matar, Olivier Bou; Zoueshtiagh, Farzam

    2010-11-01

    Surface acoustic waves (SAW) are known to be a versatile technique for the actuation of sessile drops. Droplet displacement, internal mixing or drop splitting, are amongst the elementary operations that SAW can achieve, which are useful on lab-on-chip microfluidics benches. On the purpose to understand the underlying physical mechanisms involved during these operations, we study experimentally the droplet dynamics varying different physical parameters. Here in particular, the influence of liquid viscosity and acoustic frequency is investigated: it is indeed predicted that both quantities should play a role in the acoustic-hydrodynamic coupling involved in the dynamics. The key point is to compare the relative magnitude of the attenuation length, i.e. the scale within which the acoustic wave decays in the fluid, and the size of the drop. This relative magnitude governs the relative importance of acoustic streaming and acoustic radiation pressure, which are both involved in the droplet dynamics.

  9. Measuring the acoustic response of Helmholtz resonators

    NASA Astrophysics Data System (ADS)

    Monteiro, Martín; Marti, Arturo C.; Vogt, Patrik; Kasper, Lutz; Quarthal, Dominik

    2015-04-01

    Many experiments have been proposed to investigate acoustic phenomena in college and early undergraduate levels, in particular the speed of sound,1-9 by means of different methods, such as time of flight, transit time, or resonance in tubes. In this paper we propose to measure the acoustic response curves of a glass beaker filled with different gases, used as an acoustic resonator. We show that these curves expose many interesting peaks and features, one of which matches the resonance peak predicted for a Helmholtz resonator fairly well, and gives a decent estimate for the speed of sound in some cases. The measures are obtained thanks to the capabilities of smartphones.

  10. Acoustic measurement study 40 by 80 foot subsonic wind tunnel

    NASA Technical Reports Server (NTRS)

    1974-01-01

    An acoustical study conducted during the period from September 1, 1973 to April 30, 1974 measured sound pressure levels and vibration amplitudes inside and outside of the subsonic tunnel and on the tunnel structure. A discussion of the technical aspects of the study, the field measurement and data reduction procedures, and results are presentd, and conclusions resulting from the study which bear upon near field and far field tunnel noise, upon the tunnel as an acoustical enclosure, and upon the sources of noise within the tunnel drive system are given.

  11. Acoustic emission testing of 12-nickel maraging steel pressure vessels

    NASA Technical Reports Server (NTRS)

    Dunegan, H. L.

    1973-01-01

    Acoustic emission data were obtained from three point bend fracture toughness specimens of 12-nickel maraging steel, and two pressure vessels of the same material. One of the pressure vessels contained a prefabricated flaw which was extended and sharpened by fatigue cycling. It is shown that the flawed vessel had similar characteristics to the fracture specimens, thereby allowing estimates to be made of its nearness to failure during a proof test. Both the flawed and unflawed pressure vessel survived the proof pressure and 5 cycles to the working pressure, but it was apparent from the acoustic emission response during the proof cycle and the 5 cycles to the working pressure that the flawed vessel was very near failure. The flawed vessel did not survive a second cycle to the proof pressure before failure due to flaw extension through the wall (causing a leak).

  12. Comparison of multi-microphone transfer matrix measurements with acoustic network models of swirl burners

    NASA Astrophysics Data System (ADS)

    Fischer, A.; Hirsch, C.; Sattelmayer, T.

    2006-11-01

    Utilizing the close analogy between electronic circuits and ducted acoustic systems, mathematical methods originally developed for the characterization of electronic networks are applied to the experimental acoustic plane wave characterization of swirl burners with complex geometries. The experiments presented in the paper show that the acoustic behavior of swirl generators can be quantitatively evaluated treating them as acoustic two-ports. Such acoustic two-ports are presented in forms of transfer-, scattering- and mobility matrices of the element. In the acoustic burner study dynamic pressure measurements were made at several locations of a tubular combustor test rig for two acoustically independent states, which were generated by forcing with sirens at the opposite ends of the setup. The technique for the experimental evaluation of acoustic transfer matrices of complex geometries on the basis of these dynamic pressure measurements is illustrated. As an alternative to the experiment, the evaluation of the acoustic behavior of acoustic systems is assessed using acoustic networks consisting of simple acoustic elements like ducts, bends, junctions and sudden area changes with transfer matrices, which are derived from first principles. In the paper, a network model representing the transfer characteristics of swirl burners is presented and compared with the previously measured transfer matrices. Although the burner geometry is rather complex, its acoustic behavior can be successfully mapped to a network consisting of a serial connection of nine elements with only minor adjustment of one parameter.

  13. Acoustic Measurements for Small Solid Rocket Motors

    NASA Technical Reports Server (NTRS)

    Vargas, Magda B.; Kenny, R. Jeremy

    2010-01-01

    Models have been developed to predict large solid rocket motor acoustic loads based on the scaling of small solid rocket motors. MSFC has measured several small solid rocket motors in horizontal and launch configurations to anchor these models. Solid Rocket Test Motor (SRTM) has ballistics similar to the Reusable Solid Rocket Motor (RSRM) therefore a good choice for acoustic scaling. Acoustic measurements were collected during the test firing of the Insulation Configuration Extended Length (ICXL) 7,6, and 8 (in firing order) in order to compare to RSRM horizontal firing data. The scope of this presentation includes: Acoustic test procedures and instrumentation implemented during the three SRTM firings and Data analysis method and general trends observed in the data.

  14. Reflectance measurement validation using acoustic horns

    PubMed Central

    Rasetshwane, Daniel M.; Neely, Stephen T.

    2015-01-01

    Variability in wideband acoustic reflectance (and absorbance) measurements adversely affects the clinical utility of reflectance for diagnosis of middle-ear disorders. A reflectance standard would encourage consistency across different measurement systems and help identify calibration related issues. Theoretical equations exist for the reflectance of finite-length exponential, conical, and parabolic acoustic horns. Reflectance measurements were repeatedly made in each of these three horn shapes and the results were compared to the corresponding theoretical reflectance. A method is described of adjusting acoustic impedance measurements to compensate for spreading of the wave front that propagates from the small diameter sound port of the probe to the larger diameter of the acoustic cavity. Agreement between measured and theoretical reflectance was less than 1 dB at most frequencies in the range from 0.2 to 10 kHz. Pearson correlation coefficients were greater than 0.95 between measured and theoretical time-domain reflectance within the flare region of the horns. The agreement suggests that the distributed reflectance of acoustic horns may be useful for validating reflectance measurements made in human ear canals; however, refinements to reflectance measurement methods may still be needed. PMID:26520306

  15. Reflectance measurement validation using acoustic horns.

    PubMed

    Rasetshwane, Daniel M; Neely, Stephen T

    2015-10-01

    Variability in wideband acoustic reflectance (and absorbance) measurements adversely affects the clinical utility of reflectance for diagnosis of middle-ear disorders. A reflectance standard would encourage consistency across different measurement systems and help identify calibration related issues. Theoretical equations exist for the reflectance of finite-length exponential, conical, and parabolic acoustic horns. Reflectance measurements were repeatedly made in each of these three horn shapes and the results were compared to the corresponding theoretical reflectance. A method is described of adjusting acoustic impedance measurements to compensate for spreading of the wave front that propagates from the small diameter sound port of the probe to the larger diameter of the acoustic cavity. Agreement between measured and theoretical reflectance was less than 1 dB at most frequencies in the range from 0.2 to 10 kHz. Pearson correlation coefficients were greater than 0.95 between measured and theoretical time-domain reflectance within the flare region of the horns. The agreement suggests that the distributed reflectance of acoustic horns may be useful for validating reflectance measurements made in human ear canals; however, refinements to reflectance measurement methods may still be needed.

  16. Pressure potential and stability analysis in an acoustical noncontact transportation

    NASA Astrophysics Data System (ADS)

    Li, J.; Liu, C. J.; Zhang, W. J.

    2017-01-01

    Near field acoustic traveling wave is one of the most popular principles in noncontact manipulations and transportations. The stability behavior is a key factor in the industrial applications of acoustical noncontact transportation. We present here an in-depth analysis of the transportation stability of a planar object levitated in near field acoustic traveling waves. To more accurately describe the pressure distributions on the radiation surface, a 3D nonlinear traveling wave model is presented. A closed form solution is derived based on the pressure potential to quantitatively calculate the restoring forces and moments under small disturbances. The physical explanations of the effects of fluid inertia and the effects of non-uniform pressure distributions are provided in detail. It is found that a vibration rail with tapered cross section provides more stable transportation than a rail with rectangular cross section. The present study sheds light on the issue of quantitative evaluation of stability in acoustic traveling waves and proposes three main factors that influence the stability: (a) vibration shape, (b) pressure distribution and (c) restoring force/moment. It helps to provide a better understanding of the physics behind the near field acoustic transportation and provide useful design and optimization tools for industrial applications.

  17. Automated Blood Pressure Measurement

    NASA Technical Reports Server (NTRS)

    1978-01-01

    The Vital-2 unit pictured is a semi-automatic device that permits highly accurate blood pressure measurement, even by untrained personnel. Developed by Meditron Instrument Corporation, Milford, New Hampshire, it is based in part on NASA technology found in a similar system designed for automatic monitoring of astronauts' blood pressure. Vital-2 is an advancement over the familiar arm cuff, dial and bulb apparatus customarily used for blood pressure checks. In that method, the physician squeezes the bulb to inflate the arm cuff, which restricts the flow of blood through the arteries. As he eases the pressure on the arm, he listens, through a stethoscope, to the sounds of resumed blood flow as the arteries expand and contract. Taking dial readings related to sound changes, he gets the systolic (contracting) and diastolic (expanding) blood pressure measurements. The accuracy of the method depends on the physician's skill in interpreting the sounds. Hospitals sometimes employ a more accurate procedure, but it is "invasive," involving insertion of a catheter in the artery.

  18. Acoustic Doppler discharge-measurement system

    USGS Publications Warehouse

    Simpson, Michael R.; Oltmann, Richard N.; ,

    1990-01-01

    A discharge-measurement system that uses a vessel-mounted acoustic Doppler current profiler has been developed and tested by the U.S. Geological Survey. Discharge measurements using the system require a fraction of the time needed for conventional current-meter discharge measurements and do not require shore-based navigational aids or tag lines for positioning the vessel.

  19. Drag Measurements of Porous Plate Acoustic Liners

    NASA Technical Reports Server (NTRS)

    Wolter, John D.

    2005-01-01

    This paper presents the results of direct drag measurements on a variety of porous plate acoustic liners. The existing literature describes numerous studies of drag on porous walls with injection or suction, but relatively few of drag on porous plates with neither injection nor suction. Furthermore, the porosity of the porous plate in existing studies is much lower than typically used in acoustic liners. In the present work, the acoustic liners consisted of a perforated face sheet covering a bulk acoustic absorber material. Factors that were varied in the experiment were hole diameter, hole pattern, face sheet thickness, bulk material type, and size of the gap (if any) between the face sheet and the absorber material.

  20. Sound pressure level gain in an acoustic metamaterial cavity.

    PubMed

    Song, Kyungjun; Kim, Kiwon; Hur, Shin; Kwak, Jun-Hyuk; Park, Jihyun; Yoon, Jong Rak; Kim, Jedo

    2014-12-11

    The inherent attenuation of a homogeneous viscous medium limits radiation propagation, thereby restricting the use of many high-frequency acoustic devices to only short-range applications. Here, we design and experimentally demonstrate an acoustic metamaterial localization cavity which is used for sound pressure level (SPL) gain using double coiled up space like structures thereby increasing the range of detection. This unique behavior occurs within a subwavelength cavity that is 1/10(th) of the wavelength of the incident acoustic wave, which provides up to a 13 dB SPL gain. We show that the amplification results from the Fabry-Perot resonance of the cavity, which has a simultaneously high effective refractive index and effective impedance. We also experimentally verify the SPL amplification in an underwater environment at higher frequencies using a sample with an identical unit cell size. The versatile scalability of the design shows promising applications in many areas, especially in acoustic imaging and underwater communication.

  1. Sound Pressure Level Gain in an Acoustic Metamaterial Cavity

    NASA Astrophysics Data System (ADS)

    Song, Kyungjun; Kim, Kiwon; Hur, Shin; Kwak, Jun-Hyuk; Park, Jihyun; Yoon, Jong Rak; Kim, Jedo

    2014-12-01

    The inherent attenuation of a homogeneous viscous medium limits radiation propagation, thereby restricting the use of many high-frequency acoustic devices to only short-range applications. Here, we design and experimentally demonstrate an acoustic metamaterial localization cavity which is used for sound pressure level (SPL) gain using double coiled up space like structures thereby increasing the range of detection. This unique behavior occurs within a subwavelength cavity that is 1/10th of the wavelength of the incident acoustic wave, which provides up to a 13 dB SPL gain. We show that the amplification results from the Fabry-Perot resonance of the cavity, which has a simultaneously high effective refractive index and effective impedance. We also experimentally verify the SPL amplification in an underwater environment at higher frequencies using a sample with an identical unit cell size. The versatile scalability of the design shows promising applications in many areas, especially in acoustic imaging and underwater communication.

  2. The acoustics and unsteady wall pressure of a circulation control airfoil

    NASA Astrophysics Data System (ADS)

    Silver, Jonathan C.

    A Circulation Control (CC) airfoil uses a wall jet exiting onto a rounded trailing edge to generate lift via the Coanda effect. The aerodynamics of the CC airfoil have been studied extensively. The acoustics of the airfoil are, however, much less understood. The primary goal of the present work was to study the radiated sound and unsteady surface pressures of a CC airfoil. The focus of this work can be divided up into three main categories: characterizing the unsteady surface pressures, characterizing the radiated sound, and understanding the acoustics from surface pressures. The present work is the first to present the unsteady surface pressures from the trailing edge cylinder of a circulation control airfoil. The auto-spectral density of the unsteady surface pressures at various locations around the trailing edge are presented over a wide range of the jets momentum coefficient. Coherence of pressure and length scales were computed and presented. Single microphone measurements were made at a range of angles for a fixed observer distance in the far field. Spectra are presented for select angles to show the directivity of the airfoil's radiated sound. Predictions of the acoustics were made from unsteady surface pressures via Howe's curvature noise model and a modified Curle's analogy. A summary of the current understanding of the acoustics from a CC airfoil is given along with suggestions for future work.

  3. DETONATION PRESSURE MEASUREMENTS ON PETN

    SciTech Connect

    Green, L G; Lee, E L

    2006-06-23

    PETN is widely recognized as an example of nearly ideal detonation performance. The chemical composition is such that little or no carbon is produced in the detonation products. The reaction zone width is less than currently detectable. (<1 ns) Observations on PETN have thus become a baseline for EOS model predictions. It has therefore become important to characterize the detonation parameters as accurately as possible in order to provide the most exacting comparisons of EOS predictions with experimental results. We undertook a painstaking review of the detonation pressure measurements reported in an earlier work that was presented at the Fifth Detonation Symposium and found that corrections were required in determining the shock velocity in the PMMA witness material. We also refined the impedance calculation to account for the difference between the usual ''acoustic'' method and the more accurate Riemann integral. Our review indicates that the CJ pressures previously reported for full density PETN require an average lowering of about 6 percent. The lower densities require progressively smaller corrections. We present analysis of the records, supporting hydrodynamic simulations, the Riemann integral results, and EOS parameter values derived from the revised results.

  4. Pressure Pulse Measurements Using Optical Hydrophone Principles

    NASA Astrophysics Data System (ADS)

    Ueberle, Friedrich; Jamshidi-Rad, Abtin

    2011-02-01

    Pressure pulses are used in extracorporeal lithotripsy, pain therapy and other medical applications. Typical lithotripter pulses reach positive pressure amplitudes of ca. 20 to more than 100 MPa and negative pressures of -5 to more than -20 MPa, depending on the focusing properties and energy settings of the source. The IEC standard 61846, which defines the acoustic parameters of pressure pulse fields, describes the properties of "Focus-" and "Field-" type hydrophones, which were originally specified as PVDF sensors. During recent years, two types of optical sensors were developed, which are based on the principle of measuring reflection changes of a laser beam at a glass-water surface: The fiber optic sensor using bare optical fibers and the "light spot" sensor using a thick glass block. Measurements with both hydrophone types were made with a low pressure transducer (p+max=3 MPa), and two electromagnetic lithotripter sources with the same total acoustic energy (E5MPa=90mJ), one with a wide focus (FWHM = 11 mm, p+max = 30 MPa) and the other with a small focus (FWHM = 3,5 mm, p+max = 83 MPa). The results show that both optical sensor types provide high pressure-time signal fidelity comparable to PVDF membrane sensors. Both optical hydrophones can serve as "Focus-" and "Field-" hydrophones as defined in the lithotripsy measurement standard IEC 61846.

  5. Full bandwidth calibration procedure for acoustic probes containing a pressure and particle velocity sensor.

    PubMed

    Basten, Tom G H; de Bree, Hans-Elias

    2010-01-01

    Calibration of acoustic particle velocity sensors is still difficult due to the lack of standardized sensors to compare with. Recently it is shown by Jacobsen and Jaud [J. Acoust. Soc. Am. 120, 830-837 (2006)] that it is possible to calibrate a sound pressure and particle velocity sensor in free field conditions at higher frequencies. This is done by using the known acoustic impedance at a certain distance of a spherical loudspeaker. When the sound pressure is measured with a calibrated reference microphone, the particle velocity can be calculated from the known impedance and the measured pressure. At lower frequencies, this approach gives unreliable results. The method is now extended to lower frequencies by measuring the acoustic pressure inside the spherical source. At lower frequencies, the sound pressure inside the sphere is proportional to the movement of the loudspeaker membrane. If the movement is known, the particle velocity in front of the loudspeaker can be derived. This low frequency approach is combined with the high frequency approach giving a full bandwidth calibration procedure which can be used in free field conditions using a single calibration setup. The calibration results are compared with results obtained with a standing wave tube.

  6. Acoustic Measurement of Potato Cannon Velocity

    ERIC Educational Resources Information Center

    Courtney, Michael; Courtney, Amy

    2007-01-01

    Potato cannon velocity can be measured with a digitized microphone signal. A microphone is attached to the potato cannon muzzle, and a potato is fired at an aluminum target about 10 m away. Flight time can be determined from the acoustic waveform by subtracting the time in the barrel and time for sound to return from the target. The potato…

  7. Acoustical measurements in ancient Roman theatres

    NASA Astrophysics Data System (ADS)

    Farnetani, Andrea; Fausti, Patrizio; Pompoli, Roberto; Prodi, Nicola

    2004-05-01

    The Greek and Roman theatres are among the most precious and spectacular items of cultural heritage in the Mediterranean countries. The theatres are famous not only for their impressive architecture, but also for the acoustic qualities. For this reason it is important to consider these theatres as an acoustical heritage and to study their sound field. Within the activities of the ERATO (identification Evaluation and Revival of the Acoustical heritage of ancient Theatres and Odea) project, acoustical measurements were taken in well-preserved ancient Roman theatres at Aspendos (Turkey) and Jerash (Jordan). Roman theatres have an impressive stage building that forms a back wall in the orchestra area, and it was found that, from the analysis of the acoustical parameters, the reverberation time (e.g., 1.7 s at middle frequencies in the theatre of Aspendos) is quite long compared not only with other open-space theatres but also with closed spaces. Contrary to modern halls the clarity is high and this fact, together with a low sound level in most of the seats, gives the sound field a unique character.

  8. Investigations of High Pressure Acoustic Waves in Resonators with Seal-like Features

    NASA Technical Reports Server (NTRS)

    Daniels, Christopher; Steinetz, Bruce; Finkbeiner, Joshua

    2003-01-01

    A conical resonator (having a dissonant acoustic design) was tested in four configurations: (1) baseline resonator with closed ends and no blockage, (2) closed resonator with internal blockage, (3) ventilated resonator with no blockage, and (4) ventilated resonator with an applied pressure differential. These tests were conducted to investigate the effects of blockage and ventilation holes on dynamic pressurization. Additionally, the investigation was to determine the ability of acoustic pressurization to impede flow through the resonator. In each of the configurations studied, the entire resonator was oscillated at the gas resonant frequency while dynamic pressure, static pressure, and temperature of the fluid were measured. In the final configuration, flow through the resonator was recorded for three oscillation conditions. Ambient condition air was used as the working fluid.

  9. Acoustic Determination of Methane Hydrate Disssociation Pressures

    DTIC Science & Technology

    2011-07-01

    coring operations between 1998 and 2000 and stored in liquid nitrogen at at- mospheric pressure...recent years , several groups have attempted to model the stability regimes of gas hydrates. Parrish and Prausnitz (Ref. [13]) used experi- mental data to...t c u rr e n t e x p e ri m e n t P a rr is h & P ra u s n it z , 1 9 7 2 P a rr is h & P ra u s n it z , 1 9 7 2 D ic k e n s & Q u in b

  10. An Expendable Source for Measuring Shallow Water Acoustic Propagation and Geo-Acoustic Bottom Properties

    DTIC Science & Technology

    2015-09-30

    1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. An Expendable Source for Measuring Shallow Water Acoustic ...Propagation and Geo- Acoustic Bottom Properties Harry A DeFerrari RSMAS – University of Miami 4600 Rickenbacker Causeway Miami FL. 33149...broadband source is being developed that transmits high gain m-sequence to clandestinly measure pulse response of shallow water acoustic propagation

  11. Pressure Measurement Sensor

    NASA Technical Reports Server (NTRS)

    1997-01-01

    FFPI Industries Inc. is the manufacturer of fiber-optic sensors that furnish accurate pressure measurements in internal combustion chambers. Such an assessment can help reduce pollution emitted by these engines. A chief component in the sensor owes its seven year- long development to Lewis Research Center funding to embed optical fibers and sensors in metal parts. NASA support to Texas A&M University played a critical role in developing this fiber optic technology and led to the formation of FFPI Industries and the production of fiber sensor products. The simple, rugged design of the sensor offers the potential for mass production at low cost. Widespread application of the new technology is forseen, from natural gas transmission, oil refining and electrical power generation to rail transport and the petrochemical paper product industry.

  12. A Neural Network/Acoustic Emission Analysis of Impact Damaged Graphite/Epoxy Pressure Vessels

    NASA Technical Reports Server (NTRS)

    Walker, James L.; Hill, Erik v. K.; Workman, Gary L.; Russell, Samuel S.

    1995-01-01

    Acoustic emission (AE) signal analysis has been used to measure the effects of impact damage on burst pressure in 5.75 inch diameter, inert propellant filled, filament wound pressure vessels. The AE data were collected from fifteen graphite/epoxy pressure vessels featuring five damage states and three resin systems. A burst pressure prediction model was developed by correlating the AE amplitude (frequency) distribution, generated during the first pressure ramp to 800 psig (approximately 25% of the average expected burst pressure for an undamaged vessel) to known burst pressures using a four layered back propagation neural network. The neural network, trained on three vessels from each resin system, was able to predict burst pressures with a worst case error of 5.7% for the entire fifteen bottle set.

  13. Measurement and Characterization of Space Shuttle Solid Rocket Motor Plume Acoustics

    NASA Technical Reports Server (NTRS)

    Kenny, Robert Jeremy

    2009-01-01

    NASA's current models to predict lift-off acoustics for launch vehicles are currently being updated using several numerical and empirical inputs. One empirical input comes from free-field acoustic data measured at three Space Shuttle Reusable Solid Rocket Motor (RSRM) static firings. The measurements were collected by a joint collaboration between NASA - Marshall Space Flight Center, Wyle Labs, and ATK Launch Systems. For the first time NASA measured large-thrust solid rocket motor plume acoustics for evaluation of both noise sources and acoustic radiation properties. Over sixty acoustic free-field measurements were taken over the three static firings to support evaluation of acoustic radiation near the rocket plume, far-field acoustic radiation patterns, plume acoustic power efficiencies, and apparent noise source locations within the plume. At approximately 67 m off nozzle centerline and 70 m downstream of the nozzle exit plan, the measured overall sound pressure level of the RSRM was 155 dB. Peak overall levels in the far field were over 140 dB at 300 m and 50-deg off of the RSRM thrust centerline. The successful collaboration has yielded valuable data that are being implemented into NASA's lift-off acoustic models, which will then be used to update predictions for Ares I and Ares V liftoff acoustic environments.

  14. Measuring Acoustic Noise around Kahoolawe Island.

    DTIC Science & Technology

    1981-10-01

    NAVAL OCEAN SYSTEMS CENTER SAN DIEGO, CALIFORNIA 92152 C y 2 .V ANAVAL OCEAN SYSTEMS CENTER, SAN DIEGO, CA 92152 AN ACTIV IT Y OF THE NAVAL... Ocean Systems Center (NOSC), Code 512, on NSAP Project TH-1 -80, "Measurement of Acoustic Noise Around Kahoolawe". CDR J. W. Carlmark, USN, COMTHIRDFLT N...Bioacoustics & Bionics Division Biosciences Department ,or -.. .- ?---1 1 : ’" " "’ .... .-j UNCLASSIFIED SECURITY CLASSIFICATION OF THIS PAGE (When Data

  15. Measuring acoustic emissions in an avalanche slope

    NASA Astrophysics Data System (ADS)

    Reiweger, Ingrid; Schweizer, Jürg

    2014-05-01

    Measurements of acoustic emissions are a common technique for monitoring damage and predicting imminent failure of a material. Within natural hazards it has already been used to successfully predict the break-off of a hanging glacier. To explore the applicability of the acoustic emission (AE) technique for avalanche prediction, we installed two acoustic sensors (with 30 kHz and 60 kHz resonance frequency) in an avalanche prone slope at the Mittelgrat in the Parsenn ski area above Davos, Switzerland. The slope is north-east facing, frequently wind loaded, and approximately 35° steep. The AE signals - in particular the event energy and waiting time distributions - were compared with slope stability. The latter was determined by observing avalanche activity. The results of two winter's measurements yielded that the exponent β of the inverse cumulative distribution of event energy showed a significant drop (from a value of 3.5 to roughly 2.5) at very unstable conditions, i.e. on the three days during our measurement periods when spontaneous avalanches released on our study slope.

  16. Acoustic Doppler velocimeter-induced acoustic streaming and its implications for measurement

    NASA Astrophysics Data System (ADS)

    Poindexter, C. M.; Rusello, P. J.; Variano, E. A.

    2011-05-01

    The acoustic Doppler velocimeter (ADV) is widely used for the characterization of fluid flow. Secondary flows ("acoustic streaming") generated by the ADV's acoustic pulses may affect the accuracy of measurements in experiments with small velocities. We assessed the impact of acoustic streaming on flow measurement using particle image velocimetry. The probes of two different ADVs were successively mounted in a tank of quiescent water. The probes' ultrasound emitters were aligned with a laser light sheet. Observed flow was primarily in the axial direction, accelerating from the ultrasound emitter and peaking within centimeters of the velocimeter sampling volume before dropping off. We measured the dependence of acoustic streaming velocity on ADV configuration, finding that different settings induce streaming ranging from negligible to more than 2.0 cm s-1. From these results, we describe cases where acoustic streaming affects velocity measurements and also cases where ADVs accurately measure their own acoustic streaming.

  17. Compensating for ear-canal acoustics when measuring otoacoustic emissions.

    PubMed

    Charaziak, Karolina K; Shera, Christopher A

    2017-01-01

    Otoacoustic emissions (OAEs) provide an acoustic fingerprint of the inner ear, and changes in this fingerprint may indicate changes in cochlear function arising from efferent modulation, aging, noise trauma, and/or exposure to harmful agents. However, the reproducibility and diagnostic power of OAE measurements is compromised by the variable acoustics of the ear canal, in particular, by multiple reflections and the emergence of standing waves at relevant frequencies. Even when stimulus levels are controlled using methods that circumvent standing-wave problems (e.g., forward-pressure-level calibration), distortion-product otoacoustic emission (DPOAE) levels vary with probe location by 10-15 dB near half-wave resonant frequencies. The method presented here estimates the initial outgoing OAE pressure wave at the eardrum from measurements of the conventional OAE, allowing one to separate the emitted OAE from the many reflections trapped in the ear canal. The emitted pressure level (EPL) represents the OAE level that would be recorded were the ear canal replaced by an infinite tube with no reflections. When DPOAEs are expressed using EPL, their variation with probe location decreases to the test-retest repeatability of measurements obtained at similar probe positions. EPL provides a powerful way to reduce the variability of OAE measurements and improve their ability to detect cochlear changes.

  18. 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.

  19. Ultrasonic Apparatus and Technique to Measure Changes in Intracranial Pressure

    NASA Astrophysics Data System (ADS)

    Yost, William T.; Cantrell, John H.

    2002-11-01

    Changes in intracranial pressure can be measured dynamically and non-invasively by monitoring one or more cerebrospinal fluid pulsatile components. Pulsatile components such as systolic and diastolic blood pressures are partially transferred to the cerebrospinal fluid by way of blood vessels contained in the surrounding brain tissue and membrane. As intracranial pressure varies these cerebrospinal fluid pulsatile components also vary. Thus, intracranial pressure can be dynamically measured. Furthermore, use of acoustics allows the measurement to be completely non-invasive. In the preferred embodiment, phase comparison of a reflected acoustic signal to a reference signal using a constant frequency pulsed phase-locked-loop ultrasonic device allows the pulsatile components to be monitored. Calibrating the device by inducing a known change in intracranial pressure allows conversion to changes in intracranial pressure.

  20. Ultrasonic Apparatus and Technique to Measure Changes in Intracranial Pressure

    NASA Technical Reports Server (NTRS)

    Yost, William T. (Inventor); Cantrell, John H. (Inventor)

    2002-01-01

    Changes in intracranial pressure can be measured dynamically and non-invasively by monitoring one or more cerebrospinal fluid pulsatile components. Pulsatile components such as systolic and diastolic blood pressures are partially transferred to the cerebrospinal fluid by way of blood vessels contained in the surrounding brain tissue and membrane. As intracranial pressure varies these cerebrospinal fluid pulsatile components also vary. Thus, intracranial pressure can be dynamically measured. Furthermore, use of acoustics allows the measurement to be completely non-invasive. In the preferred embodiment, phase comparison of a reflected acoustic signal to a reference signal using a constant frequency pulsed phase-locked-loop ultrasonic device allows the pulsatile components to be monitored. Calibrating the device by inducing a known change in intracranial pressure allows conversion to changes in intracranial pressure.

  1. Measurement of unsteady surface pressure on rotor blades of fans by pressure-sensitive paint

    NASA Astrophysics Data System (ADS)

    Yokoyama, Hiroshi; Miura, Kouhei; Iida, Akiyoshi

    2017-01-01

    To clarify the unsteady pressure distributions on the rotor blades of an axial fan, a pressure-sensitive paint (PSP) technique was used. To capture the image of the rotating fan as a static image, an optical derotator method with a dove prism was adopted. It was confirmed by preliminary experiments with a resonator and a speaker that the pressure fluctuations with 347 Hz can be measured by the present PSP. The measured mean pressure distributions were compared with the predicted results based on large-eddy simulations. The measured instantaneous surface pressure is instrumental to identify acoustic source of fan noise in the design stage.

  2. Acoustic measuring techniques for suspended sediment

    NASA Astrophysics Data System (ADS)

    Gruber, P.; Felix, D.; Storti, G.; Lattuada, M.; Fleckenstein, P.; Deschwanden, F.

    2016-11-01

    Acoustic signals can be used in various ways for suspended sediment monitoring. One possibility which lends itself particularly well in the context of hydropower plants (HPPs), is to use installations for acoustic discharge measurement (ADM). Such installations already exist at waterways of many HPPs. Similar to certain turbidimeters, the attenuation of the forward scattered signal travelling through the water-sediment mixture is correlated with suspended sediment concentration (SSC). This correlation can be based on reference SSCs, e.g. from gravimetric analyses of bottle samples. Without the need of additional sensors and practically maintenance-free, this method is used successfully in the HPP Fieschertal to warn the HPP operator of high SSC to prevent excessive turbine abrasion. Acoustic methods and systems that allow for estimating both SSC and particle size distribution (PSD) are under development. The simultaneous determination of SSC and PSD is not possible using a single frequency. Therefore, multi-frequency approaches are investigated for generally scattered signals. When backscattered signals are used, a stronger frequency dependency can be exploited. However, the reliable simultaneous determination of particle size (and distribution) and concentration is still a major challenge due to a low signal-to-noise ratio and an ill- posed problem of estimating concentration and size from recorded signals. The optimal setup configuration (angles, frequencies) for such a system is not unique and further investigations are recommended.

  3. Relationship between acoustic measures and judgments of intelligibility in Parkinson's disease: a within-speaker approach.

    PubMed

    Feenaughty, Lynda; Tjaden, Kris; Sussman, Joan

    2014-11-01

    This study investigated the acoustic basis of within-speaker, across-utterance variation in sentence intelligibility for 12 speakers with dysarthria secondary to Parkinson's disease (PD). Acoustic measures were also obtained for 12 healthy controls for comparison to speakers with PD. Speakers read sentences using their typical speech style. Acoustic measures of speech rate, articulatory rate, fundamental frequency, sound pressure level and F2 interquartile range (F2 IQR) were obtained. A group of listeners judged sentence intelligibility using a computerized visual-analog scale. Relationships between judgments of intelligibility and acoustic measures were determined for individual speakers with PD. Relationships among acoustic measures were also quantified. Although considerable variability was noted, articulatory rate, fundamental frequency and F2 IQR were most frequently associated with within-speaker variation in sentence intelligibility. Results suggest that diversity among speakers with PD should be considered when interpreting results from group analyses.

  4. Reconstruction of an acoustic pressure field in a resonance tube by particle image velocimetry.

    PubMed

    Kuzuu, K; Hasegawa, S

    2015-11-01

    A technique for estimating an acoustic field in a resonance tube is suggested. The estimation of an acoustic field in a resonance tube is important for the development of the thermoacoustic engine, and can be conducted employing two sensors to measure pressure. While this measurement technique is known as the two-sensor method, care needs to be taken with the location of pressure sensors when conducting pressure measurements. In the present study, particle image velocimetry (PIV) is employed instead of a pressure measurement by a sensor, and two-dimensional velocity vector images are extracted as sequential data from only a one- time recording made by a video camera of PIV. The spatial velocity amplitude is obtained from those images, and a pressure distribution is calculated from velocity amplitudes at two points by extending the equations derived for the two-sensor method. By means of this method, problems relating to the locations and calibrations of multiple pressure sensors are avoided. Furthermore, to verify the accuracy of the present method, the experiments are conducted employing the conventional two-sensor method and laser Doppler velocimetry (LDV). Then, results by the proposed method are compared with those obtained with the two-sensor method and LDV.

  5. Sensing the characteristic acoustic impedance of a fluid utilizing acoustic pressure waves

    PubMed Central

    Antlinger, Hannes; Clara, Stefan; Beigelbeck, Roman; Cerimovic, Samir; Keplinger, Franz; Jakoby, Bernhard

    2012-01-01

    Ultrasonic sensors can be used to determine physical fluid parameters like viscosity, density, and speed of sound. In this contribution, we present the concept for an integrated sensor utilizing pressure waves to sense the characteristic acoustic impedance of a fluid. We note that the basic setup generally allows to determine the longitudinal viscosity and the speed of sound if it is operated in a resonant mode as will be discussed elsewhere. In this contribution, we particularly focus on a modified setup where interferences are suppressed by introducing a wedge reflector. This enables sensing of the liquid's characteristic acoustic impedance, which can serve as parameter in condition monitoring applications. We present a device model, experimental results and their evaluation. PMID:23565036

  6. Acoustics measurements in normal jet impingement

    NASA Technical Reports Server (NTRS)

    Kleis, S. J.

    1977-01-01

    The dependence of far field acoustic measurements for a uniform jet on nozzle to plate spacing for small dimensionless spacings (h/d - 0.75 to 3.0) was investigated. Spectra from a real time analyzer were read and processed by an HP 2116 minicomputer in on-line mode. Similar data was generated for a fully developed pipe flow exit condition jet to compare with other investigations. The data base for normal jet impingement was extended to smaller values of nozzle to plate spacing. The effects of slight noise heating (30 deg rise) of the jet on the far field noise produced by the impinging jet are demonstrated.

  7. Acoustic pressure wound therapy in the treatment of stage II pressure ulcers.

    PubMed

    Thomas, Raenell

    2008-11-01

    Pressure ulcers are localized skin injuries secondary to unrelieved pressure or friction. Patients with immobility issues are at increased risk for developing pressure ulcers. In 2004, stricter federal regulations for prevention and treatment of pressure ulcers in institutional settings--eg, long-term care facilities--were introduced. Effective, low-cost treatments for pressure ulcers are needed; acoustic pressure wound therapy (APWT), a noncontact, low-frequency, therapeutic ultrasound system, is one option. A retrospective case series of six long-term care patients (two men and one woman, age range 61 to 92 years), each with one Stage II pressure ulcer, is presented. Acoustic pressure wound therapy was provided as an adjunct to standard treatment that included balsam of Peru/castor oil/trypsin ointment, hydrogel, hydrocolloid dressings, silver dressings, and offloading. Outcomes (days to healing) were determined through changes in wound dimensions. Study participants each received APWT for 3 to 4 minutes three to four times weekly. In four of the six wounds, the average number of days to healing was 22. One of the two remaining patients discontinued treatment at 95% healed; treatment for the sixth patient was ongoing due to hospitalization that delayed APWT. In a long-term care setting, APWT added to standard of care may accelerate healing of Stage II pressure ulcers.

  8. Precision of Four Acoustic Bone Measurement Devices

    NASA Technical Reports Server (NTRS)

    Miller, Christopher; Rianon, Nahid; Feiveson, Alan; Shackelford, Linda; LeBlanc, Adrian

    2000-01-01

    Though many studies have quantified the precision of various acoustic bone measurement devices, it is difficult to directly compare the results among the studies, because they used disparate subject pools, did not specify the estimation methodology, or did not use consistent definitions for various precision characteristics. In this study, we used a repeated measures design protocol to directly determine the precision characteristics of four acoustic bone measurement devices: the Mechanical Response Tissue Analyzer (MRTA), the UBA-575+, the SoundScan 2000 (S2000), and the Sahara Ultrasound Bone Analyzer. Ten men and ten women were scanned on all four devices by two different operators at five discrete time points: Week 1, Week 2, Week 3, Month 3 and Month 6. The percent coefficient of variation (%CV) and standardized coefficient of variation were computed for the following precision characteristics: interoperator effect, operator-subject interaction, short-term error variance, and long-term drift. The MRTA had high interoperator errors for its ulnar and tibial stiffness measures and a large long-term drift in its tibial stiffness measurement. The UBA-575+ exhibited large short-term error variances and long-term drift for all three of its measurements. The S2000's tibial speed of sound measurement showed a high short-term error variance and a significant operator-subject interaction but very good values (less than 1%) for the other precision characteristics. The Sahara seemed to have the best overall performance, but was hampered by a large %CV for short-term error variance in its broadband ultrasound attenuation measure.

  9. Precision of Four Acoustic Bone Measurement Devices

    NASA Technical Reports Server (NTRS)

    Miller, Christopher; Feiveson, Alan H.; Shackelford, Linda; Rianon, Nahida; LeBlanc, Adrian

    2000-01-01

    Though many studies have quantified the precision of various acoustic bone measurement devices, it is difficult to directly compare the results among the studies, because they used disparate subject pools, did not specify the estimation methodology, or did not use consistent definitions for various precision characteristics. In this study, we used a repeated measures design protocol to directly determine the precision characteristics of four acoustic bone measurement devices: the Mechanical Response Tissue Analyzer (MRTA), the UBA-575+, the SoundScan 2000 (S2000), and the Sahara Ultrasound Done Analyzer. Ten men and ten women were scanned on all four devices by two different operators at five discrete time points: Week 1, Week 2, Week 3, Month 3 and Month 6. The percent coefficient of variation (%CV) and standardized coefficient of variation were computed for the following precision characteristics: interoperator effect, operator-subject interaction, short-term error variance, and long-term drift, The MRTA had high interoperator errors for its ulnar and tibial stiffness measures and a large long-term drift in its tibial stiffness measurement. The UBA-575+ exhibited large short-term error variances and long-term drift for all three of its measurements. The S2000's tibial speed of sound measurement showed a high short-term error variance and a significant operator-subject interaction but very good values ( < 1%) for the other precision characteristics. The Sahara seemed to have the best overall performance, but was hampered by a large %CV for short-term error variance in its broadband ultrasound attenuation measure.

  10. Flight Acoustics Measurement Techniques and Applications

    NASA Technical Reports Server (NTRS)

    Preisser, J. S.; Marcolini, M. A.

    1998-01-01

    Careful consideration must be given to data acquisition and analysis techniques in the design of experiments for the measurement of noise generated by flight vehicles. Although noise measurement locations and data reduction procedures are specified for aircraft certification by FAA and ICAO directives, for example, there are virtually no established procedures for aircraft noise measurement for other purposes. To optimize the quality and quantity of information obtained in a flight acoustics experiment, microphone layout, data acquisition, and analysis must be tailored to the specific test objective. This paper will review flight acoustics technology at NASA Langley Research Center developed over the past decade. In particular, the paper will focus on flight experiments performed for three diverse objectives: (1) research applications, such as noise prediction code validation, (2) noise impact modeling, and (3) noise abatement flight procedures. To best achieve these diverse objectives, different deployments of microphone systems on the ground are required, and different data analysis techniques are needed. In all cases, accurate positioning of the aircraft synchronized in time with the data recording is necessary. However, there are some restrictions on flight operations unique to each case for the methods to properly work.

  11. Underwater hybrid near-field acoustical holography based on the measurement of vector hydrophone array

    NASA Astrophysics Data System (ADS)

    Hu, Bo; Yang, Desen; Sun, Yu

    2010-06-01

    Hybrid near-field acoustical holography (NAH) is developed for reconstructing acoustic radiation from a cylindrical source in a complex underwater environment. In hybrid NAH, we combine statistically optimized near-field acoustical holography (SONAH) and broadband acoustical holography from intensity measurements (BAHIM) to reconstruct the underwater cylindrical source field. First, the BAHIM is utilized to regenerate as much acoustic pressures on the hologram surface as necessary, and then the acoustic pressures are taken as input to the formulation implemented numerically by SONAH. The main advantages of this technology are that the complex pressure on the hologram surface can be reconstructed without reference signal, and the measurement array can be smaller than the source, thus the practicability and efficiency of this technology are greatly enhanced. Numerical examples of a cylindrical source are demonstrated. Test results show that hybrid NAH can yield a more accurate reconstruction than conventional NAH. Then, an experiment has been carried out with a vector hydrophone array. The experimental results show the advantage of hybrid NAH in the reconstruction of an acoustic field and the feasibility of using a vector hydrophone array in an underwater NAH measurement, as well as the identification and localization of noise sources.

  12. A modal test method using sound pressure transducers based on vibro-acoustic reciprocity

    NASA Astrophysics Data System (ADS)

    Zhu, W. D.; Liu, J. M.; Xu, Y. F.; Ying, H. Q.

    2014-06-01

    A modal test method that uses sound pressure transducers at fixed locations and an impact hammer roving over a test structure is developed in this work. Since sound pressure transducers are used, the current method deals with a coupled structural-acoustic system. Based on the vibro-acoustic reciprocity, the method is equivalent to one, where acoustic excitations at fixed locations are given and the resulting acceleration of the test structure is measured. The current method can eliminate mass loading due to use of accelerometers, which can destroy existence of repeated or close natural frequencies of a symmetric structure. It can also avoid effects of a nodal line of a mode and an inactive area of a local mode, and measure all the out-of-plane modes within a frequency range of interest, including global and local ones. The coupling between the structure and the acoustic field in a structural-acoustic system introduces asymmetry in the model formulation. An equivalent state space formulation is used for a damped structural-acoustic system and the associated eigenvalue problem is derived. The biorthonormality relations between the left and right eigenvectors and the relations between the structural and acoustic components in the left and right eigenvectors are proved. The frequency response functions associated with the current method are derived and their physical meanings are explained. The guidelines for using the current method, including the types of structures that are suitable for the method, the positions of the sound pressure transducers, and the orientation of the test structure relative to the transducers, are provided. Modal tests were carried out on an automotive disk brake using the traditional and current methods, where multiple accelerometers and microphones were used to measure its dynamic responses induced by impacts, respectively. The differences between the measured natural frequencies using the current method and those from the finite element

  13. Vibro-acoustics of a pressurized optical membrane

    NASA Astrophysics Data System (ADS)

    Tarazaga, Pablo A.; Johnson, Marty E.; Inman, Daniel J.

    2012-07-01

    Optical membranes are currently pursued for their ability to replace the conventional rigid mirrors that are used in space-based telescopes. Among some of the many benefits of using optical membranes is their ability to considerably reduce the weight of the structure. Given the low density of these thin-film membranes, the lower end dynamics play a more significant role than in their rigid plate-like counterparts. Space-based mirrors are subjected to a series of disturbances. Among those encountered are thermal radiation, debris impact, and slewing maneuvers. Thus, being able to model the dynamics appropriately is essential for the adequate performance of thin-film membrane mirrors. With this in mind, the work presented herein uses an impedance based modeling approach to describe the coupled dynamics of a pressurized optical membrane mirror with the end goal of performing vibration suppression of a membrane through acoustic excitation. First the effects of mass loading due to air surrounding a membrane and energy loss due to sound radiation to the far field are modeled in the case of a single membrane. These results are compared to the case of a membrane in vacuum. Second, the membrane is then coupled to a cylindrical cavity where the modeling takes into account the structural acoustic coupling between a cylindrical membrane and a rigid cylindrical cavity, similar to a drum. The coupled model also takes into account the energy loss by sound radiation to the far field due to the membrane's vibration. Third, this paper also looks at using a positive position feedback controller for vibration suppression of the membrane. This is done using a centralized acoustic source at the base of the cavity as the method of actuation. The acoustic actuation is of great interest since it does not mass load the membrane in the conventional way, as most methods of actuation would.

  14. Acoustic systems for the measurement of streamflow

    USGS Publications Warehouse

    Laenen, Antonius; Smith, Winchell

    1982-01-01

    Very little information is available concerning acoustic velocity meter (AVM) operation, performance, and limitations. This report provides a better understanding about the application of AVM instrumentation to streamflow measurment. Operational U.S. Geological Survey systems have proven that AVM equipment is accurate and dependable. AVM equipment has no practical upper limit of measureable velocity if sonic transducers are securely placed and adequately protected, and will measure velocitites as low as 0.1 meter per second which is normally less than the threshold level for mechanical or head-loss meters. In some situations the performance of AVM equipment may be degraded by multipath interference, signal bending, signal attenuation, and variable streamline orientation. Smaller, less-expensive, more conveniently operable microprocessor equipment is now available which should increase use of AVM systems in streamflow applications. (USGS)

  15. Three-dimensional visualization of shear wave propagation generated by dual acoustic radiation pressure

    NASA Astrophysics Data System (ADS)

    Mochizuki, Yuta; Taki, Hirofumi; Kanai, Hiroshi

    2016-07-01

    An elastic property of biological soft tissue is an important indicator of the tissue status. Therefore, quantitative and noninvasive methods for elasticity evaluation have been proposed. Our group previously proposed a method using acoustic radiation pressure irradiated from two directions for elastic property evaluation, in which by measuring the propagation velocity of the shear wave generated by the acoustic radiation pressure inside the object, the elastic properties of the object were successfully evaluated. In the present study, we visualized the propagation of the shear wave in a three-dimensional space by the synchronization of signals received at various probe positions. The proposed method succeeded in visualizing the shear wave propagation clearly in the three-dimensional space of 35 × 41 × 4 mm3. These results show the high potential of the proposed method to estimate the elastic properties of the object in the three-dimensional space.

  16. Acoustic Measurements of Rectangular Nozzles With Bevel

    NASA Technical Reports Server (NTRS)

    Bridges, James E.

    2012-01-01

    A series of convergent rectangular nozzles of aspect ratios 2:1, 4:1, and 8:1 were constructed with uniform exit velocity profiles. Additional nozzles were constructed that extended the wide lip on one side of these nozzles to form beveled nozzles. Far-field acoustic measurements were made and analyzed, and the results presented. The impact of aspect ratio on jet noise was similar to that of enhanced mixing devices: reduction in aft, peak frequency noise with an increase in broadside, high frequency noise. Azimuthally, it was found that rectangular jets produced more noise directed away from their wide sides than from their narrow sides. The azimuthal dependence decreased at aft angles where noise decreased. The effect of temperature, keeping acoustic Mach number constant, was minimal. Since most installations would have the observer on the wide size of the nozzle, the increased high frequency noise has a deleterious impact on the observer. Extending one wide side of the rectangular nozzle, evocative of an aft deck in an installed propulsion system, increased the noise of the jet with increasing length. The impact of both aspect ratio and bevel length were relatively well behaved, allowing a simple bilinear model to be constructed relative to a simple round jet.

  17. Acoustic Measurements of Rectangular Nozzles with Bevel

    NASA Technical Reports Server (NTRS)

    Bridges, James E.

    2012-01-01

    A series of convergent rectangular nozzles of aspect ratios 2:1, 4:1, and 8:1 were constructed with uniform exit velocity profiles. Additional nozzles were constructed that extended the wide lip on one side of these nozzles to form beveled nozzles. Far-field acoustic measurements were made and analyzed, and the results presented. The impact of aspect ratio on jet noise was similar to that of enhanced mixing devices: reduction in aft, peak frequency noise with an increase in broadside, high frequency noise. Azimuthally, it was found that rectangular jets produced more noise directed away from their wide sides than from their narrow sides. The azimuthal dependence decreased at aft angles where noise decreased. The effect of temperature, keeping acoustic Mach number constant, was minimal. Since most installations would have the observer on the wide size of the nozzle, the increased high frequency noise has a deleterious impact on the observer. Extending one wide side of the rectangular nozzle, evocative of an aft deck in an installed propulsion system, increased the noise of the jet with increasing length. The impact of both aspect ratio and bevel length were relatively well behaved, allowing a simple bilinear model to be constructed relative to a simple round jet.

  18. Resin characterization by electro-acoustic measurements.

    PubMed

    Müller, Egbert; Mann, Christian

    2007-03-09

    The electro-acoustic effects, namely the ion vibration potential (IVP) and the colloidal vibration current (CVI), colloidal vibration potential (CVP) first described by P. Debye [P. Debye, J. Chem. Phys. 1 (1933) 13], are a result of charge separation of bound or free ions at different degrees by ultrasonic waves. Today commercial instruments are available to investigate liquid homogeneous and heterogeneous systems. In the present paper the application of this technique for the characterization of salts, protein solutions and resins for biochromatography is shown and valuable information about resins can be derived in a short time. Various resins were investigated with the following results: (1) the CVI magnitude is dependent of several parameters (such as particle size distribution, volume fraction, density difference); (2) the CVI is influenced by the surface modification of the resins. Polymeric modifications decrease the value of CVI. The CVI is generally lower for high capacity resins; (3) the measurement of the electro-acoustic effects can be used to detect small changes in resins. The CVI is dependent of the amount of adsorbed protein in "native" and denatured state.

  19. Pressure field induced in the water column by acoustic-gravity waves generated from sea bottom motion

    NASA Astrophysics Data System (ADS)

    C. A. Oliveira, Tiago; Kadri, Usama

    2016-10-01

    An uplift of the ocean bottom caused by a submarine earthquake can trigger acoustic-gravity waves that travel at near the speed of sound in water and thus may act as early tsunami precursors. We study the spatiotemporal evolution of the pressure field induced by acoustic-gravity modes during submarine earthquakes, analytically. We show that these modes may all induce comparable temporal variations in pressure at different water depths in regions far from the epicenter, though the pressure field depends on the presence of a leading acoustic-gravity wave mode. Practically, this can assist in the implementation of an early tsunami detection system by identifying the pressure and frequency ranges of measurement equipment and appropriate installation locations.

  20. Study of the transit time of pressure propagation in an acoustic delay line

    NASA Astrophysics Data System (ADS)

    Song, Yunn-Fang; Chen, Ching-Iue; Chang, Chu-Nan; You, Jean-Luh; Hwang, Fu-Kwun; Hsu, Chih-Ying

    1986-12-01

    A fast sensor was used as a vacuum gauge to measure the transit time of a gas pressure through an acoustic delay line (ADL). The results were compared with the predictions of two theoretical models. We found that in the rupture pressure range of 101 to 104 Pa, the predictions of Jean and Rauss' model, based on the assumption that the flow of gas be a gas fluid, set lower boundaries for the observed transit times; while the predictions of our model, based on the molecular motion, set the upper ones.

  1. Measurement of acoustical characteristics of mosques in Saudi Arabia

    NASA Astrophysics Data System (ADS)

    Abdou, Adel A.

    2003-03-01

    The study of mosque acoustics, with regard to acoustical characteristics, sound quality for speech intelligibility, and other applicable acoustic criteria, has been largely neglected. In this study a background as to why mosques are designed as they are and how mosque design is influenced by worship considerations is given. In the study the acoustical characteristics of typically constructed contemporary mosques in Saudi Arabia have been investigated, employing a well-known impulse response. Extensive field measurements were taken in 21 representative mosques of different sizes and architectural features in order to characterize their acoustical quality and to identify the impact of air conditioning, ceiling fans, and sound reinforcement systems on their acoustics. Objective room-acoustic indicators such as reverberation time (RT) and clarity (C50) were measured. Background noise (BN) was assessed with and without the operation of air conditioning and fans. The speech transmission index (STI) was also evaluated with and without the operation of existing sound reinforcement systems. The existence of acoustical deficiencies was confirmed and quantified. The study, in addition to describing mosque acoustics, compares design goals to results obtained in practice and suggests acoustical target values for mosque design. The results show that acoustical quality in the investigated mosques deviates from optimum conditions when unoccupied, but is much better in the occupied condition.

  2. Measurement of acoustical characteristics of mosques in Saudi Arabia.

    PubMed

    Abdou, Adel A

    2003-03-01

    The study of mosque acoustics, with regard to acoustical characteristics, sound quality for speech intelligibility, and other applicable acoustic criteria, has been largely neglected. In this study a background as to why mosques are designed as they are and how mosque design is influenced by worship considerations is given. In the study the acoustical characteristics of typically constructed contemporary mosques in Saudi Arabia have been investigated, employing a well-known impulse response. Extensive field measurements were taken in 21 representative mosques of different sizes and architectural features in order to characterize their acoustical quality and to identify the impact of air conditioning, ceiling fans, and sound reinforcement systems on their acoustics. Objective room-acoustic indicators such as reverberation time (RT) and clarity (C50) were measured. Background noise (BN) was assessed with and without the operation of air conditioning and fans. The speech transmission index (STI) was also evaluated with and without the operation of existing sound reinforcement systems. The existence of acoustical deficiencies was confirmed and quantified. The study, in addition to describing mosque acoustics, compares design goals to results obtained in practice and suggests acoustical target values for mosque design. The results show that acoustical quality in the investigated mosques deviates from optimum conditions when unoccupied, but is much better in the occupied condition.

  3. Precision ozone vapor pressure measurements

    NASA Technical Reports Server (NTRS)

    Hanson, D.; Mauersberger, K.

    1985-01-01

    The vapor pressure above liquid ozone has been measured with a high accuracy over a temperature range of 85 to 95 K. At the boiling point of liquid argon (87.3 K) an ozone vapor pressure of 0.0403 Torr was obtained with an accuracy of + or - 0.7 percent. A least square fit of the data provided the Clausius-Clapeyron equation for liquid ozone; a latent heat of 82.7 cal/g was calculated. High-precision vapor pressure data are expected to aid research in atmospheric ozone measurements and in many laboratory ozone studies such as measurements of cross sections and reaction rates.

  4. Measuring aeolian sand transport using acoustic sensors

    NASA Astrophysics Data System (ADS)

    Poortinga, Ate; van Rheenen, Hans; Ellis, Jean T.; Sherman, Douglas J.

    2015-03-01

    Acoustic sensors are frequently used to measure aeolian saltation. Different approaches are used to process the signals from these instruments. The goal of this paper is to describe and discuss a method to measure aeolian saltation with acoustic sensors. In a laboratory experiment, we measured the output from an advanced signal processing scheme on the circuit board of the saltiphone. We use a software implementation of this processing scheme to re-analyse data from four miniphones obtained during a field experiment. It is shown that a set of filters remove background noise outside the frequency spectrum of aeolian saltation (at 8 kHz), whereas signals within this frequency spectrum are amplified. The resulting analogue signal is a proxy of the energy. Using an AC pulse convertor, this signal can be converted into a digital and analogue count signal or an analogue energy signal, using a rectifier and integrator. Spatio-temporal correlation between field deployed miniphones increases by using longer integration times for signal processing. To quantify aeolian grain impact, it is suggested to use the analogue energy output, as this mode is able to detect changes in frequency and amplitude. The analogue and digital count signals are able to detect an increase in frequency, but are not able to detect an increase in signal amplitude. We propose a two-stage calibration scheme consisting of (1) a factory calibration, to set the frequency spectrum of the sensor and (2) a standardized drop-test conducted before and after the experiment to evaluate the response of the sensor.

  5. Measuring Acoustic Nonlinearity by Collinear Mixing Waves

    NASA Astrophysics Data System (ADS)

    Liu, M.; Tang, G.; Jacobs, L. J.; Qu, J.

    2011-06-01

    It is well known that the acoustic nonlinearity parameter β is correlated to fatigue damage in metallic materials. Various methods have been developed to measure β. One of the most often used methods is the harmonic generation technique, in which β is obtained by measuring the magnitude of the second order harmonic waves. An inherent weakness of this method is the difficulty in distinguishing material nonlinearity from the nonlinearity of the measurement system. In this paper, we demonstrate the possibility of using collinear mixing waves to measure β. The wave mixing method is based on the interaction between two incident waves in a nonlinear medium. Under certain conditions, such interactions generate a third wave of different frequency. This generated third wave is also called resonant wave, because its amplitude is unbounded if the medium has no attenuation. Such resonant waves are less sensitive to the nonlinearity of the measurement system, and have the potential to identify the source location of the nonlinearity. In this work, we used a longitudinal wave and a shear wave as the incident waves. The resonant shear wave is measured experimentally on samples made of aluminum and steel, respectively. Numerical simulations of the tests were also performed using a finite difference method.

  6. Role of transient water pressure in quarrying: A subglacial experiment using acoustic emissions

    NASA Astrophysics Data System (ADS)

    Cohen, D.; Hooyer, T. S.; Iverson, N. R.; Thomason, J. F.; Jackson, M.

    2006-09-01

    Probably the most important mechanism of glacial erosion is quarrying: the growth and coalescence of cracks in subglacial bedrock and dislodgement of resultant rock fragments. Although evidence indicates that erosion rates depend on sliding speed, rates of crack growth in bedrock may be enhanced by changing stresses on the bed caused by fluctuating basal water pressure in zones of ice-bed separation. To study quarrying in real time, a granite step, 12 cm high with a crack in its stoss surface, was installed at the bed of Engabreen, Norway. Acoustic emission sensors monitored crack growth events in the step as ice slid over it. Vertical stresses, water pressure, and cavity height in the lee of the step were also measured. Water was pumped to the lee of the step several times over 8 days. Pumping initially caused opening of a leeward cavity, which then closed after pumping was stopped and water pressure decreased. During cavity closure, acoustic emissions emanating mostly from the vicinity of the base of the crack in the step increased dramatically. With repeated pump tests this crack grew with time until the step's lee surface was quarried. Our experiments indicate that fluctuating water pressure caused stress thresholds required for crack growth to be exceeded. Natural basal water pressure fluctuations should also concentrate stresses on rock steps, increasing rates of crack growth. Stress changes on the bed due to water pressure fluctuations will increase in magnitude and duration with cavity size, which may help explain the effect of sliding speed on erosion rates.

  7. Extreme low frequency acoustic measurement system

    NASA Technical Reports Server (NTRS)

    Shams, Qamar A. (Inventor); Zuckerwar, Allan J. (Inventor)

    2013-01-01

    The present invention is an extremely low frequency (ELF) microphone and acoustic measurement system capable of infrasound detection in a portable and easily deployable form factor. In one embodiment of the invention, an extremely low frequency electret microphone comprises a membrane, a backplate, and a backchamber. The backchamber is sealed to allow substantially no air exchange between the backchamber and outside the microphone. Compliance of the membrane may be less than ambient air compliance. The backplate may define a plurality of holes and a slot may be defined between an outer diameter of the backplate and an inner wall of the microphone. The locations and sizes of the holes, the size of the slot, and the volume of the backchamber may be selected such that membrane motion is substantially critically damped.

  8. Extreme Low Frequency Acoustic Measurement System

    NASA Technical Reports Server (NTRS)

    Shams, Qamar A. (Inventor); Zuckerwar, Allan J. (Inventor)

    2017-01-01

    The present invention is an extremely low frequency (ELF) microphone and acoustic measurement system capable of infrasound detection in a portable and easily deployable form factor. In one embodiment of the invention, an extremely low frequency electret microphone comprises a membrane, a backplate, and a backchamber. The backchamber is sealed to allow substantially no air exchange between the backchamber and outside the microphone. Compliance of the membrane may be less than ambient air compliance. The backplate may define a plurality of holes and a slot may be defined between an outer diameter of the backplate and an inner wall of the microphone. The locations and sizes of the holes, the size of the slot, and the volume of the backchamber may be selected such that membrane motion is substantially critically damped.

  9. Active control of acoustic pressure fields using smart material technologies

    NASA Technical Reports Server (NTRS)

    Banks, H. T.; Smith, R. C.

    1993-01-01

    An overview describing the use of piezoceramic patches in reducing noise in a structural acoustics setting is presented. The passive and active contributions due to patches which are bonded to an Euler-Bernoulli beam or thin shell are briefly discussed and the results are incorporated into a 2-D structural acoustics model. In this model, an exterior noise source causes structural vibrations which in turn lead to interior noise as a result of nonlinear fluid/structure coupling mechanism. Interior sound pressure levels are reduced via patches bonded to the flexible boundary (a beam in this case) which generate pure bending moments when an out-of-phase voltage is applied. Well-posedness results for the infinite dimensional system are discussed and a Galerkin scheme for approximating the system dynamics is outlined. Control is implemented by using linear quadratic regulator (LQR) optimal control theory to calculate gains for the linearized system and then feeding these gains back into the nonlinear system of interest. The effectiveness of this strategy for this problem is illustrated in an example.

  10. Outdoor Synthetic Aperture Acoustic Ground Target Measurements

    DTIC Science & Technology

    2010-04-19

    1341 (2003). [11] C. A. Dimarzio, T. Shi, F. J. Blonigen et al., “ Laser -Induced Acoustic Landmine Detection,” The Journal Of The Acoustical Society...High Frequency A/S Coupling For Ap Buried Landmine Detection Using Laser Doppler Vibrometers,” Proc. SPIE 5415(1), 35-41 (2004). [16] Bishop, S... Dolphin Echolocation Clicks For Target Discrimination,” The Journal Of The Acoustical Society Of America 124(1), 657-666 (2008). [20] Y. Nakamura

  11. Direct Measurement of Intracellular Pressure

    PubMed Central

    Petrie, Ryan J.; Koo, Hyun

    2014-01-01

    A method to directly measure the intracellular pressure of adherent, migrating cells is described in the Basic Protocol. This approach is based on the servo-null method where a microelectrode is introduced into the cell to directly measure the physical pressure of the cytoplasm. We also describe the initial calibration of the microelectrode as well as the application of the method to cells migrating inside three-dimensional (3D) extracellular matrix (ECM). PMID:24894836

  12. The effects of external acoustic pressure fields on a free-running supercavitating projectile.

    PubMed

    Cameron, Peter J K; Rogers, Peter H; Doane, John W

    2010-12-01

    Proliferation of supercavitating torpedoes has motivated research on countermeasures against them as well as on the fluid phenomenon which makes them possible. The goal of this research was to investigate an envisaged countermeasure, an acoustic field capable of slowing or diverting the weapon by disrupting the cavitation envelope. The research focused on the interactions between high pressure amplitude sound waves and a supercavity produced by a small free-flying projectile. The flight dynamics and cavity geometry measurements were compared to control experiments and theoretical considerations were made for evaluating the effects. Corrugations on the cavity/water interface caused by the pressure signal have been observed and characterized. Results also show that the accuracy of a supercavitating projectile can be adversely affected by the sound signal. This research concludes with results that indicate that it is acoustic cavitation in the medium surrounding the supercavity, caused by the high pressure amplitude sound, that is responsible for the reduced accuracy. A hypothesis has been presented addressing the means by which the acoustic cavitation could cause this effect.

  13. Systems and methods of monitoring acoustic pressure to detect a flame condition in a gas turbine

    DOEpatents

    Ziminsky, Willy Steve; Krull, Anthony Wayne; Healy, Timothy Andrew , Yilmaz, Ertan

    2011-05-17

    A method may detect a flashback condition in a fuel nozzle of a combustor. The method may include obtaining a current acoustic pressure signal from the combustor, analyzing the current acoustic pressure signal to determine current operating frequency information for the combustor, and indicating that the flashback condition exists based at least in part on the current operating frequency information.

  14. Hybrid system for magnetic and acoustic measurement.

    PubMed

    Bruno, A C; Baffa, O; Carneiro, A O

    2009-01-01

    In order to improve the spatial resolution of Biosusceptometry of Alternate Current (BAC), we are suggesting the coupling of a Doppler ultrasonic transducer with the BAC system. The Doppler transducer obtains information from the vibration of ferromagnetic particles immersed in a visco-elastic medium when it is excited by an alternating magnetic field. In this case, the same magnetic particles used as contrast for susceptometric measurement also will work as contrast for the Doppler measurement. In this work, we present the characterization of the hybrid system for susceptometric and acoustic measurements simultaneously. It was observed that the susceptometric and Doppler ultrasound signal have the same profile and maximum amplitude for frequency of magnetizing field about 200 Hz. When using ferrite particles as magnetic contrast mixed with yogurt as based material, the susceptometric and Doppler measurement have sensitivity for concentration of particles as low as 1%. The sensitivity of the Doppler is dependent of the gradient of magnetic field over the sample. In this work, the magnetic field 5 cm far from the face of the transducer was 70 microT/volts.

  15. Temperature and Pressure Dependence of Signal Amplitudes for Electrostriction Laser-Induced Thermal Acoustics

    NASA Technical Reports Server (NTRS)

    Herring, Gregory C.

    2015-01-01

    The relative signal strength of electrostriction-only (no thermal grating) laser-induced thermal acoustics (LITA) in gas-phase air is reported as a function of temperature T and pressure P. Measurements were made in the free stream of a variable Mach number supersonic wind tunnel, where T and P are varied simultaneously as Mach number is varied. Using optical heterodyning, the measured signal amplitude (related to the optical reflectivity of the acoustic grating) was averaged for each of 11 flow conditions and compared to the expected theoretical dependence of a pure-electrostriction LITA process, where the signal is proportional to the square root of [P*P /( T*T*T)].

  16. Measurement of the acoustic radiation force on a sphere embedded in a soft solid

    NASA Astrophysics Data System (ADS)

    Lidon, Pierre; Villa, Louis; Taberlet, Nicolas; Manneville, Sébastien

    2017-01-01

    The acoustic radiation force exerted on a small sphere located at the focus of an ultrasonic beam is measured in a soft gel. It is proved to evolve quadratically with the local amplitude of the acoustic field. Strong oscillations of the local pressure are observed and attributed to an acoustic Fabry-Pérot effect between the ultrasonic emitter and the sphere. Taking this effect into account with a simple model, a quantitative link between the radiation force and the acoustic pressure is proposed and compared to theoretical predictions in the absence of dissipation. The discrepancy between experiment and theory suggests that dissipative effects should be taken into account for fully modeling the observations.

  17. Low-frequency acoustic pressure, velocity, and intensity thresholds in a bottlenose dolphin (Tursiops truncatus) and white whale (Delphinapterus leucas).

    PubMed

    Finneran, James J; Carder, Donald A; Ridgway, Sam H

    2002-01-01

    The relative contributions of acoustic pressure and particle velocity to the low-frequency, underwater hearing abilities of the bottlenose dolphin (Tursiops truncatus) and white whale (Delphinapterus leucas) were investigated by measuring (masked) hearing thresholds while manipulating the relationship between the pressure and velocity. This was accomplished by varying the distance within the near field of a single underwater sound projector (experiment I) and using two underwater sound projectors and an active sound control system (experiment II). The results of experiment I showed no significant change in pressure thresholds as the distance between the subject and the sound source was changed. In contrast, velocity thresholds tended to increase and intensity thresholds tended to decrease as the source distance decreased. These data suggest that acoustic pressure is a better indicator of threshold, compared to particle velocity or mean active intensity, in the subjects tested. Interpretation of the results of experiment II (the active sound control system) was difficult because of complex acoustic conditions and the unknown effects of the subject on the generated acoustic field; however, these data also tend to support the results of experiment I and suggest that odontocete thresholds should be reported in units of acoustic pressure, rather than intensity.

  18. Low-frequency acoustic pressure, velocity, and intensity thresholds in a bottlenose dolphin (Tursiops truncatus) and white whale (Delphinapterus leucas)

    NASA Astrophysics Data System (ADS)

    Finneran, James J.; Carder, Donald A.; Ridgway, Sam H.

    2002-01-01

    The relative contributions of acoustic pressure and particle velocity to the low-frequency, underwater hearing abilities of the bottlenose dolphin (Tursiops truncatus) and white whale (Delphinapterus leucas) were investigated by measuring (masked) hearing thresholds while manipulating the relationship between the pressure and velocity. This was accomplished by varying the distance within the near field of a single underwater sound projector (experiment I) and using two underwater sound projectors and an active sound control system (experiment II). The results of experiment I showed no significant change in pressure thresholds as the distance between the subject and the sound source was changed. In contrast, velocity thresholds tended to increase and intensity thresholds tended to decrease as the source distance decreased. These data suggest that acoustic pressure is a better indicator of threshold, compared to particle velocity or mean active intensity, in the subjects tested. Interpretation of the results of experiment II (the active sound control system) was difficult because of complex acoustic conditions and the unknown effects of the subject on the generated acoustic field; however, these data also tend to support the results of experiment I and suggest that odontocete thresholds should be reported in units of acoustic pressure, rather than intensity.

  19. Method and apparatus for measuring surface changes, in porous materials, using multiple differently-configured acoustic sensors

    DOEpatents

    Hietala, Susan Leslie; Hietala, Vincent Mark; Tigges, Chris Phillip

    2001-01-01

    A method and apparatus for measuring surface changes, such as mass uptake at various pressures, in a thin-film material, in particular porous membranes, using multiple differently-configured acoustic sensors.

  20. Enhanced acoustic sensing through wave compression and pressure amplification in anisotropic metamaterials.

    PubMed

    Chen, Yongyao; Liu, Haijun; Reilly, Michael; Bae, Hyungdae; Yu, Miao

    2014-10-15

    Acoustic sensors play an important role in many areas, such as homeland security, navigation, communication, health care and industry. However, the fundamental pressure detection limit hinders the performance of current acoustic sensing technologies. Here, through analytical, numerical and experimental studies, we show that anisotropic acoustic metamaterials can be designed to have strong wave compression effect that renders direct amplification of pressure fields in metamaterials. This enables a sensing mechanism that can help overcome the detection limit of conventional acoustic sensing systems. We further demonstrate a metamaterial-enhanced acoustic sensing system that achieves more than 20 dB signal-to-noise enhancement (over an order of magnitude enhancement in detection limit). With this system, weak acoustic pulse signals overwhelmed by the noise are successfully recovered. This work opens up new vistas for the development of metamaterial-based acoustic sensors with improved performance and functionalities that are highly desirable for many applications.

  1. Acoustic systems for the measurement of streamflow

    USGS Publications Warehouse

    Laenen, Antonius; Smith, Winchell

    1983-01-01

    The acoustic velocity meter (AVM), also referred to as an ultrasonic flowmeter, has been an operational tool for the measurement of streamflow since 1965. Very little information is available concerning AVM operation, performance, and limitations. The purpose of this report is to consolidate information in such a manner as to provide a better understanding about the application of this instrumentation to streamflow measurement. AVM instrumentation is highly accurate and nonmechanical. Most commercial AVM systems that measure streamflow use the time-of-travel method to determine a velocity between two points. The systems operate on the principle that point-to-point upstream travel-time of sound is longer than the downstream travel-time, and this difference can be monitored and measured accurately by electronics. AVM equipment has no practical upper limit of measurable velocity if sonic transducers are securely placed and adequately protected. AVM systems used in streamflow measurement generally operate with a resolution of ?0.01 meter per second but this is dependent on system frequency, path length, and signal attenuation. In some applications the performance of AVM equipment may be degraded by multipath interference, signal bending, signal attenuation, and variable streamline orientation. Presently used minicomputer systems, although expensive to purchase and maintain, perform well. Increased use of AVM systems probably will be realized as smaller, less expensive, and more conveniently operable microprocessor-based systems become readily available. Available AVM equipment should be capable of flow measurement in a wide variety of situations heretofore untried. New signal-detection techniques and communication linkages can provide additional flexibility to the systems so that operation is possible in more river and estuary situations.

  2. 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.

  3. A Study of Standing Pressure Waves Within Open and Closed Acoustic Resonators

    NASA Technical Reports Server (NTRS)

    Daniels, C.; Steinetz, B.; Finkbeiner, J.; Raman, G.; Li, X.

    2002-01-01

    The first section of the results presented herein was conducted on an axisymmetric resonator configured with open ventilation ports on either end of the resonator, but otherwise closed and free from obstruction. The remaining section presents the results of a similar resonator shape that was closed, but contained an axisymmetric blockage centrally located through the axis of the resonator. Ambient air was used as the working fluid. In each of the studies, the resonator was oscillated at the resonant frequency of the fluid contained within the cavity while the dynamic pressure, static pressure, and temperature of the fluid were recorded at both ends of the resonator. The baseline results showed a marked reduction in the amplitude of the dynamic pressure waveforms over previous studies due to the use of air instead of refrigerant as the working fluid. A sharp reduction in the amplitude of the acoustic pressure waves was expected and recorded when the configuration of the resonators was modified from closed to open. A change in the resonant frequency was recorded when blockages of differing geometries were used in the closed resonator, while acoustic pressure amplitudes varied little from baseline measurements.

  4. Acoustic mechanisms that determine the ear-canal sound pressures generated by earphones.

    PubMed

    Voss, S E; Rosowski, J J; Shera, C A; Peake, W T

    2000-03-01

    In clinical measurements of hearing sensitivity, a given earphone is assumed to produce essentially the same sound-pressure level in all ears. However, recent measurements [Voss et al., Ear and Hearing (in press)] show that with some middle-ear pathologies, ear-canal sound pressures can deviate by as much as 35 dB from the normal-ear value; the deviations depend on the earphone, the middle-ear pathology, and frequency. These pressure variations cause errors in the results of hearing tests. Models developed here identify acoustic mechanisms that cause pressure variations in certain pathological conditions. The models combine measurement-based Thévenin equivalents for insert and supra-aural earphones with lumped-element models for both the normal ear and ears with pathologies that alter the ear's impedance (mastoid bowl, tympanostomy tube, tympanic-membrane perforation, and a "high-impedance" ear). Comparison of the earphones' Thévenin impedances to the ear's input impedance with these middle-ear conditions shows that neither class of earphone acts as an ideal pressure source; with some middle-ear pathologies, the ear's input impedance deviates substantially from normal and thereby causes abnormal ear-canal pressure levels. In general, for the three conditions that make the ear's impedance magnitude lower than normal, the model predicts a reduced ear-canal pressure (as much as 35 dB), with a greater pressure reduction with an insert earphone than with a supra-aural earphone. In contrast, the model predicts that ear-canal pressure levels increase only a few dB when the ear has an increased impedance magnitude; the compliance of the air-space between the tympanic membrane and the earphone determines an upper limit on the effect of the middle-ear's impedance increase. Acoustic leaks at the earphone-to-ear connection can also cause uncontrolled pressure variations during hearing tests. From measurements at the supra-aural earphone-to-ear connection, we conclude that it

  5. Acoustic Measurements of an Uninstalled Spacecraft Cabin Ventilation Fan Prototype

    NASA Technical Reports Server (NTRS)

    Koch, L. Danielle; Brown, Clifford A.; Shook, Tony D.; Winkel, James; Kolacz, John S.; Podboy, Devin M.; Loew, Raymond A.; Mirecki, Julius H.

    2012-01-01

    Sound pressure measurements were recorded for a prototype of a spacecraft cabin ventilation fan in a test in the NASA Glenn Acoustical Testing Laboratory. The axial fan is approximately 0.089 m (3.50 in.) in diameter and 0.223 m (9.00 in.) long and has nine rotor blades and eleven stator vanes. At design point of 12,000 rpm, the fan was predicted to produce a flow rate of 0.709 cu m/s (150 cfm) and a total pressure rise of 925 Pa (3.72 in. of water) at 12,000 rpm. While the fan was designed to be part of a ducted atmospheric revitalization system, no attempt was made to throttle the flow or simulate the installed configuration during this test. The fan was operated at six speeds from 6,000 to 13,500 rpm. A 13-microphone traversing array was used to collect sound pressure measurements along two horizontal planes parallel to the flow direction, two vertical planes upstream of the fan inlet and two vertical planes downstream of the fan exhaust. Measurements indicate that sound at blade passing frequency harmonics contribute significantly to the overall audible noise produced by the fan at free delivery conditions.

  6. Response of acoustic and elastic properties to pressure and crystallization of Ce-based bulk metallic glass

    NASA Astrophysics Data System (ADS)

    Zhang, B.; Wang, R. J.; Wang, W. H.

    2005-09-01

    The density and acoustic velocities of a Ce70Al10Ni10Cu10 bulk metallic glass (BMG) under hydrostatic-pressure (up to 0.5GPa ) and in crystallized state in ambient conditions were measured in situ by a pulse echo overlap method. The pressure derivatives of velocities and Grüneisen parameters as well as the equation of state (EOS) of the BMG were determined and compared to those of various other BMGs and nonmetallic glasses. Surprisingly, the BMG, unlike other BMGs with normal mode stiffness, exhibits an anomalous soft longitudinal acoustic mode under pressure similar to that of typical oxide glasses. An unusually large softening of longitudinal acoustic phonons in the BMG, relative to its crystalline state, is also observed, analogous with that in oxide glasses. The possible origin for the anomaly is the intrinsic glassy structure containing short-range covalent bonds.

  7. Acoustic Environment of Admiralty Inlet: Broadband Noise Measurements

    SciTech Connect

    Xu, Jinshan; Deng, Zhiqun; Martinez, Jayson J.; Carlson, Thomas J.; Myers, Joshua R.; Weiland, Mark A.; Jones, Mark E.

    2011-09-30

    Admiralty Inlet has been selected as a potential tidal energy site. It is located near shipping lanes, is a highly variable acoustic environment, and is frequented by the highly endangered southern resident killer whale (SRKW). Resolving environmental impacts is the first step to receiving approval to deploy tidal turbines at Admiralty Inlet. Of particular concern is the potential for blade strike or other negative interactions between the SRKW and the tidal turbine. A variety of technologies including passive and active monitoring systems are being considered as potential tools to determine the presence of SRKW in the vicinity of the turbines. Broadband noise level measurements are critical for the determination of design and operation specifications of all marine and hydrokinetic energy capture technologies. Acoustic environment data at the proposed site was acquired at different depths using a cabled vertical line array (VLA) with four calibrated hydrophones. The sound pressure level (SPL) power spectrum density was estimated based on the fast Fourier transform. This study describes the first broadband SPL measurements for this site at different depths with frequency ranging from 10 kHz to 480 kHz in combination with other information. To understand the SPL caused by this bedload transport, three different pressure sensors with temperature and conductivity were also assembled on the VLA to measure the conditions at the hydrophone deployment depth. The broadband SPL levels at frequency ranges of 3 kHz to 7 kHz as a function of depth were estimated. Only the hydrophone at an average depth of 40 m showed the strong dependence of SPL with distance from the bottom, which was possibly caused by the cobbles shifting on the seabed. Automatic Identification System data were also studied to understand the SPL measurements.

  8. Field Measurement of the Acoustic Nonlinearity Parameter in Turbine Blades

    NASA Technical Reports Server (NTRS)

    Hinton, Yolanda L.; Na, Jeong K.; Yost, William T.; Kessel, Gregory L.

    2000-01-01

    Nonlinear acoustics techniques were used to measure fatigue in turbine blades in a power generation plant. The measurements were made in the field using a reference based measurement technique, and a reference sample previously measured in the laboratory. The acoustic nonlinearity parameter showed significant increase with fatigue in the blades, as indicated by service age and areas of increased stress. The technique shows promise for effectively measuring fatigue in field applications and predicting subsequent failures.

  9. Study on demodulated signal distribution and acoustic pressure phase sensitivity of a self-interfered distributed acoustic sensing system

    NASA Astrophysics Data System (ADS)

    Shang, Ying; Yang, Yuan-Hong; Wang, Chen; Liu, Xiao-Hui; Wang, Chang; Peng, Gang-Ding

    2016-06-01

    We propose a demodulated signal distribution theory for a self-interfered distributed acoustic sensing system. The distribution region of Rayleigh backscattering including the acoustic sensing signal in the sensing fiber is investigated theoretically under different combinations of both the path difference and pulse width Additionally we determine the optimal solution between the path difference and pulse width to obtain the maximum phase change per unit length. We experimentally test this theory and realize a good acoustic pressure phase sensitivity of  -150 dB re rad/(μPa·m) of fiber in the frequency range from 200 Hz to 1 kHz.

  10. Blood Pressure Self-Measurement.

    PubMed

    Wagner, Stefan

    2016-10-19

    Blood pressure self-measurement has been used extensively as part of several clinical processes including in the home monitoring setting for mitigating white coat effect and gaining more detailed insights into the blood pressure variability of patients over time. Self-measurement of BP is also being used as part of telemonitoring and telemedicine processes, as well as in the waiting rooms and self-measurement rooms of general practice clinics, specialized hospital department's outpatient clinics, and in other types of care facilitates and institutions.The aim of this review is to provide an overview of where, when, and how blood pressure self-measurement is being used, which official clinical guidelines and procedures are available for its implementation, as well as the opportunities and challenges that are related to its use.

  11. Experimental study of coaxial nozzle exhaust noise. [acoustic measurements

    NASA Technical Reports Server (NTRS)

    Goodykoontz, J. H.; Stone, J. R.

    1979-01-01

    Experimental results are presented for static acoustic model tests of various geometrical configurations of coaxial nozzles operating over a range of flow conditions. The geometrical configurations consisted of nozzles with coplanar and non-coplanar exit planes and various exhaust area ratios. Primary and secondary nozzle flows were varied independently over a range of nozzle pressure ratios from 1.4 to 3.0 and gas temperatures from 280 to 1100 K. Acoustic data are presented for the conventional mode of coaxial nozzle operation as well as for the inverted velocity profile mode. Comparisons are presented to show the effect of configuration and flow changes on the acoustic characteristics of the nozzles.

  12. Acoustic measurements of a liquefied cohesive sediment bed under waves

    NASA Astrophysics Data System (ADS)

    Mosquera, R.; Groposo, V.; Pedocchi, F.

    2014-04-01

    In this article the response of a cohesive sediment deposit under the action of water waves is studied with the help of laboratory experiments and an analytical model. Under the same regular wave condition three different bed responses were observed depending on the degree of consolidation of the deposit: no bed motion, bed motion of the upper layer after the action of the first waves, and massive bed motion after several waves. The kinematic of the upper 3 cm of the deposit were measured with an ultrasound acoustic profiler, while the pore-water pressure inside the bed was simultaneously measured using several pore pressure sensors. A poro-elastic model was developed to interpret the experimental observations. The model showed that the amplitude of the shear stress increased down into the bed. Then it is possible that the lower layers of the deposit experience plastic deformations, while the upper layers present just elastic deformations. Since plastic deformations in the lower layers are necessary for pore pressure build-up, the analytical model was used to interpret the experimental results and to state that liquefaction of a self consolidated cohesive sediment bed would only occur if the bed yield stress falls within the range defined by the amplitude of the shear stress inside the bed.

  13. Robust intravascular optical coherence elastography driven by acoustic radiation pressure

    NASA Astrophysics Data System (ADS)

    van Soest, Gijs; Bouchard, Richard R.; Mastik, Frits; de Jong, Nico; van der Steen, Anton F. W.

    2007-07-01

    High strain spots in the vessel wall indicate the presence of vulnerable plaques. The majority of acute cardiovascular events are preceded by rupture of such a plaque in a coronary artery. Intracoronary optical coherence tomography (OCT) can be extended, in principle, to an elastography technique, mapping the strain in the vascular wall. However, the susceptibility of OCT to frame-to-frame decorrelation, caused by tissue and catheter motion, inhibits reliable tissue displacement tracking and has to date obstructed the development of OCT-based intravascular elastography. We introduce a new technique for intravascular optical coherence elastography, which is robust against motion artifacts. Using acoustic radiation force, we apply a pressure to deform the tissue synchronously with the line scan rate of the OCT instrument. Radial tissue displacement can be tracked based on the correlation between adjacent lines, instead of subsequent frames in conventional elastography. The viability of the method is demonstrated with a simulation study. The root mean square (rms) error of the displacement estimate is 0.55 μm, and the rms error of the strain is 0.6%. It is shown that high-strain spots in the vessel wall, such as observed at the sites of vulnerable atherosclerotic lesions, can be detected with the technique. Experiments to realize this new elastographic method are presented. Simultaneous optical and ultrasonic pulse-echo tracking demonstrate that the material can be put in a high-frequency oscillatory motion with an amplitude of several micrometers, more than sufficient for accurate tracking with OCT. The resulting data are used to optimize the acoustic pushing sequence and geometry.

  14. Effects of Non-Homogeneities on the Eigenmodes of Acoustic Pressure in Combustion Chambers

    NASA Astrophysics Data System (ADS)

    Kim, J. S.; Williams, F. A.

    1998-02-01

    Modifications to acoustic eigenmodes in combustion chambers such as those of liquid propellant rocket engines, produced by spatial variations of density and sound speed that arise mainly through progress of combustion processes, are analyzed by using a variational method. The variational principle shows that the eigenvalue is the ratio of a weighted acoustic kinetic energy to a weighted acoustic potential energy, and the eigenfunction is the minimizing function of this ratio. A sample calculation is made for the case in which variations of the properties occur dominantly in the longitudinal direction, with lower temperatures and higher densities prevailing near the injector. The results of the calculation exhibit two major characteristics: the longitudinal density variation aids transfer of acoustic kinetic energy from a lower mode to the adjacent higher mode, so that the pure transverse modes have substantially larger reductions (sometimes exceeding 50%) of their eigenvalues than the combined modes; and variations of the acoustic pressure gradients are found to be larger in high-density regions, so that the acoustic pressure amplitude for purely tangential modes is found to be much higher near the injector than near the nozzle. The higher head acoustic pressure may contribute to the greater sensitivity of acoustic instability to characteristics of the flames near the injectors, as commonly found in engine tests. The improved acoustic eigensolutions can also be helpful in sizing damping devices, such as baffles or acoustic liners.

  15. Applications of acoustics in the measurement of coal slab thickness

    NASA Technical Reports Server (NTRS)

    Hadden, W. J., Jr.; Mills, J. M.; Pierce, A. D.

    1980-01-01

    The determination of the possibility of employing acoustic waves at ultrasonic frequencies for measurements of thicknesses of slabs of coal backed by shale is investigated. Fundamental information concerning the acoustical properties of coal, and the relationship between these properties and the structural and compositional parameters used to characterize coal samples was also sought. The testing device, which utilizes two matched transducers, is described.

  16. Pulsed electro-acoustic (PEA) measurements of embedded charge distributions

    NASA Astrophysics Data System (ADS)

    Dennison, J. R.; Pearson, Lee H.

    2013-09-01

    Knowledge of the spatial distribution and evolution of embedded charge in thin dielectric materials has important applications in semiconductor, high-power electronic device, high-voltage DC power cable insulation, high-energy and plasma physics apparatus, and spacecraft industries. Knowing how, where, and how much charge accumulates and how it redistributes and dissipates can predict destructive charging effects. Pulsed Electro-acoustic (PEA) measurements— and two closely related methods, Pressure Wave Propagation (PWP) and Laser Intensity Modulation (LIMM)— nondestructively probe such internal charge distributions. We review the instrumentation, methods, theory and signal processing of simple PEA experiments, as well as the related PPW and LIMM methods. We emphasize system improvements required to achieve high spatial resolution for in vacuo measurements of thin dielectrics charged using electron beam injection.

  17. Cosmological implications of baryon acoustic oscillation measurements

    SciTech Connect

    Aubourg, Eric

    2015-12-01

    Here, we derive constraints on cosmological parameters and tests of dark energy models from the combination of baryon acoustic oscillation (BAO) measurements with cosmic microwave background (CMB) data and a recent reanalysis of Type Ia supernova (SN) data. Particularly, we take advantage of high-precision BAO measurements from galaxy clustering and the Lyman-α forest (LyaF) in the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS). Treating the BAO scale as an uncalibrated standard ruler, BAO data alone yield a high confidence detection of dark energy; in combination with the CMB angular acoustic scale they further imply a nearly flat universe. Adding the CMB-calibrated physical scale of the sound horizon, the combination of BAO and SN data into an “inverse distance ladder” yields a measurement of H0=67.3±1.1 km s-1 Mpc-1, with 1.7% precision. This measurement assumes standard prerecombination physics but is insensitive to assumptions about dark energy or space curvature, so agreement with CMB-based estimates that assume a flat ΛCDM cosmology is an important corroboration of this minimal cosmological model. For constant dark energy (Λ), our BAO+SN+CMB combination yields matter density Ωm=0.301±0.008 and curvature Ωk=-0.003±0.003. When we allow more general forms of evolving dark energy, the BAO+SN+CMB parameter constraints are always consistent with flat ΛCDM values at ≈1σ. And while the overall χ2 of model fits is satisfactory, the LyaF BAO measurements are in moderate (2–2.5σ) tension with model predictions. Models with early dark energy that tracks the dominant energy component at high redshift remain consistent with our expansion history constraints, and they yield a higher H0 and lower matter clustering amplitude, improving agreement with some low redshift observations. Expansion history alone yields an upper limit on the summed mass of neutrino species,

  18. Cosmological implications of baryon acoustic oscillation measurements

    DOE PAGES

    Aubourg, Eric

    2015-12-01

    Here, we derive constraints on cosmological parameters and tests of dark energy models from the combination of baryon acoustic oscillation (BAO) measurements with cosmic microwave background (CMB) data and a recent reanalysis of Type Ia supernova (SN) data. Particularly, we take advantage of high-precision BAO measurements from galaxy clustering and the Lyman-α forest (LyaF) in the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS). Treating the BAO scale as an uncalibrated standard ruler, BAO data alone yield a high confidence detection of dark energy; in combination with the CMB angular acoustic scale they further imply a nearly flat universe. Adding the CMB-calibratedmore » physical scale of the sound horizon, the combination of BAO and SN data into an “inverse distance ladder” yields a measurement of H0=67.3±1.1 km s-1 Mpc-1, with 1.7% precision. This measurement assumes standard prerecombination physics but is insensitive to assumptions about dark energy or space curvature, so agreement with CMB-based estimates that assume a flat ΛCDM cosmology is an important corroboration of this minimal cosmological model. For constant dark energy (Λ), our BAO+SN+CMB combination yields matter density Ωm=0.301±0.008 and curvature Ωk=-0.003±0.003. When we allow more general forms of evolving dark energy, the BAO+SN+CMB parameter constraints are always consistent with flat ΛCDM values at ≈1σ. And while the overall χ2 of model fits is satisfactory, the LyaF BAO measurements are in moderate (2–2.5σ) tension with model predictions. Models with early dark energy that tracks the dominant energy component at high redshift remain consistent with our expansion history constraints, and they yield a higher H0 and lower matter clustering amplitude, improving agreement with some low redshift observations. Expansion history alone yields an upper limit on the summed mass of neutrino species, Σmν<0.56 eV (95% confidence), improving to Σmν<0.25 eV if we include

  19. Pressurized Wideband Acoustic Stapedial Reflex Thresholds: Normal Development and Relationships to Auditory Function in Infants.

    PubMed

    Hunter, Lisa L; Keefe, Douglas H; Feeney, M Patrick; Fitzpatrick, Denis F

    2017-02-01

    This study analyzed effects of pressurization on wideband acoustic stapedial-muscle reflex (ASR) tests in infants cared for in normal newborn (NN) and neonatal intensive care units (NICU). Effects of hearing-screening outcomes on ASR threshold measurements were also evaluated, and a subsequent longitudinal study established normative threshold ranges over the first year after birth. An initial experiment compared thresholds in newborns measured at ambient pressure in the ear canal and at the tympanometric peak pressure. ASR thresholds for broadband noise were higher for ears that did not pass newborn hearing screening and ASR threshold was 14 dB higher for real-ear compared to coupler conditions. Effects of pressurization were significant for ears that passed screening; thus, ASR testing in infants should be conducted at tympanometric peak pressure. ASR threshold was significantly higher for ears that referred on transient evoked otoacoustic emissions and Auditory Brainstem Response (ABR) screening tests and also for ears with conductive and sensorineural hearing loss diagnosed by ABR. Developmental ASR changes were significant over the first year for both normal and NICU infants. Wideband pressurized ASR thresholds are a clinically relevant measure of newborn hearing screening and diagnostic outcomes.

  20. A comparison between heterodyne and homodyne interferometry to realise the SI unit of acoustic pressure in water

    NASA Astrophysics Data System (ADS)

    Koukoulas, Triantafillos; Robinson, Stephen; Rajagopal, Srinath; Zeqiri, Bajram

    2016-04-01

    Optical approaches for hydrophone calibrations offer significant advantages over existing methods based on reciprocity. In particular, heterodyne and homodyne interferometry can accurately measure particle velocity and displacements at a specific point in space thus enabling the acoustical pressure to be measured in an absolute, direct, assumption-free manner, with traceability through the SI definition of the metre. The calibration of a hydrophone can then be performed by placing the active element of the sensor at the point where the acoustic pressure field was measured and monitoring its electrical output. However, it is crucial to validate the performance and accuracy of such optical methods by direct comparison rather than through device calibration. Here we report on the direct comparison of two such optical interferometers used in underwater acoustics and ultrasonics in terms of acoustic pressure estimation and their associated uncertainties in the frequency range 200 kHz-3.5 MHz, with results showing agreement better than 1% in terms of pressure and typical expanded uncertainties better than 3% for both reported methods.

  1. Identification of vibration excitations from acoustic measurements using near field acoustic holography and the force analysis technique

    NASA Astrophysics Data System (ADS)

    Pézerat, C.; Leclère, Q.; Totaro, N.; Pachebat, M.

    2009-10-01

    This study presents a method of using acoustic holography and the force analysis technique to identify vibration sources from radiated noise measurements. The structure studied is a plate excited by a shaker on which three measurements were performed: the first is a reference measurement of plate velocity obtained by scanning laser vibrometry, the second is based on sound pressure measurements in the near field of the structure, and the third is the measurement of normal acoustic velocities by using a p-U probe recently developed by Microflown Technologies. This was followed by the application of classical NAH, known as pressure-to-velocity holography and velocity-to-velocity holography to predict the plate velocity field from acoustic measurements at distances of 1 and 5 cm. Afterwards, the force analysis technique, also known as the RIFF technique, is applied with these five data sets. The principle is to inject the displacement field of the structure into its equation of motion and extract the resulting force distribution. This technique requires regularization done by a low-pass filter in the wavenumber domain. Apart from pressure-to-velocity holography at 5 cm, the reconstructed force distribution allows localizing the excitation point in the measurement area. FAT regularization is also shown to improve results as its cutoff wavenumber is optimized with the natural wavenumber of the plate. Lastly, quantitative force values are extracted from force distributions at all frequencies of the band 0-4 kHz studied and compared with the force spectrum measured directly by a piezoelectric sensor.

  2. Acoustic-velocity measurements in materials using a regenerative method

    DOEpatents

    Laine, E.F.

    1982-09-30

    Acoustic energy is propatated through earth material between an electro-acoustic generator and a receiver which converts the received acoustic energy into electrical signals. A closed loop is formed by a variable gain amplifier system connected between the receiver and the generator. The gain of the amplifier system is increased until sustained oscillations are produced in the closed loop. The frequency of the oscillations is measured as an indication of the acoustic propagation velocity through the earth material. The amplifier gain is measured as an indication of the acoustic attenuation through the earth materials. The method is also applicable to the non-destructive testing of structural materials, such as steel, aluminum and concrete.

  3. Acoustic velocity measurements in materials using a regenerative method

    DOEpatents

    Laine, Edwin F.

    1986-01-01

    Acoustic energy is propagated through earth material between an electro-acoustic generator and a receiver which converts the received acoustic energy into electrical signals. A closed loop is formed by a variable gain amplifier system connected between the receiver and the generator. The gain of the amplifier system is increased until sustained oscillations are produced in the closed loop. The frequency of the oscillations is measured as an indication of the acoustic propagation velocity through the earth material. The amplifier gain is measured as an indication of the acoustic attenuation through the earth materials. The method is also applicable to the non-destructive testing of structural materials, such as steel, aluminum and concrete.

  4. An Ultrasonic Caliper Device for Measuring Acoustic Nonlinearity

    NASA Astrophysics Data System (ADS)

    Hunter, Christopher; Sapozhnikov, Oleg A.; Maxwell, Adam D.; Khokhlova, Vera A.; Wang, Yak-Nam; MacConaghy, Brian; Kreider, Wayne

    In medical and industrial ultrasound, it is often necessary to measure the acoustic properties of a material. A specific medical application requires measurements of sound speed, attenuation, and nonlinearity to characterize livers being evaluated for transplantation. For this application, a transmission-mode caliper device is proposed in which both transmit and receive transducers are directly coupled to a test sample, the propagation distance is measured with an indicator gage, and receive waveforms are recorded for analysis. In this configuration, accurate measurements of nonlinearity present particular challenges: diffraction effects can be considerable while nonlinear distortions over short distances typically remain small. To enable simple estimates of the nonlinearity coeffcient from a quasi-linear approximation to the lossless Burgers' equation, the calipers utilize a large transmitter and plane waves are measured at distances of 15-50 mm. Waves at 667 kHz and pressures between 0.1 and 1 MPa were generated and measured in water at different distances; the nonlinearity coeffcient of water was estimated from these measurements with a variability of approximately 10%. Ongoing efforts seek to test caliper performance in other media and improve accuracy via additional transducer calibrations.

  5. Unrestrained acoustic plethysmograph for measuring tidal volume in mice.

    PubMed

    Reynolds, Jeffrey S; Frazer, David G

    2006-09-01

    The traditional method for measurement of tidal volume in unrestrained mice relies on pressure changes induced by a freely respiring animal in a whole body plethysmograph. These changes have been assumed to be the result of thermo-hygrometric differences between respired air and gas within the chamber. It is known, however, that gas compression in the lung can also contribute significantly to changes in plethysmograph pressure. This study describes an acoustic plethysmograph for mice that is capable of measuring the tidal volume time series without the errors associated with the traditional method. The plethysmograph was designed as a resonating cavity at a fixed frequency. It had a sharp resonant peak and was tuned so that changes in body volume produced nearly linear changes in sound amplitude. The plethysmograph was tested with a water filled balloon connected to a syringe pump. The volume of the balloon was varied as a triangle wave with an amplitude of 250 microL. The RMS error between measured and delivered volume was 4.43 microL. A volume step test, performed to assess the response time of the system, showed that the plethysmograph responded in less than one millisecond.

  6. Neural Network Burst Pressure Prediction in Graphite/Epoxy Pressure Vessels from Acoustic Emission Amplitude Data

    NASA Technical Reports Server (NTRS)

    Hill, Eric v. K.; Walker, James L., II; Rowell, Ginger H.

    1995-01-01

    Acoustic emission (AE) data were taken during hydroproof for three sets of ASTM standard 5.75 inch diameter filament wound graphite/epoxy bottles. All three sets of bottles had the same design and were wound from the same graphite fiber; the only difference was in the epoxies used. Two of the epoxies had similar mechanical properties, and because the acoustic properties of materials are a function of their stiffnesses, it was thought that the AE data from the two sets might also be similar; however, this was not the case. Therefore, the three resin types were categorized using dummy variables, which allowed the prediction of burst pressures all three sets of bottles using a single neural network. Three bottles from each set were used to train the network. The resin category, the AE amplitude distribution data taken up to 25 % of the expected burst pressure, and the actual burst pressures were used as inputs. Architecturally, the network consisted of a forty-three neuron input layer (a single categorical variable defining the resin type plus forty-two continuous variables for the AE amplitude frequencies), a fifteen neuron hidden layer for mapping, and a single output neuron for burst pressure prediction. The network trained on all three bottle sets was able to predict burst pressures in the remaining bottles with a worst case error of + 6.59%, slightly greater than the desired goal of + 5%. This larger than desired error was due to poor resolution in the amplitude data for the third bottle set. When the third set of bottles was eliminated from consideration, only four hidden layer neurons were necessary to generate a worst case prediction error of - 3.43%, well within the desired goal.

  7. Pressure Sensitivity Kernels Applied to Time-reversal Acoustics

    DTIC Science & Technology

    2009-06-29

    diversity in passive time reversal com- munications,” Journal of the Acoustical Society of America, October 2006, Vol. 120, Issue 4, pp. 2067-2076. xvi 5...communications. J. Acoustic Soc. Am., 115:2468–2468, 2004. [3] P. Gerstoft. Inversion of seismo-acoustic data using genetic algorithms and a posteriori...average of focal spots tends to have high stability.[6] The presence of spatial diversity (large arrays) has the same effect as an ensemble average and

  8. Scale Model Thruster Acoustic Measurement Results

    NASA Technical Reports Server (NTRS)

    Vargas, Magda; Kenny, R. Jeremy

    2013-01-01

    The Space Launch System (SLS) Scale Model Acoustic Test (SMAT) is a 5% scale representation of the SLS vehicle, mobile launcher, tower, and launch pad trench. The SLS launch propulsion system will be comprised of the Rocket Assisted Take-Off (RATO) motors representing the solid boosters and 4 Gas Hydrogen (GH2) thrusters representing the core engines. The GH2 thrusters were tested in a horizontal configuration in order to characterize their performance. In Phase 1, a single thruster was fired to determine the engine performance parameters necessary for scaling a single engine. A cluster configuration, consisting of the 4 thrusters, was tested in Phase 2 to integrate the system and determine their combined performance. Acoustic and overpressure data was collected during both test phases in order to characterize the system's acoustic performance. The results from the single thruster and 4- thuster system are discussed and compared.

  9. The Acoustic Field Scattered from Some Approximate Pressure Release Materials Coating a Finite Cylinder.

    NASA Astrophysics Data System (ADS)

    Caille, Gary William

    1988-12-01

    The objective was to determine if a pressure release boundary condition can be achieved by coating an elastic shell with a viscoelastic material. One necessary condition is that the coating must acoustically decouple the shell from the scattering problem. Two closed cell rubbers and two cork-rubber composites (nitrile and neoprene based) were investigated. The dynamic viscoelastic constants of the materials were determined by wave propagation techniques. The far field scattering form functions for an infinite cylindrical shell coated with the viscoelastic material were calculated using the complete elastic equations of motion. The form functions were experimentally measured for the different materials at different thicknesses as verification of the theory. A thick finite right cylindrical shell was coated with.25 inches of closed cell neoprene and the normalized scattered pressure measured. The pressure release normalized scattered pressure was determined for the end on incident plane wave case using the acoustic radiation Simplified Helmholtz Integral Program (SHIP). The pressure release normalized scattered pressure was determined for the side incident case using a modified Combined Helmholtz Integral Equation Formulation (CHIEF) radiation program. The material property measurements showed the closed cell rubbers have longitudinal wave propagation speeds of approximately 150 m/sec and attenuations of 30 dB/cm. The cork-rubber composites have longitudinal wave speeds of approximately 300 m/sec and attenuations of 7 dB/cm. The scattering measurements demonstrated that a thin shell (inner radius to outer radius ratio of.97) could be made to scatter in a pressure release manner with a.25 inches of nitrile. The rubber-cork composites could not produce the pressure release effect for nondimensionalized wave number (product of the wave number and the radius of the cylinder) values less than 4 with reasonable thicknesses. The coated finite thick shell, with side

  10. Near field acoustic holography measurements of carbon nanotube thin film speakers.

    PubMed

    Asgarisabet, Mahsa; Barnard, Andrew R; Bouman, Troy M

    2016-12-01

    Carbon nanotube (CNT) thin film speakers produce sound with the thermoacoustic effect. Better understanding of the physical acoustic properties of these speakers will drive future design improvements. Measuring acoustic properties at the surface of the CNT thin film is difficult because the films, themselves, do not vibrate, are fragile and have a high surface temperature. In order to measure the surface particle velocity and sound pressure level (SPL), near field acoustic holography (NAH) has been used by employing probe microphones. NAH images the acoustic quantities of the source system using the set of acoustic pressure measurements on a hologram parallel to the source surface. It is shown that the particle velocity at the surface of an open-air, double-sided speaker is nominally zero, as expected. However, the SPL distribution is not uniform on the source surface, contrary to common lumped parameter model assumptions. Also, particle velocity and sound intensity distributions on the hologram have been obtained in this study. Finally, measured directivity patterns of the planar CNT speaker are reported.

  11. Comparison of acoustic and mechanical excitation for modal response measurements

    NASA Astrophysics Data System (ADS)

    Musson, B. G.; Stevens, J. R.

    An acoustic field is examined as an alternate to mechanical excitation of a test specimen to measure modal response. A square, flat plate with clamped edges is used because classical analytical solutions to its modal analysis are readily available. A small hammer with a built-in force transducer is used to mechanically excite the plate, and the plate is excited with electro-pneumatic acoustic drivers coupled to a progressive-wave test fixture. Band limited random amplitude acoustic waves over a frequency range of 50 to 1000 Hz are applied at grazing incidence to the plate. The acoustic field is characterized and a microphone at a single fixed position is used to provide the reference forcing function. Results are compared with the analytical solutions and with the mechanically excited results. Conclusions are presented concerning the equivalence of acoustic and mechanical excitation for obtaining modal response.

  12. High-pressure acoustic properties of glycerol studied by Brillouin spectroscopy

    NASA Astrophysics Data System (ADS)

    Jeong, Min-Seok; Ko, Jae-Hyeon; Ko, Young Ho; Kim, Kwang Joo

    2015-12-01

    Acoustic properties of glycerol was investigated in a wide pressure range from ambient pressure to 30.9 GPa by using a multi-pass Fabry-Perot interferometer and a diamond anvil cell. Pressure dependences of the sound velocity and the Brillouin linewidth showed substantial changes at low pressures below ~4 GPa. This was attributed to the coupling between the main structural relaxation process and the longitudinal acoustic waves. The pressure dependence of the refractive index and the density of glycerol could be obtained by using two scattering geometries and the Lorentz-Lorenz relation.

  13. Acoustic Detection Of Loose Particles In Pressure Sensors

    NASA Technical Reports Server (NTRS)

    Kwok, Lloyd C.

    1995-01-01

    Particle-impact-noise-detector (PIND) apparatus used in conjunction with computer program analyzing output of apparatus to detect extraneous particles trapped in pressure sensors. PIND tester essentially shaker equipped with microphone measuring noise in pressure sensor or other object being shaken. Shaker applies controlled vibration. Output of microphone recorded and expressed in terms of voltage, yielding history of noise subsequently processed by computer program. Data taken at sampling rate sufficiently high to enable identification of all impacts of particles on sensor diaphragm and on inner surfaces of sensor cavities.

  14. Role of transient water pressure in quarrying: A subglacial experiment using acoustic emissions

    USGS Publications Warehouse

    Cohen, D.; Hooyer, T.S.; Iverson, N.R.; Thomason, J.F.; Jackson, M.

    2006-01-01

    Probably the most important mechanism of glacial erosion is quarrying: the growth and coalescence of cracks in subglacial bedrock and dislodgement of resultant rock fragments. Although evidence indicates that erosion rates depend on sliding speed, rates of crack growth in bedrock may be enhanced by changing stresses on the bed caused by fluctuating basal water pressure in zones of ice-bed separation. To study quarrying in real time, a granite step, 12 cm high with a crack in its stoss surface, was installed at the bed of Engabreen, Norway. Acoustic emission sensors monitored crack growth events in the step as ice slid over it. Vertical stresses, water pressure, and cavity height in the lee of the step were also measured. Water was pumped to the lee of the step several times over 8 days. Pumping initially caused opening of a leeward cavity, which then closed after pumping was stopped and water pressure decreased. During cavity closure, acoustic emissions emanating mostly from the vicinity of the base of the crack in the step increased dramatically. With repeated pump tests this crack grew with time until the step's lee surface was quarried. Our experiments indicate that fluctuating water pressure caused stress thresholds required for crack growth to be exceeded. Natural basal water pressure fluctuations should also concentrate stresses on rock steps, increasing rates of crack growth. Stress changes on the bed due to water pressure fluctuations will increase in magnitude and duration with cavity size, which may help explain the effect of sliding speed on erosion rates. Copyright 2006 by the American Geophysical Union.

  15. Subharmonic scattering of phospholipid-shell microbubbles at low acoustic pressure amplitudes.

    PubMed

    Frinking, Peter J A; Brochot, Jean; Arditi, Marcel

    2010-08-01

    Subharmonic scattering of phospholipid-shell microbubbles excited at relatively low acoustic pressure amplitudes (<30 kPa) has been associated with echo responses from compression-only bubbles having initial surface tension values close to zero. In this work, the relation between sbharmonics and compression-only behavior of phospholipid-shell microbubbles was investigated, experimentally and by simulation, as a function of the initial surface tension by applying ambient overpressures of 0 and 180 mmHg. The microbubbles were excited using a 64-cycle transmit burst with a center frequency of 4 MHz and peak-negative pressure amplitudes ranging from 20 of 150 kPa. In these conditions, an increase in subharmonic response of 28.9 dB (P < 0.05) was measured at 50 kPa after applying an overpressure of 180 mmHg. Simulations using the Marmottant model, taking into account the effect of ambient overpressure on bubble size and initial surface tension, confirmed the relation between subharmonics observed in the pressure-time curves and compression-only behavior observed in the radius-time curves. The trend of an increase in subharmonic response as a function of ambient overpressure, i.e., as a function of the initial surface tension, was predicted by the model. Subharmonics present in the echo responses of phospholipid-shell microbubbles excited at low acoustic pressure amplitudes are indeed related to the echo responses from compression-only bubbles. The increase in subharmonics as a function of ambient overpressure may be exploited for improving methods for noninvasive pressure measurement in heart cavities or big vessels in the human body.

  16. Effect of static pressure on acoustic energy radiated by cavitation bubbles in viscous liquids under ultrasound.

    PubMed

    Yasui, Kyuichi; Towata, Atsuya; Tuziuti, Toru; Kozuka, Teruyuki; Kato, Kazumi

    2011-11-01

    The effect of static pressure on acoustic emissions including shock-wave emissions from cavitation bubbles in viscous liquids under ultrasound has been studied by numerical simulations in order to investigate the effect of static pressure on dispersion of nano-particles in liquids by ultrasound. The results of the numerical simulations for bubbles of 5 μm in equilibrium radius at 20 kHz have indicated that the optimal static pressure which maximizes the energy of acoustic waves radiated by a bubble per acoustic cycle increases as the acoustic pressure amplitude increases or the viscosity of the solution decreases. It qualitatively agrees with the experimental results by Sauter et al. [Ultrason. Sonochem. 15, 517 (2008)]. In liquids with relatively high viscosity (∼200 mPa s), a bubble collapses more violently than in pure water when the acoustic pressure amplitude is relatively large (∼20 bar). In a mixture of bubbles of different equilibrium radius (3 and 5 μm), the acoustic energy radiated by a 5 μm bubble is much larger than that by a 3 μm bubble due to the interaction with bubbles of different equilibrium radius. The acoustic energy radiated by a 5 μm bubble is substantially increased by the interaction with 3 μm bubbles.

  17. Automatic blood pressure measuring system (M092)

    NASA Technical Reports Server (NTRS)

    Nolte, R. W.

    1977-01-01

    The Blood Pressure Measuring System is described. It measures blood pressure by the noninvasive Korotkoff sound technique on a continual basis as physical stress is imposed during experiment M092, Lower Body Negative Pressure, and experiment M171, Metabolic Activity.

  18. Challenges and regulatory considerations in the acoustic measurement of high-frequency (>20 MHz) ultrasound.

    PubMed

    Nagle, Samuel M; Sundar, Guru; Schafer, Mark E; Harris, Gerald R; Vaezy, Shahram; Gessert, James M; Howard, Samuel M; Moore, Mary K; Eaton, Richard M

    2013-11-01

    This article examines the challenges associated with making acoustic output measurements at high ultrasound frequencies (>20 MHz) in the context of regulatory considerations contained in the US Food and Drug Administration industry guidance document for diagnostic ultrasound devices. Error sources in the acoustic measurement, including hydrophone calibration and spatial averaging, nonlinear distortion, and mechanical alignment, are evaluated, and the limitations of currently available acoustic measurement instruments are discussed. An uncertainty analysis of acoustic intensity and power measurements is presented, and an example uncertainty calculation is done on a hypothetical 30-MHz high-frequency ultrasound system. This analysis concludes that the estimated measurement uncertainty of the acoustic intensity is +73%/-86%, and the uncertainty in the mechanical index is +37%/-43%. These values exceed the respective levels in the Food and Drug Administration guidance document of 30% and 15%, respectively, which are more representative of the measurement uncertainty associated with characterizing lower-frequency ultrasound systems. Recommendations made for minimizing the measurement uncertainty include implementing a mechanical positioning system that has sufficient repeatability and precision, reconstructing the time-pressure waveform via deconvolution using the hydrophone frequency response, and correcting for hydrophone spatial averaging.

  19. Acoustic wayfinding: A method to measure the acoustic contrast of different paving materials for blind people.

    PubMed

    Secchi, Simone; Lauria, Antonio; Cellai, Gianfranco

    2017-01-01

    Acoustic wayfinding involves using a variety of auditory cues to create a mental map of the surrounding environment. For blind people, these auditory cues become the primary substitute for visual information in order to understand the features of the spatial context and orient themselves. This can include creating sound waves, such as tapping a cane. This paper reports the results of a research about the "acoustic contrast" parameter between paving materials functioning as a cue and the surrounding or adjacent surface functioning as a background. A number of different materials was selected in order to create a test path and a procedure was defined for the verification of the ability of blind people to distinguish different acoustic contrasts. A method is proposed for measuring acoustic contrast generated by the impact of a cane tip on the ground to provide blind people with environmental information on spatial orientation and wayfinding in urban places.

  20. Quantitative measurements of acoustic emissions from cavitation at the surface of a stone in response to a lithotripter shock wave.

    PubMed

    Chitnis, Parag V; Cleveland, Robin O

    2006-04-01

    Measurements are presented of acoustic emissions from cavitation collapses on the surface of a synthetic kidney stone in response to shock waves (SWs) from an electrohydraulic lithotripter. A fiber optic probe hydrophone was used for pressure measurements, and passive cavitation detection was used to identify acoustic emissions from bubble collapse. At a lithotripter charging voltage of 20 kV, the focused SW incident on the stone surface resulted in a peak pressure of 43 +/- 6 MPa compared to 23 +/- 4 MPa in the free field. The focused SW incident upon the stone appeared to be enhanced due to the acoustic emissions from the forced cavitation collapse of the preexisting bubbles. The peak pressure of the acoustic emission from a bubble collapse was 34 +/- 15 MPa, that is, the same magnitude as the SWs incident on the stone. These data indicate that stresses induced by focused SWs and cavitation collapses are similar in magnitude thus likely play a similar role in stone fragmentation.

  1. ATK Launch Vehicle (ALV-X1) Liftoff Acoustic Environments: Prediction vs. Measurement

    NASA Technical Reports Server (NTRS)

    Houston, Janice; Counter, Douglas; Kenny, Jeremy; Murphy, John

    2009-01-01

    The ATK Launch Vehicle (ALV-X1) provided an opportunity to measure liftoff acoustic noise data. NASA Marshall Space Flight Center (MSFC) engineers were interested in the ALV-X1 launch because the First Stage motor and launch pad conditions, including a relativity short deflector ducting, provide a potential analogue to future Ares I launches. This paper presents the measured liftoff acoustics on the vehicle and tower. Those measured results are compared to predictions based upon the method described in NASA SP-8072 "Acoustic Loads Generated by the Propulsion System" and the Vehicle Acoustic Environment Prediction Program (VAEPP) which was developed by MSFC acoustics engineers. One-third octave band sound pressure levels will be presented. This data is useful for the ALV-X1 in validating the pre-launch environments and loads predictions. Additionally, the ALV-X1 liftoff data can be scaled to define liftoff environments for the NASA Constellation program Ares vehicles. Vehicle liftoff noise is caused by the supersonic jet flow interaction with surrounding atmosphere or more simply, jet noise. As the vehicle's First Stage motor is ignited, an acoustic noise field is generated by the exhaust. This noise field persists due to the supersonic jet noise and reflections from the launch pad and tower, then changes as the vehicle begins to liftoff from the launch pad. Depending on launch pad and adjacent tower configurations, the liftoff noise is generally very high near the nozzle exit and decreases rapidly away from the nozzle. The liftoff acoustic time range of interest is typically 0 to 20 seconds after ignition. The exhaust plume thermo-fluid mechanics generates sound at approx.10 Hz to 20 kHz. Liftoff acoustic noise is usually the most severe dynamic environment for a launch vehicle or payload in the mid to high frequency range (approx.50 to 2000 Hz). This noise environment can induce high-level vibrations along the external surfaces of the vehicle and surrounding

  2. Analytic Formulation and Numerical Implementation of an Acoustic Pressure Gradient Prediction

    NASA Technical Reports Server (NTRS)

    Lee, Seongkyu; Brentner, Kenneth S.; Farassat, Fereidoun

    2007-01-01

    The scattering of rotor noise is an area that has received little attention over the years, yet the limited work that has been done has shown that both the directivity and intensity of the acoustic field may be significantly modified by the presence of scattering bodies. One of the inputs needed to compute the scattered acoustic field is the acoustic pressure gradient on a scattering surface. Two new analytical formulations of the acoustic pressure gradient have been developed and implemented in the PSU-WOPWOP rotor noise prediction code. These formulations are presented in this paper. The first formulation is derived by taking the gradient of Farassat's retarded-time Formulation 1A. Although this formulation is relatively simple, it requires numerical time differentiation of the acoustic integrals. In the second formulation, the time differentiation is taken inside the integrals analytically. The acoustic pressure gradient predicted by these new formulations is validated through comparison with the acoustic pressure gradient determined by a purely numerical approach for two model rotors. The agreement between analytic formulations and numerical method is excellent for both stationary and moving observers case.

  3. Energy Transform and Initial Acoustic Pressure Distribution in Microwave-induced Thermoacoustic Tomography.

    PubMed

    Yan, Jing; Tao, Chunjing; Wu, Shizeng

    2005-01-01

    A study of Microwave-induced Thermoacoustic Tomography is presented in this paper. Microwaves illuminate biological tissues to generate acoustic waves by thermoelastic expansion when electromagnetic energy was absorbed by human tissues. The generated acoustic waves carry information about different electromagnetic properties of different tissues which will be collected and processed to reconstruct human cross section image. In this paper, digital electromagnetic human body model with 1cm resolution was founded according to algorithm requirements. Firstly we analyzed the transform and interrelation among electromagnetic energy, heat energy and acoustic energy. On the basis of established human model: (1) we calculated initial acoustic pressure distribution in cross section image under plane microwave radiation with different frequency. It shows that microwave absorption properties and initial acoustic pressure were different with the change of frequency; (2) using single pulse to illuminate human model, initial acoustic pressure maps of thorax cross section at different time steps were analyzed. These results provided a research basis for further study and calculation of acoustic pressure in microwave-induced thermoacoustic tomography.

  4. Wavenumber-frequency Spectra of Pressure Fluctuations Measured via Fast Response Pressure Sensitive Paint

    NASA Technical Reports Server (NTRS)

    Panda, J.; Roozeboom, N. H.; Ross, J. C.

    2016-01-01

    The recent advancement in fast-response Pressure-Sensitive Paint (PSP) allows time-resolved measurements of unsteady pressure fluctuations from a dense grid of spatial points on a wind tunnel model. This capability allows for direct calculations of the wavenumber-frequency (k-?) spectrum of pressure fluctuations. Such data, useful for the vibro-acoustics analysis of aerospace vehicles, are difficult to obtain otherwise. For the present work, time histories of pressure fluctuations on a flat plate subjected to vortex shedding from a rectangular bluff-body were measured using PSP. The light intensity levels in the photographic images were then converted to instantaneous pressure histories by applying calibration constants, which were calculated from a few dynamic pressure sensors placed at selective points on the plate. Fourier transform of the time-histories from a large number of spatial points provided k-? spectra for pressure fluctuations. The data provides first glimpse into the possibility of creating detailed forcing functions for vibro-acoustics analysis of aerospace vehicles, albeit for a limited frequency range.

  5. Towards a reference cavitating vessel Part III—design and acoustic pressure characterization of a multi-frequency sonoreactor

    NASA Astrophysics Data System (ADS)

    Wang, Lian; Memoli, Gianluca; Hodnett, Mark; Butterworth, Ian; Sarno, Dan; Zeqiri, Bajram

    2015-08-01

    A multi-frequency cavitation vessel (RV-multi) has been commissioned at the National Physical Laboratory (NPL, UK), with the aim of establishing a standard source of acoustic cavitation in water, with reference to which details of the cavitation process can be studied and cavitation measurement techniques evaluated. The vessel is a cylindrical cavity with a maximum capacity up to 17 L, and is designed to work at six frequency ranges, from 21 kHz to 136 kHz, under controlled temperature conditions. This paper discusses the design of RV-multi and reports experiments carried out to establish the reproducibility of the acoustic pressure field established within the vessel and its operating envelope, including sensitivity to aspects such as water depth and temperature. The acoustic field distribution was determined along the radial and depth directions within the vessel using a miniature hydrophone, for two input voltage levels under low power transducer excitation conditions (e.g. below the cavitation threshold). Particular care was taken in determining peak acoustic pressure locations, as these are critical for accompanying cavitation studies. Perturbations of the vessel by the measuring hydrophone were also monitored with a bottom-mounted pressure sensor.

  6. Classroom acoustics in Omaha, Nebraska: Measurements and outreach

    NASA Astrophysics Data System (ADS)

    Bowden, Erica E.; Wang, Lily M.; Bradley, David T.

    2002-11-01

    This project collected data detailing the current status of classroom acoustics while simultaneously increasing awareness of educational acoustics and exposure to acoustical engineering research in local schools. In 8 Omaha-area schools, 2 acoustical aspects which directly influence speech intelligibility were measured and studied: (1) background noise levels resulting from a building's mechanical systems; and (2) reverberation times within the classroom. Prior to each measurement session, a presentation on good classroom acoustic principles was presented to the teacher and students in that classroom. Subsequently, the teacher and students assisted the principal investigator and research assistants in the measurement of the acoustic data from their classroom. In total, 13 classrooms were studied, with the assistance of 425 middle and high school students in 14 different classes. The background noise results have been associated with commonly used noise criterion curves. Results are compared to recommended background noise levels and reverberation times suggested by ANSI standard S12.60-2002. The resulting database provides knowledge on the current status of classrooms in Omaha, and may be indicative of classroom situations across the midwestern United States.

  7. An objective method and measuring equipment for noise control and acoustic diagnostics of motorcars. [acoustic diagnostics on automobile engines

    NASA Technical Reports Server (NTRS)

    Kacprowski, J.; Motylewski, J.; Miazga, J.

    1974-01-01

    An objective method and apparatus for noise control and acoustic diagnostics of motorcar engines are reported. The method and apparatus let us know whether the noisiness of the vehicle under test exceeds the admissible threshold levels given by appropriate standards and if so what is the main source of the excessive noise. The method consists in measuring both the overall noise level and the sound pressure levels in definite frequency bands while the engine speed is controlled as well and may be fixed at prescribed values. Whenever the individually adjusted threshold level has been exceeded in any frequency band, a self-sustaining control signal is sent.

  8. Numerical acoustic characteristics and optimum design of the pressure reducing valve

    NASA Astrophysics Data System (ADS)

    Guo, P. C.; Sun, L. G.; Sun, S. H.; Feng, J. J.; Wu, K. G.; Luo, X. Q.

    2016-11-01

    The pressure reducing valves are widely used in the technological water supplied ways of gravity flow. A credible pressure reducing valve can provide stable cooling water for units with extremely low maintenance cost and labor intensity in a fairly long period of time. In this paper, a three-dimensional numerical simulation of flow field and acoustic characteristics towards a combined type pressure reducing valve was carried out based on ANSYS Fluent and the FW-H equation. The numerical results achieve the regulation of noise generation, transmission and attenuation. It shows that the sound pressure level of monitoring points seem to be higher and large gradient at low frequencies under the same flow velocity, while it presents reverse results with the increment of frequency and maintains a constant valve finally. At the same time, the monitoring points in the vicinity of throttling cone shows higher sound pressure level and upstream noise is lower than downstream's. Aiming at the problem of valve noise, a modified measure to reduce the flow-induced noise was proposed.

  9. On reconstruction of acoustic pressure fields using the Helmholtz equation least squares method

    PubMed

    Wu

    2000-05-01

    This paper presents analyses and implementation of the reconstruction of acoustic pressure fields radiated from a general, three-dimensional complex vibrating structure using the Helmholtz equation least-squares (HELS) method. The structure under consideration emulates a full-size four-cylinder engine. To simulate sound radiation from a vibrating structure, harmonic excitations are assumed to act on arbitrarily selected surfaces. The resulting vibration responses are solved by the commercial FEM (finite element method) software I-DEAS. Once the normal component of the surface velocity distribution is determined, the surface acoustic pressures are calculated using standard boundary element method (BEM) codes. The radiated acoustic pressures over several planar surfaces at certain distances from the source are calculated by the Helmholtz integral formulation. These field pressures are taken as the input to the HELS formulation to reconstruct acoustic pressures on the entire source surface, as well as in the field. The reconstructed acoustic pressures thus obtained are then compared with benchmark values. Numerical results demonstrate that good agreements can be obtained with relatively few expansion functions. The HELS method is shown to be very effective in the low-to-mid frequency regime, and can potentially become a powerful noise diagnostic tool.

  10. Response of transonic diffuser flows to abrupt increases of back pressure: Wall pressure measurements

    NASA Astrophysics Data System (ADS)

    Bogar, T. J.; Sajben, M.

    1986-10-01

    The propagation of compression pulses in a supercritically operated transonic diffuser was investigated by use of pressure measurements along the top wall of the model. The pulses were generated at the downstream end of the diffuser by the abrupt injection of a secondary flow of air. Two types of waves were observed: (1) an upstream-traveling acoustic wave and (2) a downstream-traveling convective wave which resulted from the impingement of the acoustic wave on the shock. Wave speeds were determined for a range of diffuser pressure ratios including separated, strong-shock flows and fully attached, weak-shock flows. Streamwise distributions of initial and reflected pulse amplitudes were determined for one weak and one strong-shock case over a 3-to-1 range of initial pulse strengths.

  11. Measurements of Finite Dust Temperature Effects in the Dispersion Relation of the Dust Acoustic Wave

    NASA Astrophysics Data System (ADS)

    Snipes, Erica; Williams, Jeremiah

    2009-04-01

    A dusty plasma is a four-component system composed of ions, electrons, neutral particles and charged microparticles. The presence of these charged microparticles gives rise to new plasma wave modes, including the dust acoustic wave. Recent measurements [1, 2] of the dispersion relationship for the dust acoustic wave in a glow discharge have shown that finite temperature effects are observed at higher values of neutral pressure. Other work [3] has shown that these effects are not observed at lower values of neutral pressure. We present the results of ongoing work examining finite temperature effects in the dispersion relation as a function of neutral pressure. [4pt] [1] E. Thomas, Jr., R. Fisher, and R. L. Merlino, Phys. Plasmas 14, 123701 (2007). [0pt] [2] J. D. Williams, E. Thomas Jr., and L. Marcus, Phys. Plasmas 15, 043704 (2008). [0pt] [3] T. Trottenberg, D. Block, and A. Piel, Phys. Plasmas 13, 042105 (2006).

  12. On acoustic intensity measurements in the presence of mean flow

    NASA Technical Reports Server (NTRS)

    Munro, D. H.; Ingard, K. U.

    1979-01-01

    A theoretical analysis demonstrates that the technique of measuring acoustic intensity by means of cross correlation between nearby microphones cannot, in general, be extended to situations in which there is mean flow. However, it may be possible to use this technique to measure intensities in ducts with mean flow at frequencies below their cutoff frequencies.

  13. Approach to Eliminate Couplant-Effect in Acoustic Nonlinearity Measurements

    SciTech Connect

    Sun, L.; Kulkarni, S. S.; Achenbach, J. D.; Krishnaswamy, S.

    2006-03-06

    An approach to eliminate couplant-effect in acoustic nonlinearity measurements for fatigued components is proposed in this paper. Measurements are performed on a fatigued steel 4340 specimen using both the conventional and proposed techniques. It is observed that the coefficients of variation of the nonlinearity parameter obtained using the proposed technique is approximately half of that obtained using the conventional technique.

  14. An optoacoustic point source for acoustic scale model measurements.

    PubMed

    Bolaños, Javier Gómez; Pulkki, Ville; Karppinen, Pasi; Hæggström, Edward

    2013-04-01

    A massless acoustic source is proposed for scale model work. This source is generated by focusing a pulsed laser beam to rapidly heat the air at the focal point. This produces an expanding small plasma ball which generates a sonic impulse that may be used as an acoustic point source. Repeatability, frequency response, and directivity of the source were measured to show that it can serve as a massless point source. The impulse response of a rectangular space was determined using this type of source. A good match was found between the predicted and the measured impulse responses of the space.

  15. Dynamic tire pressure sensor for measuring ground vibration.

    PubMed

    Wang, Qi; McDaniel, James Gregory; Wang, Ming L

    2012-11-07

    This work presents a convenient and non-contact acoustic sensing approach for measuring ground vibration. This approach, which uses an instantaneous dynamic tire pressure sensor (DTPS), possesses the capability to replace the accelerometer or directional microphone currently being used for inspecting pavement conditions. By measuring dynamic pressure changes inside the tire, ground vibration can be amplified and isolated from environmental noise. In this work, verifications of the DTPS concept of sensing inside the tire have been carried out. In addition, comparisons between a DTPS, ground-mounted accelerometer, and directional microphone are made. A data analysis algorithm has been developed and optimized to reconstruct ground acceleration from DTPS data. Numerical and experimental studies of this DTPS reveal a strong potential for measuring ground vibration caused by a moving vehicle. A calibration of transfer function between dynamic tire pressure change and ground acceleration may be needed for different tire system or for more accurate application.

  16. Dynamic Tire Pressure Sensor for Measuring Ground Vibration

    PubMed Central

    Wang, Qi; McDaniel, James Gregory; Wang, Ming L.

    2012-01-01

    This work presents a convenient and non-contact acoustic sensing approach for measuring ground vibration. This approach, which uses an instantaneous dynamic tire pressure sensor (DTPS), possesses the capability to replace the accelerometer or directional microphone currently being used for inspecting pavement conditions. By measuring dynamic pressure changes inside the tire, ground vibration can be amplified and isolated from environmental noise. In this work, verifications of the DTPS concept of sensing inside the tire have been carried out. In addition, comparisons between a DTPS, ground-mounted accelerometer, and directional microphone are made. A data analysis algorithm has been developed and optimized to reconstruct ground acceleration from DTPS data. Numerical and experimental studies of this DTPS reveal a strong potential for measuring ground vibration caused by a moving vehicle. A calibration of transfer function between dynamic tire pressure change and ground acceleration may be needed for different tire system or for more accurate application. PMID:23202206

  17. Dynamic-pressure measurements using an electronically scanned pressure module

    NASA Technical Reports Server (NTRS)

    Chapin, W. G.

    1983-01-01

    Frequency response was measured for different lengths and diameters of tubing between a sinusoidal pressure source and a pressure sensing module from an electronically scanned pressure measuring system. Measurements were made for straight runs of both steel and vinyl tubing. For steel tubing, measured results are compared with results calculated by using equations developed by Tijdeman and Bergh. Measurements were also made with a bend in the vinyl tubing at the module. In addition, measurements were made with two coils placed in the tubing near the middle of the run.

  18. End tidal carbon dioxide measurement using an electro acoustic sensor.

    PubMed

    Folke, M; Hok, B; Ekstrom, M; Backlund, Y

    2004-01-01

    End tidal carbon dioxide measurement with an electro-acoustic sensor is demonstrated. The sensor consists of an acoustic resonator coupled to a low cost electro-acoustic element. By simultaneous measurements with a reference sensor, the new device was tested on subjects performing exercise, hypo- and hyperventilation whereby the CO2concentration ranged from 2.1 to 7.0 kPa. The output from the experimental device correlated well with the reference CO2readings with a correlation coefficient of 0.976. Response time for expiration less than 0.8 seconds was noted. The new device could be useful in situations where selectivity to other gases is not important.

  19. Measurements and computational fluid dynamics predictions of the acoustic impedance of orifices

    NASA Astrophysics Data System (ADS)

    Su, J.; Rupp, J.; Garmory, A.; Carrotte, J. F.

    2015-09-01

    The response of orifices to incident acoustic waves, which is important for many engineering applications, is investigated with an approach combining both experimental measurements and numerical simulations. This paper presents experimental data on acoustic impedance of orifices, which is subsequently used for validation of a numerical technique developed for the purpose of predicting the acoustic response of a range of geometries with moderate computational cost. Measurements are conducted for orifices with length to diameter ratios, L/D, of 0.5, 5 and 10. The experimental data is obtained for a range of frequencies using a configuration in which a mean (or bias) flow passes from a duct through the test orifices before issuing into a plenum. Acoustic waves are provided by a sound generator on the upstream side of the orifices. Computational fluid dynamics (CFD) calculations of the same configuration have also been performed. These have been undertaken using an unsteady Reynolds averaged Navier-Stokes (URANS) approach with a pressure based compressible formulation with appropriate characteristic based boundary conditions to simulate the correct acoustic behaviour at the boundaries. The CFD predictions are in very good agreement with the experimental data, predicting the correct trend with both frequency and orifice L/D in a way not seen with analytical models. The CFD was also able to successfully predict a negative resistance, and hence a reflection coefficient greater than unity for the L / D = 0.5 case.

  20. On the implementation of an automated acoustic output optimization algorithm for subharmonic aided pressure estimation

    PubMed Central

    Dave, J. K.; Halldorsdottir, V. G.; Eisenbrey, J. R.; Merton, D. A.; Liu, J. B.; Machado, P.; Zhao, H.; Park, S.; Dianis, S.; Chalek, C. L.; Thomenius, K. E.; Brown, D. B.; Forsberg, F.

    2013-01-01

    Incident acoustic output (IAO) dependent subharmonic signal amplitudes from ultrasound contrast agents can be categorized into occurrence, growth or saturation stages. Subharmonic aided pressure estimation (SHAPE) is a technique that utilizes growth stage subharmonic signal amplitudes for hydrostatic pressure estimation. In this study, we developed an automated IAO optimization algorithm to identify the IAO level eliciting growth stage subharmonic signals and also studied the effect of pulse length on SHAPE. This approach may help eliminate the problems of acquiring and analyzing the data offline at all IAO levels as was done in previous studies and thus, pave the way for real-time clinical pressure monitoring applications. The IAO optimization algorithm was implemented on a Logiq 9 (GE Healthcare, Milwaukee, WI) scanner interfaced with a computer. The optimization algorithm stepped the ultrasound scanner from 0 to 100 % IAO. A logistic equation fitting function was applied with the criterion of minimum least squared error between the fitted subharmonic amplitudes and the measured subharmonic amplitudes as a function of the IAO levels and the optimum IAO level was chosen corresponding to the inflection point calculated from the fitted data. The efficacy of the optimum IAO level was investigated for in vivo SHAPE to monitor portal vein (PV) pressures in 5 canines and was compared with the performance of IAO levels, below and above the optimum IAO level, for 4, 8 and 16 transmit cycles. The canines received a continuous infusion of Sonazoid microbubbles (1.5 μl/kg/min; GE Healthcare, Oslo, Norway). PV pressures were obtained using a surgically introduced pressure catheter (Millar Instruments, Inc., Houston, TX) and were recorded before and after increasing PV pressures. The experiments showed that optimum IAO levels for SHAPE in the canines ranged from 6 to 40 %. The best correlation between changes in PV pressures and in subharmonic amplitudes (r = -0.76; p = 0

  1. Cryogenic High-Pressure Shear-Coaxial Jets Exposed to Transverse Acoustic Forcing

    DTIC Science & Technology

    2011-12-13

    Air Force Research Laboratory (AFMC) AFRL/RZSA 10 E. Saturn Blvd. Edwards AFB CA 93524-7680 9. SPONSORING / MONITORING AGENCY NAME(S) AND...pressure antinode ( PAN ). The role of injector exit geometry on the flow response was examined using two shear coaxial injectors with different outer-to...jets to pressure perturbations due to transverse acoustic forcing at a pressure antinode ( PAN ). The role of injector exit geometry on the flow

  2. A novel instrument to measure acoustic resonances of the vocal tract during phonation

    NASA Astrophysics Data System (ADS)

    Epps, J.; Smith, J. R.; Wolfe, J.

    1997-10-01

    Acoustic resonances of the vocal tract give rise to formants (broad bands of acoustic power) in the speech signal when the vocal tract is excited by a periodic signal from the vocal folds. This paper reports a novel instrument which uses a real-time, non-invasive technique to measure these resonances accurately during phonation. A broadband acoustic current source is located just outside the mouth of the subject and the resulting acoustic pressure is measured near the lips. The contribution of the speech signal to the pressure spectrum is then digitally suppressed and the resonances are calculated from the input impedance of the vocal tract as a function of the frequency. The external excitation signal has a much smaller harmonic spacing than does the periodic signal from the vocal folds and consequently the resonances are determined much more accurately due to the closer sampling. This is particularly important for higher pitched voices and we demonstrate that this technique can be markedly superior to the curve-fitting technique of linear prediction. The superior frequency resolution of this instrument which results from external vocal tract excitation can provide the precise, stable, effective, articulatory feedback considered essential for some language-learning and speech-therapy applications.

  3. Noncontact measurement of intraocular pressure using a modified Michelson interferometer

    NASA Astrophysics Data System (ADS)

    Drescher, Joerg; Stork, Wilhelm; Hey, Stefan; Gundlach, Arnd; Mueller-Glaser, Klaus-Dieter; Kreiner, Christine F.

    1999-06-01

    This paper describes a new method to examine the intraocular pressure (IOP) without any contact with the eye. In our new approach the IOP is determined indirectly from the acoustic properties of the eye, as the resonance frequencies of the bulbus are shifting with increasing IOP. In a first step simulations were made with the Finite Element Method to explore the correlation between the IOP and the acoustic properties of the bulbus. The results showed a significant rise of the resonance-frequencies with increasing IOP. Simultaneously a in-vitro measurement system was built comprising a modified michelson interferometer to measure the vibrations, a transducer to stimulate the eye and a controlling PC. With this system measurements were made with artificial eyes and enucleated pig eyes to prove the correlation experimentally. The eyes were stimulated both contacting the eye with a transducer by a stick and contactless with sonic waves. Several series of measurements showed a proportional constant of 1,25 Hz/mmHg in average, which can be detected easily. The standard deviation measuring different pig eyes was 4,5 mmHg. Next a in-vivo system was developed to study the acoustic behavior of the human eye in the real environment. The in-vivo system consists of a miniaturized semiconductor-laser interferometer complying laser safety requirements, an automatic positioning unit and an excitation unit to stimulate vibrations of the eye. Sub-micrometer vibrations of the eye can be measured in-vivo with this system.

  4. Conditioned pressure spectra and coherence measurements in the core of a turbofan engine

    NASA Technical Reports Server (NTRS)

    Karchmer, A.

    1981-01-01

    Multiple and partial coherence functions and the corresponding conditioned coherent output spectra are computed between fluctuating pressures measured at two locations within the tailpipe of a turbofan engine and far-field acoustic pressure. The results are compared with the ordinary coherent output spectrum as obtained between a single tailpipe pressure measurement and the far-field acoustic pressure. The comparison indicates apparent additional "coherent output" (i.e., core-noise) beyond that detectable with an ordinary coherent measurement, thus suggesting the tailpipe as a core-noise source region. Further evidence suggests, however, that these differences may be attributed to the presence of transverse acoustic modes in the tailpipe and that the tailpipe is not, in fact, a significant source region.

  5. Variation of Pressure Waveforms in Measurements of Extracorporeal Shock Wave Lithotripter

    NASA Astrophysics Data System (ADS)

    Inose, Naoto; Ide, Masao

    1993-05-01

    In this paper, we describe measurement of variation in pressure waveforms of the acoustic field of an extra-corporeal shock-wave lithotripter (ESWL). Variations in the measured acoustic fields and pressure waveform of an underwater spark-gap-type ESWL with an exhausted spark plug electrode have been reported by researchers using crystal sensors. If the ESWL spark plugs become exhausted, patients feel pain during kidney, biliary stone disintegration. We studied the relationship between exhaustion of electrodes and the variation of pressure waveforms and shock-wave fields of the ESWL using a newly developed hydrophone.

  6. Measuring Intracranial Pressure And Volume Noninvasively

    NASA Technical Reports Server (NTRS)

    Cantrell, John H.; Yost, William T.

    1994-01-01

    Ultrasonic technique eliminates need to drill into brain cavity. Intracranial dynamics instrument probes cranium ultrasonically to obtain data for determination of intracranial pressure (ICP) and pressure-volume index (PVI). Instrument determines sensitivity of skull to changes in pressure and by use of mechanical device to exert external calibrated pressure on skull. By monitoring volume of blood flowing into jugular vein, one determines change of volume of blood in cranial system. By measuring response of skull to increasing pressure (where pressure increased by tilting patient known amount) and by using cranial blood pressure, one determines intial pressure in cerebrospinal fluid. Once PVI determined, ICP determined.

  7. ACOUSTIC LOCATION OF LEAKS IN PRESSURIZED UNDER- GROUND PETROLEUM PIPELINES

    EPA Science Inventory

    Experiments were conducted at the Underground Storage Tank (UST) Test Apparatus Pipeline in which three acoustic sensors separated by a maximum distance of 38.1 m (125 ft) were used to monitor signals produced by 11.4-, 5.7-, and 3.8-L/h (3.0-, 1.5-, and 1.0-gal/h) leaks in th...

  8. Vapor Pressure Measurements in a Closed System

    ERIC Educational Resources Information Center

    Iannone, Mark

    2006-01-01

    An alternative method that uses a simple apparatus to measure vapor pressure versus temperature in a closed system, in which the total pressure is the vapor pressure of the liquid sample, is described. The use of this apparatus gives students a more direct picture of vapor pressure than the isoteniscope method and results have generally been quite…

  9. A comparison of the acoustic and aerodynamic measurements of a model rotor tested in two anechoic wind tunnels

    NASA Technical Reports Server (NTRS)

    Boxwell, D. A.; Schmitz, F. H.; Splettstoesser, W. R.; Schultz, K. J.; Lewy, S.; Caplot, M.

    1986-01-01

    Two aeroacoustic facilities--the CEPRA 19 in France and the DNW in the Netherlands--are compared. The two facilities have unique acoustic characteristics that make them appropriate for acoustic testing of model-scale helicopter rotors. An identical pressure-instrumented model-scale rotor was tested in each facility and acoustic test results are compared with full-scale-rotor test results. Blade surface pressures measured in both tunnels were used to correlated nominal rotor operating conditions in each tunnel, and also used to assess the steadiness of the rotor in each tunnel's flow. In-the-flow rotor acoustic signatures at moderate forward speeds (35-50 m/sec) are presented for each facility and discussed in relation to the differences in tunnel geometries and aeroacoustic characteristics. Both reports are presented in appendices to this paper. ;.);

  10. A new method to measure the acoustic surface impedance outdoors.

    PubMed

    Carpinello, S; L'Hermite, Ph; Bérengier, M; Licitra, G

    2004-01-01

    In the European countries noise pollution is considered to be one of the most important environmental problems. With respect to traffic noise, different researchers are working on the reduction of noise at the source, on the modelling of the acoustic absorption of the road structure and on the effects of the pavement on the propagation. The aim of this paper is to propose a new method to measure the acoustic impedance of surfaces located outdoors, which allows us to further noise propagation models, in order to evaluate exactly the noise exposure.

  11. Advances in non-invasive measures of vocal acoustics.

    PubMed

    LaBlance, G R; Steckol, K F; Cooper, M H

    1991-10-01

    Objective assessment of vocal pitch, loudness, and quality is a crucial adjunct to endoscopy in the diagnosis and treatment of vocal pathology. Historically, this assessment was made through subjective, perceptual measures that were questionable in terms of validity and reliability. Recent advances in electronic technology now permit objective analysis of the acoustic characteristics of voice. Kay Elemetric's Visi-Pitch, DSP 5500 Digital Spectrograph, and Nasometer are representative of these new instruments and are used as illustrations in the discussion of the assessment of speech acoustics.

  12. Acoustic ship signature measurements by cross-correlation method.

    PubMed

    Fillinger, Laurent; Sutin, Alexander; Sedunov, Alexander

    2011-02-01

    Cross-correlation methods were applied for the estimation of the power spectral density and modulation spectrum of underwater noise generated by moving vessels. The cross-correlation of the signal from two hydrophones allows the separation of vessel acoustic signatures in a busy estuary. Experimental data recorded in the Hudson River are used for demonstration that cross-correlation method measured the same ship noise and ship noise modulation spectra as conventional methods. The cross-correlation method was then applied for the separation of the acoustic signatures of two ships present simultaneously. Presented methods can be useful for ship traffic monitoring and small ship classification, even in noisy harbor environments.

  13. High-frequency attenuation measurements using an acoustic microscope.

    PubMed

    Gracewski, S M; Waag, R C; Schenk, E A

    1988-06-01

    An acoustic microscope was used to measure excess attenuation of aqueous solutions of sugars and proteins at 1.0 GHz. Interference pattern spacing and peak amplitude reduction of V(z) curves, obtained with these solutions as the acoustic microscope coupling liquid, were related to the solution wavespeed and attenuation, respectively. Consistent with published results for lower frequencies, solutions with molecular weight greater than 10,000 had a higher specific absorption than those with a molecular weight less than 1000 and within these two molecular weight ranges specific absorption was independent of concentration.

  14. A Comparative Study of Two Acoustic Measures of Hypernasality

    ERIC Educational Resources Information Center

    Vogel, Adam P.; Ibrahim, Hasherah M.; Reilly, Sheena; Kilpatrick, Nicky

    2009-01-01

    Purpose: This study aimed to compare 2 quantitative acoustic measures of nasality in children with cleft lip and palate (CLP) and healthy controls using formalized perceptual assessment as a guide. Method: Fifty participants (23 children with CLP and 27 age- and gender-matched healthy controls) aged between 4 and 12 years produced a variety of…

  15. Measuring acoustic properties of materials and jet nozzles

    NASA Technical Reports Server (NTRS)

    Dean, P. D.; Plumblee, H. E.; Salikuddin, M.

    1980-01-01

    Method measures acoustic properties of sound-absorbent materials and jet-nozzle system. Advantages of impulse method over other methods are that test time and complication are reduced. Results obtained from impulse method have been compared with those from existing methods, both experimental and theoretical, and show excellent agreement.

  16. Measurement of the total acoustic output power of HITU transducers

    NASA Astrophysics Data System (ADS)

    Jenderka, Klaus-V.; Beissner, Klaus

    2010-03-01

    The majority of High Intensity Therapeutic Ultrasound (HITU) applications use strongly focused ultrasound fields generating very high local intensities in the focal region. The metrology of these high-power ultrasound fields is a challenge for the established measurement procedures and devices. This paper describes the results of measurements by means of the radiation force for a total acoustic output power up to 400 W at 1.5 MHz and up to 200 W at 2.45 MHz. For this purpose, a radiation force balance set-up was adapted for the determination of large acoustic output powers. For two types of HITU transducers, the relationship between the total acoustic output power and the applied net electrical power was determined at close transducer-target distance. Further, dependence of the measured electro-acoustic radiation conductance on the transducer-target distance was investigated at reduced power levels, considering the appearance of focal anomalies. Concluding, a list of the main uncertainty contributions, and an estimate of the uncertainty for the used radiation force balance set-up is given for measurements at high power levels.

  17. Laboratory comparisons of acoustic and optical sensors for microbubble measurement

    NASA Technical Reports Server (NTRS)

    Su, Ming Yang; Todoroff, Douglas; Cartmill, John

    1994-01-01

    This paper presents the results of a recent comparison between three microbubble size spectrum measurement systems. These systems are the light-scattering bubble counter, the photographic bubble-imaging system, and the acoustic resonator array. Good agreement was formed among these three systems over the bubble size range appropriate for each system.

  18. Voice Acoustical Measurement of the Severity of Major Depression

    ERIC Educational Resources Information Center

    Cannizzaro, Michael; Harel, Brian; Reilly, Nicole; Chappell, Phillip; Snyder, Peter J.

    2004-01-01

    A number of empirical studies have documented the relationship between quantifiable and objective acoustical measures of voice and speech, and clinical subjective ratings of severity of Major Depression. To further explore this relationship, speech samples were extracted from videotape recordings of structured interviews made during the…

  19. Experimental and numerical characterization of the sound pressure in standing wave acoustic levitators.

    PubMed

    Stindt, A; Andrade, M A B; Albrecht, M; Adamowski, J C; Panne, U; Riedel, J

    2014-01-01

    A novel method for predictions of the sound pressure distribution in acoustic levitators is based on a matrix representation of the Rayleigh integral. This method allows for a fast calculation of the acoustic field within the resonator. To make sure that the underlying assumptions and simplifications are justified, this approach was tested by a direct comparison to experimental data. The experimental sound pressure distributions were recorded by high spatially resolved frequency selective microphone scanning. To emphasize the general applicability of the two approaches, the comparative studies were conducted for four different resonator geometries. In all cases, the results show an excellent agreement, demonstrating the accuracy of the matrix method.

  20. Dexterous manipulation of microparticles using Bessel-function acoustic pressure fields

    NASA Astrophysics Data System (ADS)

    Courtney, Charles R. P.; Drinkwater, Bruce W.; Demore, Christine E. M.; Cochran, Sandy; Grinenko, Alon; Wilcox, Paul D.

    2013-03-01

    We show that Bessel-function acoustic pressure fields can be used to trap and controllably position microparticles. A circular, 16-element ultrasound array generates and manipulates an acoustic field within a chamber, trapping microparticles and agglomerates. Changes in the phase of the sinusoidal signals applied to the array elements result in the movement of the Bessel-function pressure field and hence the microparticles. This demonstrates ultrasonic manipulation analogous to holographic optical tweezers. The manipulation limits of the device are explained by the existence of unwanted resonances within the manipulation chamber.

  1. Measurement of acoustic shielding by a turbulent jet

    NASA Technical Reports Server (NTRS)

    Yu, J. C.; Fratello, D. J.

    1985-01-01

    The acoustic shielding properties of a turbulent jet have been investigated experimentally. The experimental arrangement consisted of an acoustic point source and a turbulent shielding jet. The source and jet parameters investigated include the source frequency, source spectrum, jet velocity, jet heating by simulation and the lateral and longitudinal source positions with respect to the shielding jet. It is found that the maximum sound attenuation provided by the shielding jet depends on the balance between refraction and diffraction. Over the frequency range investigated, the redistribution of sound by the shielding air jet is power conserving. Comparison between measurement and prediction based on an idealized cylindrical uniform jet model indicates that the spreading and decay of the flow field in real jets are important. Comparisons between the present data trends and those reported for jet-by-jet shielding suggest that the major effects observed in the latter are acoustical rather than aerodynamical.

  2. Acoustic measurements of air entrainment by breaking waves

    NASA Astrophysics Data System (ADS)

    Terrill, Eric James

    1998-11-01

    Wave breaking at the surface of the ocean plays an important role in air-sea interaction processes. Bubbles entrained by breaking waves not only enhance the transfer of atmospheric gases to the ocean, but also modify the phase speed and attenuation of acoustic waves propagating through the bubbly medium. The development of acoustic instruments to measure bubbles and the results obtained from a number of field and laboratory experiments are presented. The first part of this dissertation addresses sound speed measurements made in the North Atlantic as part of the Acoustic Surface Reverberation Experiment (ASREX). An autonomous buoy system that directly measures the sound speed in the surface wave layer was developed. Data obtained with the instrument spanned several storm cycles with wind speeds and significant wave heights reaching 20 m/s and 8 m, respectively. The use of Wood's relation (1946) allows the calculation of the void fraction of air based on the low-frequency sound speed measurements. The highly variable near-surface sound speed/void fraction field is analyzed with respect to wind and surface wave- breaking parameters. The second part of this dissertation presents the development of a broadband acoustic technique which simultaneously measures the phase speed and attenuation at acoustic frequencies ranging from 4-100 kHz. The acoustic data is inverted for the size distribution of bubbles using algorithms that are based upon the physics of sound propagation through a bubbly mixture. This acoustic technique was evaluated in the large wave channel at the Hydraulics Laboratory, Scripps Institution of Oceanography, using mechanically generated breaking waves in seawater. Field measurements of bubble concentrations that result from wave breaking were made in both shallow water off Scripps Pier, California and in deep water near Point Conception, California using the broadband technique. Significant variability is observed in the bubble field, characterized by

  3. Acoustic scattering by circular cylinders of various aspect ratios. [pressure gradient microphones

    NASA Technical Reports Server (NTRS)

    Maciulaitis, A.

    1979-01-01

    The effects of acoustic scattering on the useful frequency range of pressure gradient microphones were investigated experimentally between ka values of 0.407 and 4.232 using two circular cylindrical models (L/D = 0.5 and 0.25) having a 25 cm outside diameter. Small condenser microphones, attached to preamplifiers by flexible connectors, were installed from inside the cylindrical bodies, and flush mounted on the exterior surface of the cylinders. A 38 cm diameter woofer in a large speaker enclosure was used as the sound source. Surface pressure augmentation and phase differences were computed from measured data for various sound wave incidence angles. Results are graphically compared with theoretical predictions supplied by NASA for ka = 0.407, 2.288, and 4.232. All other results are tabulated in the appendices. With minor exceptions, the experimentally determined pressure augmentations agreed within 0.75 dB with theoretical predictions. The agreement for relative phase angles was within 5 percent without any exceptions. Scattering parameter variations with ka and L/D ratio, as computed from experimental data, are also presented.

  4. Cuff for Blood-Vessel Pressure Measurements

    NASA Technical Reports Server (NTRS)

    Shimizu, M.

    1982-01-01

    Pressure within blood vessel is measured by new cufflike device without penetration of vessel. Device continuously monitors blood pressure for up to 6 months or longer without harming vessel. Is especially useful for vessels smaller than 4 or 5 millimeters in diameter. Invasive methods damage vessel wall, disturb blood flow, and cause clotting. They do not always give reliable pressure measurements over prolonged periods.

  5. Measuring Time-Averaged Blood Pressure

    NASA Technical Reports Server (NTRS)

    Rothman, Neil S.

    1988-01-01

    Device measures time-averaged component of absolute blood pressure in artery. Includes compliant cuff around artery and external monitoring unit. Ceramic construction in monitoring unit suppresses ebb and flow of pressure-transmitting fluid in sensor chamber. Transducer measures only static component of blood pressure.

  6. High Precision Pressure Measurement with a Funnel

    ERIC Educational Resources Information Center

    Lopez-Arias, T.; Gratton, L. M.; Oss, S.

    2008-01-01

    A simple experimental device for high precision differential pressure measurements is presented. Its working mechanism recalls that of a hydraulic press, where pressure is supplied by insufflating air under a funnel. As an application, we measure air pressure inside a soap bubble. The soap bubble is inflated and connected to a funnel which is…

  7. Ultrasonic wave based pressure measurement in small diameter pipeline.

    PubMed

    Wang, Dan; Song, Zhengxiang; Wu, Yuan; Jiang, Yuan

    2015-12-01

    An effective non-intrusive method of ultrasound-based technique that allows monitoring liquid pressure in small diameter pipeline (less than 10mm) is presented in this paper. Ultrasonic wave could penetrate medium, through the acquisition of representative information from the echoes, properties of medium can be reflected. This pressure measurement is difficult due to that echoes' information is not easy to obtain in small diameter pipeline. The proposed method is a study on pipeline with Kneser liquid and is based on the principle that the transmission speed of ultrasonic wave in pipeline liquid correlates with liquid pressure and transmission speed of ultrasonic wave in pipeline liquid is reflected through ultrasonic propagation time providing that acoustic distance is fixed. Therefore, variation of ultrasonic propagation time can reflect variation of pressure in pipeline. Ultrasonic propagation time is obtained by electric processing approach and is accurately measured to nanosecond through high resolution time measurement module. We used ultrasonic propagation time difference to reflect actual pressure in this paper to reduce the environmental influences. The corresponding pressure values are finally obtained by acquiring the relationship between variation of ultrasonic propagation time difference and pressure with the use of neural network analysis method, the results show that this method is accurate and can be used in practice.

  8. The acoustic velocity, refractive index, and equation of state of liquid ammonia dihydrate under high pressure and high temperature.

    PubMed

    Ma, Chunli; Wu, Xiaoxin; Huang, Fengxian; Zhou, Qiang; Li, Fangfei; Cui, Qiliang

    2012-09-14

    High-pressure and high-temperature Brillouin scattering studies have been performed on liquid of composition corresponding to the ammonia dihydrate stoichiometry (NH(3)·2H(2)O) in a diamond anvil cell. Using the measured Brillouin frequency shifts from 180° back- and 60° platelet-scattering geometries, the acoustic velocity, refractive index, density, and adiabatic bulk modulus have been determined under pressure up to freezing point along the 296, 338, 376, and 407 K isotherms. Along these four isotherms, the acoustic velocities increase smoothly with increasing pressure but decrease with the increased temperature. However, the pressure dependence of the refractive indexes on the four isotherms exhibits a change in slope around 1.5 GPa. The bulk modulus increases linearly with pressure and its slope, dB/dP, decreases from 6.83 at 296 K to 4.41 at 407 K. These new datasets improve our understanding of the pressure- and temperature-induced molecular structure changes in the ammonia-water binary system.

  9. Acoustic model of micro-pressure wave emission from a high-speed train tunnel

    NASA Astrophysics Data System (ADS)

    Miyachi, T.

    2017-03-01

    The micro-pressure wave (MPW) radiated from a tunnel portal can, if audible, cause serious problems around tunnel portals in high-speed railways. This has created a need to develop an acoustic model that considers the topography around a radiation portal in order to predict MPWs more accurately and allow for higher speed railways in the future. An acoustic model of MPWs based on linear acoustic theory is developed in this study. First, the directivity of sound sources and the acoustical effect of topography are investigated using a train launcher facility around a portal on infinitely flat ground and with an infinite vertical baffle plate. The validity of linear acoustic theory is then discussed through a comparison of numerical results obtained using the finite difference method (FDM) and experimental results. Finally, an acoustic model is derived that considers sound sources up to the second order and Green's function to represent the directivity and effect of topography, respectively. The results predicted by this acoustic model are shown to be in good agreement with both numerical and experimental results.

  10. Burst prediction by acoustic emission in filament-wound pressure vessels

    NASA Technical Reports Server (NTRS)

    Gorman, Michael R.

    1990-01-01

    Acoustic emission in 51-cm diameter graphite/epoxy pressure vessels was monitored during pressurization (hydrotesting). Several vessels were subjected to impact by a blunt impactor, but only after the vessels had been proofed; that is, pressurized to 80 percent of nominal burst pressure as determined from control (unimpacted) vessels. AE activity was then monitored throughout a series of successively higher pressure cycles ranging from 10 to 60 percent of ultimate. Each cycle included a ramp up to pressure followed by a 4-min hold period and then pressure unload. The event rate was high, and especially modified AE analyzers had to be used to acquire the data. This paper presents the AE event count versus pressure history of these tests and demonstrates the ability of the AE technique to monitor the growth of damage and to estimate the effect on ultimate strength. The number of events that occurred during pressure holds proved to be a reasonable estimator of vessel performance.

  11. Vapor pressure measured with inflatable plastic bag

    NASA Technical Reports Server (NTRS)

    1965-01-01

    Deflated plastic bag in a vacuum chamber measures initial low vapor pressures of materials. The bag captures the test sample vapors and visual observation of the vapor-inflated bag under increasing external pressures yields pertinent data.

  12. Cosmic sound: Measuring the Universe with baryonic acoustic oscillations

    NASA Astrophysics Data System (ADS)

    Hütsi, Gert

    2006-05-01

    During the last ten to fifteen years cosmology has turned from a data-starved to a data-driven science. Several key parameters of the Universe have now been measured with an accuracy better than 10%. Surprisingly, it has been found that instead of slowing down, the expansion of the Universe proceeds at an ever increasing rate. From this we infer the existence of a negative pressure component -- the so-called Dark Energy (DE) -- that makes up more than two thirds of the total matter-energy content of our Universe. It is generally agreed amongst cosmologists and high energy physicists that understanding the nature of the DE poses one of the biggest challenges for the modern theoretical physics. Future cosmological datasets, being superior in both quantity and quality to currently existing data, hold the promise for unveiling many of the properties of the mysterious DE component. With ever larger datasets, as the statistical errors decrease, one needs to have a very good control over the possible systematic uncertainties. To make progress, one has to concentrate the observational effort towards the phenomena that are theoretically best understood and also least ``contaminated'' by complex astrophysical processes or several intervening foregrounds. Currently by far the cleanest cosmological information has been obtained through measurements of the angular temperature fluctuations of the Cosmic Microwave Background (CMB). The typical angular size of the CMB temperature fluctuations is determined by the distance the sound waves in the tightly coupled baryon-photon fluid can have traveled since the Big Bang until the epoch of recombination. A similar scale is also expected to be imprinted in the large-scale matter distribution as traced by, for instance, galaxies or galaxy clusters. Measurements of the peaks in the CMB angular power spectrum fix the physical scale of the sound horizon with a high precision. By identifying the corresponding features in the low redshift

  13. Acoustic properties of pistonphones at low frequencies in the presence of pressure leakage and heat conduction

    NASA Astrophysics Data System (ADS)

    Zhang, Fan; He, Wen; He, Longbiao; Rong, Zuochao

    2015-12-01

    The wide concern on absolute pressure calibration of acoustic transducers at low frequencies prompts the development of the pistonphone method. At low frequencies, the acoustic properties of pistonphones are governed by the pressure leakage and the heat conduction effects. However, the traditional theory for these two effects applies a linear superposition of two independent correction models, which differs somewhat from their coupled effect at low frequencies. In this paper, acoustic properties of pistonphones at low frequencies in full consideration of the pressure leakage and heat conduction effects have been quantitatively studied, and the explicit expression for the generated sound pressure has been derived. With more practical significance, a coupled correction expression for these two effects of pistonphones has been derived. In allusion to two typical pistonphones, the NPL pistonphone and our developed infrasonic pistonphone, comparisons were done for the coupled correction expression and the traditional one, whose results reveal that the traditional one produces maximum insufficient errors of about 0.1 dB above the lower limiting frequencies of two pistonphones, while at lower frequencies, excessive correction errors with an explicit limit of about 3 dB are produced by the traditional expression. The coupled correction expression should be adopted in the absolute pressure calibration of acoustic transducers at low frequencies. Furthermore, it is found that the heat conduction effect takes a limiting deviation of about 3 dB for the pressure amplitude and a small phase difference as frequency decreases, while the pressure leakage effect remarkably drives the pressure amplitude to attenuate and the phase difference tends to be 90° as the frequency decreases. The pressure leakage effect plays a more important role on the low frequency property of pistonphones.

  14. Measurement and mathematical simulation of acoustic characteristics of an artificially lengthened vocal tract

    NASA Astrophysics Data System (ADS)

    Radolf, Vojtěch; Horáček, Jaromír; Dlask, Pavel; Otčenášek, Zdeněk; Geneid, Ahmed; Laukkanen, Anne-Maria

    2016-03-01

    Phonation into tubes is used for voice training and therapy. In the present study, the formant frequencies were estimated from measurements of the acoustic pressure and the acoustic input impedance for a plexiglass model of the vocal tract (VT) prolonged by a glass tube. Similar transfer function measurements were performed with a human VT in vivo. The experimental results matched the mathematical modelling and confirmed the legitimacy of assuming rigid walls in mathematical simulations of the acoustic characteristics of an artificial VT model prolonged by a tube. However, this study also proved a considerable influence from soft tissues in the yielding walls of human VT cavities on the first formant frequency, F1. The measured F1 for the VT model corresponded to the computed value of 78 Hz. The experiments in a human instead resulted in a much higher value of F1: about 200 Hz. The results confirm that a VT model with yielding walls must be considered for mathematical modelling of the occluded or semi-occluded human vocal tract, e.g. prolonged by tubes or straws. This is explained by an acoustic-structural interaction of the vocal tract cavities with a mechanical low-frequency resonance of the soft tissue in the larynx.

  15. Variabilities detected by acoustic emission from filament-wound Aramid fiber/epoxy composite pressure vessels

    NASA Technical Reports Server (NTRS)

    Hamstad, M. A.

    1978-01-01

    Two hundred and fifty Aramid fiber/epoxy pressure vessels were filament-wound over spherical aluminum mandrels under controlled conditions typical for advanced filament-winding. A random set of 30 vessels was proof-tested to 74% of the expected burst pressure; acoustic emission data were obtained during the proof test. A specially designed fixture was used to permit in situ calibration of the acoustic emission system for each vessel by the fracture of a 4-mm length of pencil lead (0.3 mm in diameter) which was in contact with the vessel. Acoustic emission signatures obtained during testing showed larger than expected variabilities in the mechanical damage done during the proof tests. To date, identification of the cause of these variabilities has not been determined.

  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. Indirect Blood Pressure Measuring Device

    NASA Technical Reports Server (NTRS)

    Hum, L.; Cole, C. E.

    1973-01-01

    Design and performance of a blood pressure recording device for pediatric use are reported. A strain gage transducer with a copper-beryllium strip as force sensing element is used to monitor skin movements and to convert them into electrical signals proportional to those displacements. Experimental tests with this device in recording of force developed above the left femoral artery of a dog accurately produced a blood pressure curve.

  18. Surface Acoustic Wave Based Pressure Sensor with Ground Shielding over Cavity on 41° YX LiNbO3

    NASA Astrophysics Data System (ADS)

    Lee, Keekeun; Wang, Wen; Kim, Geunyoung; Yang, Sangsik

    2006-07-01

    A surface acoustic wave (SAW)-based pressure sensor was fabricated for stable mechanical compression force measurement. A single phase unidirectional transducer (SPUDT) and two acoustic tracks were employed to minimize inherent insertion loss and improve reflectivity from the reflectors. The coupling of modes (COM) theory and finite element methods (FEMs) were used to determine optimal design parameters. A LiNbO3 diaphragm was bonded to a heavily doped silicon substrate with a cavity of ˜250 μm deep, in which gold was lined all over the inner cavity to reduce the coupling loss of SAW energy to the surrounding atmosphere. As a mechanical compression force was applied to the diaphragm, the diaphragm bent, resulting in phase shifts of the reflected peaks. The phase shifts were modulated depending on the amount of mechanical compression applied. The measured reflection coefficient S11 showed good agreement with simulated results.

  19. Acoustic and manual measurements of methane ebullition in peatlands

    NASA Astrophysics Data System (ADS)

    Varner, R. K.; Palace, M. W.; Lennartz, J. M.; Wik, M.; Crill, P. M.; Ewing, S. A.; Harden, J. W.; Turetsky, M. R.

    2013-12-01

    Controls on the magnitude and frequency of methane (CH4) release through ebullition (bubbling) in water saturated ecosystems such as bogs, fens and lakes are important to both the atmospheric and ecosystems science community. In order to understand the response of these ecosystems to future climate forcing, we need to systematically monitor ebullition from these ecosystems over many seasons and across a multitude of landscape morphologies. We have developed and field tested an inexpensive array of sampling/monitoring instruments to identify the frequency and magnitude of bubbling events which allows us to correlate bubble data with potential drivers such as changes in hydrostatic pressure, wind and temperature. The instrument consists of a nested, inverted funnel design with a hydrophone for detecting bubbles that rise through the peat. The design offers a way to sample the gas collected in the funnels to determine the concentration of CH4. Laboratory calibration of the instrument resulted in an equation that relates frequency of bubbles hitting the hydrophone with bubble volume. Audio data was recorded continuously using a digital audio recorder attached to two ebullition sensors and could be deployed remotely for up to 20 days. Time, fundamental frequency, and estimated bubble size were determined using MATLAB code. Manual bubble flux measurements were also made for comparison to the acoustically sensed ebullition. Instruments were deployed in summers 2011-2013 at a temperate fen (Sallie's Fen, NH, USA) and a subarctic mire (Stordalen, Abisko, Sweden). We also recorded ebullition at two locations in subarctic Alaska (APEX Research Site, Fairbanks, AK and Innoko National Wildlife Refuge) during summer 2011. Ebullition was observed at all sites with highest daily rates in fen versus bog sites. Observed distributions of bubble events correlate with published models of ebullition based on peat density.

  20. Differential Intracochlear Sound Pressure Measurements in Human Temporal Bones with an Off-the-Shelf Sensor

    PubMed Central

    Salcher, Rolf; Püschel, Klaus; Lenarz, Thomas; Maier, Hannes

    2016-01-01

    The standard method to determine the output level of acoustic and mechanical stimulation to the inner ear is measurement of vibration response of the stapes in human cadaveric temporal bones (TBs) by laser Doppler vibrometry. However, this method is reliable only if the intact ossicular chain is stimulated. For other stimulation modes an alternative method is needed. The differential intracochlear sound pressure between scala vestibuli (SV) and scala tympani (ST) is assumed to correlate with excitation. Using a custom-made pressure sensor it has been successfully measured and used to determine the output level of acoustic and mechanical stimulation. To make this method generally accessible, an off-the-shelf pressure sensor (Samba Preclin 420 LP, Samba Sensors) was tested here for intracochlear sound pressure measurements. During acoustic stimulation, intracochlear sound pressures were simultaneously measurable in SV and ST between 0.1 and 8 kHz with sufficient signal-to-noise ratios with this sensor. The pressure differences were comparable to results obtained with custom-made sensors. Our results demonstrated that the pressure sensor Samba Preclin 420 LP is usable for measurements of intracochlear sound pressures in SV and ST and for the determination of differential intracochlear sound pressures. PMID:27610377

  1. Load influence on gear noise. [mathematical model for determining acoustic pressure level as function of load

    NASA Technical Reports Server (NTRS)

    Merticaru, V.

    1974-01-01

    An original mathematical model is proposed to derive equations for calculation of gear noise. These equations permit the acoustic pressure level to be determined as a function of load. Application of this method to three parallel gears is reported. The logical calculation scheme is given, as well as the results obtained.

  2. A microwave pressure sounder. [for remote measurement of atmospheric pressure

    NASA Technical Reports Server (NTRS)

    Peckham, G. E.; Flower, D. A.

    1981-01-01

    A technique for the remote measurement of atmospheric surface pressure will be described. Such measurements could be made from a satellite in polar orbit and would cover many areas for which conventional meteorological data are not available. An active microwave instrument is used to measure the strength of return echoes from the ocean surface at a number of frequencies near the 60 GHz oxygen absorption band. Factors which affect the accuracy with which surface pressure can be deduced from these measurements will be discussed and an instrument designed to test the method by making measurements from an aircraft will be described.

  3. Palpatory Method of Measuring Diastolic Blood Pressure

    PubMed Central

    Sahu, Dinesh; Bhaskaran, M

    2010-01-01

    Background: Most common method for measuring blood pressure is palpatory but only systolic pressure can be measured with this method. In this study we are describing palpatory method of measuring diastolic blood pressure as well. Patients & Methods: We have studied in 200 patients and compared systolic as well as diastolic blood pressures with two methods, auscutatory and palpatory. Systolic and diastolic blood pressure were measured by one of the authors with new palpatory method and noted down. Then an independent observer, who was blinded to the palpatory method's values, measured blood pressure by auscultatory method and noted down. The values were compared in term of range and percentage. Results: The difference were analysed and found that 102 (51%) patients had systolic and diastolic blood pressure measured by palpatory method, within ± 2 mmHg of auscutatory method, 37 (19%) patients had within ± 4 mmHg, 52 (25%) patients had same readings as with auscutatory method, and in 9 (0.5%) patients it could not be measured. Conclusion: The palpatory method would be very useful where frequent blood pressure measurement are being done manually like in wards, in busy OPD, patient on treadmill and also whenever stethoscope is not available. The blood pressure can be measured in noisy environment too. PMID:21547184

  4. Field Assessment of Acoustic-Doppler Based Discharge Measurements

    USGS Publications Warehouse

    Mueller, D.S.; ,

    2002-01-01

    The use of equipment based on the Doppler principle for measuring water velocity and computing discharge is common within the U.S. Geological Survey (USGS). The instruments and software have changed appreciably during the last 5 years; therefore, the USGS has begun a field validation of the instruments currently (2002) available for making discharge measurements from a moving boat in streams of various sizes. Instruments manufactured by SonTek/YSI2 and RD Instruments, Inc. were used to collect discharge data at five different sites. One or more traditional discharge measurements were made by the use of a Price AA current meter and standard USGS procedures with the acoustic instruments at each site during data collection. The discharges measured with the acoustic instruments were compared with the discharges measured with Price AA meters and the current USGS stage-discharge rating for each site. The mean discharges measured by each acoustic instrument were within 5 percent of the Price AA-based measurement and (or) discharge from the stage-discharge rating. Additional analysis of the data collected indicates that the coefficient of variation of the discharge measurements consistently was less for the RD Instruments, Inc. Rio Grandes than it was for the SonTek/YSI RiverSurveyors. The bottom-tracking referenced measurement had a lower coefficient of variation than the differentially corrected global positioning system referenced measurements. It was observed that the higher frequency RiverSurveyors measured a moving bed more often than the lower frequency Rio Grandes. The detection of a moving bed caused RiverSurveyors to be consistently biased low when referenced to bottom tracking. Differentially corrected global positioning system data may be used to remove the bias observed in the bottom-tracking referenced measurements.

  5. Evaluation of the Acoustic Measurement Capability of the NASA Langley V/STOL Wind Tunnel Open Test Section with Acoustically Absorbent Ceiling and Floor Treatments

    NASA Technical Reports Server (NTRS)

    Theobald, M. A.

    1978-01-01

    The single source location used for helicopter model studies was utilized in a study to determine the distances and directions upstream of the model accurate at which measurements of the direct acoustic field could be obtained. The method used was to measure the decrease of sound pressure levels with distance from a noise source and thereby determine the Hall radius as a function of frequency and direction. Test arrangements and procedures are described. Graphs show the normalized sound pressure level versus distance curves for the glass fiber floor treatment and for the foam floor treatment.

  6. Nonlinear acoustic measurements ahead of a notch during fatigue

    NASA Astrophysics Data System (ADS)

    Martin, R. W.; Mooers, R. D.; Hutson, A. L.; Sathish, S.; Blodgett, M. P.

    2013-01-01

    This paper presents measurements of relative nonlinear acoustic parameter (βrel), ahead of a notch in Al 7075-T651 dog bone samples, subjected to fatigue. It is compared with crack growth measurements on the same samples. Measurements performed on two samples subjected to identical fatigue conditions that failed at vastly different number of fatigue cycles are described. The βrel measurement for both samples as a function of fatigue cycles was fit a Boltzmann curve. The role of changing βrel ahead of a notch is explored as a possible approach for remain life evaluation.

  7. Acoustic property measurements in a photoacoustic imager

    NASA Astrophysics Data System (ADS)

    Willemink, René G. H.; Manohar, Srirang; Slump, Cornelis H.; van der Heijden, Ferdi; van Leeuwen, Ton

    2007-07-01

    Photoacoustics is a hybrid imaging technique that combines the contrast available to optical imaging with the resolution that is possessed by ultrasound imaging. The technique is based on generating ultrasound from absorbing structures in tissue using pulsed light. In photoacoustic (PA) computerized tomography (CT) imaging, reconstruction of the optical absorption in a subject, is performed for example by filtered backprojection. The backprojection is performed along circular paths in image space instead of along straight lines as in X-ray CT imaging. To achieve this, the speed-of-sound through the subject is usually assumed constant. An unsuitable speed-of-sound can degrade resolution and contrast. We discuss here a method of actually measuring the speed-of- sound distribution using ultrasound transmission through the subject under photoacoustic investigation. This is achieved in a simple approach that does not require any additional ultrasound transmitter. The method uses a passive element (carbon fiber) that is placed in the imager in the path of the illumination which generates ultrasound by the photoacoustic effect and behaves as an ultrasound source. Measuring the time-of-flight of this ultrasound transient by the same detector used for conventional photoacoustics, allows a speed-of-sound image to be reconstructed. This concept is validated on phantoms.

  8. Foot Plantar Pressure Measurement System: A Review

    PubMed Central

    Razak, Abdul Hadi Abdul; Zayegh, Aladin; Begg, Rezaul K.; Wahab, Yufridin

    2012-01-01

    Foot plantar pressure is the pressure field that acts between the foot and the support surface during everyday locomotor activities. Information derived from such pressure measures is important in gait and posture research for diagnosing lower limb problems, footwear design, sport biomechanics, injury prevention and other applications. This paper reviews foot plantar sensors characteristics as reported in the literature in addition to foot plantar pressure measurement systems applied to a variety of research problems. Strengths and limitations of current systems are discussed and a wireless foot plantar pressure system is proposed suitable for measuring high pressure distributions under the foot with high accuracy and reliability. The novel system is based on highly linear pressure sensors with no hysteresis. PMID:23012576

  9. Spatial resolution in plantar pressure measurement revisited.

    PubMed

    Pataky, Todd C

    2012-08-09

    Plantar pressures are typically measured using sensors of finite area, so the accuracy with which one can measure true maximum pressure is dependent on sensor size. Measurement accuracy has been modeled previously for one patient's metatarsals (Lord, 1997), but has not been modeled either for general subjects or for other parts of the foot. The purposes of this study were (i) to determine whether Lord's (1997) model is also valid for heel and hallux pressures, and (ii) to examine how sensor size relates to measurement accuracy in the context of four factors common to many measurement settings: pressure pulse size, foot positioning, pressure change quantification, and gross pressure redistribution. Lord's (1997) model was first generalized and was then validated using 10 healthy walking subjects, with relatively low RMSE values on the order of 20 kPa. Next, postural data were used to show that gross pressure redistributions can be accurately quantified (p<0.002), even with rather gross sensor sizes of 30 mm. Finally, numerical analyses revealed that the relation between sensor size and measurement accuracy is highly complex, with deep dependency on the measurement context. In particular, the critical sensor widths required to achieve 90% accuracy ranged from 1.7 mm to 17.4 mm amongst the presently investigated scenarios. Since measurement accuracy varies so extensively with so many factors, the current results cannot yield specific recommendations regarding spatial resolution. It is concluded simply that no particular spatial resolution can yield a constant measurement accuracy across common plantar pressure measurement tasks.

  10. Atypical prosody in Asperger syndrome: perceptual and acoustic measurements.

    PubMed

    Filipe, Marisa G; Frota, Sónia; Castro, São Luís; Vicente, Selene G

    2014-08-01

    It is known that individuals with Asperger syndrome (AS) may show no problems with regard to what is said (e.g., lexical content) but tend to have difficulties in how utterances are produced, i.e., they may show prosodic impairments. In the present study, we focus on the use of prosodic features to express grammatical meaning. Specifically, we explored the sentence type difference between statements and questions that is conveyed by intonation, using perceptual and acoustic measurements. Children aged 8 and 9 years with AS (n = 12) were matched according to age and nonverbal intelligence with typically developing peers (n = 17). Although children with AS could produce categorically accurate prosodic patterns, their prosodic contours were perceived as odd by adult listeners, and acoustic measurements showed alterations in duration and pitch. Additionally, children with AS had greater variability in fundamental frequency contours compared to typically developing peers.

  11. Determining Transmission Loss from Measured External and Internal Acoustic Environments

    NASA Technical Reports Server (NTRS)

    Scogin, Tyler; Smith, A. M.

    2012-01-01

    An estimate of the internal acoustic environment in each internal cavity of a launch vehicle is needed to ensure survivability of Space Launch System (SLS) avionics. Currently, this is achieved by using the noise reduction database of heritage flight vehicles such as the Space Shuttle and Saturn V for liftoff and ascent flight conditions. Marshall Space Flight Center (MSFC) is conducting a series of transmission loss tests to verify and augment this method. For this test setup, an aluminum orthogrid curved panel representing 1/8th of the circumference of a section of the SLS main structure was mounted in between a reverberation chamber and an anechoic chamber. Transmission loss was measured across the panel using microphones. Data measured during this test will be used to estimate the internal acoustic environments for several of the SLS launch vehicle internal spaces.

  12. Numerical and experimental investigation of a low-frequency measurement technique: differential acoustic resonance spectroscopy

    NASA Astrophysics Data System (ADS)

    Yin, Hanjun; Zhao, Jianguo; Tang, Genyang; Ma, Xiaoyi; Wang, Shangxu

    2016-06-01

    Differential acoustic resonance spectroscopy (DARS) has been developed to determine the elastic properties of saturated rocks within the kHz frequency range. This laboratory technique is based on considerations from perturbation theory, wherein the resonance frequencies of the resonant cavity with and without a perturbation sample are used to estimate the acoustic properties of the test sample. In order to better understand the operating mechanism of DARS and therefore optimize the procedure, it is important to develop an accurate and efficient numerical model. Accordingly, this study presents a new multiphysics model by coupling together considerations from acoustics, solid mechanics, and electrostatics. The numerical results reveal that the newly developed model can successfully simulate the acoustic pressure field at different resonance modes, and that it can accurately reflect the measurement process. Based on the understanding of the DARS system afforded by the numerical simulation, we refine the system configuration by utilizing cavities of different lengths and appropriate radii to broaden the frequency bandwidth and ensure testing accuracy. Four synthetic samples are measured to test the performance of the optimized DARS system, in conjunction with ultrasonic and static measurements. For nonporous samples, the estimated bulk moduli are shown to be independent of the different measurement methods (i.e. DARS or ultrasonic techniques). In contrast, for sealed porous samples, the differences in bulk moduli between the low- and high-frequency techniques can be clearly observed; this discrepancy is attributed to frequency dispersion. In summary, the optimized DARS system with an extended frequency range of 500-2000 Hz demonstrates considerable utility in investigating the frequency dependence of the acoustic properties of reservoir rocks.

  13. Validation of streamflow measurements made with acoustic doppler current profilers

    USGS Publications Warehouse

    Oberg, K.; Mueller, D.S.

    2007-01-01

    The U.S. Geological Survey and other international agencies have collaborated to conduct laboratory and field validations of acoustic Doppler current profiler (ADCP) measurements of streamflow. Laboratory validations made in a large towing basin show that the mean differences between tow cart velocity and ADCP bottom-track and water-track velocities were -0.51 and -1.10%, respectively. Field validations of commercially available ADCPs were conducted by comparing streamflow measurements made with ADCPs to reference streamflow measurements obtained from concurrent mechanical current-meter measurements, stable rating curves, salt-dilution measurements, or acoustic velocity meters. Data from 1,032 transects, comprising 100 discharge measurements, were analyzed from 22 sites in the United States, Canada, Sweden, and The Netherlands. Results of these analyses show that broadband ADCP streamflow measurements are unbiased when compared to the reference discharges regardless of the water mode used for making the measurement. Measurement duration is more important than the number of transects for reducing the uncertainty of the ADCP streamflow measurement. ?? 2007 ASCE.

  14. Acoustic temperature profile measurement technique for large combustion chambers

    NASA Technical Reports Server (NTRS)

    Venkateshan, S. P.; Shakkottai, P.; Kwack, E. Y.; Back, L. H.

    1989-01-01

    Measurement of times of flight of sound waves can be used to determine temperatures in a gas. This paper describes a system, based on this principle, that is capable of giving the temperature profile in a nonisothermal gas volume, for example, prevalent in a large furnace. The apparatus is simple, rugged, accurate, and capable of being automated for process control applications. It is basically an acoustic waveguide where the outside temperature profile is transferred to a chosen gas contained inside the guide.

  15. Elevation correction factor for absolute pressure measurements

    NASA Technical Reports Server (NTRS)

    Panek, Joseph W.; Sorrells, Mark R.

    1996-01-01

    With the arrival of highly accurate multi-port pressure measurement systems, conditions that previously did not affect overall system accuracy must now be scrutinized closely. Errors caused by elevation differences between pressure sensing elements and model pressure taps can be quantified and corrected. With multi-port pressure measurement systems, the sensing elements are connected to pressure taps that may be many feet away. The measurement system may be at a different elevation than the pressure taps due to laboratory space or test article constraints. This difference produces a pressure gradient that is inversely proportional to height within the interface tube. The pressure at the bottom of the tube will be higher than the pressure at the top due to the weight of the tube's column of air. Tubes with higher pressures will exhibit larger absolute errors due to the higher air density. The above effect is well documented but has generally been taken into account with large elevations only. With error analysis techniques, the loss in accuracy from elevation can be easily quantified. Correction factors can be applied to maintain the high accuracies of new pressure measurement systems.

  16. Nonlinear Response of Composite Panels Under Combined Acoustic Excitation and Aerodynamic Pressure

    NASA Technical Reports Server (NTRS)

    Abdel-Motagaly, K.; Duan, B.; Mei, C.

    1999-01-01

    A finite element formulation is presented for the analysis of large deflection response of composite panels subjected to aerodynamic pressure- at supersonic flow and high acoustic excitation. The first-order shear deformation theory is considered for laminated composite plates, and the von Karman nonlinear strain-displacement relations are employed for the analysis of large deflection panel response. The first-order piston theory aerodynamics and the simulated Gaussian white noise are employed for the aerodynamic and acoustic loads, respectively. The nonlinear equations of motion for an arbitrarily laminated composite panel subjected to a combined aerodynamic and acoustic pressures are formulated first in structure node degrees-of-freedom. The system equations are then transformed and reduced to a set of coupled nonlinear equations in modal coordinates. Modal participation is defined and the in-vacuo modes to be retained in the analysis are based on the modal participation values. Numerical results include root mean square values of maximum deflections, deflection and strain response time histories, probability distributions, and power spectrum densities. Results showed that combined acoustic and aerodynamic loads have to be considered for panel analysis and design at high dynamic pressure values.

  17. Acoustic measurements for the combustion diagnosis of diesel engines fuelled with biodiesels

    NASA Astrophysics Data System (ADS)

    Zhen, Dong; Wang, Tie; Gu, Fengshou; Tesfa, Belachew; Ball, Andrew

    2013-05-01

    In this paper, an experimental investigation was carried out on the combustion process of a compression ignition (CI) engine running with biodiesel blends under steady state operating conditions. The effects of biodiesel on the combustion process and engine dynamics were analysed for non-intrusive combustion diagnosis based on a four-cylinder, four-stroke, direct injection and turbocharged diesel engine. The signals of vibration, acoustic and in-cylinder pressure were measured simultaneously to find their inter-connection for diagnostic feature extraction. It was found that the sound energy level increases with the increase of engine load and speed, and the sound characteristics are closely correlated with the variation of in-cylinder pressure and combustion process. The continuous wavelet transform (CWT) was employed to analyse the non-stationary nature of engine noise in a higher frequency range. Before the wavelet analysis, time synchronous average (TSA) was used to enhance the signal-to-noise ratio (SNR) of the acoustic signal by suppressing the components which are asynchronous. Based on the root mean square (RMS) values of CWT coefficients, the effects of biodiesel fractions and operating conditions (speed and load) on combustion process and engine dynamics were investigated. The result leads to the potential of airborne acoustic measurements and analysis for engine condition monitoring and fuel quality evaluation.

  18. Acoustic field characterization of the Duolith: Measurements and modeling of a clinical shock wave therapy device

    PubMed Central

    Perez, Camilo; Chen, Hong; Matula, Thomas J.; Karzova, Maria; Khokhlova, Vera A.

    2013-01-01

    Extracorporeal shock wave therapy (ESWT) uses acoustic pulses to treat certain musculoskeletal disorders. In this paper the acoustic field of a clinical portable ESWT device (Duolith SD1) was characterized. Field mapping was performed in water for two different standoffs of the electromagnetic head (15 or 30 mm) using a fiber optic probe hydrophone. Peak positive pressures at the focus ranged from 2 to 45 MPa, while peak negative pressures ranged from −2 to −11 MPa. Pulse rise times ranged from 8 to 500 ns; shock formation did not occur for any machine settings. The maximum standard deviation in peak pressure at the focus was 1.2%, indicating that the Duolith SD1 generates stable pulses. The results compare qualitatively, but not quantitatively with manufacturer specifications. Simulations were carried out for the short standoff by matching a Khokhlov-Zabolotskaya-Kuznetzov equation to the measured field at a plane near the source, and then propagating the wave outward. The results of modeling agree well with experimental data. The model was used to analyze the spatial structure of the peak pressures. Predictions from the model suggest that a true shock wave could be obtained in water if the initial pressure output of the device were doubled. PMID:23927207

  19. Fiber-optic interferometric sensors for measurements of pressure fluctuations - Experimental evaluation

    NASA Technical Reports Server (NTRS)

    Cho, Y. C.; Soderman, P. T.

    1993-01-01

    A fiber optic interferometric sensor that is being developed at NASA Ames Research Center for pressure fluctuation measurements in wind tunnels is considered. Preliminary evaluation indicates that the fiber optic interferometric sensor can be successfully used as an aeroacoustic sensor and is capable of providing a powerful instrument to solve complex acoustic measurement problems in wind tunnels.

  20. The Dynamics of Vapor Bubbles in Acoustic Pressure Fields

    NASA Technical Reports Server (NTRS)

    Hao, Y.; Prosperetti, A.

    1999-01-01

    In spite of a superficial similarity with gas bubbles, the intimate coupling between dynamical and thermal processes confers to oscillating vapor bubbles some unique characteristics. This paper examines numerically the validity of some asymptotic-theory predictions such as the existence of two resonant radii and a limit size for a given sound amplitude and frequency. It is found that a small vapor bubble in a sound field of sufficient amplitude grows quickly through resonance and continues to grow thereafter at a very slow rate, seemingly indefinitely. Resonance phenomena therefore play a role for a few cycles at most, and reaching a limit size-if one exists at all-is found to require far more than several tens of thousands of cycles. It is also found that some small bubbles may grow or collapse depending on the phase of the sound field. The model accounts in detail for the thermo-fluid-mechanic processes in the vapor. In the second part of the paper, an approximate formulation valid for bubbles small with respect to the thermal penetration length in the vapor is derived and its accuracy examined, The present findings have implications for acoustically enhanced boiling heat transfer and other special applications such as boiling in microgravity.

  1. Automatic blood pressure measuring system (M091)

    NASA Technical Reports Server (NTRS)

    1977-01-01

    The Leg Volume Measuring System is used to measure leg calf girth changes that occur during exposure to lower body negative pressure as a result of pooling of blood and other fluids in the lower extremities.

  2. Optical Measurement Of Sound Pressure

    NASA Technical Reports Server (NTRS)

    Trinh, Eugene H.; Gaspar, Mark; Leung, Emily W.

    1989-01-01

    Noninvasive technique does not disturb field it measures. Sound field deflects laser beam proportionally to its amplitude. Knife edge intercepts undeflected beam, allowing only deflected beam to reach photodetector. Apparatus calibrated by comparing output of photodetector with that of microphone. Optical technique valuable where necessary to measure in remote, inaccessible, or hostile environment or to avoid perturbation of measured region.

  3. Digital PIV Measurements of Acoustic Particle Displacements in a Normal Incidence Impedance Tube

    NASA Technical Reports Server (NTRS)

    Humphreys, William M., Jr.; Bartram, Scott M.; Parrott, Tony L.; Jones, Michael G.

    1998-01-01

    Acoustic particle displacements and velocities inside a normal incidence impedance tube have been successfully measured for a variety of pure tone sound fields using Digital Particle Image Velocimetry (DPIV). The DPIV system utilized two 600-mj Nd:YAG lasers to generate a double-pulsed light sheet synchronized with the sound field and used to illuminate a portion of the oscillatory flow inside the tube. A high resolution (1320 x 1035 pixel), 8-bit camera was used to capture double-exposed images of 2.7-micron hollow silicon dioxide tracer particles inside the tube. Classical spatial autocorrelation analysis techniques were used to ascertain the acoustic particle displacements and associated velocities for various sound field intensities and frequencies. The results show that particle displacements spanning a range of 1-60 microns can be measured for incident sound pressure levels of 100-130 dB and for frequencies spanning 500-1000 Hz. The ability to resolve 1 micron particle displacements at sound pressure levels in the 100 dB range allows the use of DPIV systems for measurement of sound fields at much lower sound pressure levels than had been previously possible. Representative impedance tube data as well as an uncertainty analysis for the measurements are presented.

  4. Flow velocity measurement with the nonlinear acoustic wave scattering

    SciTech Connect

    Didenkulov, Igor; Pronchatov-Rubtsov, Nikolay

    2015-10-28

    A problem of noninvasive measurement of liquid flow velocity arises in many practical applications. To this end the most often approach is the use of the linear Doppler technique. The Doppler frequency shift of signal scattered from the inhomogeneities distributed in a liquid relatively to the emitted frequency is proportional to the sound frequency and velocities of inhomogeneities. In the case of very slow flow one needs to use very high frequency sound. This approach fails in media with strong sound attenuation because acoustic wave attenuation increases with frequency and there is limit in increasing sound intensity, i.e. the cavitation threshold. Another approach which is considered in this paper is based on the method using the difference frequency Doppler Effect for flows with bubbles. This method is based on simultaneous action of two high-frequency primary acoustic waves with closed frequencies on bubbles and registration of the scattered by bubbles acoustic field at the difference frequency. The use of this method is interesting since the scattered difference frequency wave has much lower attenuation in a liquid. The theoretical consideration of the method is given in the paper. The experimental examples confirming the theoretical equations, as well as the ability of the method to be applied in medical diagnostics and in technical applications on measurement of flow velocities in liquids with strong sound attenuation is described. It is shown that the Doppler spectrum form depends on bubble concentration velocity distribution in the primary acoustic beams crossing zone that allows one to measure the flow velocity distribution.

  5. Cavity gas pressure measurements on DIAMOND FORTUNE

    SciTech Connect

    Smith, C.W.; Breeze, S.P.

    1993-10-01

    Five measurements were made of the gas pressure in the cavity as a function of time on the DIAMOND FORTUNE event. The measurements were obtained with a fast and slow blowdown technique; an additional transducer on the cavity side of the explosive valve provided valuable data. Data from three of the five transducers are nearly coincident data from the other two show temperature-related shifts. The timeframe of the credible measurements extends from 0.1 second to four hours. The pressure at two seconds was 2,100 kPa (300 Psi). On the logarithmic time scale this level decays monotonically to 210 kPa (30 Psi) at 1,000 seconds. During the next decade of time the cavity pressure approached atmospheric pressure. Over the initial few seconds the measured amplitude is close to the S-Cubed prediction; with increased time the measured pressure decays at a faster rate.

  6. Evaluation of Acoustic Emission SHM of PRSEUS Composite Pressure Cube Tests

    NASA Technical Reports Server (NTRS)

    Horne, Michael R.; Madaras, Eric I.

    2013-01-01

    A series of tests of the Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) pressure cube were conducted during third quarter 2011 at NASA Langley Research Center (LaRC) in the Combined Loads Test facility (COLTS). This is a report of the analysis of the Acoustic Emission (AE) data collected during those tests. The AE signals of the later tests are consistent with the final failure progression through two of the pressure cube panels. Calibration tests and damage precursor AE indications, from preliminary checkout pressurizations, indicated areas of concern that eventually failed. Hence those tests have potential for vehicle health monitoring.

  7. Determining low-frequency source location from acoustic phase measurements

    NASA Astrophysics Data System (ADS)

    Poole, Travis L.; Frisk, George V.

    2002-11-01

    For low-frequency cw sound sources in shallow water, the time rate-of-change of the measured acoustic phase is well approximated by the time rate-of-change of the source-receiver separation distance. An algorithm for determining a locus of possible source locations based on this idea has been developed. The locus has the general form of a hyperbola, which can be used to provide a bearing estimation at long ranges, and an estimate of source location at short ranges. The algorithm uses only acoustic phase data and receiver geometry as input, and can be used even when the source frequency is slightly unstable and/or imprecisely known. The algorithm has been applied to data from low-frequency experiments (20-300 Hz), both for stable and unstable source frequencies, and shown to perform well. [Work supported by ONR and WHOI Academic Programs Office.

  8. Acoustic Intensity Measurements in the Presence of Low Mach Number Flow

    DTIC Science & Technology

    1993-09-01

    broadband acoustic holography ,3 intensity measurements in the presence of flow,"𔄁𔄀. 7 in-situ evaluation of the acoustic impedance and sound absorption...Cross Spectra" Ph.D. Thesis, Catholic University, (1987). 3. Loyau, T., Pascal, J., Gaillard, P., "Broadband Acoustic Holography Reconstruction From...AD-A269 995 The Pennsylvania State University APPLIED RESEARCH LABORATORY P.O. Box 30 State College, PA 16804 ACOUSTIC INTENSITY MEASUREMENTS IN THE

  9. Acoustic-Seismic Coupling in Porous Ground - Measurements and Analysis for On-Site-Inspection Support

    NASA Astrophysics Data System (ADS)

    Liebsch, Mattes; Gorschlüter, Felix; Altmann, Jürgen

    2014-05-01

    During on-site inspections (OSI) of the Comprehensive Nuclear Test Ban Treaty Organisation (CTBTO) a local seismic network can be installed to measure seismic aftershock signals of an assumed underground nuclear explosion. These signals are caused by relaxation processes in and near the cavity created by the explosion and when detected can lead to a localisation of the cavity. This localisation is necessary to take gas samples from the ground which are analysed for radioactive noble gas isotopes to confirm or dismiss the suspicion of a nuclear test. The aftershock signals are of very low magnitude so they can be masked by different sources, in particular periodic disturbances caused by vehicles and aircraft in the inspection area. Vehicles and aircraft (mainly helicopters) will be used for the inspection activities themselves, e.g. for overhead imagery or magnetic-anomaly sensing. While vehicles in contact with the ground can excite soil vibrations directly, aircraft and vehicles alike emit acoustic waves which excite soil vibrations when hitting the ground. These disturbing signals are of periodic nature while the seismic aftershock signals are pulse-shaped, so their separation is possible. The understanding of the coupling of acoustic waves to the ground is yet incomplete, a better understanding is necessary to improve the performance of an OSI, e.g. to address potential consequences for the sensor placement, the helicopter trajectories etc. In a project funded by the Young Scientist Research Award of the CTBTO to one of us (ML), we investigated the acoustic-seismic coupling of airborne signals of jet aircraft and artificially induced ones by a speaker. During a measurement campaign several acoustic and seismic sensors were placed below the take-off trajectory of an airport at 4 km distance. Therefore taking off and landing jet aircraft passed nearly straightly above the setup. Microphones were placed close to the ground to record the sound pressure of incident

  10. Measuring Viscosities of Gases at Atmospheric Pressure

    NASA Technical Reports Server (NTRS)

    Singh, Jag J.; Mall, Gerald H.; Hoshang, Chegini

    1987-01-01

    Variant of general capillary method for measuring viscosities of unknown gases based on use of thermal mass-flowmeter section for direct measurement of pressure drops. In technique, flowmeter serves dual role, providing data for determining volume flow rates and serving as well-characterized capillary-tube section for measurement of differential pressures across it. New method simple, sensitive, and adaptable for absolute or relative viscosity measurements of low-pressure gases. Suited for very complex hydrocarbon mixtures where limitations of classical theory and compositional errors make theoretical calculations less reliable.

  11. Acoustic pressure waves induced in human heads by RF pulses from high-field MRI scanners.

    PubMed

    Lin, James C; Wang, Zhangwei

    2010-04-01

    The current evolution toward greater image resolution from magnetic resonance image (MRI) scanners has prompted the exploration of higher strength magnetic fields and use of higher levels of radio frequencies (RFs). Auditory perception of RF pulses by humans has been reported during MRI with head coils. It has shown that the mechanism of interaction for the auditory effect is caused by an RF pulse-induced thermoelastic pressure wave inside the head. We report a computational study of the intensity and frequency of thermoelastic pressure waves generated by RF pulses in the human head inside high-field MRI and clinical scanners. The U.S. Food and Drug Administration (U.S. FDA) guides limit the local specific absorption rate (SAR) in the body-including the head-to 8 W kg(-1). We present results as functions of SAR and show that for a given SAR the peak acoustic pressures generated in the anatomic head model were essentially the same at 64, 300, and 400 MHz (1.5, 7.0, and 9.4 T). Pressures generated in the anatomic head are comparable to the threshold pressure of 20 mPa for sound perception by humans at the cochlea for 4 W kg(-1). Moreover, results indicate that the peak acoustic pressure in the brain is only 2 to 3 times the auditory threshold at the U.S. FDA guideline of 8 W kg(-1). Even at a high SAR of 20 W kg(-1), where the acoustic pressure in the brain could be more than 7 times the auditory threshold, the sound pressure levels would not be more than 17 db above threshold of perception at the cochlea.

  12. Acoustic force measurement in a dual-temperature resonant chamber

    NASA Technical Reports Server (NTRS)

    Robey, Judith L.; Trinh, Eugene H.; Wang, Taylor G.

    1987-01-01

    The acoustic radiation force was measured for a dual-temperature resonant chamber. This rectangular chamber has its long dimension approximately 8.5 times the square cross-sectional dimension, and the opposite ends are at widely different temperatures. Force profiles were obtained for two hot end temperatures of 520 C and 760 C, while the cool end remained at approximately room temperature. Force magnitudes as high as 17 dyn for a sample 1.2 cm in diameter at 760 C and at 162-dB input level were measured.

  13. Measuring acoustic nonlinearity parameter using collinear wave mixing

    NASA Astrophysics Data System (ADS)

    Liu, Minghe; Tang, Guangxin; Jacobs, Laurence J.; Qu, Jianmin

    2012-07-01

    This study introduces a new acoustic nonlinearity parameter βT. It is shown that βT is associated with the interaction between a longitudinal wave and a shear wave in isotropic elastic solids with quadratic nonlinearity. Experimental measurements are conducted to demonstrate that the collinear wave mixing technique is capable of measuring βT nondestructively. Further, it is shown that βT is well-correlated with the plastic deformation in Al-6061 alloys. These results indicate that collinear wave mixing is a promising method for nondestructive assessment of plastic deformation, and possibly, fatigue damage in metallic materials.

  14. Introducing DIASCoPE: Directly Integrated Acoustic System Combined with Pressure Experiments — Changing the Paradigm from Product to Process

    NASA Astrophysics Data System (ADS)

    Whitaker, M. L.; Baldwin, K. J.; Huebsch, W. B.; Tercé, N.; Bejina, F.; Bystricky, M.; Chen, H.; Vaughan, M. T.; Weidner, D. J.

    2014-12-01

    Understanding the properties and behaviors of materials and multi-phase aggregates under conditions of high pressure and temperature is vital to unraveling the mysteries that lie beneath the surface of the planet. Advances in in situexperimental techniques using synchrotron radiation at these extreme conditions have helped to provide answers to fundamental questions that were previously unattainable. Synchrotron-based ultrasonic interferometry measurements have proven to be especially important in determining acoustic velocities and thermoelastic properties of materials at high pressures and temperatures. However, due to relatively slow data collection times, it has been difficult to measure the effects of processes as they occur, and instead the measurement is made on the end product of these processes. DIASCoPE is an important step toward addressing this problem.Over the last three years, we have designed and developed an on-board ultrasonic acoustic velocity measurement system that cuts data collection time down by over an order of magnitude. We can now measure P- and S-wave travel times in samples at extreme conditions in less than one second. Moreover, the system has been fully integrated with the multi-anvil apparatus and the EPICS control system at beamline X17B2 of the National Synchrotron Light Source, allowing for greater ease of control andfull automation of experimental data collection. The DIASCoPE has completed the testing and commissioning phase, and the first data collected using this powerful new system will be presented here.DIASCoPE represents a major step forward in acoustic velocity collection time reduction that will finally allow us to begin to witness what effects various processes in the deep Earth may have on the physical properties of materials at extreme conditions as they occur. These new capabilities will allow us to change the focus of study from the product to the process itself and will lead to a greater understanding of the

  15. Procedures for ambient-pressure and tympanometric tests of aural acoustic reflectance and admittance in human infants and adults

    PubMed Central

    Keefe, Douglas H.; Hunter, Lisa L.; Feeney, M. Patrick; Fitzpatrick, Denis F.

    2015-01-01

    Procedures are described to measure acoustic reflectance and admittance in human adult and infant ears at frequencies from 0.2 to 8 kHz. Transfer functions were measured at ambient pressure in the ear canal, and as down- or up-swept tympanograms. Acoustically estimated ear-canal area was used to calculate ear reflectance, which was parameterized by absorbance and group delay over all frequencies (and pressures), with substantial data reduction for tympanograms. Admittance measured at the probe tip in adults was transformed into an equivalent admittance at the eardrum using a transmission-line model for an ear canal with specified area and ear-canal length. Ear-canal length was estimated from group delay around the frequency above 2 kHz of minimum absorbance. Illustrative measurements in ears with normal function are described for an adult, and two infants at 1 month of age with normal hearing and a conductive hearing loss. The sensitivity of this equivalent eardrum admittance was calculated for varying estimates of area and length. Infant-ear patterns of absorbance peaks aligned in frequency with dips in group delay were explained by a model of resonant canal-wall mobility. Procedures will be applied in a large study of wideband clinical diagnosis and monitoring of middle-ear and cochlear function. PMID:26723319

  16. Evaluation of disfluent speech by means of automatic acoustic measurements.

    PubMed

    Lustyk, Tomas; Bergl, Petr; Cmejla, Roman

    2014-03-01

    An experiment was carried out to determine whether the level of the speech fluency disorder can be estimated by means of automatic acoustic measurements. These measures analyze, for example, the amount of silence in a recording or the number of abrupt spectral changes in a speech signal. All the measures were designed to take into account symptoms of stuttering. In the experiment, 118 audio recordings of read speech by Czech native speakers were employed. The results indicate that the human-made rating of the speech fluency disorder in read speech can be predicted on the basis of automatic measurements. The number of abrupt spectral changes in the speech segments turns out to be the most appropriate measure to describe the overall speech performance. The results also imply that there are measures with good results describing partial symptoms (especially fixed postures without audible airflow).

  17. Velocity measurements in whole blood using acoustic resolution photoacoustic Doppler

    PubMed Central

    Brunker, Joanna; Beard, Paul

    2016-01-01

    Acoustic resolution photoacoustic Doppler velocimetry promises to overcome the spatial resolution and depth penetration limitations of current blood flow measuring methods. Despite successful implementation using blood-mimicking fluids, measurements in blood have proved challenging, thus preventing in vivo application. A common explanation for this difficulty is that whole blood is insufficiently heterogeneous relative to detector frequencies of tens of MHz compatible with deep tissue photoacoustic measurements. Through rigorous experimental measurements we provide new insight that refutes this assertion. We show for the first time that, by careful choice of the detector frequency and field-of-view, and by employing novel signal processing methods, it is possible to make velocity measurements in whole blood using transducers with frequencies in the tens of MHz range. These findings have important implications for the prospects of making deep tissue measurements of blood flow relevant to the study of microcirculatory abnormalities associated with cancer, diabetes, atherosclerosis and other conditions. PMID:27446707

  18. Measurement of static pressure on aircraft

    NASA Technical Reports Server (NTRS)

    Gracey, William

    1958-01-01

    Existing data on the errors involved in the measurement of static pressure by means of static-pressure tubes and fuselage vents are presented. The errors associated with the various design features of static-pressure tubes are discussed for the condition of zero angle of attack and for the case where the tube is inclined to flow. Errors which result from variations in the configuration of static-pressure vents are also presented. Errors due to the position of a static-pressure tube in the flow field of the airplane are given for locations ahead of the fuselage nose, ahead of the wing tip, and ahead of the vertical tail fin. The errors of static-pressure vents on the fuselage of an airplane are also presented. Various methods of calibrating static-pressure installations in flight are briefly discussed.

  19. Measuring Pressure Has a New Standard

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The Force-Balanced Piston Gauge (FPG) tests and calibrates instrumentation operating in the low pressure range. The system provides a traceable, primary calibration standard for measuring pressures in the range of near 0 to 15 kPa (2.2 psi) in both gauge and absolute measurement modes. The hardware combines a large area piston-cylinder with a load cell measuring the force resulting from pressures across the piston. The mass of the piston can be tared out, allowing measurement to start from zero. A pressure higher than the measured pressure, which keeps the piston centered, lubricates an innovative conical gap located between the piston and the cylinder, eliminating the need for piston rotation. A pressure controller based on the control of low gas flow automates the pressure control. DHI markets the FPG as an automated primary standard for very low-gauge and absolute pressures. DHI is selling the FPG to high-end metrology laboratories on a case by case basis, with a full commercial release to follow.

  20. An Acoustic Measure for Word Prominence in Spontaneous Speech

    PubMed Central

    Wang, Dagen; Narayanan, Shrikanth

    2010-01-01

    An algorithm for automatic speech prominence detection is reported in this paper. We describe a comparative analysis on various acoustic features for word prominence detection and report results using a spoken dialog corpus with manually assigned prominence labels. The focus is on features such as spectral intensity and speech rate that are directly extracted from speech based on a correlation-based approach without requiring explicit linguistic or phonetic knowledge. Additionally, various pitch-based measures are studied with respect to their discriminating ability for prominence detection. A parametric scheme for modeling pitch plateau is proposed and this feature alone is found to outperform the traditional local pitch statistics. Two sets of experiments are used to explore the usefulness of the acoustic score generated using these features. The first set focuses on a more traditional way of word prominence detection based on a manually-tagged corpus. A 76.8% classification accuracy was achieved on a corpus of role-playing spoken dialogs. Due to difficulties in manually tagging speech prominence into discrete levels (categories), the second set of experiments focuses on evaluating the score indirectly. Specifically, through experiments on the Switchboard corpus, it is shown that the proposed acoustic score can discriminate between content word and function words in a statistically significant way. The relation between speech prominence and content/function words is also explored. Since prominent words tend to be predominantly content words, and since content words can be automatically marked from text-derived part of speech (POS) information, it is shown that the proposed acoustic score can be indirectly cross-validated through POS information. PMID:20454538

  1. Method and apparatus for background signal reduction in opto-acoustic absorption measurement

    NASA Technical Reports Server (NTRS)

    Rosengren, L. G. (Inventor)

    1976-01-01

    The sensitivity of an opto-acoustic absorption detector is increased to make it possible to measure trace amounts of constituent gases. A second beam radiation path is created through the sample cell identical to a first path except as to length, alternating the beam through the two paths and minimizing the detected pressure difference for the two paths while the beam wavelength is tuned away from the absorption lines of the sample. Then with the beam wavelength tuned to the absorption line of any constituent of interest, the pressure difference is a measure of trace amounts of the constituent. The same improved detector may also be used for measuring the absorption coefficient of known concentrations of absorbing gases.

  2. Diffraction correction for precision surface acoustic wave velocity measurements

    NASA Astrophysics Data System (ADS)

    Ruiz M., Alberto; Nagy, Peter B.

    2002-09-01

    Surface wave dispersion measurements can be used to nondestructively characterize shot-peened, laser shock-peened, burnished, and otherwise surface-treated specimens. In recent years, there have been numerous efforts to separate the contribution of surface roughness from those of near-surface material variations, such as residual stress, texture, and increased dislocation density. As the accuracy of the dispersion measurements was gradually increased using state-of-the-art laser-ultrasonic scanning and sophisticated digital signal processing methods, it was recognized that a perceivable dispersive effect, similar to the one found on rough shot-peened specimens, is exhibited by untreated smooth surfaces as well. This dispersion effect is on the order of 0.1%, that is significantly higher than the experimental error associated with the measurements and comparable to the expected velocity change produced by near-surface compressive residual stresses in metals below their yield point. This paper demonstrates that the cause of this apparent dispersion is the diffraction of the surface acoustic wave (SAW) as it travels over the surface of the specimen. The results suggest that a diffraction correction may be introduced to increase the accuracy of surface wave dispersion measurements. A simple diffraction correction model was developed for surface waves and this correction was subsequently validated by laser-interferometric velocity measurements on aluminum specimens. copyright 2002 Acoustical Society of America.

  3. Measuring pressure under burns pressure garments using the Oxford Pressure Monitor.

    PubMed

    Harries, C A; Pegg, S P

    1989-06-01

    Pressure garments are used extensively in the treatment of hypertrophic scarring following burn injuries. The Oxford Pressure Monitor was used to measure garment-scar interface pressure (mmHg) using a number of fabric types over various body parts. The results indicate a wide range of pressure values between different garments and body parts with the greatest pressures found over the dorsum of hands and feet. The problems of achieving 'optimal pressure' over hypertrophic scarring are discussed with emphasis on the need for more accurate measuring equipment.

  4. Accurate, reproducible measurement of blood pressure.

    PubMed Central

    Campbell, N R; Chockalingam, A; Fodor, J G; McKay, D W

    1990-01-01

    The diagnosis of mild hypertension and the treatment of hypertension require accurate measurement of blood pressure. Blood pressure readings are altered by various factors that influence the patient, the techniques used and the accuracy of the sphygmomanometer. The variability of readings can be reduced if informed patients prepare in advance by emptying their bladder and bowel, by avoiding over-the-counter vasoactive drugs the day of measurement and by avoiding exposure to cold, caffeine consumption, smoking and physical exertion within half an hour before measurement. The use of standardized techniques to measure blood pressure will help to avoid large systematic errors. Poor technique can account for differences in readings of more than 15 mm Hg and ultimately misdiagnosis. Most of the recommended procedures are simple and, when routinely incorporated into clinical practice, require little additional time. The equipment must be appropriate and in good condition. Physicians should have a suitable selection of cuff sizes readily available; the use of the correct cuff size is essential to minimize systematic errors in blood pressure measurement. Semiannual calibration of aneroid sphygmomanometers and annual inspection of mercury sphygmomanometers and blood pressure cuffs are recommended. We review the methods recommended for measuring blood pressure and discuss the factors known to produce large differences in blood pressure readings. PMID:2192791

  5. Blade Tip Pressure Measurements Using Pressure Sensitive Paint

    NASA Technical Reports Server (NTRS)

    Wong, Oliver D.; Watkins, Anthony Neal; Goodman, Kyle Z.; Crafton, James; Forlines, Alan; Goss, Larry; Gregory, James W.; Juliano, Thomas J.

    2012-01-01

    This paper discusses the application of pressure sensitive paint using laser-based excitation for measurement of the upper surface pressure distribution on the tips of rotor blades in hover and simulated forward flight. The testing was conducted in the Rotor Test Cell and the 14- by 22-ft Subsonic Tunnel at the NASA Langley Research Center on the General Rotor Model System (GRMS) test stand. The Mach-scaled rotor contained three chordwise rows of dynamic pressure transducers for comparison with PSP measurements. The rotor had an 11 ft 1 in. diameter, 5.45 in. main chord and a swept, tapered tip. Three thrust conditions were examined in hover, C(sub T) = 0.004, 0.006 and 0.008. In forward flight, an additional thrust condition, C(sub T) = 0.010 was also examined. All four thrust conditions in forward flight were conducted at an advance ratio of 0.35.

  6. Remote query pressure measurement using magnetoelastic sensors

    NASA Astrophysics Data System (ADS)

    Grimes, C. A.; Stoyanov, P. G.; Kouzoudis, D.; Ong, K. G.

    1999-12-01

    Two magnetostriction-based methods for measuring atmospheric pressure are presented. Each technique correlates changes in pressure with the characteristic resonant frequency of a magnetoelastic magnetostrictive thick-film sensor. In each case the sensor is monitored remotely, using an adjacently located pickup coil, without the use of physical connections to the sensor.

  7. Evaluation of Acoustic Emission NDE of Kevlar Composite Over Wrapped Pressure Vessels

    NASA Technical Reports Server (NTRS)

    Horne, Michael R.; Madaras, Eric I.

    2008-01-01

    Pressurization and failure tests of small Kevlar/epoxy COPV bottles were conducted during 2006 and 2007 by Texas Research Institute Austin, Inc., at TRI facilities. This is a report of the analysis of the Acoustic Emission (AE) data collected during those tests. Results of some of the tests indicate a possibility that AE can be used to track the stress-rupture degradation of COPV vessels.

  8. Photo-acoustic tomography in a rotating measurement setting

    NASA Astrophysics Data System (ADS)

    Bal, Guillaume; Moradifam, Amir

    2016-10-01

    Photo-acoustic tomography (PAT) aims to leverage the photo-acoustic coupling between optical absorption of light sources and ultrasound (US) emission to obtain high contrast reconstructions of optical parameters with the high resolution of sonic waves. Quantitative PAT often involves a two-step procedure: first the map of sonic emission is reconstructed from US boundary measurements; and second optical properties of biological tissues are evaluated. We consider here a practical measurement setting in which such a separation does not apply. We assume that the optical source and an array of ultrasonic transducers are mounted on a rotating frame (in two or three dimensions) so that the light source rotates at the same time as the US measurements are acquired. As a consequence, we no longer have the option to reconstruct a map of sonic emission corresponding to a given optical illumination. We propose here a framework where the two steps are combined into one and an absorption map is directly reconstructed from the available US measurements.

  9. Analytic Formulation and Numerical Implementation of an Acoustic Pressure Gradient Prediction

    NASA Technical Reports Server (NTRS)

    Lee, Seongkyu; Brentner, Kenneth S.; Farassat, F.; Morris, Philip J.

    2008-01-01

    Two new analytical formulations of the acoustic pressure gradient have been developed and implemented in the PSU-WOPWOP rotor noise prediction code. The pressure gradient can be used to solve the boundary condition for scattering problems and it is a key aspect to solve acoustic scattering problems. The first formulation is derived from the gradient of the Ffowcs Williams-Hawkings (FW-H) equation. This formulation has a form involving the observer time differentiation outside the integrals. In the second formulation, the time differentiation is taken inside the integrals analytically. This formulation avoids the numerical time differentiation with respect to the observer time, which is computationally more efficient. The acoustic pressure gradient predicted by these new formulations is validated through comparison with available exact solutions for a stationary and moving monopole sources. The agreement between the predictions and exact solutions is excellent. The formulations are applied to the rotor noise problems for two model rotors. A purely numerical approach is compared with the analytical formulations. The agreement between the analytical formulations and the numerical method is excellent for both stationary and moving observer cases.

  10. Numerical simulation of the processes in the normal incidence tube for high acoustic pressure levels

    NASA Astrophysics Data System (ADS)

    Fedotov, E. S.; Khramtsov, I. V.; Kustov, O. Yu.

    2016-10-01

    Numerical simulation of the acoustic processes in an impedance tube at high levels of acoustic pressure is a way to solve a problem of noise suppressing by liners. These studies used liner specimen that is one cylindrical Helmholtz resonator. The evaluation of the real and imaginary parts of the liner acoustic impedance and sound absorption coefficient was performed for sound pressure levels of 130, 140 and 150 dB. The numerical simulation used experimental data having been obtained on the impedance tube with normal incidence waves. At the first stage of the numerical simulation it was used the linearized Navier-Stokes equations, which describe well the imaginary part of the liner impedance whatever the sound pressure level. These equations were solved by finite element method in COMSOL Multiphysics program in axisymmetric formulation. At the second stage, the complete Navier-Stokes equations were solved by direct numerical simulation in ANSYS CFX in axisymmetric formulation. As the result, the acceptable agreement between numerical simulation and experiment was obtained.

  11. Acoustic measurement of the Deepwater Horizon Macondo well flow rate

    PubMed Central

    Camilli, Richard; Di Iorio, Daniela; Bowen, Andrew; Reddy, Christopher M.; Techet, Alexandra H.; Yoerger, Dana R.; Whitcomb, Louis L.; Seewald, Jeffrey S.; Sylva, Sean P.; Fenwick, Judith

    2012-01-01

    On May 31, 2010, a direct acoustic measurement method was used to quantify fluid leakage rate from the Deepwater Horizon Macondo well prior to removal of its broken riser. This method utilized an acoustic imaging sonar and acoustic Doppler sonar operating onboard a remotely operated vehicle for noncontact measurement of flow cross-section and velocity from the well’s two leak sites. Over 2,500 sonar cross-sections and over 85,000 Doppler velocity measurements were recorded during the acquisition process. These data were then applied to turbulent jet and plume flow models to account for entrained water and calculate a combined hydrocarbon flow rate from the two leak sites at seafloor conditions. Based on the chemical composition of end-member samples collected from within the well, this bulk volumetric rate was then normalized to account for contributions from gases and condensates at initial leak source conditions. Results from this investigation indicate that on May 31, 2010, the well’s oil flow rate was approximately 0.10 ± 0.017 m3 s-1 at seafloor conditions, or approximately 85 ± 15 kg s-1 (7.4 ± 1.3 Gg d-1), equivalent to approximately 57,000 ± 9,800 barrels of oil per day at surface conditions. End-member chemical composition indicates that this oil release rate was accompanied by approximately an additional 24 ± 4.2 kg s-1 (2.1 ± 0.37 Gg d-1) of natural gas (methane through pentanes), yielding a total hydrocarbon release rate of 110 ± 19 kg s-1 (9.5 ± 1.6 Gg d-1). PMID:21903931

  12. Acoustic measurement of the Deepwater Horizon Macondo well flow rate.

    PubMed

    Camilli, Richard; Di Iorio, Daniela; Bowen, Andrew; Reddy, Christopher M; Techet, Alexandra H; Yoerger, Dana R; Whitcomb, Louis L; Seewald, Jeffrey S; Sylva, Sean P; Fenwick, Judith

    2012-12-11

    On May 31, 2010, a direct acoustic measurement method was used to quantify fluid leakage rate from the Deepwater Horizon Macondo well prior to removal of its broken riser. This method utilized an acoustic imaging sonar and acoustic Doppler sonar operating onboard a remotely operated vehicle for noncontact measurement of flow cross-section and velocity from the well's two leak sites. Over 2,500 sonar cross-sections and over 85,000 Doppler velocity measurements were recorded during the acquisition process. These data were then applied to turbulent jet and plume flow models to account for entrained water and calculate a combined hydrocarbon flow rate from the two leak sites at seafloor conditions. Based on the chemical composition of end-member samples collected from within the well, this bulk volumetric rate was then normalized to account for contributions from gases and condensates at initial leak source conditions. Results from this investigation indicate that on May 31, 2010, the well's oil flow rate was approximately 0.10 ± 0.017 m(3) s(-1) at seafloor conditions, or approximately 85 ± 15 kg s(-1) (7.4 ± 1.3 Gg d(-1)), equivalent to approximately 57,000 ± 9,800 barrels of oil per day at surface conditions. End-member chemical composition indicates that this oil release rate was accompanied by approximately an additional 24 ± 4.2 kg s(-1) (2.1 ± 0.37 Gg d(-1)) of natural gas (methane through pentanes), yielding a total hydrocarbon release rate of 110 ± 19 kg s(-1) (9.5 ± 1.6 Gg d(-1)).

  13. 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.

  14. Measurement and Applications of Radiation Pressure

    NASA Astrophysics Data System (ADS)

    Ma, Dakang; Garrett, Joseph; Murray, Joseph; Munday, Jeremy; Munday Lab Team

    Light reflected off a material or absorbed within it exerts radiation pressure through the transfer of momentum. Measuring and utilizing radiation pressure have aroused growing interest in a wide spectrum of research fields. Micromechanical transducers and oscillators are good candidates for measuring radiation pressure, but accompanying photothermal effects often obscure the measurement. In this work, we investigate the accurate measurement of the radiation force on microcantilevers in ambient conditions and ways to separate radiation pressure and photothermal effects. Further, we investigate an optically broadband switchable device based on polymer dispersed liquid crystal which has potential applications in solar sails and maneuvering spacecraft without moving parts. The authors would like to thank NASA Early Career Faculty Award and NASA Smallsat Technology Partnership Award for their funding support.

  15. The Belt Method for Measuring Pressure Distribution

    NASA Technical Reports Server (NTRS)

    Corson, Blake W , Jr

    1943-01-01

    The measurement of pressure distribution may be accomplished rapidly for any number of locations deemed necessary in model or full-scale investigations by use of the "belt" method. Reasonable accuracy may be obtained by careful use of this method.

  16. Measurement of stiffness of standing trees and felled logs using acoustics: A review.

    PubMed

    Legg, Mathew; Bradley, Stuart

    2016-02-01

    This paper provides a review on the use of acoustics to measure stiffness of standing trees, stems, and logs. An outline is given of the properties of wood and how these are related to stiffness and acoustic velocity throughout the tree. Factors are described that influence the speed of sound in wood, including the different types of acoustic waves which propagate in tree stems and lumber. Acoustic tools and techniques that have been used to measure the stiffness of wood are reviewed. The reasons for a systematic difference between direct and acoustic measurements of stiffness for standing trees, and methods for correction, are discussed. Other techniques, which have been used in addition to acoustics to try to improve stiffness measurements, are also briefly described. Also reviewed are studies which have used acoustic tools to investigate factors that influence the stiffness of trees. These factors include different silvicultural practices, geographic and environmental conditions, and genetics.

  17. Measurement of food texture by an acoustic vibration method

    NASA Astrophysics Data System (ADS)

    Sakurai, Naoki; Taniwaki, Mitsuru; Iwatani, Shin-ichiro; Akimoto, Hidemi

    2011-09-01

    Food texture was measured by a new acoustic vibration method. A piezoelectric sensor sandwiched between a probe and piston was inserted into a food sample by delivery of silicon oil to a cylinder by a pump. Vibration emitted from the food sample on insertion of the probe was monitored by voltage outputs of the sensor. The voltage signals were passed through 19 half octave bands to calculate texture index for each band. The texture index was defined as vibration energy of the probe caused by the food rupture and/or breakage per unit time.

  18. Passive Wake Acoustics Measurements at Denver International Airport

    NASA Technical Reports Server (NTRS)

    Wang, Frank Y.; Wassaf, Hadi; Dougherty, Robert P.; Clark, Kevin; Gulsrud, Andrew; Fenichel, Neil; Bryant, Wayne H.

    2004-01-01

    From August to September 2003, NASA conducted an extensive measurement campaign to characterize the acoustic signal of wake vortices. A large, both spatially as well as in number of elements, phased microphone array was deployed at Denver International Airport for this effort. This paper will briefly describe the program background, the microphone array, as well as the supporting ground-truth and meteorological sensor suite. Sample results to date are then presented and discussed. It is seen that, in the frequency range processed so far, wake noise is generated predominantly from a very confined area around the cores.

  19. An Acoustic Emission and Acousto-Ultrasonic Analysis of Impact Damaged Composite Pressure Vessels

    NASA Technical Reports Server (NTRS)

    Walker, James L.; Workman, Gary L.; Workman, Gary L.

    1996-01-01

    The research presented herein summarizes the development of acoustic emission (AE) and acousto-ultrasonic (AU) techniques for the nondestructive evaluation of filament wound composite pressure vessels. Vessels fabricated from both graphite and kevlar fibers with an epoxy matrix were examined prior to hydroburst using AU and during hydroburst using AE. A dead weight drop apparatus featuring both blunt and sharp impactor tips was utilized to produce a single known energy 'damage' level in each of the vessels so that the degree to which the effects of impact damage could be measured. The damage levels ranged from barely visible to obvious fiber breakage and delamination. Independent neural network burst pressure prediction models were developed from a sample of each fiber/resin material system. Here, the cumulative AE amplitude distribution data collected from low level proof test (25% of the expected burst for undamaged vessels) were used to measure the effects of the impact on the residual burst pressure of the vessels. The results of the AE/neural network model for the inert propellant filled graphite/epoxy vessels 'IM7/3501-6, IM7/977-2 and IM7/8553-45' demonstrated that burst pressures can be predicted from low level AE proof test data, yielding an average error of 5.0%. The trained network for the IM7/977-2 class vessels was also able to predict the expected burst pressure of taller vessels (three times longer hoop region length) constructed of the same material and using the same manufacturing technique, with an average error of 4.9%. To a lesser extent, the burst pressure prediction models could also measure the effects of impact damage to the kevlar/epoxy 'Kevlar 49/ DPL862' vessels. Here though, due to the higher attenuation of the material, an insufficient amount of AE amplitude information was collected to generate robust network models. Although, the worst case trial errors were less than 6%, when additional blind predictions were attempted, errors as

  20. Sound field separation with sound pressure and particle velocity measurements.

    PubMed

    Fernandez-Grande, Efren; Jacobsen, Finn; Leclère, Quentin

    2012-12-01

    In conventional near-field acoustic holography (NAH) it is not possible to distinguish between sound from the two sides of the array, thus, it is a requirement that all the sources are confined to only one side and radiate into a free field. When this requirement cannot be fulfilled, sound field separation techniques make it possible to distinguish between outgoing and incoming waves from the two sides, and thus NAH can be applied. In this paper, a separation method based on the measurement of the particle velocity in two layers and another method based on the measurement of the pressure and the velocity in a single layer are proposed. The two methods use an equivalent source formulation with separate transfer matrices for the outgoing and incoming waves, so that the sound from the two sides of the array can be modeled independently. A weighting scheme is proposed to account for the distance between the equivalent sources and measurement surfaces and for the difference in magnitude between pressure and velocity. Experimental and numerical studies have been conducted to examine the methods. The double layer velocity method seems to be more robust to noise and flanking sound than the combined pressure-velocity method, although it requires an additional measurement surface. On the whole, the separation methods can be useful when the disturbance of the incoming field is significant. Otherwise the direct reconstruction is more accurate and straightforward.

  1. Centrifugal pump inlet pressure site affects measurement.

    PubMed

    Augustin, Simon; Horton, Alison; Butt, Warwick; Bennett, Martin; Horton, Stephen

    2010-09-01

    During extracorporeal life support (ECLS), blood is exposed to a myriad of unphysiological factors that can affect outcome. One aspect of this is the sub-atmospheric pressure generated by the ECLS pump and imparted to blood elements along the pump inlet line. This pressure can be measured on the inlet line close to the pump head by adding a connector, or at the venous cannula connection site. We compared the two measurement sites located at both points; between the venous cannula-inlet tubing and inlet tubing-pump, with a range of cannulae and flows. We also investigated the effects on inlet pressure from pump afterload and increasing inlet tubing length.

  2. Determination of rotor harmonic blade loads from acoustic measurements

    NASA Technical Reports Server (NTRS)

    Kasper, P. K.

    1975-01-01

    The magnitude of discrete frequency sound radiated by a rotating blade is strongly influenced by the presence of a nonuniform distribution of aerodynamic forces over the rotor disk. An analytical development and experimental results are provided for a technique by which harmonic blade loads are derived from acoustic measurements. The technique relates, on a one-to-one basis, the discrete frequency sound harmonic amplitudes measured at a point on the axis of rotation to the blade-load harmonic amplitudes. This technique was applied to acoustic data from two helicopter types and from a series of test results using the NASA-Langley Research Center rotor test facility. The inferred blade-load harmonics for the cases considered tended to follow an inverse power law relationship with harmonic blade-load number. Empirical curve fits to the data showed the harmonic fall-off rate to be in the range of 6 to 9 db per octave of harmonic order. These empirical relationships were subsequently used as input data in a compatible far field rotational noise prediction model. A comparison between predicted and measured off-axis sound harmonic levels is provided for the experimental cases considered.

  3. Analysis of acoustic reduction using spectral similarity measures.

    PubMed

    Hämäläinen, Annika; Gubian, Michele; ten Bosch, Louis; Boves, Lou

    2009-12-01

    Articulatory and acoustic reduction can manifest itself in the temporal and spectral domains. This study introduces a measure of spectral reduction, which is based on the speech decoding techniques commonly used in automatic speech recognizers. Using data for four frequent Dutch affixes from a large corpus of spontaneous face-to-face conversations, it builds on an earlier study examining the effects of lexical frequency on durational reduction in spoken Dutch [Pluymaekers, M. et al. (2005). J. Acoust. Soc. Am. 118, 2561-2569], and compares the proposed measure of spectral reduction with duration as a measure of reduction. The results suggest that the spectral reduction scores capture other aspects of reduction than duration. While duration can--albeit to a moderate degree--be predicted by a number of linguistically motivated variables (such as word frequency, segmental context, and speech rate), the spectral reduction scores cannot. This suggests that the spectral reduction scores capture information that is not directly accounted for by the linguistically motivated variables. The results also show that the spectral reduction scores are able to predict a substantial amount of the variation in duration that the linguistically motivated variables do not account for.

  4. Neural network burst pressure prediction in impact damaged Kevlar/epoxy bottles from acoustic emission amplitude data

    SciTech Connect

    Walker, J.L.; Workman, G.L.; Russell, S.S.

    1994-12-31

    Acoustic emission (AE) signal analysis has been used to measure the effect of impact damage on the burst pressure of 5.75 inch diameter filament wound Kevlar/epoxy pressure vessels. A calibrated dead weight drop fixture, featuring both sharp and blunt hemispherical impact tups, generated impact damages with energies up to twenty ft-lb{sub f} in the mid hoop region of each vessel. Burst pressures were obtained by hydrostatically testing twenty-seven damaged and undamaged bottles, eleven of which were filled with inert propellant to simulate a rocket motor. Burst pressure prediction models were developed by correlating the differential AE amplitude distributions, Generated during the first pressure ramp to 25% of the expected burst pressure for the undamaged vessels, to known burst pressures using back propagation neural networks. Independent networks were created for the inert propellant filled vessels and the unfilled vessels using a small subset of each during the training phases. The remaining bottles served as the test sets. The eleven filled vessels had an average prediction error of 5.6%, while the unfilled bottles averaged 5.4%. Both of these results were within the 95% prediction interval, but a portion of the vessel burst pressure errors were greater than the {+-}5% worst case error obtained in previous work. in conclusion, the AE amplitude distribution data collected at low proof loads provided a suitable input for neural network burst pressure prediction in damaged and undamaged Kevlar/epoxy bottles. This included pressure vessels both with and without propellant backing. Work is ongoing to decrease the magnitude of the prediction error through network restructuring.

  5. Relations among subglottal pressure, breathing, and acoustic parameters of sentence-level prominence in German.

    PubMed

    Petrone, Caterina; Fuchs, Susanne; Koenig, Laura L

    2017-03-01

    This study investigates whether acoustic correlates of prominence are related to actions of the respiratory system resulting in local changes of subglottal pressure (Psub). Simultaneous recordings were made of acoustics; intraoral pressure (Pio), as an estimate of Psub; and thoracic and abdominal volume changes. Ten German speakers read sentences containing a verb ending with /t/ followed by a noun starting with /t/. These /t#t/ sequences were typically realized as one /t:/ with a long intraoral pressure plateau. Sentence-level prominence was manipulated by shifting the position of contrastive focus within the sentences. The slope and peak values of Pio within the /t#t/ sequence were used to estimate differences in Psub across focus positions. Results show that prominence production is related to changes in the slope and maximum value of the pressure plateau. While pressure increases led to higher intensity, the increases did not relate to f0, hence, suggesting that local f0 changes primarily reflect laryngeal activity. Finally, strong individual differences were observed in the respiratory data. These findings confirm past reports of local Psub increases corresponding to sentence-level prominence. Speaker-specific activations of the respiratory system are interpreted in terms of motor equivalence, with laryngeal mechanisms also appearing to contribute to Psub changes.

  6. Characterization of intense ion beam energy density and beam induced pressure on the target with acoustic diagnostics

    SciTech Connect

    Pushkarev, A. I.; Isakova, Yu. I.; Khailov, I. P.; Yu, Xiao

    2013-08-15

    We have developed the acoustic diagnostics based on a piezoelectric transducer for characterization of high-intensity pulsed ion beams. The diagnostics was tested using the TEMP-4M accelerator (150 ns, 250–300 kV). The beam is composed of C{sup +} ions (85%) and protons, the beam energy density is 0.5–5 J/cm{sup 2} (depending on diode geometry). A calibration dependence of the signal from a piezoelectric transducer on the ion beam energy density is obtained using thermal imaging diagnostics. It is shown that the acoustic diagnostics allows for measurement of the beam energy density in the range of 0.1–2 J/cm{sup 2}. The dependence of the beam generated pressure on the input energy density is also determined and compared with the data from literature. The developed acoustic diagnostics do not require sophisticated equipment and can be used for operational control of pulsed ion beam parameters with a repetition rate of 10{sup 3} pulses/s.

  7. Pancreas tumor interstitial pressure catheter measurement

    NASA Astrophysics Data System (ADS)

    Nieskoski, Michael D.; Gunn, Jason; Marra, Kayla; Trembly, B. Stuart; Pogue, Brian W.

    2016-03-01

    This paper highlights the methodology in measuring interstitial pressure in pancreatic adenocarcinoma tumors. A Millar Mikrotip pressure catheter (SPR-671) was used in this study and a system was built to amplify and filter the output signal for data collection. The Millar pressure catheter was calibrated prior to each experiment in a water column at 37°C, range of 0 to 60 inH2O (112 mmHg), resulting in a calibration factor of 33 mV / 1 inH2O. The interstitial pressures measured in two orthotopically grown pancreatic adenocarcinoma tumor were 57 mmHg and 48 mmHg, respectively. Verteporfin uptake into the pancreatic adenocarcinoma tumor was measured using a probe-based experimental dosimeter.

  8. Blood pressure measurement using finger cuff.

    PubMed

    Lee, J; Choi, E; Jeong, H; Kim, K; Park, J

    2005-01-01

    Many research groups have studied blood pressure measurement in finger artery because of its convenience. But, low accuracy prohibits many hypertension patients from using this device. So, we suggest measurement algorithm that measure systolic and diastolic blood pressure in finger artery. And we also develop calibration method that decreases the error from difference of finger circumference by subjects. We apply our methods for 90 subjects (age form 20 to 49, 55 male, 35 female) to test feasibility of our method by AAMI SP10 standard. The mean difference of our system is ±4.7mmHg for systolic pressure, ±4.2mmHg for systolic pressure. It proved that the feasibility of our method is clinically acceptable.(under ±5mmHg).

  9. Acoustic seal

    NASA Technical Reports Server (NTRS)

    Steinetz, Bruce M. (Inventor)

    2006-01-01

    The invention relates to a sealing device having an acoustic resonator. The acoustic resonator is adapted to create acoustic waveforms to generate a sealing pressure barrier blocking fluid flow from a high pressure area to a lower pressure area. The sealing device permits noncontacting sealing operation. The sealing device may include a resonant-macrosonic-synthesis (RMS) resonator.

  10. Acoustic Seal

    NASA Technical Reports Server (NTRS)

    Steinetz, Bruce M. (Inventor)

    2006-01-01

    The invention relates to a sealing device having an acoustic resonator. The acoustic resonator is adapted to create acoustic waveforms to generate a sealing pressure barrier blocking fluid flow from a high pressure area to a lower pressure area. The sealing device permits noncontacting sealing operation. The sealing device may include a resonant-macrosonic-synthesis (RMS) resonator.

  11. Pressure and temperature dependences of the acoustic behaviors of biocompatible silk studied by using Brillouin spectroscopy

    NASA Astrophysics Data System (ADS)

    Lee, Byoung Wan; Ryeom, Junho; Ko, Jae-Hyeon; Kim, Dong Wook; Park, Chan Hum; Park, Jaehoon; Ko, Young Ho; Kim, Kwang Joo

    2016-07-01

    The elastic properties of a biocompatible silk film were investigated under temperature and pressure variations by using Brillouin spectroscopy. The Brillouin frequency shift decreased monotonically upon heating and showed a sudden change at the glass transition temperature. The existence of water molecules in the film increased the longitudinal modulus by approximately 10% and induced a relaxation peak in the hypersonic damping at ~60 ◦ C. The pressure dependences of the sound velocities of the longitudinal and the transverse acoustic modes and the refractive index were determined for the first time at pressures up to ~15.5 GPa. All these properties increased upon compression; these changes indicated that the free volume in the silk film collapsed at a pressure of about 3 GPa.

  12. Acoustic characterization of high intensity focused ultrasound fields: A combined measurement and modeling approach

    PubMed Central

    Canney, Michael S.; Bailey, Michael R.; Crum, Lawrence A.; Khokhlova, Vera A.; Sapozhnikov, Oleg A.

    2008-01-01

    Acoustic characterization of high intensity focused ultrasound (HIFU) fields is important both for the accurate prediction of ultrasound induced bioeffects in tissues and for the development of regulatory standards for clinical HIFU devices. In this paper, a method to determine HIFU field parameters at and around the focus is proposed. Nonlinear pressure waveforms were measured and modeled in water and in a tissue-mimicking gel phantom for a 2 MHz transducer with an aperture and focal length of 4.4 cm. Measurements were performed with a fiber optic probe hydrophone at intensity levels up to 24 000 W∕cm2. The inputs to a Khokhlov–Zabolotskaya–Kuznetsov-type numerical model were determined based on experimental low amplitude beam plots. Strongly asymmetric waveforms with peak positive pressures up to 80 MPa and peak negative pressures up to 15 MPa were obtained both numerically and experimentally. Numerical simulations and experimental measurements agreed well; however, when steep shocks were present in the waveform at focal intensity levels higher than 6000 W∕cm2, lower values of the peak positive pressure were observed in the measured waveforms. This underrepresentation was attributed mainly to the limited hydrophone bandwidth of 100 MHz. It is shown that a combination of measurements and modeling is necessary to enable accurate characterization of HIFU fields. PMID:19062878

  13. Acoustic characterization of high intensity focused ultrasound fields: a combined measurement and modeling approach.

    PubMed

    Canney, Michael S; Bailey, Michael R; Crum, Lawrence A; Khokhlova, Vera A; Sapozhnikov, Oleg A

    2008-10-01

    Acoustic characterization of high intensity focused ultrasound (HIFU) fields is important both for the accurate prediction of ultrasound induced bioeffects in tissues and for the development of regulatory standards for clinical HIFU devices. In this paper, a method to determine HIFU field parameters at and around the focus is proposed. Nonlinear pressure waveforms were measured and modeled in water and in a tissue-mimicking gel phantom for a 2 MHz transducer with an aperture and focal length of 4.4 cm. Measurements were performed with a fiber optic probe hydrophone at intensity levels up to 24,000 W/cm(2). The inputs to a Khokhlov-Zabolotskaya-Kuznetsov-type numerical model were determined based on experimental low amplitude beam plots. Strongly asymmetric waveforms with peak positive pressures up to 80 MPa and peak negative pressures up to 15 MPa were obtained both numerically and experimentally. Numerical simulations and experimental measurements agreed well; however, when steep shocks were present in the waveform at focal intensity levels higher than 6000 W/cm(2), lower values of the peak positive pressure were observed in the measured waveforms. This underrepresentation was attributed mainly to the limited hydrophone bandwidth of 100 MHz. It is shown that a combination of measurements and modeling is necessary to enable accurate characterization of HIFU fields.

  14. Numerical investigation and electro-acoustic modeling of measurement methods for the in-duct acoustical source parameters.

    PubMed

    Jang, Seung-Ho; Ih, Jeong-Guon

    2003-02-01

    It is known that the direct method yields different results from the indirect (or load) method in measuring the in-duct acoustic source parameters of fluid machines. The load method usually comes up with a negative source resistance, although a fairly accurate prediction of radiated noise can be obtained from any method. This study is focused on the effect of the time-varying nature of fluid machines on the output results of two typical measurement methods. For this purpose, a simplified fluid machine consisting of a reservoir, a valve, and an exhaust pipe is considered as representing a typical periodic, time-varying system and the measurement situations are simulated by using the method of characteristics. The equivalent circuits for such simulations are also analyzed by considering the system as having a linear time-varying source. It is found that the results from the load method are quite sensitive to the change of cylinder pressure or valve profile, in contrast to those from the direct method. In the load method, the source admittance turns out to be predominantly dependent on the valve admittance at the calculation frequency as well as the valve and load admittances at other frequencies. In the direct method, however, the source resistance is always positive and the source admittance depends mainly upon the zeroth order of valve admittance.

  15. The measurement of maximum cylinder pressures

    NASA Technical Reports Server (NTRS)

    Hicks, Chester W

    1929-01-01

    The work presented in this report was undertaken at the Langley Memorial Aeronautical Laboratory of the National Advisory Committee for Aeronautics to determine a suitable method for measuring the maximum pressures occurring in aircraft engine cylinders. The study and development of instruments for the measurement of maximum cylinder pressures has been conducted in connection with carburetor and oil engine investigations on a single cylinder aircraft-type engine. Five maximum cylinder-pressure devices have been designed, and tested, in addition to the testing of three commercial indicators. Values of maximum cylinder pressures are given as obtained with various indicators for the same pressures and for various kinds and values of maximum cylinder pressures, produced chiefly by variation of the injection advance angle in high-speed oil engine. The investigations indicate that the greatest accuracy in determining maximum cylinder pressures can be obtained with an electric, balanced-pressure, diaphragm or disk-type indicator so constructed as to have a diaphragm or disk of relatively large area and minimum seat width and mass.

  16. Wideband acoustic immittance measures: developmental characteristics (0 to 12 months).

    PubMed

    Kei, Joseph; Sanford, Chris A; Prieve, Beth A; Hunter, Lisa L

    2013-07-01

    Rapid developmental changes of the peripheral auditory system in normal infants occur in the first year of life. Specifically, the postnatal development of the external and middle ear affects all measures of external and middle ear function including wideband acoustic immittance(WAI). This article provides an overview of WAI studies in newborns and infants from a developmental perspective. Normative WAI data in newborns are fairly consistent across studies. However, there are discrepancies in some WAI measures between studies, possibly due to differences in sampling, methodology, and instrumentation. Accuracy of WAI measurements is compromised when a good probe seal cannot be maintained during testing or an inaccurate estimate of the cross-sectional area of the ear canal of newborns occurs. Comparison of WAI data between age groups from 0 to 12 months reveals maturation effects. Additional age-specific longitudinal and cross-sectional normative WAI data for infants from birth to 12 months are required to validate and consolidate existing data.

  17. A model for the pressure excitation spectrum and acoustic impedance of sound absorbers in the presence of grazing flow

    NASA Technical Reports Server (NTRS)

    Rice, E. J.

    1973-01-01

    The acoustic impedance of sound absorbers in the presence of grazing flow is essential information when analyzing sound propagation within ducts. A unification of the theory of the nonlinear acoustic resistance of Helmholtz resonators including grazing flow is presented. The nonlinear resistance due to grazing flow is considered to be caused by an exciting pressure spectrum produced by the interaction of the grazing flow and the jets flowing from the resonator orifices. With this exciting pressure spectrum the resonator can be treated in the same manner as a resonator without grazing flow but with an exciting acoustic spectrum.

  18. Classification of heart valve condition using acoustic measurements

    SciTech Connect

    Clark, G.

    1994-11-15

    Prosthetic heart valves and the many great strides in valve design have been responsible for extending the life spans of many people with serious heart conditions. Even though the prosthetic valves are extremely reliable, they are eventually susceptible to long-term fatigue and structural failure effects expected from mechanical devices operating over long periods of time. The purpose of our work is to classify the condition of in vivo Bjork-Shiley Convexo-Concave (BSCC) heart valves by processing acoustic measurements of heart valve sounds. The structural failures of interest for Bscc valves is called single leg separation (SLS). SLS can occur if the outlet strut cracks and separates from the main structure of the valve. We measure acoustic opening and closing sounds (waveforms) using high sensitivity contact microphones on the patient`s thorax. For our analysis, we focus our processing and classification efforts on the opening sounds because they yield direct information about outlet strut condition with minimal distortion caused by energy radiated from the valve disc.

  19. Turbulent Diffusivity under High Winds from Acoustic Measurements of Bubbles

    NASA Astrophysics Data System (ADS)

    Wang, D. W.; Wijesekera, H. W.; Jarosz, E.; Teague, W. J.; Pegau, W. S.

    2015-12-01

    Breaking surface waves generate layers of bubble clouds as air parcels entrain into the upper-ocean by the action of turbulent motions. The turbulent diffusivity in the bubble cloud layer was investigated by combining measurements of surface winds, waves, bubble acoustic backscatter, currents, and hydrography. These measurements were made at water depths of 60-90 m on the shelf of the Gulf of Alaska near Kayak Island during late December 2012, a period where the ocean was experiencing winds and significant wave heights up to 22 m s-1 and 9 m, respectively. Vertical profiles of acoustic backscatter decayed exponentially from the wave surface with e-folding lengths of about 0.6 to 6 m, while the bubble penetration depths were about 3 to 30 m. Both e-folding lengths and bubble depths were highly correlated with surface wind and wave conditions. The turbulent diffusion coefficients, inferred from e-folding length and bubble depth, varied from about 0.01 m2 s-1 to 0.4 m2 s-1. Our analysis suggests that the turbulent diffusivity in the bubble layer can be parameterized as a function of the cube of the wind friction velocity with a proportionality coefficient that depends weakly on wave age. Furthermore, in the bubble layer, on average, the shear production of the turbulent kinetic energy estimated by the diffusion coefficients was a similar order magnitude as the dissipation rate predicted by the wall boundary-layer theory.

  20. Modeling of Structural-Acoustic Interaction Using Coupled FE/BE Method and Control of Interior Acoustic Pressure Using Piezoelectric Actuators

    NASA Technical Reports Server (NTRS)

    Mei, Chuh; Shi, Yacheng

    1997-01-01

    A coupled finite element (FE) and boundary element (BE) approach is presented to model full coupled structural/acoustic/piezoelectric systems. The dual reciprocity boundary element method is used so that the natural frequencies and mode shapes of the coupled system can be obtained, and to extend this approach to time dependent problems. The boundary element method is applied to interior acoustic domains, and the results are very accurate when compared with limited exact solutions. Structural-acoustic problems are then analyzed with the coupled finite element/boundary element method, where the finite element method models the structural domain and the boundary element method models the acoustic domain. Results for a system consisting of an isotropic panel and a cubic cavity are in good agreement with exact solutions and experiment data. The response of a composite panel backed cavity is then obtained. The results show that the mass and stiffness of piezoelectric layers have to be considered. The coupled finite element and boundary element equations are transformed into modal coordinates, which is more convenient for transient excitation. Several transient problems are solved based on this formulation. Two control designs, a linear quadratic regulator (LQR) and a feedforward controller, are applied to reduce the acoustic pressure inside the cavity based on the equations in modal coordinates. The results indicate that both controllers can reduce the interior acoustic pressure and the plate deflection.

  1. Measurements of Low-Frequency Acoustic Attenuation in Soils.

    DTIC Science & Technology

    2007-11-02

    Engineering Research Laboratory to design an acoustic subsurface imaging system, a set of experiments was conducted in which the attenuation and the velocity...support of the U.S. Army Construction Engineering Research Laboratory’s efforts to design an acoustic subsurface imaging system which would ideally be...of acoustic waves such as those generated by a subsurface imaging system. An experiment reported in the literature characterized the acoustic

  2. Modeling and Measuring Acoustic Backscatter from Fish Aggregations

    DTIC Science & Technology

    1999-09-30

    of the abundance, spatial distribution, schooling behaviour and acoustic backscatter of the Namibian pilchard. Cruise Report 99-4, Dr. Fridtjof ... Nansen . 103 pp. Rudstam, L, Horne, J., Fleischer, G. Report from the Great Lakes Acoustic Workshop III: Translation of acoustic data to fish abundance

  3. Nearfield Acoustical Holography

    NASA Astrophysics Data System (ADS)

    Hayek, Sabih I.

    Nearfield acoustical holography (NAH) is a method by which a set of acoustic pressure measurements at points located on a specific surface (called a hologram) can be used to image sources on vibrating surfaces on the acoustic field in three-dimensional space. NAH data are processed to take advantage of the evanescent wavefield to image sources that are separated less that one-eighth of a wavelength.

  4. Working meeting on blood pressure measurement: suggestions for measuring blood pressure to use in populations surveys.

    PubMed

    2003-11-01

    As part of the Pan American Hypertension Initiative (PAHI), the Pan American Health Organization and the National Heart, Lung, and Blood Institute of the National Institutes of Health of the United States of America conducted a working meeting to discuss blood pressure (BP) measurement methods used in various hypertension prevalence surveys and clinical trials, with the objective of developing a BP measurement protocol for use in hypertension prevalence surveys in the Americas. No such common protocol has existed in the Americas, so it has been difficult to compare hypertension prevention and intervention strategies. This piece describes a proposed standard method for measuring blood pressure for use in population surveys in the Region of the Americas. The piece covers: considerations for developing a common blood pressure measurement protocol, critical issues in measuring blood pressure in national surveys, minimum procedures for blood pressure measurement during surveillance, and quality assessment of blood pressure.

  5. Relationship between acoustic measures and speech naturalness ratings in Parkinson's disease: A within-speaker approach.

    PubMed

    Klopfenstein, Marie

    2015-01-01

    This study investigated the acoustic basis of across-utterance, within-speaker variation in speech naturalness for four speakers with dysarthria secondary to Parkinson's disease (PD). Speakers read sentences and produced spontaneous speech. Acoustic measures of fundamental frequency, phrase-final syllable lengthening, intensity and speech rate were obtained. A group of listeners judged speech naturalness using a nine-point Likert scale. Relationships between judgements of speech naturalness and acoustic measures were determined for individual speakers with PD. Relationships among acoustic measures also were quantified. Despite variability between speakers, measures of mean F0, intensity range, articulation rate, average syllable duration, duration of final syllables, vocalic nucleus length of final unstressed syllables and pitch accent of final syllables emerged as possible acoustic variables contributing to within-speaker variations in speech naturalness. Results suggest that acoustic measures correlate with speech naturalness, but in dysarthric speech they depend on the speaker due to the within-speaker variation in speech impairment.

  6. Comparison of the Effects of using Tygon Tubing in Rocket Propulsion Ground Test Pressure Transducer Measurements

    NASA Technical Reports Server (NTRS)

    Farr, Rebecca A.; Wiley, John T.; Vitarius, Patrick

    2005-01-01

    This paper documents acoustics environments data collected during liquid oxygen- ethanol hot-fire rocket testing at NASA Marshall Space Flight Center in November- December 2003. The test program was conducted during development testing of the RS-88 development engine thrust chamber assembly in support of the Orbital Space Plane Crew Escape System Propulsion Program Pad Abort Demonstrator. In addition to induced environments analysis support, coincident data collected using other sensors and methods has allowed benchmarking of specific acoustics test measurement methodologies during propulsion tests. Qualitative effects on data characteristics caused by using tygon sense lines of various lengths in pressure transducer measurements is discussed here.

  7. Measuring unsteady pressure on rotating compressor blades

    NASA Technical Reports Server (NTRS)

    Englund, D. R.; Grant, H. P.; Lanati, G. A.

    1979-01-01

    Miniature semiconductor strain gage pressure transducers mounted in several arrangements were studied. Both surface mountings and recessed flush mountings were tested. Test parameters included mounting arrangement, blade material, temperature, local strain in the acceleration normal to the transducer diaphragm, centripetal acceleration, and pressure. Test results show no failures of transducers or mountings and indicate an uncertainty of unsteady pressure measurement of approximately + or - 6 percent + 0.1 kPa for a typical application. Two configurations were used on a rotating fan flutter program. Examples of transducer data and correction factors are presented.

  8. Acoustic measurement of the surface tension of levitated drops

    NASA Technical Reports Server (NTRS)

    Trinh, E. H.; Marston, P. L.; Robey, J. L.

    1988-01-01

    The measurement of the frequency of the fundamental mode of shape oscillation of acoustically levitated drops has been carried out to determine the surface tension of the drop material. Sound fields of about 20 kHz in frequency allow the suspension of drops a few millimeters in size, as well as the necessary drive for oscillations. The surface tension of water, hexadecane, silicone oil, and aqueous solutions of glycerin levitated in air has been measured, and the results have been compared with those obtained with standard ring tensiometry. The two sets of data are in good agreement, the largest discrepancy being about 10 percent. Uncertainties in the effects of the nonspherical static shape of drops levitated in the earth's gravitational field and the rotation state of the sample are the major contributors to the experimental error. A decrease of the resonance frequency of the fundamental mode indicates a soft nonlinearity as the oscillation amplitude increases.

  9. Measured acoustic properties of variable and low density bulk absorbers

    NASA Technical Reports Server (NTRS)

    Dahl, M. D.; Rice, E. J.

    1985-01-01

    Experimental data were taken to determine the acoustic absorbing properties of uniform low density and layered variable density samples using a bulk absober with a perforated plate facing to hold the material in place. In the layered variable density case, the bulk absorber was packed such that the lowest density layer began at the surface of the sample and progressed to higher density layers deeper inside. The samples were placed in a rectangular duct and measurements were taken using the two microphone method. The data were used to calculate specific acoustic impedances and normal incidence absorption coefficients. Results showed that for uniform density samples the absorption coefficient at low frequencies decreased with increasing density and resonances occurred in the absorption coefficient curve at lower densities. These results were confirmed by a model for uniform density bulk absorbers. Results from layered variable density samples showed that low frequency absorption was the highest when the lowest density possible was packed in the first layer near the exposed surface. The layers of increasing density within the sample had the effect of damping the resonances.

  10. A film bulk acoustic resonator-based high-performance pressure sensor integrated with temperature control system

    NASA Astrophysics Data System (ADS)

    Zhang, Mengying; Zhao, Zhan; Du, Lidong; Fang, Zhen

    2017-04-01

    This paper presented a high-performance pressure sensor based on a film bulk acoustic resonator (FBAR). The support film of the FBAR chip was made of silicon nitride and the part under the resonator area was etched to enhance the sensitivity and improve the linearity of the pressure sensor. A micro resistor temperature sensor and a micro resistor heater were integrated in the chip to monitor and control the operating temperature. The sensor chip was fabricated, and packaged in an oscillator circuit for differential pressure detection. When the detected pressure ranged from  ‑100 hPa to 600 hPa, the sensitivity of the improved FBAR pressure sensor was  ‑0.967 kHz hPa‑1, namely  ‑0.69 ppm hPa‑1, which was 19% higher than that of existing sensors with a complete support film. The nonlinearity of the improved sensor was less than  ±0.35%, while that of the existing sensor was  ±5%. To eliminate measurement errors from humidity, the temperature control system integrated in the sensor chip controlled the temperature of the resonator up to 75 °C, with accuracy of  ±0.015 °C and power of 20 mW.

  11. Measurement of sound speed vs. depth in South Pole ice: pressure waves and shear waves

    SciTech Connect

    IceCube Collaboration; Klein, Spencer

    2009-06-04

    We have measured the speed of both pressure waves and shear waves as a function of depth between 80 and 500 m depth in South Pole ice with better than 1% precision. The measurements were made using the South Pole Acoustic Test Setup (SPATS), an array of transmitters and sensors deployed in the ice at the South Pole in order to measure the acoustic properties relevant to acoustic detection of astrophysical neutrinos. The transmitters and sensors use piezoceramics operating at {approx}5-25 kHz. Between 200 m and 500 m depth, the measured profile is consistent with zero variation of the sound speed with depth, resulting in zero refraction, for both pressure and shear waves. We also performed a complementary study featuring an explosive signal propagating vertically from 50 to 2250 m depth, from which we determined a value for the pressure wave speed consistent with that determined for shallower depths, higher frequencies, and horizontal propagation with the SPATS sensors. The sound speed profile presented here can be used to achieve good acoustic source position and emission time reconstruction in general, and neutrino direction and energy reconstruction in particular. The reconstructed quantities could also help separate neutrino signals from background.

  12. 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.

  13. Measuring Extreme Vacuum Pressure with Ultraintense Lasers

    NASA Astrophysics Data System (ADS)

    Paredes, Angel; Novoa, David; Tommasini, Daniele

    2012-12-01

    We show that extreme vacuum pressures can be measured with current technology by detecting the photons produced by the relativistic Thomson scattering of ultraintense laser light by the electrons of the medium. We compute the amount of radiation scattered at different frequencies and angles when a Gaussian laser pulse crosses a vacuum tube and design strategies for the efficient measurement of pressure. In particular, we show that a single day experiment at a high repetition rate petawatt laser facility such as Vega, that will be operating in 2014 in Salamanca, will be sensitive, in principle, to pressures p as low as 10-16Pa, and will be able to provide highly reliable measurements for p≳10-14Pa.

  14. Prediction and Measurement of the Vibration and Acoustic Radiation of Panels Subjected to Acoustic Loading

    NASA Technical Reports Server (NTRS)

    Turner, Travis L.; Rizzi, Stephen A.

    1995-01-01

    Interior noise and sonic fatigue are important issues in the development and design of advanced subsonic and supersonic aircraft. Conventional aircraft typically employ passive treatments, such as constrained layer damping and acoustic absorption materials, to reduce the structural response and resulting acoustic levels in the aircraft interior. These techniques require significant addition of mass and only attenuate relatively high frequency noise transmitted through the fuselage. Although structural acoustic coupling is in general very important in the study of aircraft fuselage interior noise, analysis of noise transmission through a panel supported in an infinite rigid baffle (separating two semi-infinite acoustic domains) can be useful in evaluating the effects of active/adaptive materials, complex loading, etc. Recent work has been aimed at developing adaptive and/or active methods of controlling the structural acoustic response of panels to reduce the transmitted noise1. A finite element formulation was recently developed to study the dynamic response of shape memory alloy (SMA) hybrid composite panels (conventional composite panel with embedded SMA fibers) subject to combined acoustic and thermal loads2. Further analysis has been performed to predict the far-field acoustic radiation using the finite element dynamic panel response prediction3. The purpose of the present work is to validate the panel vibration and acoustic radiation prediction methods with baseline experimental results obtained from an isotropic panel, without the effect of SMA.

  15. Application of acoustic doppler velocimeters for streamflow measurements

    USGS Publications Warehouse

    Rehmel, M.

    2007-01-01

    The U.S. Geological Survey (USGS) principally has used Price AA and Price pygmy mechanical current meters for measurement of discharge. New technologies have resulted in the introduction of alternatives to the Price meters. One alternative, the FlowTracker acoustic Doppler velocimeter, was designed by SonTek/YSI to make streamflow measurements in wadeable conditions. The device measures a point velocity and can be used with standard midsection method algorithms to compute streamflow. The USGS collected 55 quality-assurance measurements with the FlowTracker at 43 different USGS streamflow-gaging stations across the United States, with mean depths from 0.05to0.67m, mean velocities from 13 to 60 cm/s, and discharges from 0.02 to 12.4m3/s. These measurements were compared with Price mechanical current meter measurements. Analysis of the comparisons shows that the FlowTracker discharges were not statistically different from the Price meter discharges at a 95% confidence level. ?? 2007 ASCE.

  16. Measurement of ultrasonic power and electro-acoustic efficiency of high power transducers.

    PubMed

    Lin, S; Zhang, F

    2000-01-01

    In this paper, an improved method for the measurement of acoustic power and electro-acoustic efficiency of high power ultrasonic transducers is presented. The measuring principle is described, the experimental results are given. In comparison with traditional methods, the method presented in this paper has the advantages of simplicity, economy and practicality. The most important is that it can measure the output acoustic power and the electro-acoustic efficiency of the transducer under the condition of high power and practical applications, such as ultrasonic cleaning and soldering.

  17. An instrument for measuring turbulent pressure fluctuations

    NASA Astrophysics Data System (ADS)

    Papadimitrakis, Yiannis Alex; Hsu, En Yu; Street, Robert L.

    1986-04-01

    An instrument is described for laboratory measurements of the fluctuating static pressure in the turbulent boundary layer above progressive water waves. It consists of a disk-shaped sensing head properly designed to minimize the dynamic pressure variation to an acceptable level, a commercially available piezocrystal transducer housed inside a casing, and a forward-bent connecting tube. Pressure fluctuations sampled by the disk are converted into an electrical signal by the piezocrystal transducer. Through low-pass filtering, only the frequency range of interest is retained. The instrument was tested successfully for frequency response, dynamic and mechanical noise sensitivity, and response to spurious pressure fluctuations (produced when operating in a Eulerian wave-following mode) inside a cylindrical chamber and in a wind-wave facility, and some sample results along with the calibration procedures and data analysis are presented.

  18. Regularization method for measurement of structural intensity using nearfield acoustical holography.

    PubMed

    Saijyou, Kenji; Okawara, Chiaki

    2005-04-01

    The regularization method for measurement of structural intensity using nearfield acoustical holography is proposed. Spatial derivatives of normal displacement are necessary to obtain the structural intensity. The derivative operations amplify high-wave-number components of measurement noise. Therefore, the estimation of an appropriate wave-number filter is crucial for implementation of the measurement of structural intensity. In conventional methods, this wave-number filter is determined from the flexural wavelength. And the same wave-number filter is applied to obtain all spatial derivatives. As a result, structural intensity obtained from the pressure hologram, whose signal-to-noise ratio is low, is seriously contaminated by the noise. To overcome this difficulty, regularization theory is applied to determine the appropriate wave-number filter for each order of derivatives. The effectiveness of the proposed method is demonstrated by experiments.

  19. Measurement of Elastic Properties of Tissue by Shear Wave Propagation Generated by Acoustic Radiation Force

    NASA Astrophysics Data System (ADS)

    Tabaru, Marie; Azuma, Takashi; Hashiba, Kunio

    2010-07-01

    Acoustic radiation force (ARF) imaging has been developed as a novel elastography technology to diagnose hepatic disease and breast cancer. The accuracy of shear wave speed estimation, which is one of the applications of ARF elastography, is studied. The Young's moduli of pig liver and foie gras samples estimated from the shear wave speed were compared with those measured the static Young's modulus measurement. The difference in the two methods was 8%. Distance attenuation characteristics of the shear wave were also studied using finite element method (FEM) analysis. We found that the differences in the axial and lateral beam widths in pressure and ARF are 16 and 9% at F-number=0.9. We studied the relationship between two branch points in distance attenuation characteristics and the shape of ARF. We found that the maximum measurable length to estimate shear wave speed for one ARF excitation was 8 mm.

  20. Measurement of Elastic Properties of Tissue by Shear Wave Propagation Generated by Acoustic Radiation Force

    NASA Astrophysics Data System (ADS)

    Marie Tabaru,; Takashi Azuma,; Kunio Hashiba,

    2010-07-01

    Acoustic radiation force (ARF) imaging has been developed as a novel elastography technology to diagnose hepatic disease and breast cancer. The accuracy of shear wave speed estimation, which is one of the applications of ARF elastography, is studied. The Young’s moduli of pig liver and foie gras samples estimated from the shear wave speed were compared with those measured the static Young’s modulus measurement. The difference in the two methods was 8%. Distance attenuation characteristics of the shear wave were also studied using finite element method (FEM) analysis. We found that the differences in the axial and lateral beam widths in pressure and ARF are 16 and 9% at F-number=0.9. We studied the relationship between two branch points in distance attenuation characteristics and the shape of ARF. We found that the maximum measurable length to estimate shear wave speed for one ARF excitation was 8 mm.

  1. International Congress on Acoustic Intensity Measurement: Measurement Techniques and Applications, 2nd, Senlis, France, September 23-26, 1985, Proceedings

    NASA Astrophysics Data System (ADS)

    Recent developments in acoustic-intensity measurement are discussed in reviews and reports of theoretical and experimental investigations. Instrumentation, vector acoustics, sound radiation, intensity in the presence of flow, intensity in structures, sound power, source localization, impedance, absorption, and transmission are the fields covered by the contributions. Specific topics addressed include microphone configurations for intensity probes, the rotational structure of intensity fields, acoustic intensity and numerical simulation, sound-power measurement in the presence of background noise, and techniques for measuring the absorption coefficient of acoustic materials. Graphs, drawings, diagrams, tables of numerical data, and photographs of test setups are provided.

  2. Optical pressure/density measuring means

    DOEpatents

    Veligdan, J.T.

    1995-05-09

    An apparatus and method are disclosed for rapidly and accurately determining the pressure of a fluid medium in either a static or dynamic state. The pressure is determined by making a measurement of the velocity of a light beam that is directed through the fluid medium along a pathway that enables an integrated pressure measurement to be made along the pathway, rather than making such a measurement only at a single point in the medium. A HeNe laser is configured to emit a beam of two frequencies separated by about 2 MHz. One of these beam frequencies is directed through the fluid medium and is reflected back through the medium to a non-linear diode detector. The other beam frequency is passed directly to a diode detector without traversing said medium. The diode detector is operated to determine the frequency shift or beat frequency between the two beam frequencies. Any variation in the frequency of said reflected beam that is caused by a change in its velocity as it is passed through the fluid medium causes a change in the beat frequency. This beat frequency change is then converted to an output signal value corresponding to the pressure of the medium. The measurement instrument apparatus is remotely positioned relative to the medium being measured, thus the apparatus is immune from electro-magnetic interference and can operate in conditions of high radiation, corrosion and extraordinarily high temperature. 4 figs.

  3. Optical pressure/density measuring means

    DOEpatents

    Veligdan, James T.

    1995-05-09

    An apparatus and method for rapidly and accurately determining the pressure of a fluid medium in either a static or dynamic state. The pressure is determined by making a measurement of the velocity of a light beam that is directed through the fluid medium along a pathway that enables an integrated pressure measurement to be made along the pathway, rather than making such a measurement only at a single point in the medium. A HeNe laser is configured to emit a beam of two frequencies separated by about 2 MHz. One of these beam frequencies is directed through the fluid medium and is reflected back through the medium to a non-linear diode detector. The other beam frequency is passed directly to a diode detector without traversing said medium. The diode detector is operated to determine the frequency shift or beat frequency between the two beam frequencies. Any variation in the frequency of said reflected beam that is caused by a change in its velocity as it is passed through the fluid medium causes a change in the beat frequency. This beat frequency change is then converted to an output signal value corresponding to the pressure of the medium. The measurement instrument apparatus is remotely positioned relative to the medium being measured, thus the apparatus is immune from electro-magnetic interference and can operate in conditions of high radiation, corrosion and extraordinarily high temperature.

  4. Acoustic measurements of a full-scale coaxial helicopter

    NASA Technical Reports Server (NTRS)

    Mosher, M.; Peterson, R. L.

    1983-01-01

    Acoustic data were obtained during a full-scale test of the XH-59A Advancing Blade Concept (ABC) Technology Demonstrator in the NASA Ames 40- by 80-Foot Wind Tunnel. The XH-59A is a research helicopter with two coaxial rotors and hingeless blades. Performance, vibration, noise at various forward speeds, rotor lift coefficients, and rotor shaft angles of attack were investigated. In general, the noise level is shown to increase with rotor lift coefficient except under certain operating conditions where it is increased by significant impulsive blade/vortex interactions. The impulsivity appears to depend upon how the lift is distributed between the two rotors. The noise levels measured are shown to be slightly higher than on a modern conventional rotor tested in the same facility.

  5. Determination of particle size distributions from acoustic wave propagation measurements

    SciTech Connect

    Spelt, P.D.; Norato, M.A.; Sangani, A.S.; Tavlarides, L.L.

    1999-05-01

    The wave equations for the interior and exterior of the particles are ensemble averaged and combined with an analysis by Allegra and Hawley [J. Acoust. Soc. Am. {bold 51}, 1545 (1972)] for the interaction of a single particle with the incident wave to determine the phase speed and attenuation of sound waves propagating through dilute slurries. The theory is shown to compare very well with the measured attenuation. The inverse problem, i.e., the problem of determining the particle size distribution given the attenuation as a function of frequency, is examined using regularization techniques that have been successful for bubbly liquids. It is shown that, unlike the bubbly liquids, the success of solving the inverse problem is limited since it depends strongly on the nature of particles and the frequency range used in inverse calculations. {copyright} {ital 1999 American Institute of Physics.}

  6. Effects of ingested atmospheric turbulence on measured tail rotor acoustics

    NASA Technical Reports Server (NTRS)

    Signor, David B.; Yamauchi, Gloria K.; Mosher, Marianne; Hagen, Martin J.; George, Albert R.

    1992-01-01

    Results from an outdoor hover test of a full-scale Lynx tail rotor are presented. The investigation was designed to further the understanding of the acoustics of an isolated tail rotor hovering out-of-ground effect in atmospheric turbulence, without the effects of the main rotor wake or other helicopter components. Measurements include simultaneous rotor performance, noise, inflow, and far-field atmospheric turbulence. Results with grid-generated inflow turbulence are also presented. The effects of turbulence ingestion on rotor noise are quantified. Turbulence ingestion noise is found to be the dominant noise mechanism at locations near the rotor axis. At these locations, the sound radiated by the hovering rotor increases with both increasing atmospheric wind speed and ingested rms turbulent velocity.

  7. Measurements of atmospheric turbulence effects on tail rotor acoustics

    NASA Technical Reports Server (NTRS)

    Hagen, Martin J.; Yamauchi, Gloria K.; Signor, David B.; Mosher, Marianne

    1994-01-01

    Results from an outdoor hover test of a full-scale Lynx tail rotor are presented. The investigation was designed to further the understanding of the acoustics of an isolated tail rotor hovering out-of-ground effect in atmospheric turbulence, without the effects of the main rotor wake or other helicopter components. Measurements include simultaneous rotor performance, noise, inflow, and far-field atmospheric turbulence. Results with grid-generated inflow turbulence are also presented. The effects of atmospheric turbulence ingestion on rotor noise are quantified. In contradiction to current theories, increasing rotor inflow and rotor thrust were found to increase turbulence ingestion noise. This is the final report of Task 13A--Helicopter Tail Rotor Noise, of the NASA/United Kingdom Defense Research Agency cooperative Aeronautics Research Program.

  8. Surface Acoustic Wave Vibration Sensors for Measuring Aircraft Flutter

    NASA Technical Reports Server (NTRS)

    Wilson, William C.; Moore, Jason P.; Juarez, Peter D.

    2016-01-01

    Under NASA's Advanced Air Vehicles Program the Advanced Air Transport Technology (AATT) Project is investigating flutter effects on aeroelastic wings. To support that work a new method for measuring vibrations due to flutter has been developed. The method employs low power Surface Acoustic Wave (SAW) sensors. To demonstrate the ability of the SAW sensor to detect flutter vibrations the sensors were attached to a Carbon fiber-reinforced polymer (CFRP) composite panel which was vibrated at six frequencies from 1Hz to 50Hz. The SAW data was compared to accelerometer data and was found to resemble sine waves and match each other closely. The SAW module design and results from the tests are presented here.

  9. Picosecond Acoustic Measurement of Anisotropic Properties of Thin Films

    SciTech Connect

    Perton, M.; Rossignol, C.; Chigarev, N.; Audoin, B.

    2007-03-21

    Properties of thin metallic films have been studied extensively by means of laser-picosecond ultrasonics. Generation of longitudinal and shear waves via thermoelastic mechanism and large source has been only demonstrated for waves vectors along the normal to the interface. However, such measurements cannot provide complete information about elastic properties of films. As it has been already shown for nanosecond ultrasonics, the knowledge of group or phase velocities in several directions for sources with small lateral size allows determining the stiffness tensor coefficients of a sample. The experimental set-up was prepared to obtain the thinnest size for the source to achieve acoustic diffraction. The identification of the stiffness tensor components, based on the inversion of the bulk waves phase velocities, is applied to signals simulated and experimentally recorded for a material with hexagonal properties. First estimation of stiffness tensor coefficients for thin metallic film 2.1 {mu}m has been performed.

  10. Measurement of the Acoustic Nonlinearity Parameter for Biological Media.

    NASA Astrophysics Data System (ADS)

    Cobb, Wesley Nelson

    In vitro measurements of the acoustic nonlinearity parameter are presented for several biological media. With these measurements it is possible to predict the distortion of a finite amplitude wave in biological tissues of current diagnostic and research interest. The measurement method is based on the finite amplitude distortion of a sine wave that is emmitted by a piston source. The growth of the second harmonic component of this wave is measured by a piston receiver which is coaxial with and has the same size as the source. The experimental measurements and theory are compared in order to determine the nonlinearity parameter. The density, sound speed, and attenuation for the medium are determined in order to make this comparison. The theory developed for this study accounts for the influence of both diffraction and attenuation on the experimental measurements. The effects of dispersion, tissue inhomogeneity and gas bubbles within the excised tissues are studied. To test the measurement method, experimental results are compared with established values for the nonlinearity parameter of distilled water, ethylene glycol and glycerol. The agreement between these values suggests that the measurement uncertainty is (+OR-) 5% for liquids and (+OR-) 10% for solid tissues. Measurements are presented for dog blood and bovine serum albumen as a function of concentration. The nonlinearity parameters for liver, kidney and spleen are reported for both human and canine tissues. The values for the fresh tissues displayed little variation (6.8 to 7.8). Measurements for fixed, normal and cirrhotic tissues indicated that the nonlinearity parameter does not depend strongly on pathology. However, the values for fixed tissues were somewhat higher than those of the fresh tissues.

  11. Acoustic-Seismic Coupling of Broadband Signals - Analysis of Potential Disturbances during CTBT On-Site Inspection Measurements

    NASA Astrophysics Data System (ADS)

    Liebsch, Mattes; Altmann, Jürgen

    2015-04-01

    For the verification of the Comprehensive Nuclear Test Ban Treaty (CTBT) the precise localisation of possible underground nuclear explosion sites is important. During an on-site inspection (OSI) sensitive seismic measurements of aftershocks can be performed, which, however, can be disturbed by other signals. To improve the quality and effectiveness of these measurements it is essential to understand those disturbances so that they can be reduced or prevented. In our work we focus on disturbing signals caused by airborne sources: When the sound of aircraft (as often used by the inspectors themselves) hits the ground, it propagates through pores in the soil. Its energy is transferred to the ground and soil vibrations are created which can mask weak aftershock signals. The understanding of the coupling of acoustic waves to the ground is still incomplete. However, it is necessary to improve the performance of an OSI, e.g. to address potential consequences for the sensor placement, the helicopter trajectories etc. We present our recent advances in this field. We performed several measurements to record sound pressure and soil velocity produced by various sources, e.g. broadband excitation by jet aircraft passing overhead and signals artificially produced by a speaker. For our experimental set-up microphones were placed close to the ground and geophones were buried in different depths in the soil. Several sensors were shielded from the directly incident acoustic signals by a box coated with acoustic damping material. While sound pressure under the box was strongly reduced, the soil velocity measured under the box was just slightly smaller than outside of it. Thus these soil vibrations were mostly created outside the box and travelled through the soil to the sensors. This information is used to estimate characteristic propagation lengths of the acoustically induced signals in the soil. In the seismic data we observed interference patterns which are likely caused by the

  12. Magnetic Barkhausen noise and magneto acoustic emission in pressure vessel steel

    NASA Astrophysics Data System (ADS)

    Neyra Astudillo, Miriam Rocío; López Pumarega, María Isabel; Núñez, Nicolás Marcelo; Pochettino, Alberto; Ruzzante, José

    2017-03-01

    Magnetic Barkhausen Noise (MBN) and Magneto Acoustic Emission (MAE) were studied in A508 Class II forged steel used for pressure vessels in nuclear power stations. The magnetic experimental determinations were completed with a macro graphic study of sulfides and the texture analysis of the material. The analysis of these results allows us to determine connections between the magnetic anisotropy, texture and microstructure of the material. Results clearly suggest that the plastic flow direction is different from the forging direction indicated by the material supplier

  13. High Temperature Dynamic Pressure Measurements Using Silicon Carbide Pressure Sensors

    NASA Technical Reports Server (NTRS)

    Okojie, Robert S.; Meredith, Roger D.; Chang, Clarence T.; Savrun, Ender

    2014-01-01

    Un-cooled, MEMS-based silicon carbide (SiC) static pressure sensors were used for the first time to measure pressure perturbations at temperatures as high as 600 C during laboratory characterization, and subsequently evaluated in a combustor rig operated under various engine conditions to extract the frequencies that are associated with thermoacoustic instabilities. One SiC sensor was placed directly in the flow stream of the combustor rig while a benchmark commercial water-cooled piezoceramic dynamic pressure transducer was co-located axially but kept some distance away from the hot flow stream. In the combustor rig test, the SiC sensor detected thermoacoustic instabilities across a range of engine operating conditions, amplitude magnitude as low as 0.5 psi at 585 C, in good agreement with the benchmark piezoceramic sensor. The SiC sensor experienced low signal to noise ratio at higher temperature, primarily due to the fact that it was a static sensor with low sensitivity.

  14. Preliminary Analysis of Acoustic Measurements from the NASA-Gulfstream Airframe Noise Flight Test

    NASA Technical Reports Server (NTRS)

    Khorrami, Mehdi R.; Lockhard, David D.; Humphreys, Willliam M.; Choudhari, Meelan M.; Van De Ven, Thomas

    2008-01-01

    The NASA-Gulfstream joint Airframe Noise Flight Test program was conducted at the NASA Wallops Flight Facility during October, 2006. The primary objective of the AFN flight test was to acquire baseline airframe noise data on a regional jet class of transport in order to determine noise source strengths and distributions for model validation. To accomplish this task, two measuring systems were used: a ground-based microphone array and individual microphones. Acoustic data for a Gulfstream G550 aircraft were acquired over the course of ten days. Over twenty-four test conditions were flown. The test matrix was designed to provide an acoustic characterization of both the full aircraft and individual airframe components and included cruise to landing configurations. Noise sources were isolated by selectively deploying individual components (flaps, main landing gear, nose gear, spoilers, etc.) and altering the airspeed, glide path, and engine settings. The AFN flight test program confirmed that the airframe is a major contributor to the noise from regional jets during landing operations. Sound pressure levels from the individual microphones on the ground revealed the flap system to be the dominant airframe noise source for the G550 aircraft. The corresponding array beamform maps showed that most of the radiated sound from the flaps originates from the side edges. Using velocity to the sixth power and Strouhal scaling of the sound pressure spectra obtained at different speeds failed to collapse the data into a single spectrum. The best data collapse was obtained when the frequencies were left unscaled.

  15. Accelerometer measurements of acoustic-to-seismic coupling above buried objects.

    PubMed

    Attenborough, Keith; Qin, Qin; Jefferis, Jonathan; Heald, Gary

    2007-12-01

    The surface velocity of sand inside a large PVC container, induced by the sound pressure from either a large loudspeaker radiating into an inverted cone and pipe or a Bruel and Kjaer point source loudspeaker mounted with its axis vertical, has been measured using accelerometers. Results of white noise and stepped frequency excitation are presented. Without any buried object the mass loading of an accelerometer creates resonances in the spectral ratio of sand surface velocity to incident acoustic pressure, i.e., the acoustic-to-seismic (A/S) admittance spectra. The A/S responses above a buried compliant object are larger and distinctive. The linear A/S admittance spectra in the presence of a buried electronic components box have been studied as a function of burial depth and sand state. The nonlinear responses above the buried box have been studied as a function of depth, sand state, and amplitude. Predictions of a modified one-dimensional lumped parameter model have been found to be consistent with the observed nonlinear responses. Also the modified model has been used to explain features of the A/S responses observed when using an accelerometer without any buried object.

  16. Improved method of measuring pressure coupled response for composite solid propellants

    NASA Astrophysics Data System (ADS)

    Su, Wanxing; Wang, Ningfei; Li, Junwei; Zhao, Yandong; Yan, Mi

    2014-04-01

    Pressure coupled response is one of the main causes of combustion instability in the solid rocket motor. It is also a characteristic parameter for predicting the stability. The pressure coupled response function is usually measured by different methods to evaluate the performance of new propellant. Based on T-burner and "burning surface doubled and secondary attenuation", an improved method for measuring the pressure coupled response of composite propellant is introduced in this article. A computational fluid dynamics (CFD) study has also been conducted to validate the method and to understand the pressure oscillation phenomenon in T-burner. Three rounds of tests were carried out on the same batch of aluminized AP/HTPB composite solid propellant. The experimental results show that the sample propellant had a high response function under the conditions of high pressure (~11.5 MPa) and low frequency (~140 Hz). The numerically predicted oscillation frequency and amplitude are consistent with the experimental results. One practical solid rocket motor using this sample propellant was found to experience pressure oscillation at the end of burning. This confirms that the sample propellant is prone to combustion instability. Finally, acoustic pressure distribution and phase difference in T-burner were analyzed. Both the experimental and numerical results are found to be associated with similar acoustic pressure distribution. And the phase difference analysis showed that the pressure oscillations at the head end of the T-burner are 180° out of phase from those in the aft end of the T-burner.

  17. Relationships between vocal function measures derived from an acoustic microphone and a subglottal neck-surface accelerometer

    PubMed Central

    Mehta, Daryush D.; Van Stan, Jarrad H.; Hillman, Robert E.

    2016-01-01

    Monitoring subglottal neck-surface acceleration has received renewed attention due to the ability of low-profile accelerometers to confidentially and noninvasively track properties related to normal and disordered voice characteristics and behavior. This study investigated the ability of subglottal neck-surface acceleration to yield vocal function measures traditionally derived from the acoustic voice signal and help guide the development of clinically functional accelerometer-based measures from a physiological perspective. Results are reported for 82 adult speakers with voice disorders and 52 adult speakers with normal voices who produced the sustained vowels /a/, /i/, and /u/ at a comfortable pitch and loudness during the simultaneous recording of radiated acoustic pressure and subglottal neck-surface acceleration. As expected, timing-related measures of jitter exhibited the strongest correlation between acoustic and neck-surface acceleration waveforms (r ≤ 0.99), whereas amplitude-based measures of shimmer correlated less strongly (r ≤ 0.74). Additionally, weaker correlations were exhibited by spectral measures of harmonics-to-noise ratio (r ≤ 0.69) and tilt (r ≤ 0.57), whereas the cepstral peak prominence correlated more strongly (r ≤ 0.90). These empirical relationships provide evidence to support the use of accelerometers as effective complements to acoustic recordings in the assessment and monitoring of vocal function in the laboratory, clinic, and during an individual’s daily activities. PMID:27066520

  18. Acoustic streaming in an ultrasonic air pump with three-dimensional finite-difference time-domain analysis and comparison to the measurement.

    PubMed

    Wada, Yuji; Koyama, Daisuke; Nakamura, Kentaro

    2014-12-01

    The direct finite-difference fluid simulation of acoustic streaming on a fine-meshed three-dimensional model using a graphics processing unit (GPU)-based calculation array is discussed. Airflows are induced by an acoustic traveling wave when an intense sound field is generated in a gap between a bending transducer and a reflector. The calculation results showed good agreement with measurements in a pressure distribution. Several flow vortices were observed near the boundary layer of the reflector and the transducer, which have often been observed near the boundary of acoustic tubes, but have not been observed in previous calculations for this type of ultrasonic air pump.

  19. Measurement of Bubble Size Distribution Based on Acoustic Propagation in Bubbly Medium

    NASA Astrophysics Data System (ADS)

    Wu, Xiongjun; Hsiao, Chao-Tsung; Choi, Jin-Keun; Chahine, Georges

    2013-03-01

    Acoustic properties are strongly affected by bubble size distribution in a bubbly medium. Measurement of the acoustic transmission becomes increasingly difficulty as the void fraction of the bubbly medium increases due to strong attenuation, while acoustic reflection can be measured more easily with increasing void fraction. The ABS ACOUSTIC BUBBLE SPECTROMETER®\\copyright, an instrument for bubble size measurement that is under development tries to take full advantage of the properties of acoustic propagation in bubbly media to extract bubble size distribution. Properties of both acoustic transmission and reflection in the bubbly medium from a range of short single-frequency bursts of acoustic waves at different frequencies are measured in an effort to deduce the bubble size distribution. With the combination of both acoustic transmission and reflection, assisted with validations from photography, the ABS ACOUSTIC BUBBLE SPECTROMETER®\\copyright has the potential to measure bubble size distributions in a wider void fraction range. This work was sponsored by Department of Energy SBIR program

  20. Ambient noise interferes with auscultatory blood pressure measurement during exercise.

    PubMed

    Lightfoot, J T; Tuller, B; Williams, D F

    1996-04-01

    This study was designed to investigate whether the acoustical characteristics of the Korotkoff sounds (K-sounds) were altered during exercise and/or masked by the ambient noise. After signing informed consent, 11 subjects (8 females, 3 males; 27 +/- 2 yr; 166.2 +/- 3.2 cm; 62 +/- 5 kg; means +/- SD) underwent a cycle ergometer exercise test that increased in workload by 30 W every 3 min until volitional fatigue. Heart rate, auscultatory systolic (SBP) and diastolic blood pressure (DBP), and oxygen consumption were monitored 1 and 2 min into each work stage. The auscultatory K-sounds were recorded with a microphone mounted in a stethoscope tube for later frequency (Hz) and sound pressure level (dB SPL) analysis. Frequency and SPL of ambient noise (99 +/- 13 Hz and 64 +/- 1 db at maximum, respectively) increased during the exercise test to magnitudes similar to the SBP and DBP K-sounds (166 Hz, 66 db; and 128 Hz, 69 db, respectively). Additionally, the ambient noise was responsible for a significant damping of the frequency and SPL of the measured blood pressure K-sounds and a rise in the measured frequency of the SBP K-sounds. Furthermore, we observed "inaudible" K-sounds at lower frequencies than adjoining audible K-sounds (100 Hz vs 126 Hz), supporting the known underestimation of SBP by auscultation. The increase in ambient noise during exercise testing dampens and may mask the auscultatory K-sounds, thus making detection of the proper K-sounds during exercise difficult at best. Furthermore, the presence of inaudible K-sounds may further explain the published discrepancies between auscultatory and intraarterial blood pressure measurements during exercise.

  1. Acoustic measurements of F-16 aircraft operating in hush house, NSN 4920-02-070-2721

    NASA Astrophysics Data System (ADS)

    Miller, V. R.; Plzak, G. A.; Chinn, J. M.

    1981-09-01

    The purpose of this test program was to measure the acoustic environment in the hush house facility located at Kelly Air Force Base, Texas, during operation of the F-16 aircraft to ensure that aircraft structural acoustic design limits were not exceeded. The acoustic measurements showed that no sonic fatigue problems are anticipated with the F-16 aircraft aft fuselage structure during operation in the hush house. The measured acoustic levels were less than those measured in an F-16 aircraft water cooled hush house at Hill AFB, but were increased over that measured during ground run up. It was recommended that the acoustic loads measured in this program should be specified in the structural design criteria for aircraft which will be subjected to hush house operation or defining requirements for associated equipment.

  2. Cell Deformation by Single-beam Acoustic Trapping: A Promising Tool for Measurements of Cell Mechanics

    PubMed Central

    Hwang, Jae Youn; Kim, Jihun; Park, Jin Man; Lee, Changyang; Jung, Hayong; Lee, Jungwoo; Shung, K. Kirk

    2016-01-01

    We demonstrate a noncontact single-beam acoustic trapping method for the quantification of the mechanical properties of a single suspended cell with label-free. Experimentally results show that the single-beam acoustic trapping force results in morphological deformation of a trapped cell. While a cancer cell was trapped in an acoustic beam focus, the morphological changes of the immobilized cell were monitored using bright-field imaging. The cell deformability was then compared with that of a trapped polystyrene microbead as a function of the applied acoustic pressure for a better understanding of the relationship between the pressure and degree of cell deformation. Cell deformation was found to become more pronounced as higher pressure levels were applied. Furthermore, to determine if this acoustic trapping method can be exploited in quantifying the cell mechanics in a suspension and in a non-contact manner, the deformability levels of breast cancer cells with different degrees of invasiveness due to acoustic trapping were compared. It was found that highly-invasive breast cancer cells exhibited greater deformability than weakly-invasive breast cancer cells. These results clearly demonstrate that the single-beam acoustic trapping technique is a promising tool for non-contact quantitative assessments of the mechanical properties of single cells in suspensions with label-free. PMID:27273365

  3. Outcomes Measurement in Voice Disorders: Application of an Acoustic Index of Dysphonia Severity

    ERIC Educational Resources Information Center

    Awan, Shaheen N.; Roy, Nelson

    2009-01-01

    Purpose: The purpose of this experiment was to assess the ability of an acoustic model composed of both time-based and spectral-based measures to track change following voice disorder treatment and to serve as a possible treatment outcomes measure. Method: A weighted, four-factor acoustic algorithm consisting of shimmer, pitch sigma, the ratio of…

  4. Conditionally Increased Acoustic Pressures in Nonfetal Diagnostic Ultrasound Examinations Without Contrast Agents: A Preliminary Assessment.

    PubMed

    Nightingale, Kathryn R; Church, Charles C; Harris, Gerald; Wear, Keith A; Bailey, Michael R; Carson, Paul L; Jiang, Hui; Sandstrom, Kurt L; Szabo, Thomas L; Ziskin, Marvin C

    2015-07-01

    The mechanical index (MI) has been used by the US Food and Drug Administration (FDA) since 1992 for regulatory decisions regarding the acoustic output of diagnostic ultrasound equipment. Its formula is based on predictions of acoustic cavitation under specific conditions. Since its implementation over 2 decades ago, new imaging modes have been developed that employ unique beam sequences exploiting higher-order acoustic phenomena, and, concurrently, studies of the bioeffects of ultrasound under a range of imaging scenarios have been conducted. In 2012, the American Institute of Ultrasound in Medicine Technical Standards Committee convened a working group of its Output Standards Subcommittee to examine and report on the potential risks and benefits of the use of conditionally increased acoustic pressures (CIP) under specific diagnostic imaging scenarios. The term "conditionally" is included to indicate that CIP would be considered on a per-patient basis for the duration required to obtain the necessary diagnostic information. This document is a result of that effort. In summary, a fundamental assumption in the MI calculation is the presence of a preexisting gas body. For tissues not known to contain preexisting gas bodies, based on theoretical predications and experimentally reported cavitation thresholds, we find this assumption to be invalid. We thus conclude that exceeding the recommended maximum MI level given in the FDA guidance could be warranted without concern for increased risk of cavitation in these tissues. However, there is limited literature assessing the potential clinical benefit of exceeding the MI guidelines in these tissues. The report proposes a 3-tiered approach for CIP that follows the model for employing elevated output in magnetic resonance imaging and concludes with summary recommendations to facilitate Institutional Review Board (IRB)-monitored clinical studies investigating CIP in specific tissues.

  5. Conditionally Increased Acoustic Pressures in Nonfetal Diagnostic Ultrasound Examinations Without Contrast Agents: A Preliminary Assessment

    PubMed Central

    Nightingale, Kathryn R.; Church, Charles C.; Harris, Gerald; Wear, Keith A.; Bailey, Michael R.; Carson, Paul L.; Jiang, Hui; Sandstrom, Kurt L.; Szabo, Thomas L.; Ziskin, Marvin C.

    2016-01-01

    The mechanical index (MI) has been used by the US Food and Drug Administration (FDA) since 1992 for regulatory decisions regarding the acoustic output of diagnostic ultrasound equipment. Its formula is based on predictions of acoustic cavitation under specific conditions. Since its implementation over 2 decades ago, new imaging modes have been developed that employ unique beam sequences exploiting higher-order acoustic phenomena, and, concurrently, studies of the bioeffects of ultrasound under a range of imaging scenarios have been conducted. In 2012, the American Institute of Ultrasound in Medicine Technical Standards Committee convened a working group of its Output Standards Subcommittee to examine and report on the potential risks and benefits of the use of conditionally increased acoustic pressures (CIP) under specific diagnostic imaging scenarios. The term “conditionally” is included to indicate that CIP would be considered on a per-patient basis for the duration required to obtain the necessary diagnostic information. This document is a result of that effort. In summary, a fundamental assumption in the MI calculation is the presence of a preexisting gas body. For tissues not known to contain preexisting gas bodies, based on theoretical predications and experimentally reported cavitation thresholds, we find this assumption to be invalid. We thus conclude that exceeding the recommended maximum MI level given in the FDA guidance could be warranted without concern for increased risk of cavitation in these tissues. However, there is limited literature assessing the potential clinical benefit of exceeding the MI guidelines in these tissues. The report proposes a 3-tiered approach for CIP that follows the model for employing elevated output in magnetic resonance imaging and concludes with summary recommendations to facilitate Institutional Review Board (IRB)-monitored clinical studies investigating CIP in specific tissues. PMID:26112617

  6. Experimental setup for measurement of acoustic power dissipation in lined ducts for higher order modes propagation with air mean-flow conditions.

    PubMed

    Ville, Jean-Michel; Foucart, Felix

    2003-10-01

    A flow duct acoustic facility was developed to measure liner efficiency in attenuating higher order acoustic duct modes propagation conditions with mean air flow. The method is based on measurement, upstream and downstream of a liner, of the acoustic power produced by a periodic source. Directly measured total or modal acoustic powers are deduced from the local measurement, in both cross sections, of acoustic pressure, axial acoustic particle velocity, and axial mean flow velocity which are supplied by a probe made of a microphone and a single hot film. In this paper, the equipment, signal processing, and the data treatment process of this facility are first described. Then, information on the accuracy of the methodology is provided by a validation test performed with a rigid wall duct section. Finally, the results of an experiment carried out with a locally reacting liner and a mean flow velocity of 20 m/s will be presented. Measurements of the main attenuation frequency and of the main total acoustic power dissipated agree with the values for which the liner was designed. These results point out the limitations of the method presented to sources with high-level periodic sounds to provide a sufficient signal-to-noise ratio, the noise being produced by fluctuations of the turbulent flow.

  7. Comparison of measured and calculated sound pressure levels around a large horizontal axis wind turbine generator

    NASA Technical Reports Server (NTRS)

    Shepherd, Kevin P.; Willshire, William L., Jr.; Hubbard, Harvey H.

    1989-01-01

    Results are reported from a large number of simultaneous acoustic measurements around a large horizontal axis downwind configuration wind turbine generator. In addition, comparisons are made between measurements and calculations of both the discrete frequency rotational harmonics and the broad band noise components. Sound pressure time histories and noise radiation patterns as well as narrow band and broadband noise spectra are presented for a range of operating conditions. The data are useful for purposes of environmental impact assessment.

  8. Monitoring glucose in vivo by measuring laser-induced acoustic profiles

    NASA Astrophysics Data System (ADS)

    Bednov, Andrey A.; Karabutov, Alexander A.; Savateeva, Elena V.; March, Wayne F.; Oraevsky, Alexander A.

    2000-05-01

    The optoacoustic method of monitoring absorbed optical energy distribution in tissues was employed to measure changes in glucose concentration in vivo. Glucose osmotic and hydrophilic properties cause reduction of tissue scattering as a result of glucose concentration increase around scattering particles and fibers. The opto-acoustic (OA) method utilizes time-resolved measurements of laser- induced ultrasonic profile in tissue resembling the distribution of absorbed optical energy. This opto-acoustic profile yields effective optical attenuation coefficient, which decreases with decrease of scattering. Glucose effect has been investigated initially in phantoms resembling optical properties of sclera and polystyrene microspheres water solution colored with potassium chromate and then in sclera in vitro and in sclera of live rabbits. The forward mode of opto-acoustic detection was used in the experiments in vitro. Experiments were performed in UV spectral range at the wavelength of (lambda) equals 355-nm. Experimental results demonstrated that an increase in glucose concentration from 5 mM to 60 mM was expressed in the 3 percent reduction of (mu) eff in aqueous solution of polystyrene microspheres. The effect of glucose on sclera in vitro was more prominent and measured as 10 percent reduction of (mu) eff with increase of glucose concentration from 1 mM to 50 mM. It was found that both the amplitude and the profile of OA signal were influenced by mechanical pressure applied to sclera specimen toward the surface of OA transducer. In experiments in live tissue, the backward detection mode was employed, as the only one side access to the tissue surface was available. In experiments in vivo the opto-acoustic profiles were measured in rabbit's sclera before and after intravenous glucose administering. The glucose concentration in rabbit blood was simultaneously measured using commercial device employing chemical analysis of blood. Experimental results demonstrated that a 1

  9. Passive Acoustic Tomography Tested for Measuring Gas Temperatures

    NASA Technical Reports Server (NTRS)

    Fralick, Gustave C.; Kleppe, John

    2004-01-01

    The requirements of higher performance, better fuel economy, and lower emissions place an increasing premium on knowing the internal operating parameters of jet engines. One of the most important is the gas temperature in the post combustor section of the engine. Typically the gas temperature is measured with a thermocouple probe or by some optical technique such as Rayleigh scattering. Probes, while providing valuable information, have several limitations. The probe signal must be corrected for radiation and conduction losses, probes provide only a point measurement, and probes must be constructed of materials whose melting points are lower than the temperature of the environment into which they are inserted. Some of the disadvantages of probes are overcome by various optical techniques. Nothing needs to be inserted into the flow, and the temperature can be directly related to the signal by known physical laws. However, optical techniques require optical access (i.e., a window) and a light source (such as a laser), and they are very sensitive to the presence of particles in the flow. To overcome these problems, researchers from the NASA Glenn Research Center and The University of Nevada are developing a technique that uses sound instead of light to measure gas temperature. Like optical techniques, it is nonintrusive--no probe need be exposed to the combustion environment--and the temperature is directly related to a measured quantity--the speed of sound, which is proportional to the square root of the absolute temperature. The temperature profile inside the engine is constructed from the differences in arrival time between correlated signals from an array of microphones placed around the circumference of the engine. In much the same way as a complete picture of the inside of your body can be constructed from an array of x-ray photographs taken at different angles, the temperature profile in the engine is constructed from the angular array of microphones. It is

  10. Noninvasive measurement of central venous pressure

    NASA Technical Reports Server (NTRS)

    Webster, J. G.; Mastenbrook, S. M., Jr.

    1972-01-01

    A technique for the noninvasive measurement of CVP in man was developed. The method involves monitoring venous velocity at a point in the periphery with a transcutaneous Doppler ultrasonic velocity meter while the patient performs a forced expiratory maneuver. The idea is the CVP is related to the value of pressure measured at the mouth which just stops the flow in the vein. Two improvements were made over the original procedure. First, the site of venous velocity measurement was shifted from a vein at the antecubital fossa (elbow) to the right external jugular vein in the neck. This allows for sensing more readily events occurring in the central veins. Secondly, and perhaps most significantly, a procedure for obtaining a curve of relative mean venous velocity vs mouth pressure was developed.

  11. Basic principles for measurement of intramuscular pressure

    NASA Technical Reports Server (NTRS)

    Hargens, A. R.; Ballard, R. E.

    1995-01-01

    We review historical and methodological approaches to measurements of intramuscular pressure (IMP) in humans. These techniques provide valuable measures of muscle tone and activity as well as diagnostic criteria for evaluation of exertional compartment syndrome. Although the wick and catheter techniques provide accurate measurements of IMP at rest, their value for exercise studies and diagnosis of exertional compartment syndrome is limited because of low frequency response and hydrostatic (static and inertial) pressure artifacts. Presently, most information on diagnosis of exertional compartment syndromes during dynamic exercise is available using the Myopress catheter. However, future research and clinical diagnosis using IMP can be optimized by the use of a miniature transducer-tipped catheter such as the Millar Mikro-tip.

  12. The application of acoustic emission technique to fatigue crack measurement. [in aluminum alloys

    NASA Technical Reports Server (NTRS)

    Singh, J. J.; Davis, W. T.; Crews, J. H., Jr.

    1974-01-01

    The applicability of acoustic emission technique to measure fatigue cracks in aluminum alloy specimens was investigated. There are several variables, such as the metallurgical and the physical treatment of the specimen, that can affect the level of acoustic activity of a fatigue specimen. It is therefore recommended that the acoustic emission technique be supplemented by other nondestructive evaluation methods to obtain quantitative data on crack growth.

  13. Experimental and Theoretical Measurements of Concentration Distributions in Acoustic Focusing Devices

    SciTech Connect

    Rose, K A; Fisher, K; Jung, B; Ness, K; Mariella Jr., R P

    2008-06-16

    We describe a modeling approach to capture the particle motion within an acoustic focusing microfluidic device. Our approach combines finite element models for the acoustic forces with analytical models for the fluid motion and uses these force fields to calculate the particle motion in a Brownian dynamics simulation. We compare results for the model with experimental measurements of the focusing efficiency within a microfabricated device. The results show good qualitative agreement over a range of acoustic driving voltages and particle sizes.

  14. Evaluation of acoustic emission technique for crack growth measurement in aeronautical structures

    NASA Technical Reports Server (NTRS)

    Singh, J. J.; Davis, W. T.

    1974-01-01

    An investigation has been conducted concerning the possibility to use the acoustic emission technique for the measurement of fatigue crack growth in aluminum alloy specimens. Two types of aluminum alloys were tested in the investigation. It was found that the acoustic emission technique provides a reliable indication of changes in the crack dimensions over relatively short periods of time. The level of acoustic activity serves as an indicator of the size of the cracks.

  15. Method for noninvasive intracranial pressure measurement

    SciTech Connect

    Sinha, Dipen N.

    2000-01-01

    An ultrasonic-based method for continuous, noninvasive intracranial pressure (ICP) measurement and monitoring is described. The stress level in the skull bone is affected by pressure. This also changes the interfacial conditions between the dura matter and the skull bone. Standing waves may be set up in the skull bone and the layers in contact with the bone. At specific frequencies, there are resonance peaks in the response of the skull which can be readily detected by sweeping the excitation frequency on an excitation transducer in contact with a subject's head, while monitoring the standing wave characteristics from the signal received on a second, receiving transducer similarly in contact with the subject's head. At a chosen frequency, the phase difference between the excitation signal and the received signal can be determined. This difference can be related to the intracranial pressure and changes therein.

  16. New ultrasonic Bleustein-Gulyaev wave method for measuring the viscosity of liquids at high pressure.

    PubMed

    Kiełczyński, P; Szalewski, M; Siegoczyński, R M; Rostocki, A J

    2008-02-01

    In this paper, a new method for measuring the viscosity of liquids at high pressure is presented. To this end the authors have applied an ultrasonic method using the Bleustein-Gulyaev (BG) surface acoustic wave. By applying the perturbation method, we can prove that the change in the complex propagation constant of the BG wave produced by the layer of liquid loading the waveguide surface is proportional to the shear mechanical impedance of the liquid. In the article, a measuring setup employing the BG wave for the purpose of measuring the viscosity of liquids at high pressure (up to 1 GPa) is presented. The results of high-pressure viscosity measurements of triolein and castor oil are also presented. In this paper the model of a Newtonian liquid was applied. Using this new method it is also possible to measure the viscosity of liquids during the phase transition and during the decompression process (hysteresis of the dependence of viscosity on pressure).

  17. New ultrasonic Bleustein-Gulyaev wave method for measuring the viscosity of liquids at high pressure

    NASA Astrophysics Data System (ADS)

    Kiełczyński, P.; Szalewski, M.; Siegoczyński, R. M.; Rostocki, A. J.

    2008-02-01

    In this paper, a new method for measuring the viscosity of liquids at high pressure is presented. To this end the authors have applied an ultrasonic method using the Bleustein-Gulyaev (BG) surface acoustic wave. By applying the perturbation method, we can prove that the change in the complex propagation constant of the BG wave produced by the layer of liquid loading the waveguide surface is proportional to the shear mechanical impedance of the liquid. In the article, a measuring setup employing the BG wave for the purpose of measuring the viscosity of liquids at high pressure (up to 1GPa) is presented. The results of high-pressure viscosity measurements of triolein and castor oil are also presented. In this paper the model of a Newtonian liquid was applied. Using this new method it is also possible to measure the viscosity of liquids during the phase transition and during the decompression process (hysteresis of the dependence of viscosity on pressure).

  18. Measurement of transmission loss characteristics using acoustic intensity techniques at the KU-FRL Acoustic Test Facility

    NASA Technical Reports Server (NTRS)

    Roskam, J.

    1983-01-01

    The transmission loss characteristics of panels using the acoustic intensity technique is presented. The theoretical formulation, installation of hardware, modifications to the test facility, and development of computer programs and test procedures are described. A listing of all the programs is also provided. The initial test results indicate that the acoustic intensity technique is easily adapted to measure transmission loss characteristics of panels. Use of this method will give average transmission loss values. The fixtures developed to position the microphones along the grid points are very useful in plotting the intensity maps of vibrating panels.

  19. Quantitative Measurement of Highly Focused Ultrasound Pressure Field by Optical Shadowgraph

    NASA Astrophysics Data System (ADS)

    Miyasaka, R.; Harigane, S.; Yoshizawa, S.; Umemura, S.

    2014-06-01

    In the development of medical ultrasound techniques, fast and accurate pressure field measurement is important. The most common method to measure an ultrasound pressure field is mechanically scanning a hydrophone, which takes a long time and might disturb the acoustic field. In this study, we used an optical shadowgraph method. To perform this method quantitatively, it is important to define the optical propagation length precisely. For this purpose, a holographic diffuser was used as the imaging screen. Combined with a computed tomography (CT) algorithm, a pressure field was reconstructed, and the result was compared with that of hydrophone measurement. By using two shadowgraph data from short and long propagation lengths, the pressure field was successfully reconstructed even at a pressure level for high intensity focused ultrasound (HIFU) treatment.

  20. The effects of pressure sensor acoustics on airdata derived from a High-angle-of-attack Flush Airdata Sensing (HI-FADS) system

    NASA Technical Reports Server (NTRS)

    Whitmore, Stephen A.; Moes, Timothy R.

    1991-01-01

    The accuracy of a nonintrusive high angle-of-attack flush airdata sensing (HI-FADS) system was verified for quasi-steady flight conditions up to 55 deg angle of attack during the F-18 High Alpha Research Vehicle (HARV) Program. The system is a matrix of nine pressure ports arranged in annular rings on the aircraft nose. The complete airdata set is estimated using nonlinear regression. Satisfactory frequency response was verified to the system Nyquist frequency (12.5 Hz). The effects of acoustical distortions within the individual pressure sensors of the nonintrusive pressure matrix on overall system performance are addressed. To quantify these effects, a frequency-response model describing the dynamics of acoustical distortion is developed and simple design criteria are derived. The model adjusts measured HI-FADS pressure data for the acoustical distortion and quantifies the effects of internal sensor geometries on system performance. Analysis results indicate that sensor frequency response characteristics very greatly with altitude, thus it is difficult to select satisfactory sensor geometry for all altitudes. The solution used presample filtering to eliminate resonance effects, and short pneumatic tubing sections to reduce lag effects. Without presample signal conditioning the system designer must use the pneumatic transmission line to attenuate the resonances and accept the resulting altitude variability.

  1. Resonant Acoustic Measurement of Vapor Phase Transport Phenomenon

    NASA Astrophysics Data System (ADS)

    Schuhmann, R. J.; Garrett, S. L.; Matson, J. V.

    2002-12-01

    A major impediment to accurate non steady-state diffusion measurements is the ability to accurately measure and track a rapidly changing gas concentration without disturbing the system. Non-destructive methods that do not interfere with system dynamics have been developed in the past. These methods, however, have tended to be cumbersome or inaccurate at low concentrations. A new experimental approach has been developed to measure gaseous diffusion in free air and through porous materials. The method combines the traditional non steady-state laboratory methodology with resonant acoustic gas analysis. A phase-locked-loop (PLL) resonance frequency tracker is combined with a thermally insulated copper resonator. A piston sealed with a metal bellows excites the fundamental standing wave resonance of the resonator. The PLL maintains a constant phase difference (typically 90§) between the accelerometer mounted on the piston and a microphone near the piston to track the resonance frequency in real time. A capillary or glass bead filled core is fitted into an o-ring sealed opening at the end of the resonator opposite the bellows. The rate at which the tracer gas is replaced by air within the resonator is controlled by the diffusion coefficient of the gas in free air through the capillary (DA) or by the effective diffusion coefficient of the gas through the core (De). The mean molecular weight of the gas mixture in the resonator is directly determined six times each minute from the ratio of the absolute temperature to the square of the fundamental acoustic resonance frequency. Average system stability (temperature divided by frequency squared) is better than 350 ppm. DA values for a 0.3-inch diameter capillary were in excellent agreement with published values. De values for porous media samples (0.5 mm glass beads) of four different lengths (1 through 4 inches) using three different tracer gases (He, CH4, Kr) will be reported. Comments will be offered regarding tracer gas

  2. Ultrahigh-pressure acoustic wave velocities of SiO2-Al2O3 glasses up to 200 GPa

    NASA Astrophysics Data System (ADS)

    Ohira, Itaru; Murakami, Motohiko; Kohara, Shinji; Ohara, Koji; Ohtani, Eiji

    2016-12-01

    Extensive experimental studies on the structure and density of silicate glasses as laboratory analogs of natural silicate melts have attempted to address the nature of dense silicate melts that may be present at the base of the mantle. Previous ultrahigh-pressure experiments, however, have been performed on simple systems such as SiO2 or MgSiO3, and experiments in more complex system have been conducted under relatively low-pressure conditions below 60 GPa. The effect of other metal cations on structural changes that occur in dense silicate glasses under ultrahigh pressures has been poorly understood. Here, we used a Brillouin scattering spectroscopic method up to pressures of 196.9 GPa to conduct in situ high-pressure acoustic wave velocity measurements of SiO2-Al2O3 glasses in order to understand the effect of Al2O3 on pressure-induced structural changes in the glasses as analogs of aluminosilicate melts. From 10 to 40 GPa, the transverse acoustic wave velocity ( V S ) of Al2O3-rich glass (SiO2 + 20.5 mol% Al2O3) was greater than that of Al2O3-poor glass (SiO2 + 3.9 mol% Al2O3). This result suggests that SiO2-Al2O3 glasses with higher proportions of Al ions with large oxygen coordination numbers (5 and 6) become elastically stiffer up to 40 GPa, depending on the Al2O3 content, but then soften above 40 GPa. At pressures from 40 to ~100 GPa, the increase in V S with increasing pressure became less steep than below 40 GPa. Above ~100 GPa, there were abrupt increases in the P-V S gradients ( dV S /dP) at 130 GPa in Al2O3-poor glass and at 116 GPa in Al2O3-rich glass. These changes resemble previous experimental results on SiO2 glass and MgSiO3 glass. Given that changes of dV S / dP have commonly been related to changes in the Si-O coordination states in the glasses, our results, therefore, may indicate a drastic structural transformation in SiO2-Al2O3 glasses above 116 GPa, possibly associated with an average Si-O coordination number change to higher than 6. Compared

  3. Compensated vibrating optical fiber pressure measuring device

    DOEpatents

    Fasching, George E.; Goff, David R.

    1987-01-01

    A microbending optical fiber is attached under tension to a diaphragm to se a differential pressure applied across the diaphragm which it causes it to deflect. The fiber is attached to the diaphragm so that one portion of the fiber, attached to a central portion of the diaphragm, undergoes a change in tension; proportional to the differential pressure applied to the diaphragm while a second portion attached at the periphery of the diaphragm remains at a reference tension. Both portions of the fiber are caused to vibrate at their natural frequencies. Light transmitted through the fiber is attenuated by both portions of the tensioned sections of the fiber by an amount which increases with the curvature of fiber bending so that the light signal is modulated by both portions of the fiber at separate frequencies. The modulated light signal is transduced into a electrical signal. The separate modulation signals are detected to generate separate signals having frequencies corresponding to the reference and measuring vibrating sections of the continuous fiber, respectively. A signal proportional to the difference between these signals is generated which is indicative of the measured pressure differential across the diaphragm. The reference portion of the fiber is used to compensate the pressure signal for zero and span changes resulting from ambient temperature and humidity effects upon the fiber and the transducer fixture.

  4. Dynamics of encapsulated microbubbles for contrast ultrasound imaging and drug delivery: from pressure dependent subharmonic to collapsing jet and acoustic streaming

    NASA Astrophysics Data System (ADS)

    Sarkar, Kausik

    2016-11-01

    Intravenously injected microbubbles used as ultrasound contrast enhancing agents are encapsulated by a nanometer-thick layer of lipids, proteins or polymers to stabilize them against premature dissolution. Over the years, we have developed interfacial rheological models for the encapsulation and used them to characterize several contrast agents by acoustic means. We will present an overview of our research emphasizing recent efforts in two directions. The first is on using subharmonic signals from the contrast microbubbles for non-invasive pressure estimation. Experimental measurement and modeling show that the subharmonic signal can both increase or decrease with pressure depending on frequency. Secondly, we will discuss boundary element (BEM) simulation of the collapse of an encapsulated microbubbles forming a jet near a blood vessel wall. Different rheology models of the encapsulation have been rigorously implemented in the BEM formulation. We will discuss the resulting stresses and the acoustic streaming near the wall leading to sonoporation and other bioeffects. Partially supported by Natinal Science Foundation.

  5. Directional Acoustic Density Sensor

    DTIC Science & Technology

    2010-09-13

    fluctuations of fluid density at a point . (2) DESCRIPTION OF THE PRIOR ART [0004] Conventional vector sensors measure particle velocity, v (vx,Vytvz...dipole-type or first order sensor that is realized by measuring particle velocity at a point , (which is the vector sensor sensing approach for...underwater sensors), or by measuring the gradient of the acoustic pressure at two closely spaced (less than the wavelength of an acoustic wave) points as it

  6. Thick Films acoustic sensors devoted to MTR environment measurements. Thick Films acoustic sensors devoted to Material Testing Reactor environment measurements

    SciTech Connect

    Very, F.; Rosenkrantz, E.; Combette, P.; Ferrandis, J.Y.; Fourmentel, D.; Destouches, C.; Villard, J.F.

    2015-07-01

    The development of advanced instrumentation for in-pile experiments in Material Testing Reactor constitutes a main goal for the improvement of the nuclear fuel behavior knowledge. An acoustic method for fission gas release detection was tested with success during a first experiment called REMORA 3 in 2010 and 2011, and the results were used to differentiate helium and fission gas release kinetics under transient operating conditions. This experiment was lead at OSIRIS reactor (CEA Saclay, France). The maximal temperature on the sensor during the irradiation was about 150 deg. C. In this paper we present a thick film transducer produce by screen printing process. The screen printing of piezoelectric offers a wide range of possible applications for the development of acoustic sensors and piezoelectric structure for measurements in high temperature environment. We firstly produced a Lead Zirconate Titanate (PZT) based paste composed of Pz27 powder from Ferroperm, CF7575 glass, and organic solvent ESL 400. Likewise a Bismuth Titanate based paste synthesized in our laboratory was produced. With these inks we produced thick film up to 130 μm by screen printing process. Material properties characterizations of these thick-film resonators are essential for device design and applications. The piezoelectric coefficients d33 and pyro-electric P(T) coefficient are investigated. The highest P(T) and d33 are respectively 80 μC.m{sup -2}.K{sup -1} and 130 μC.N{sup -1} for the PZT transducer -which validates the fabrication process-. In view of the development of this transducer oriented for high temperature and irradiation environment, we investigated the electrical properties of the transducers for different ranges of frequencies and temperature - from 20 Hz up to 40 MHz between 30 and 400 deg. C. We highlight the evolution of the impedance response and piezoelectric parameters of screen printed piezoelectric structures on alumina. Shortly an irradiation will be realized in

  7. Acoustic study of the elastic and inelastic properties of high-pressure polyethylene samples with different irradiation histories

    NASA Astrophysics Data System (ADS)

    Kardashev, B. K.; Nikanorov, S. P.; Kravchenko, V. S.; Malinov, V. I.; Punin, V. T.

    2007-11-01

    The influence of vibrational deformation amplitude ɛ on the dynamic elasticity modulus (Young’s modulus E) and internal friction (logarithmic decrement δ) of high-pressure polyethylene samples with different histories is studied. Acoustic measurements are made by a resonance method using the longitudinal vibrations of a composite piezoelectric vibrator at a frequency of ≈ 100 kHz. The dependences E(ɛ) and δ(ɛ) are taken at room temperature. From the acoustic data, the elasticity and microplasticity of the samples are estimated. It is found that the microplasticity remains almost unaffected upon irradiation and aging, while the elasticity modulus and breaking elongation per unit length considerably depend on the history and clearly correlated with each other. The observed effects are explained by the fact that atom-atom interaction and defects inside polymer macromolecules substantially influence the elastic modulus and breaking strength, while the inelastic microplastic strain is most likely associated with molecule-molecule interaction, which is affected by irradiation insignificantly.

  8. Unsteady Pressure and Velocity Measurements in Pumps

    DTIC Science & Technology

    2006-11-01

    to reproduce the data with controlled experiments . For example, the rotor exit flow measured by means of a stationary high response probe will be...Turbomachinery by Means of High-Frequency Pressure Transducers. ASME, J. of Turbomachinery, Vol. 114, pp. 100-107. [3] Castorph, D. (1975): Messung ...Dreiß, A.; Kosyna, G. (1997): Experimental Investigations of Cavitation-States in a Radial Pump Impeller. JSME CENTENNIAL GRAND CONGRESS Proceedings of

  9. Automatic Blood Pressure Measurements During Exercise

    NASA Technical Reports Server (NTRS)

    Weaver, Charles S.

    1985-01-01

    Microprocessor circuits and a computer algorithm for automatically measuring blood pressure during ambulatory monitoring and exercise stress testing have been under development at SRI International. A system that records ECG, Korotkov sound, and arm cuff pressure for off-line calculation of blood pressure has been delivered to NASA, and an LSLE physiological monitoring system that performs the algorithm calculations in real-time is being constructed. The algorithm measures the time between the R-wave peaks and the corresponding Korotkov sound on-set (RK-interval). Since the curve of RK-interval versus cuff pressure during deflation is predictable and slowly varying, windows can be set around the curve to eliminate false Korotkov sound detections that result from noise. The slope of this curve, which will generally decrease during exercise, is the inverse of the systolic slope of the brachial artery pulse. In measurements taken during treadmill stress testing, the changes in slopes of subjects with coronary artery disease were markedly different from the changes in slopes of healthy subjects. Measurements of slope and O2 consumption were also made before and after ten days of bed rest during NASA/Ames Research Center bed rest studies. Typically, the maximum rate of O2 consumption during the post-bed rest test is less than the maximum rate during the pre-bed rest test. The post-bed rest slope changes differ from the pre-bed rest slope changes, and the differences are highly correlated with the drop in the maximum rate of O2 consumption. We speculate that the differences between pre- and post-bed rest slopes are due to a drop in heart contractility.

  10. The Belt voice: Acoustical measurements and esthetic correlates

    NASA Astrophysics Data System (ADS)

    Bounous, Barry Urban

    This dissertation explores the esthetic attributes of the Belt voice through spectral acoustical analysis. The process of understanding the nature and safe practice of Belt is just beginning, whereas the understanding of classical singing is well established. The unique nature of the Belt sound provides difficulties for voice teachers attempting to evaluate the quality and appropriateness of a particular sound or performance. This study attempts to provide answers to the question "does Belt conform to a set of measurable esthetic standards?" In answering this question, this paper expands on a previous study of the esthetic attributes of the classical baritone voice (see "Vocal Beauty", NATS Journal 51,1) which also drew some tentative conclusions about the Belt voice but which had an inadequate sample pool of subjects from which to draw. Further, this study demonstrates that it is possible to scientifically investigate the realm of musical esthetics in the singing voice. It is possible to go beyond the "a trained voice compared to an untrained voice" paradigm when evaluating quantitative vocal parameters and actually investigate what truly beautiful voices do. There are functions of sound energy (measured in dB) transference which may affect the nervous system in predictable ways and which can be measured and associated with esthetics. This study does not show consistency in measurements for absolute beauty (taste) even among belt teachers and researchers but does show some markers with varying degrees of importance which may point to a difference between our cognitive learned response to singing and our emotional, more visceral response to sounds. The markers which are significant in determining vocal beauty are: (1) Vibrancy-Characteristics of vibrato including speed, width, and consistency (low variability). (2) Spectral makeup-Ratio of partial strength above the fundamental to the fundamental. (3) Activity of the voice-The quantity of energy being produced. (4

  11. Advances in Fast Response Acoustically Derived Air Temperature Measurements

    NASA Astrophysics Data System (ADS)

    Bogoev, Ivan; Jacobsen, Larry; Horst, Thomas; Conrad, Benjamin

    2016-04-01

    Fast-response accurate air-temperature measurements are required when estimating turbulent fluxes of heat, water and carbon dioxide by open-path eddy-covariance technique. In comparison with contact thermometers like thermocouples, ultra-sonic thermometers do not suffer from solar radiation loading, water vapor condensation and evaporative cooling effects. Consequently they have the potential to provide more accurate true air temperature measurements. The absolute accuracy of the ultrasonic thermometer is limited by the following parameters: the distance between the transducer pairs, transducer delays associated with the electrical-acoustic signal conversion that vary with temperature, components of the wind vector that are normal to the ultrasonic paths, and humidity. The distance between the transducer pairs is commonly obtained by coordinate measuring machine. Improved accuracy demonstrated in this study results from increased stiffness in the anemometer head to better maintain the ultrasonic path-length distances. To further improve accuracy and account for changes in transducer delays and distance as a function of temperature, these parameters are characterized in a zero-wind chamber over the entire operating temperature range. When the sonic anemometer is combined with a co-located fast-response water vapor analyzer, like in the IRGASON instrument, speed of sound can be compensated for humidity effects on a point-by-point basis resulting in a true fast-response air temperature measurement. Laboratory test results show that when the above steps are implemented in the calibration of the ultrasonic thermometer air-temperature accuracy better than ±0.5 degrees Celsius can be achieved over the entire operating range. The approach is also validated in a field inter-comparison with an aspirated thermistor probe mounted in a radiation shield.

  12. 21 CFR 890.1600 - Intermittent pressure measurement system.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Intermittent pressure measurement system. 890.1600... Intermittent pressure measurement system. (a) Identification. An intermittent pressure measurement system is an evaluative device intended for medical purposes, such as to measure the actual pressure between the...

  13. 21 CFR 890.1600 - Intermittent pressure measurement system.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Intermittent pressure measurement system. 890.1600... Intermittent pressure measurement system. (a) Identification. An intermittent pressure measurement system is an evaluative device intended for medical purposes, such as to measure the actual pressure between the...

  14. Vibration and acoustic properties of honeycomb sandwich structures subject to variable incident plane-wave angle pressure loads

    NASA Astrophysics Data System (ADS)

    Yan, Jiaxue

    Honeycomb structures are widely used in many areas for their material characteristics such as high strength-to-weight ratio, stiffness-to-weight, sound transmission, and other properties. Honeycomb structures are generally constructed from periodically spaced tessellations of unit cells. It can be shown that the effective stiffness and mass properties of honeycomb are controlled by the local geometry and wall thickness of the particular unit cells used. Of particular interest are regular hexagonal (6-sided) honeycomb unit cell geometries which exhibit positive effective Poisson's ratio, and modified 6-sided auxetic honeycomb unit cells with Poisson's ratio which is effectively negative; a property not found in natural materials. One important honeycomb meta-structure is sandwich composites designed with a honeycomb core bonded between two panel layers. By changing the geometry of the repetitive unit cell, and overall depth and material properties of the honeycomb core, sandwich panels with different vibration and acoustic properties can be designed to shift resonant frequencies and improve intensity and Sound Transmission Loss (STL). In the present work, a honeycomb finite element model based on beam elements is programmed in MATLAB and verified with the commercial finite element software ABAQUS for frequency extraction and direct frequency response analysis. The MATLAB program was used to study the vibration and acoustic properties of different kinds of honeycomb sandwich panels undergoing in-plane loading with different incident pressure wave angles and frequency. Results for the root mean square intensity IRMS based on normal velocity on the transmitted side of the panel measure vibration magnitude are reported for frequencies between 0 and 1000 Hz. The relationship between the sound transmission loss computed with ABAQUS and the inverse of the intensity of surface velocity is established. In the present work it is demonstrated that the general trend between the

  15. Dummy head microphone and its application to the measurements of electro-acoustic equipments

    NASA Astrophysics Data System (ADS)

    1984-12-01

    An acoustic measurement system using a dummy head microphone was developed. The system consists of a dummy head microphone and an equipment for digital signal processing, and the system can be used to measure characteristics of hearing aids and headphones. The ear simulator, newly developed for practical use, is terminated in a simple resistance element of 320 cgs acoustic ohms. The dummy head microphone with the ear simulator shows the good agreement with the acoustical characteristics of the averaged human external ear. Several measured results of hearing aids and headphones using the measurement system are shown.

  16. Acoustic measurements of F-15 aircraft operating in hush house, NSN 4920-02-070-2721

    NASA Astrophysics Data System (ADS)

    Miller, V. R.; Plzak, G. A.; Chinn, J. M.

    1981-09-01

    The purpose of this test program was to measure the acoustic environment in the hush house facility located at Kelly Air Force Base, Texas, during operation of the F-15 aircraft to ensure that aircraft structural acoustic design limits were not exceeded. The acoustic measurements showed that no potential sonic fatigue problems are anticipated with the F-15 aircraft structure during operation in the hush house. However, since these acoustic levels were increased over those measuring during run up on a concrete pad, it is recommended that F-15 equipment qualification levels be checked. The data indicated that the noise field within the hush house is diffuse and that the acoustical energy in the hangar area is radiated from the region between the engine exhaust and the hush house muffler front edge toward the forward part of the hangar.

  17. A fast full frequency range measurement of nonlinear distortions in the vibration of acoustic transducers and acoustically driven membranes

    NASA Astrophysics Data System (ADS)

    Aerts, J. R. M.; Dirckx, J. J. J.

    2007-11-01

    Recently, a new method was proposed to measure nonlinear distortions in weak nonlinear systems using specially designed broadband excitation signals (odd random phase multisines). During one single experiment, the output response level, the noise level and the level of the nonlinear distortions are simultaneously measured. We implement this method in an opto-acoustic set-up which allows us to measure vibrations with high accuracy. To demonstrate the method, we present results obtained on the membrane of an earphone speaker and a latex membrane. On the earphone good agreement is found between measurements of the produced sound field and the actual membrane vibration using heterodyne interferometry. The results show that heterodyne vibrometry can be used to detect nonlinear distortions which are up to 80 dB below the output level in an acoustically driven system.

  18. Principles of Blood Pressure Measurement - Current Techniques, Office vs Ambulatory Blood Pressure Measurement.

    PubMed

    Vischer, Annina S; Burkard, Thilo

    2016-07-15

    Blood pressure measurement has a long history and a crucial role in clinical medicine. Manual measurement using a mercury sphygmomanometer and a stethoscope remains the Gold Standard. However, this technique is technically demanding and commonly leads to faulty values. Automatic devices have helped to improve and simplify the technical aspects, but a standardised procedure of obtaining comparable measurements remains problematic and may therefore limit their validity in clinical practice. This underlines the importance of less error-prone measurement methods such as ambulatory or home blood pressure measurements and automated office blood pressure measurements. These techniques may help to uncover patients with otherwise unrecognised or overestimated arterial hypertension. Additionally these techniques may yield a better prognostic value.

  19. Effects of Various Architectural Parameters on Six Room Acoustical Measures in Auditoria.

    NASA Astrophysics Data System (ADS)

    Chiang, Wei-Hwa

    The effects of architectural parameters on six room acoustical measures were investigated by means of correlation analyses, factor analyses and multiple regression analyses based on data taken in twenty halls. Architectural parameters were used to estimate acoustical measures taken at individual locations within each room as well as the averages and standard deviations of all measured values in the rooms. The six acoustical measures were Early Decay Time (EDT10), Clarity Index (C80), Overall Level (G), Bass Ratio based on Early Decay Time (BR(EDT)), Treble Ratio based on Early Decay Time (TR(EDT)), and Early Inter-aural Cross Correlation (IACC80). A comprehensive method of quantifying various architectural characteristics of rooms was developed to define a large number of architectural parameters that were hypothesized to effect the acoustical measurements made in the rooms. This study quantitatively confirmed many of the principles used in the design of concert halls and auditoria. Three groups of room architectural parameters such as the parameters associated with the depth of diffusing surfaces were significantly correlated with the hall standard deviations of most of the acoustical measures. Significant differences of statistical relations among architectural parameters and receiver specific acoustical measures were found between a group of music halls and a group of lecture halls. For example, architectural parameters such as the relative distance from the receiver to the overhead ceiling increased the percentage of the variance of acoustical measures that was explained by Barron's revised theory from approximately 70% to 80% only when data were taken in the group of music halls. This study revealed the major architectural parameters which have strong relations with individual acoustical measures forming the basis for a more quantitative method for advancing the theoretical design of concert halls and other auditoria. The results of this study provide

  20. Measurement resolution of noise directivity patterns from acoustic flight tests

    NASA Technical Reports Server (NTRS)

    Conner, David A.

    1989-01-01

    The measurement resolution of noise directivity patterns from acoustic flight tests was investigated. Directivity angle resolution is affected by the data reduction parameters, the aircraft velocity and flyover altitude, and by deviations of the aircraft from the desired flight path. Equations are developed which determine bounds for the lateral and longitudinal directivity angle resolution as a function of the nominal directivity angle. The equations are applied to a flight test data base and the effects of several flight conditions and data reduction parameters on the directivity angle resolution are presented. The maximum directivity angle resolution typically occurs when the aircraft is at or near the overhead position. In general, directivity angle resolution improves with decreasing velocity, increasing altitude, increasing sampling rate, decreasing block size, and decreasing block averages. Deviations from the desired ideal flight path will increase the resolution. For the flight experiment considered in this study, an average of two flyovers were required at each test condition to obtain an acceptable flight path. The ability of the pilot to maintain the flight track improved with decreasing altitude, decreasing velocity, and practice. Due to the prevailing wind conditions, yaw angles of as much as 20 deg were required to maintain the desired flight path.

  1. On measuring the absolute scale of baryon acoustic oscillations

    NASA Astrophysics Data System (ADS)

    Sutherland, Will

    2012-10-01

    The baryon acoustic oscillation (BAO) feature in the distribution of galaxies provides a fundamental standard ruler which is widely used to constrain cosmological parameters. In most analyses, the comoving length of the ruler is inferred from a combination of cosmic microwave background (CMB) observations and theory. However, this inferred length may be biased by various non-standard effects in early universe physics; this can lead to biased inferences of cosmological parameters such as H0, Ωm and w, so it would be valuable to measure the absolute BAO length by combining a galaxy redshift survey and a suitable direct low-z distance measurement. One obstacle is that low-redshift BAO surveys mainly constrain the ratio rS/DV(z), where DV is a dilation scale which is not directly observable by standard candles. Here, we find a new approximation DV(z)≃34DL(43z)(1+43z)-1(1-0.02455 z3+0.0105 z4) which connects DV to the standard luminosity distance DL at a somewhat higher redshift; this is shown to be very accurate (relative error <0.2 per cent) for all Wilkinson Microwave Anisotropy Probe compatible Friedmann models at z < 0.4, with very weak dependence on cosmological parameters H0, Ωm, Ωk, w. This provides a route to measure the absolute BAO length using only observations at z ≲ 0.3, including Type Ia supernovae, and potentially future H0-free physical distance indicators such as gravitational lenses or gravitational wave standard sirens. This would provide a zero-parameter check of the standard cosmology at 103 ≲ z ≲ 105, and can constrain the number of relativistic species Neff with fewer degeneracies than the CMB.

  2. Measurements of mean flow and acoustic power for a subsonic jet impinging normal to a large rigid surface

    NASA Technical Reports Server (NTRS)

    Schloth, A. P.

    1976-01-01

    An experimental study was made to measure the mean flow field and acoustic power of a subsonic jet impinging normal to a large rigid surface. A 6.25 cm diameter, circular cool air jet was used at heights of 20, 10, and 5 jet diameters above the surface. The jet exit Mach number was varied from 0.28 to 0.93. Impact and static pressure surveys were made in directions both axial and lateral to the jet axis and also parallel and perpendicular to the surface. Acoustic power was calculated from microphone measurements made during each test run using a diffuse field calibration for the test facility. Results indicate that the flow field for jet impingement is characterized mainly by a strong rise in static pressure in the impingement region near the surface and by boundary layer development in the wall jet region. Acoustic power measurements generally followed a U(8) law for both the free jet and jet impingement although there was some variation especially at high Mach number and for close impingement distances. Overall noise levels increased with decreasing jet-to-surface height. Normalized power spectra correlated well for all cases when the Strouhal number was greater than 0.2; the correlation was poor when the Strouhal number was low.

  3. Prediction of blade-vortex interaction noise from measured blade pressure

    NASA Technical Reports Server (NTRS)

    Nakamura, Y.

    1981-01-01

    The impulsive nature of noise due to the interaction of a rotor blade with a tip vortex is studied. The time signature of this noise is calculated theoretically based on the measured blade surface pressure fluctuation of an operational load survey rotor in slow descending flight and is compared with the simultaneous microphone measurement. Particularly, the physical understanding of the characteristic features of a waveform is extensively studied in order to understand the generating mechanism and to identify the important parameters. The interaction trajectory of a tip vortex on an acoustic planform is shown to be a very important parameter for the impulsive shape of the noise. The unsteady nature of the pressure distribution at the very leading edge is also important to the pulse shape. The theoretical model using noncompact liner acoustics predicts the general shape of interaction impulse pretty well except for peak amplitude which requires more continuous information along the span at the leading edge.

  4. Influence of Architectural Features and Styles on Various Acoustical Measures in Churches

    NASA Astrophysics Data System (ADS)

    Carvalho, Antonio Pedro Oliveira De.

    This work reports on acoustical field measurements made in a major survey of 41 Catholic churches in Portugal that were built in the last 14 centuries. A series of monaural and binaural acoustical measurements was taken at multiple source/receiver positions in each church using the impulse response with noise burst method. The acoustical measures were Reverberation Time (RT), Early Decay Time (EDT), Clarity (C80), Definition (D), Center Time (TS), Loudness (L), Bass Ratios based on the Reverberation Time and Loudness rm (BR_-RT and rm BR_-L), Rapid Speech Transmission Index (RASTI), and the binaural Coherence (COH). The scope of this research is to investigate how the acoustical performance of Catholic churches relates to their architectural features and to determine simple formulas to predict acoustical measures by the use of elementary architectural parameters. Prediction equations were defined among the acoustical measures to estimate values at individual locations within each room as well as the mean values in each church. Best fits with rm R^2~0.9 were not uncommon among many of the measures. Within and interchurch differences in the data for the acoustical measures were also analyzed. The variations of RT and EDT were identified as much smaller than the variations of the other measures. The churches tested were grouped in eight architectural styles, and the effect of their evolution through time on these acoustical measures was investigated. Statistically significant differences were found regarding some architectural styles that can be traced to historical changes in Church history, especially to the Reformation period. Prediction equations were defined to estimate mean acoustical measures by the use of fifteen simple architectural parameters. The use of the Sabine and Eyring reverberation time equations was tested. The effect of coupled spaces was analyzed, and a new algorithm for the application of the Sabine equation was developed, achieving an average of

  5. Coupling of Low Speed Fan Stator Vane Unsteady Pressures to Duct Modes: Measured versus Predicted

    NASA Technical Reports Server (NTRS)

    Sutliff, Daniel L.; Heidelberg, Laurence J.; Envia, Edmane

    1999-01-01

    Uniform-flow annular-duct Green's functions are the essential elements of the classical acoustic analogy approach to the problem of computing the noise generated by rotor-stator interaction inside the fan duct. This paper investigates the accuracy of this class of Green's functions for predicting the duct noise levels when measured stator vane unsteady surface pressures are used as input to the theoretical formulation. The accuracy of the method is evaluated by comparing the predicted and measured acoustic power levels for the NASA 48 inch low speed Active Noise Control Fan. The unsteady surface pressures are measured,by an array of microphones imbedded in the suction and pressure sides of a single vane, while the duct mode levels are measured using a rotating rake system installed in the inlet and exhaust sections of the fan duct. The predicted levels are computed using properly weighted integrals of measured surface pressure distribution. The data-theory comparisons are generally quite good particularly when the mode cut-off criterion is carefully interpreted. This suggests that, at least for low speed fans, the uniform-flow annular-duct Green's function theory can be reliably used for prediction of duct mode levels if the cascade surface pressure distribution is accurately known.

  6. Relative measurement of acoustic nonlinear parameters and comparison of sensitivity to thermal aging

    NASA Astrophysics Data System (ADS)

    Seo, Hogeon; Ren, Gang; Kim, Jongbeom; Jhang, Kyung-Young

    2015-03-01

    The acoustic nonlinearity measurement of ultrasonic waves are being extensively researched as a promising nondestructive evaluation element. In the condition of constant propagation distance and wave number, many researchers have measured the second-order relative acoustic nonlinear parameter, β', that can be simply defined as the ratio of the amplitude of the second harmonic frequency component to the amplitude squared of the fundamental frequency component and compared them in order to identify the acoustic nonlinearity variation according to material degradation. In this study, we extended this concept to the third-order relative acoustic nonlinear parameter, γ', by defining it as the ratio of the amplitude of the third harmonic frequency component to the amplitude cubed of the fundamental frequency component. To investigate its effectiveness as a nondestructive evaluation element for the material property degradation, both the second-order acoustic relative nonlinear parameter and the third-order relative acoustic nonlinear parameter were measured for the aluminum specimens processed by heat treatment for the different times and then contrasted each other. From the experimental results, the third-order acoustic relative nonlinear parameter was more sensitive than the second-order relative acoustic nonlinear parameter that has been widely used although the amplitude of the third harmonic frequency component was lower than the amplitude of the second harmonic frequency component.

  7. Transcranial measurements of the acoustic field produced by a low frequency focused ultrasound system

    NASA Astrophysics Data System (ADS)

    Voie, Arne; Fisher, David; Ahadi, Golnaz; Hölscher, Thilo

    2012-11-01

    The purpose of this study was to ascertain the effects of the skull on the location, shape and power of the acoustic field produced by a 150 mm radius hemispherical array operating at 220 kHz. We wanted to determine whether phase aberrations were significant at this frequency, the amount of attenuation, and whether CT data could be predictive of the trans-skull field. The effects of five calvaria were evaluated. Acoustic field data and CT scans for each skull specimen were imported into MATLAB® for measurements and visualization in two and three dimensions. We examined the effects of skull density, porosity, thickness, and sonication incident angles, and estimated the relative contributions of longitudinal and shear transmission to the total transmitted power. Power transmission through the skulls varied between 4% and 23% (mean: 12%). The range of focal position shifts was from 0.50 mm to 4.32 mm (mean: 1.95 mm). The 3 dB dimensions of the focused ultrasound (FUS) intensity focal volume increased on average by 39% (low: 4%, high: 122%). The 6 dB pressure focal volume increased by an average of 130 ± 75%. In general, the main effects of the skulls were power reduction, field dispersion and slight shift of focal peak location.

  8. Acoustic power measurement of high intensity focused ultrasound in medicine based on radiation force.

    PubMed

    Shou, Wende; Huang, Xiaowei; Duan, Shimei; Xia, Rongmin; Shi, Zhonglong; Geng, Xiaoming; Li, Faqi

    2006-12-22

    How to measure the acoustic power of HIFU is one of the most important tasks in its medical application. In the paper a whole series of formula for calculating the radiation force related to the acoustic power radiated by a single element focusing transducer and by the focusing transducer array were given. Various system of radiation force balance (RFB) to measure the acoustic power of HIFU in medicine were designed and applied in China. In high power experiments, the dependence of radiation force acting the absorbing target on the target position at the beam axis of focusing transducer was fined. There is a peak value of "radiation force" acting the absorbing target in the focal region when the acoustic power through the focal plane exceeds some threshold. In order to avoid this big measurement error caused by the 'peak effect' in focal region, the distance between the absorbing target of RFB and the focusing transducer or transducer array was defined to be equal to or less than 0.7 times of the focal length in the National Standard of China for the measurements of acoustic power and field characteristics of HIFU. More than six different therapeutic equipments of HIFU have been examined by RFB for measuring the acoustic power since 1998. These results show that RFB with the absorbing target is valid in the acoustic power range up to 500W with good linearity for the drive voltage squared of focusing transducer or array. The uncertainty of measurement is within +/-15%.

  9. Calibration of an acoustic system for measuring 2-D temperature distribution around hydrothermal vents.

    PubMed

    Fan, Wei; Chen, Chen-Tung Arthur; Chen, Ying

    2013-04-01

    One of the fundamental purposes of quantitative acoustic surveys of seafloor hydrothermal vents is to measure their 2-D temperature distributions. Knowing the system latencies and the acoustic center-to-center distances between the underwater transducers in an acoustic tomography system is fundamental to the overall accuracy of the temperature reconstruction. However, commercial transducer sources typically do not supply the needed data. Here we present a novel calibration algorithm to automatically determine the system latencies and the acoustic center-to-center distances. The possible system latency error and the resulting temperature error are derived and analyzed. We have also developed the experimental setup for calibration. To validate the effectiveness of the proposed calibration method, an experimental study was performed on acoustic imaging of underwater temperature fields in Lake Qiezishan, located at Longling County, Yunnan Province, China. Using the calibrated data, the reconstructed temperature distributions closely resemble the actual distributions measured with thermocouples, thus confirming the effectiveness of our algorithm.

  10. 21 CFR 870.1130 - Noninvasive blood pressure measurement system.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Noninvasive blood pressure measurement system. 870... Noninvasive blood pressure measurement system. (a) Identification. A noninvasive blood pressure measurement... three pressures can be derived through the use of tranducers placed on the surface of the body....

  11. Local oscillator phase noise limitation on the resolution of acoustic delay line wireless passive sensor measurement

    NASA Astrophysics Data System (ADS)

    Chrétien, N.; Friedt, J.-M.; Martin, G.

    2014-06-01

    The role of the phase noise of a local oscillator driving a pulsed-mode RADAR used for probing surface acoustic wave sensors is investigated. The echo delay, representative of the acoustic velocity, and hence the physical quantity probed by the sensor, is finely measured as a phase. Considering that the intrinsic oscillator phase fluctuation defines the phase noise measurement resolution, we experimentally and theoretically assess the relation between phase noise, measurement range, and measurand resolution.

  12. Measuring Turbulence from Moored Acoustic Doppler Velocimeters. A Manual to Quantifying Inflow at Tidal Energy Sites

    SciTech Connect

    Kilcher, Levi; Thomson, Jim; Talbert, Joe; DeKlerk, Alex

    2016-03-01

    This work details a methodology for measuring hub height inflow turbulence using moored acoustic Doppler velocimiters (ADVs). This approach is motivated by the shortcomings of alternatives. For example, remote velocity measurements (i.e., from acoustic Doppler profilers) lack sufficient precision for device simulation, and rigid tower-mounted measurements are very expensive and technically challenging in the tidal environment. Moorings offer a low-cost, site-adaptable and robust deployment platform, and ADVs provide the necessary precision to accurately quantify turbulence.

  13. Sound Velocity Measurement of Stishovite at High Pressures up to 19 GPa

    NASA Astrophysics Data System (ADS)

    Zhou, C.; Jin, Z.; Wang, Y.; Zhang, Y.; WANG, C.

    2015-12-01

    An experimental system for measurement of the elastic wave velocities of solid polycrystalline samples at high pressures has been installed at the State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences (Wuhan). The ultrasonic system with LiNbO3 transducer can both generate and receive high frequency (MHz) signal. Combination with a Walker-type multianvil, the travel time through the polycrystalline sample at high pressures can be obtained. We carried out sound velocity measurements on polycrystalline stishovite up to 19 GPa at room temperature. And the experimental result shows an acoustic softening at high pressures. The experimental technique provides the offline experimental measurement of various materials to the high pressures corresponding to the Earth's mantle transition zone.

  14. Laser-Induced Acoustic Desorption Atmospheric Pressure Photoionization via VUV-Generating Microplasmas

    NASA Astrophysics Data System (ADS)

    Benham, Kevin; Hodyss, Robert; Fernández, Facundo M.; Orlando, Thomas M.

    2016-11-01

    We demonstrate the first application of laser-induced acoustic desorption (LIAD) and atmospheric pressure photoionization (APPI) as a mass spectrometric method for detecting low-polarity organics. This was accomplished using a Lyman-α (10.2 eV) photon generating microhollow cathode discharge (MHCD) microplasma photon source in conjunction with the addition of a gas-phase molecular dopant. This combination provided a soft desorption and a relatively soft ionization technique. Selected compounds analyzed include α-tocopherol, perylene, cholesterol, phenanthrene, phylloquinone, and squalene. Detectable surface concentrations as low as a few pmol per spot sampled were achievable using test molecules. The combination of LIAD and APPI provided a soft desorption and ionization technique that can allow detection of labile, low-polarity, structurally complex molecules over a wide mass range with minimal fragmentation.

  15. Stabilization and Low-Frequency Oscillation of Capillary Bridges with Modulated Acoustic Radiation Pressure

    NASA Technical Reports Server (NTRS)

    Marston, Philip L.; Marr-Lyon, Mark J.; Morse, S. F.; Thiessen, David B.

    1996-01-01

    In the work reported here it is demonstrated that acoustic radiation pressure may be used in simulated low gravity to produce stable bridges significantly beyond the Rayleigh limit with S as large as 3.6. The bridge (PDMS mixed with a dense liquid) has the same density as the surrounding water bath containing an ultrasonic standing wave. Modulation was first used to excite specific bridge modes. In the most recent work reported here the shape of the bridge is optically sensed and the ultrasonic drive is electronically adjusted such that the radiation stress distribution dynamically quenches the most unstable mode. This active control simulates passive stabilization suggested for low gravity. Feedback increases the mode frequency in the naturally stable region since the effective stiffness of the mode is increased.

  16. Laser-Induced Acoustic Desorption Atmospheric Pressure Photoionization via VUV-Generating Microplasmas.

    PubMed

    Benham, Kevin; Hodyss, Robert; Fernández, Facundo M; Orlando, Thomas M

    2016-11-01

    We demonstrate the first application of laser-induced acoustic desorption (LIAD) and atmospheric pressure photoionization (APPI) as a mass spectrometric method for detecting low-polarity organics. This was accomplished using a Lyman-α (10.2 eV) photon generating microhollow cathode discharge (MHCD) microplasma photon source in conjunction with the addition of a gas-phase molecular dopant. This combination provided a soft desorption and a relatively soft ionization technique. Selected compounds analyzed include α-tocopherol, perylene, cholesterol, phenanthrene, phylloquinone, and squalene. Detectable surface concentrations as low as a few pmol per spot sampled were achievable using test molecules. The combination of LIAD and APPI provided a soft desorption and ionization technique that can allow detection of labile, low-polarity, structurally complex molecules over a wide mass range with minimal fragmentation. Graphical Abstract ᅟ.

  17. Comparison of sonochemiluminescence images using image analysis techniques and identification of acoustic pressure fields via simulation.

    PubMed

    Tiong, T Joyce; Chandesa, Tissa; Yap, Yeow Hong

    2017-05-01

    One common method to determine the existence of cavitational activity in power ultrasonics systems is by capturing images of sonoluminescence (SL) or sonochemiluminescence (SCL) in a dark environment. Conventionally, the light emitted from SL or SCL was detected based on the number of photons. Though this method is effective, it could not identify the sonochemical zones of an ultrasonic systems. SL/SCL images, on the other hand, enable identification of 'active' sonochemical zones. However, these images often provide just qualitative data as the harvesting of light intensity data from the images is tedious and require high resolution images. In this work, we propose a new image analysis technique using pseudo-colouring images to quantify the SCL zones based on the intensities of the SCL images and followed by comparison of the active SCL zones with COMSOL simulated acoustic pressure zones.

  18. Apparatus and method for non-contact, acoustic resonance determination of intraocular pressure

    DOEpatents

    Sinha, Dipen N.; Wray, William O.

    1994-01-01

    Apparatus and method for measuring intraocular pressure changes in an eye under investigation by detection of vibrational resonances therein. An ultrasonic transducer operating at its resonant frequency is amplitude modulated and swept over a range of audio frequencies in which human eyes will resonate. The output therefrom is focused onto the eye under investigation, and the resonant vibrations of the eye observed using a fiber-optic reflection vibration sensor. Since the resonant frequency of the eye is dependent on the pressure therein, changes in intraocular pressure may readily be determined after a baseline pressure is established.

  19. Apparatus and method for non-contact, acoustic resonance determination of intraocular pressure

    DOEpatents

    Sinha, D.N.; Wray, W.O.

    1994-12-27

    The apparatus and method for measuring intraocular pressure changes in an eye under investigation by detection of vibrational resonances therein. An ultrasonic transducer operating at its resonant frequency is amplitude modulated and swept over a range of audio frequencies in which human eyes will resonate. The output therefrom is focused onto the eye under investigation, and the resonant vibrations of the eye observed using a fiber-optic reflection vibration sensor. Since the resonant frequency of the eye is dependent on the pressure therein, changes in intraocular pressure may readily be determined after a baseline pressure is established. 3 figures.

  20. Pressure probe and hot-film probe rsponses to acoustic excitation in mean flow

    NASA Technical Reports Server (NTRS)

    Parrott, T. L.; Jones, M. G.

    1986-01-01

    An experiment was conducted to compare the relative responses of a hot-film probe and a pressure probe positioned in a flow duct carrying mean flow and progressive acoustic waves. The response of each probe was compared with that of a condenser-type microphone flush mounted in the duct wall for flow Mach numbers up to about 0.5. The response of the pressure probe was less than that of the flush-mounted microphone by not more than about 2.1 dB at the highest centerline Mach number. This decreased response of the probe can likely be attributed to flow-induced impedance changes at the probe sensor orifices. The response of the hot-film probe, expressed in terms of fluctuating pressure, was greater than that of the flush-mounted microphone by as much as 6.0 dB at the two higher centerline Mach numbers. Removal of the contribution from fluctuating temperature in the hot-film analytical model greatly improved the agreement between the two transducer responses.

  1. Experimental feasibility of investigating acoustic waves in Couette flow with entropy and pressure gradients

    NASA Technical Reports Server (NTRS)

    Parrott, Tony L.; Zorumski, William E.; Rawls, John W., Jr.

    1990-01-01

    The feasibility is discussed for an experimental program for studying the behavior of acoustic wave propagation in the presence of strong gradients of pressure, temperature, and flow. Theory suggests that gradients effects can be experimentally observed as resonant frequency shifts and mode shape changes in a waveguide. A convenient experimental geometry for such experiments is the annular region between two co-rotating cylinders. Radial temperature gradients in a spinning annulus can be generated by differentially heating the two cylinders via electromagnetic induction. Radial pressure gradients can be controlled by varying the cylinder spin rates. Present technology appears adequate to construct an apparatus to allow independent control of temperature and pressure gradients. A complicating feature of a more advanced experiment, involving flow gradients, is the requirement for independently controlled cylinder spin rates. Also, the boundary condition at annulus terminations must be such that flow gradients are minimally disturbed. The design and construction of an advanced apparatus to include flow gradients will require additional technology development.

  2. Extension of the angular spectrum method to calculate pressure from a spherically curved acoustic source.

    PubMed

    Vyas, Urvi; Christensen, Douglas A

    2011-11-01

    The angular spectrum method is an accurate and computationally efficient method for modeling acoustic wave propagation. The use of the typical 2D fast Fourier transform algorithm makes this a fast technique but it requires that the source pressure (or velocity) be specified on a plane. Here the angular spectrum method is extended to calculate pressure from a spherical transducer-as used extensively in applications such as magnetic resonance-guided focused ultrasound surgery-to a plane. The approach, called the Ring-Bessel technique, decomposes the curved source into circular rings of increasing radii, each ring a different distance from the intermediate plane, and calculates the angular spectrum of each ring using a Fourier series. Each angular spectrum is then propagated to the intermediate plane where all the propagated angular spectra are summed to obtain the pressure on the plane; subsequent plane-to-plane propagation can be achieved using the traditional angular spectrum method. Since the Ring-Bessel calculations are carried out in the frequency domain, it reduces calculation times by a factor of approximately 24 compared to the Rayleigh-Sommerfeld method and about 82 compared to the Field II technique, while maintaining accuracies of better than 96% as judged by those methods for cases of both solid and phased-array transducers.

  3. Measurements of the force fields within an acoustic standing wave using holographic optical tweezers

    SciTech Connect

    Bassindale, P. G.; Drinkwater, B. W.; Phillips, D. B.; Barnes, A. C.

    2014-04-21

    Direct measurement of the forces experienced by micro-spheres in an acoustic standing wave device have been obtained using calibrated optical traps generated with holographic optical tweezers. A micro-sphere, which is optically trapped in three dimensions, can be moved through the acoustic device to measure forces acting upon it. When the micro-sphere is subjected to acoustic forces, it's equilibrium position is displaced to a position where the acoustic forces and optical forces are balanced. Once the optical trapping stiffness has been calibrated, observation of this displacement enables a direct measurement of the forces acting upon the micro-sphere. The measured forces are separated into a spatially oscillating component, attributed to the acoustic radiation force, and a constant force, attributed to fluid streaming. As the drive conditions of the acoustic device were varied, oscillating forces (>2.5 pN{sub pp}) and streaming forces (<0.2 pN) were measured. A 5 μm silica micro-sphere was used to characterise a 6.8 MHz standing wave, λ = 220 μm, to a spatial resolution limited by the uncertainty in the positioning of the micro-sphere (here to within 2 nm) and with a force resolution on the order of 10 fN. The results have application in the design and testing of acoustic manipulation devices.

  4. Measurements of Infrared and Acoustic Source Distributions in Jet Plumes

    NASA Technical Reports Server (NTRS)

    Agboola, Femi A.; Bridges, James; Saiyed, Naseem

    2004-01-01

    The aim of this investigation was to use the linear phased array (LPA) microphones and infrared (IR) imaging to study the effects of advanced nozzle-mixing techniques on jet noise reduction. Several full-scale engine nozzles were tested at varying power cycles with the linear phased array setup parallel to the jet axis. The array consisted of 16 sparsely distributed microphones. The phased array microphone measurements were taken at a distance of 51.0 ft (15.5 m) from the jet axis, and the results were used to obtain relative overall sound pressure levels from one nozzle design to the other. The IR imaging system was used to acquire real-time dynamic thermal patterns of the exhaust jet from the nozzles tested. The IR camera measured the IR radiation from the nozzle exit to a distance of six fan diameters (X/D(sub FAN) = 6), along the jet plume axis. The images confirmed the expected jet plume mixing intensity, and the phased array results showed the differences in sound pressure level with respect to nozzle configurations. The results show the effects of changes in configurations to the exit nozzles on both the flows mixing patterns and radiant energy dissipation patterns. By comparing the results from these two measurements, a relationship between noise reduction and core/bypass flow mixing is demonstrated.

  5. Laser-Doppler acoustic probing of granular media with in-depth property gradient and varying pore pressures

    SciTech Connect

    Bodet, L.; Dhemaied, A.; Mourgues, R.; Tournat, V.; Rejiba, F.

    2012-05-24

    Non-contacting ultrasonic techniques recently proved to be efficient in the physical modeling of seismic-wave propagation at various application scales, as for instance in the context of geological analogue and seismic modeling. An innovative experimental set-up is proposed here to perform laser-Doppler acoustic probing of unconsolidated granular media with varying pore pressures. The preliminary experiments presented here provide reproducible results and exploitable data, thus validating both the proposed medium preparation and pressure gradient generation procedure.

  6. Measuring baryon acoustic oscillations from the clustering of voids

    NASA Astrophysics Data System (ADS)

    Liang, Yu; Zhao, Cheng; Chuang, Chia-Hsun; Kitaura, Francisco-Shu; Tao, Charling

    2016-07-01

    We investigate the necessary methodology to optimally measure the baryon acoustic oscillation (BAO) signal from voids, based on galaxy redshift catalogues. To this end, we study the dependence of the BAO signal on the population of voids classified by their sizes. We find for the first time the characteristic features of the correlation function of voids including the first robust detection of BAOs in mock galaxy catalogues. These show an anti-correlation around the scale corresponding to the smallest size of voids in the sample (the void exclusion effect), and dips at both sides of the BAO peak, which can be used to determine the significance of the BAO signal without any priori model. Furthermore, our analysis demonstrates that there is a scale-dependent bias for different populations of voids depending on the radius, with the peculiar property that the void population with the largest BAO significance corresponds to tracers with approximately zero bias on the largest scales. We further investigate the methodology on an additional set of 1000 realistic mock galaxy catalogues reproducing the SDSS-III/BOSS CMASS DR11 data, to control the impact of sky mask and radial selection function. Our solution is based on generating voids from randoms including the same survey geometry and completeness, and a post-processing cleaning procedure in the holes and at the boundaries of the survey. The methodology and optimal selection of void populations validated in this work have been used to perform the first BAO detection from voids in observations, presented in a companion paper.

  7. Acoustic field modulation in regenerators

    NASA Astrophysics Data System (ADS)

    Hu, J. Y.; Wang, W.; Luo, E. C.; Chen, Y. Y.

    2016-12-01

    The regenerator is a key component that transfers energy between heat and work. The conversion efficiency is significantly influenced by the acoustic field in the regenerator. Much effort has been spent to quantitatively determine this influence, but few comprehensive experimental verifications have been performed because of difficulties in modulating and measuring the acoustic field. In this paper, a method requiring two compressors is introduced and theoretically investigated that achieves acoustic field modulation in the regenerator. One compressor outputs the acoustic power for the regenerator; the other acts as a phase shifter. A RC load dissipates the acoustic power out of both the regenerator and the latter compressor. The acoustic field can be modulated by adjusting the current in the two compressors and opening the RC load. The acoustic field is measured with pressure sensors instead of flow-field imaging equipment, thereby greatly simplifying the experiment.

  8. Imaging and detection of mines from acoustic measurements

    NASA Astrophysics Data System (ADS)

    Witten, Alan J.; DiMarzio, Charles A.; Li, Wen; McKnight, Stephen W.

    1999-08-01

    A laboratory-scale acoustic experiment is described where a buried target, a hockey puck cut in half, is shallowly buried in a sand box. To avoid the need for source and receiver coupling to the host sand, an acoustic wave is generated in the subsurface by a pulsed laser suspended above the air-sand interface. Similarly, an airborne microphone is suspended above this interface and moved in unison with the laser. After some pre-processing of the data, reflections for the target, although weak, could clearly be identified. While the existence and location of the target can be determined by inspection of the data, its unique shape can not. Since target discrimination is important in mine detection, a 3D imaging algorithm was applied to the acquired acoustic data. This algorithm yielded a reconstructed image where the shape of the target was resolved.

  9. AST Launch Vehicle Acoustics

    NASA Technical Reports Server (NTRS)

    Houston, Janice; Counter, D.; Giacomoni, D.

    2015-01-01

    The liftoff phase induces acoustic loading over a broad frequency range for a launch vehicle. These external acoustic environments are then used in the prediction of internal vibration responses of the vehicle and components which result in the qualification levels. Thus, predicting these liftoff acoustic (LOA) environments is critical to the design requirements of any launch vehicle. If there is a significant amount of uncertainty in the predictions or if acoustic mitigation options must be implemented, a subscale acoustic test is a feasible pre-launch test option to verify the LOA environments. The NASA Space Launch System (SLS) program initiated the Scale Model Acoustic Test (SMAT) to verify the predicted SLS LOA environments and to determine the acoustic reduction with an above deck water sound suppression system. The SMAT was conducted at Marshall Space Flight Center and the test article included a 5% scale SLS vehicle model, tower and Mobile Launcher. Acoustic and pressure data were measured by approximately 250 instruments. The SMAT liftoff acoustic results are presented, findings are discussed and a comparison is shown to the Ares I Scale Model Acoustic Test (ASMAT) results.

  10. Partial pressure measurements with an active spectrometer

    SciTech Connect

    Brooks, N.H.; Jensen, T.H.; Colchin, R.J.; Maingi, R.; Wade, M.R.; Finkenthal, D.F.; Naumenko, N.; Tugarinov, S.

    1998-07-01

    Partial pressure neutral ga measurements have been made using a commercial Penning gauge in conjunction with an active spectrometer. In prior work utilizing bandpass filters and conventional spectrometers, trace concentrations of the hydrogen isotopes H, D, T and of the noble gases He, Ne and Ar were determined from characteristic spectral lines in the light emitted by the neutral species of these elements. For all the elements mentioned, the sensitivity was limited by spectral contamination from a pervasive background of molecular hydrogen radiation. The active spectrometer overcomes this limitations by means of a digital lock-in method and correlation with reference spectra. Preliminary measurements of an admixture containing a trace amount of neon in deuterium show better than a factor of 20 improvement in sensitivity over conventional techniques. This can be further improved by correlating the relative intensities of multiple lines to sets of reference spectra.

  11. Acoustic Measurement and Model Predictions for the Aural Nondetectability of Two Night-Vision Goggles

    DTIC Science & Technology

    2013-11-01

    Acoustic Measurement and Model Predictions for the Aural Nondetectability of Two Night - Vision Goggles by Jeremy Gaston, Tim Mermagen, and...SUBTITLE Acoustic Measurement and Model Predictions for the Aural Nondetectability of Two Night - Vision Goggles 5a. CONTRACT NUMBER 5b. GRANT NUMBER...13. SUPPLEMENTARY NOTES 14. ABSTRACT This study evaluates two different night - vision goggles (NVGs) to determine if the devices meet level II

  12. Electronic dummy for acoustical testing

    NASA Technical Reports Server (NTRS)

    Bauer, B. B.; Di Mattia, A. L.; Rosencheck, A. J.; Stern, M.; Torick, E. L.

    1967-01-01

    Electronic Dummy /ED/ used for acoustical testing represents the average male torso from the Xiphoid process upward and includes an acoustic replica of the human head. This head simulates natural flesh, and has an artificial voice and artificial ears that measure sound pressures at the eardrum or the entrance to the ear canal.

  13. Miniature, Cooled Pressure-Measuring Probe

    NASA Technical Reports Server (NTRS)

    Ashby, George C., Jr.; Eves, John W.; White, David R.

    1994-01-01

    Probe designed to reduce settling time dramatically. Pressure-sensing transducer mounted in probe and connected to tip by short tube having cross-sectional area substantially smaller than conventional connecting tubes. Probe includes stainless-steel cylindrical exterior housing holding closed pressure chamber in which piezoelectric pressure transducer mounted. Open connecting tube passes portion of high-velocity, high-temperature fluid stream into closed pressure chamber. Any change of pressure in sampled stream propagates into closed pressure chamber with settling time inversely proportional to cross-sectional area of connecting tube. Cooling chamber formed around pressure chamber connected to source of water or other cooling fluid via inlet and outlet tubes.

  14. Fish Acoustics: Physics-Based Modeling and Measurement

    DTIC Science & Technology

    2011-01-01

    physical scattering mechanisms. To demonstrate this point, the target strength of a canonical gas-filled sphere is computed using a standard...high-frequency sound scattering by swimbladdered fish,” Journal of the Acoustical Society of America, Vol. 78, pp. 688-700 (1985). 9. Gauss , R. C

  15. Instrumental Dimensioning of Normal and Pathological Phonation Using Acoustic Measurements

    ERIC Educational Resources Information Center

    Putzer, Manfred; Barry, William J.

    2008-01-01

    The present study deals with the dimensions of normal and pathological phonation. Separation of normal voices from pathological voices is tested under different aspects. Using a new parametrization of voice-quality properties in the acoustic signal, the vowel productions of 534 speakers (267 M, 267 F) without any reported voice pathology and the…

  16. Acoustic measurements of soil-pipeflow and internal erosion

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Internal erosion of soil pipes can lead to embankment failures, landslides, and gully erosion. Therefore, non-intrusive methods are needed to detect and monitor soil pipeflow and the resulting internal erosion. This paper presents a laboratory study using both active and passive acoustic techniques ...

  17. Acoustic measurements of soil pipeflow and internal erosion

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Internal erosion of soil pipes can lead to embankment failures, landslides, and gully erosion therefore non-intrusive methods are needed to detect and monitor soil pipeflow and the resulting internal erosion. This paper presents a laboratory study using both active and passive acoustic techniques to...

  18. Phenomenological Description of Acoustic Emission Processes Occurring During High-Pressure Sand Compaction

    NASA Astrophysics Data System (ADS)

    Delgado-Martín, Jordi; Muñoz-Ibáñez, Andrea; Grande-García, Elisa; Rodríguez-Cedrún, Borja

    2016-04-01

    Compaction, pore collapse and grain crushing have a significant impact over the hydrodynamic properties of sand formations. The assessment of the crushing stress threshold constitutes valuable information in order to assess the behavior of these formations provided that it can be conveniently identified. Because of the inherent complexities of the direct observation of sand crushing, different authors have developed several indirect methods, being acoustic emission a promising one. However, previous researches have evidenced that there are different processes triggering acoustic emissions which need to be carefully accounted. Worth mentioning among them are grain bearing, grain to container friction, intergranular friction and crushing. The work presented here addresses this purpose. A broadband acoustic emission sensor (PA MicroHF200) connected to a high-speed data acquisition system and control software (AeWIN for PCI1 2.10) has been attached to a steel ram and used to monitor the different processes occurring during the oedometric compaction of uniform quartz sand up to an axial load of about 110 MPa and constant temperature. Load was stepwise applied using a servocontrolled hydraulic press acting at a constant load rate. Axial strain was simultaneously measured with the aid of a LDT device. Counts, energy, event duration, rise time and amplitude were recorded along each experiment and after completion selected waveforms were transformed from the time to the frequency domain via FFT transform. Additional simplified tests were performed in order to isolate the frequency characteristics of the dominant processes occurring during sand compaction. Our results show that, from simple tests, it is possible to determine process-dependent frequency components. When considering more complex experiments, many of the studied processes overlap but it is still possible to identify when a particular one dominates as well as the likely onset of crushing.

  19. Ultrasound and microbubble mediated drug delivery: acoustic pressure as determinant for uptake via membrane pores or endocytosis.

    PubMed

    De Cock, Ine; Zagato, Elisa; Braeckmans, Kevin; Luan, Ying; de Jong, Nico; De Smedt, Stefaan C; Lentacker, Ine

    2015-01-10

    Although promising results are achieved in ultrasound mediated drug delivery, its underlying biophysical mechanisms remain to be elucidated. Pore formation as well as endocytosis has been reported during ultrasound application. Due to the plethora of ultrasound settings used in literature, it is extremely difficult to draw conclusions on which mechanism is actually involved. To our knowledge, we are the first to show that acoustic pressure influences which route of drug uptake is addressed, by inducing different microbubble-cell interactions. To investigate this, FITC-dextrans were used as model drugs and their uptake was analyzed by flow cytometry. In fluorescence intensity plots, two subpopulations arose in cells with FITC-dextran uptake after ultrasound application, corresponding to cells having either low or high uptake. Following separation of the subpopulations by FACS sorting, confocal images indicated that the low uptake population showed endocytic uptake. The high uptake population represented uptake via pores. Moreover, the distribution of the subpopulations shifted to the high uptake population with increasing acoustic pressure. Real-time confocal recordings during ultrasound revealed that membrane deformation by microbubbles may be the trigger for endocytosis via mechanostimulation of the cytoskeleton. Pore formation was shown to be caused by microbubbles propelled towards the cell. These results provide a better insight in the role of acoustic pressure in microbubble-cell interactions and the possible consequences for drug uptake. In addition, it pinpoints the need for a more rational, microbubble behavior based choice of acoustic parameters in ultrasound mediated drug delivery experiments.

  20. Acoustic backscattering by deepwater fish measured in situ from a manned submersible

    NASA Astrophysics Data System (ADS)

    Benoit-Bird, Kelly J.; Au, Whitlow W. L.; Kelley, Christopher D.; Taylor, Christopher

    2003-02-01

    An outstanding problem in fisheries acoustics is the depth dependence of scattering characteristics of swimbladder-bearing fish, and the effects of pressure on the target strength of physoclistous fish remain unresolved. In situ echoes from deepwater snappers were obtained with a sonar transducer mounted on a manned submersible next to a low-light video camera, permitting simultaneous echo recording and identification of species, fish size and orientation. The sonar system, consisting of a transducer, single board computer, hard disk, and analog-to-digital converter, used a 80 μs, broadband signal (bandwidth 35 kHz, center frequency 120 kHz). The observed relationship between fish length and in situ target strength shows no difference from the relationship measured at the surface. No differences in the species-specific temporal echo characteristics were observed between surface and in situ measures. This indicates that the size and shape of the snappers' swimbladders are maintained both at the surface and at depths of up to 250 m. Information obtained through controlled backscatter measurements of tethered, anesthetized fish at the surface can be applied to free-swimming fish at depth. This is the first published account of the use of a manned submersible to measure in situ scattering from identified, individual animals with known orientations. The distinct advantage of this technique compared with other in situ techniques is the ability to observe the target fish, obtaining accurate species, size, and orientation information.

  1. Fluid-filled blood pressure measurement systems.

    PubMed

    Li, J K; van Brummelen, A G; Noordergraaf, A

    1976-05-01

    The performance of catheter-manometer systems for the measurement of pulsatile pressure has been evaluated by both experimental techniques and theoretical considerations. The former approach has shown, on occasion, multiple maxima in the amplitude response. The latter has been approached in a variety of ways, ranging from extreme lumping to application of transmission line theory while employing different configurations in the system's representation. Multiple maxima have also been seen, The present paper identifies the sources of the differences found and compares the relative merits of various theoretical approaches. It introduces the compliance of the system as a figure of merit and provides a simple first-order approximation formula for evaluation of the quality of a system. Damping and impedance matching to improve the system's frequency response were studied. It was found that they were not needed in a very stiff or a very compliant system, nor should one worry about the representation of such a system.

  2. Non-invasive estimation of static and pulsatile intracranial pressure from transcranial acoustic signals.

    PubMed

    Levinsky, Alexandra; Papyan, Surik; Weinberg, Guy; Stadheim, Trond; Eide, Per Kristian

    2016-05-01

    The aim of the present study was to examine whether a method for estimation of non-invasive ICP (nICP) from transcranial acoustic (TCA) signals mixed with head-generated sounds estimate the static and pulsatile invasive ICP (iICP). For that purpose, simultaneous iICP and mixed TCA signals were obtained from patients undergoing continuous iICP monitoring as part of clinical management. The ear probe placed in the right outer ear channel sent a TCA signal with fixed frequency (621 Hz) that was picked up by the left ear probe along with acoustic signals generated by the intracranial compartment. Based on a mathematical model of the association between mixed TCA and iICP, the static and pulsatile nICP values were determined. Total 39 patients were included in the study; the total number of observations for prediction of static and pulsatile iICP were 5789 and 6791, respectively. The results demonstrated a good agreement between iICP/nICP observations, with mean difference of 0.39 mmHg and 0.53 mmHg for static and pulsatile ICP, respectively. In summary, in this cohort of patients, mixed TCA signals estimated the static and pulsatile iICP with rather good accuracy. Further studies are required to validate whether mixed TCA signals may become useful for measurement of nICP.

  3. Age effects in the human middle ear: Wideband acoustical measures

    NASA Astrophysics Data System (ADS)

    Feeney, M. Patrick; Sanford, Chris A.

    2004-12-01

    Studies that have examined age effects in the human middle ear using either admittance measures at 220 or 660 Hz or multifrequency tympanometry from 200 to 2000 Hz have had conflicting results. Several studies have suggested an increase in admittance with age, while several others have suggested a decrease in admittance with age. A third group of studies found no significant age effect. This study examined 226 Hz tympanometry and wideband energy reflectance and impedance at ambient pressure in a group of 40 young adults and a group of 30 adults with age >=60 years. The groups did not differ in admittance measures of the middle ear at 226 Hz. However, significant age effects were found in wideband energy reflectance and impedance. In particular, in older adults there was a comparative decrease in reflectance from 800 to 2000 Hz but an increase near 4000 Hz. The results suggest a decrease in middle-ear stiffness with age. The findings of this study hold relevance for understanding the aging process in the auditory system, for the establishment of normative data for wideband energy reflectance, for the possibility of a conductive component to presbycusis, and for the interpretation of otoacoustic emission measurements. .

  4. Field evaluation of boat-mounted acoustic Doppler instruments used to measure streamflow

    USGS Publications Warehouse

    Mueller, D.S.; ,

    2003-01-01

    The use of instruments based on the Doppler principle for measuring water velocity and computing discharge is common within the U.S. Geological Survey (USGS). The instruments and software have changed appreciably during the last 5 years; therefore, the USGS has begun field validation of the instruments used to make discharge measurements from a moving boat. Instruments manufactured by SonTek/YSI and RD Instruments, Inc. were used to collect discharge data at five different sites. One or more traditional discharge measurements were made using a Price AA current meter and standard USGS procedures concurrent with the acoustic instruments at each site. Discharges measured with the acoustic instruments were compared with discharges measured with Price AA current meters and the USGS stage-discharge rating for each site. The mean discharges measured by each acoustic instrument were within 5 percent of the Price AA-based measurement and (or) discharge from the stage-discharge rating.

  5. Measured acoustic characteristics of ducted supersonic jets at different model scales

    NASA Technical Reports Server (NTRS)

    Jones, R. R., III; Ahuja, K. K.; Tam, Christopher K. W.; Abdelwahab, M.

    1993-01-01

    A large-scale (about a 25x enlargement) model of the Georgia Tech Research Institute (GTRI) hardware was installed and tested in the Propulsion Systems Laboratory of the NASA Lewis Research Center. Acoustic measurements made in these two facilities are compared and the similarity in acoustic behavior over the scale range under consideration is highlighted. The study provide the acoustic data over a relatively large-scale range which may be used to demonstrate the validity of scaling methods employed in the investigation of this phenomena.

  6. The use of electro-acoustic impedance measurements in detecting early clinical otosclerosis.

    PubMed

    Van Wagoner, R S; Campbell, J D

    1976-02-01

    The first evidence that sodium fluoride (NaFl) can stop the otosclerotic process was recently presented. This development has placed new emphasis on the early detection of clinical otosclerosis. Electro-acoustic impedance measurements often detect minute changes in absolute impedance and compliance of the ossicular chain. The most valuable diagnostic information, however, is a negative on-off (biphasic) type of acoustic reflex. These results are often evident prior to the detection of positive clinical signs of otosclerosis. The negative on-off acoustic reflex is reviewed in this paper along with case discussions involving medical/surgical management of early otosclerosis.

  7. Acoustic Response of Underwater Munitions near a Sediment Interface: Measurement Model Comparisons and Classification Schemes

    DTIC Science & Technology

    2015-04-23

    FINAL REPORT Acoustic Response of Underwater Munitions near a Sediment Interface: Measurement Model Comparisons and Classification Schemes SERDP...6 Figure 2. Effect of fish on acoustic color templates during GULFEX12 …………… 8 Figure 3. Selection of targets deployed during TREX13 and BAYEX14...deployed during TREX13 and BAYEX14 …… 29 Figure 16. Ray diagrams for the acoustic ray model …………………………… 29 Figure 17. Model-model and data-model

  8. The Ability to Structure Acoustic Material as a Measure of Musical Aptitude. 4. Experiences with Modifications of the Acoustic Structuring Test. Research Bulletin. No. 51.

    ERIC Educational Resources Information Center

    Karma, Kai

    Four new versions of an acoustic structuring test were developed, administered, and analyzed in order to produce better tests and to contribute to better understanding of the abilities measured by these tests. The tests consist of tape recordings of patterns of musical notes played on an electric organ or an acoustic guitar. Item analyses and…

  9. 21 CFR 886.4280 - Intraocular pressure measuring device.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Intraocular pressure measuring device. 886.4280... (CONTINUED) MEDICAL DEVICES OPHTHALMIC DEVICES Surgical Devices § 886.4280 Intraocular pressure measuring device. (a) Identification. An intraocular pressure measuring device is a manual or AC-powered...

  10. 21 CFR 886.4280 - Intraocular pressure measuring device.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Intraocular pressure measuring device. 886.4280... (CONTINUED) MEDICAL DEVICES OPHTHALMIC DEVICES Surgical Devices § 886.4280 Intraocular pressure measuring device. (a) Identification. An intraocular pressure measuring device is a manual or AC-powered...

  11. 21 CFR 886.4280 - Intraocular pressure measuring device.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Intraocular pressure measuring device. 886.4280... (CONTINUED) MEDICAL DEVICES OPHTHALMIC DEVICES Surgical Devices § 886.4280 Intraocular pressure measuring device. (a) Identification. An intraocular pressure measuring device is a manual or AC-powered...

  12. Flutter spectral measurements using stationary pressure transducers

    NASA Technical Reports Server (NTRS)

    Kurkov, A. P.

    1980-01-01

    Engine-order sampling was used to eliminate the integral harmonics from the flutter spectra corresponding to a case-mounted static pressure transducer. Using the optical displacement data, it was demonstrated that the blade-order sampling of pressure data may yield erroneous results due to the interference caused by blade vibration. Two methods are presented which effectively eliminate this interference yielding the blade-pressure-difference spectra. The phase difference between the differential-pressure and the displacement spectra was evaluated.

  13. Method of measuring reactive acoustic power density in a fluid

    DOEpatents

    Wheatley, J.C.; Swift, G.W.; Migliori, A.

    1985-09-03

    A method for determining reactive acoustic power density level and its direction in a fluid using a single sensor is disclosed. In the preferred embodiment, an apparatus for conducting the method, which is termed a thermoacoustic couple, consists of a stack of thin, spaced apart polymeric plates, selected ones of which include multiple bimetallic thermocouple junctions positioned along opposite end edges thereof. The thermocouple junctions are connected in series in the nature of a thermopile, and are arranged so as to be responsive to small temperature differences between the opposite edges of the plates. The magnitude of the temperature difference, as represented by the magnitude of the electrical potential difference generated by the thermopile, is found to be directly related to the level of acoustic power density in the gas. 5 figs.

  14. Method of measuring reactive acoustic power density in a fluid

    DOEpatents

    Wheatley, John C.; Swift, Gregory W.; Migliori, Albert

    1985-01-01

    A method for determining reactive acoustic power density level and its direction in a fluid using a single sensor is disclosed. In the preferred embodiment, an apparatus for conducting the method, which is termed a thermoacoustic couple, consists of a stack of thin, spaced apart polymeric plates, selected ones of which include multiple bimetallic thermocouple junctions positioned along opposite end edges thereof. The thermocouple junctions are connected in series in the nature of a thermopile, and are arranged so as to be responsive to small temperature differences between the opposite edges of the plates. The magnitude of the temperature difference, as represented by the magnitude of the electrical potential difference generated by the thermopile, is found to be directly related to the level of acoustic power density in the gas.

  15. Experimental Acoustic Velocity Measurements in a Tidally Affected Stream

    USGS Publications Warehouse

    Storm, J.B.; ,

    2002-01-01

    The U.S. Geological Survey (USGS) constructed a continuous steamgaging station on the tidally affected Escatawpa River at Interstate 10 near Orange Grove, Mississippi, in August 2001. The gage collects water quantity parameters of stage and stream velocity, and water quality parameters of water temperature, specific conductance, and salinity. Data are transmitted to the local USGS office via the GOES satellite and are presented on a near real-time web page. Due to tidal effects, the stream has multiple flow regimes which include downstream, bi-directional, and reverse flows. Advances in acoustic technology have made it possible to gage streams of this nature where conventional methods have been unsuccessful. An experimental mount was designed in an attempt to recognize, describe, and quantify these flow regimes by using acoustic Doppler equipment.

  16. A dynamic pressure view cell for acoustic stimulation of fluids—Micro-bubble generation and fluid movement in porous media

    NASA Astrophysics Data System (ADS)

    Stewart, Robert A.; Shaw, J. M.

    2015-09-01

    The development and baseline operation of an acoustic view cell for observing fluids, and fluid-fluid and fluid-solid interfaces in porous media over the frequency range of 10-5000 Hz is described. This range includes the industrially relevant frequency range 500-5000 Hz that is not covered by existing devices. Pressure waveforms of arbitrary shape are generated in a 17.46 mm ID by 200 mm and 690.5 mm long glass tubes at flow rates up to 200 ml/min using a syringe pump. Peak-to-peak amplitudes exceeding 80 kPa are readily realized at frequencies from 10 to 5000 Hz in bubble free fluids when actuated with 20 Vpp as exemplified using castor oil. At resonant frequencies, peak-to-peak pressure amplitudes exceeding 500 kPa were obtained (castor oil at 2100 Hz when actuated with 20 Vpp). Impacts of vibration on macroscopic liquid-liquid and liquid-vapour interfaces and interface movement are illustrated. Pressure wave transmission and attenuation in a fluid saturated porous medium, randomly packed 250-330 μm spherical silica beads, is also demonstrated. Attenuation differences and frequency shifts in resonant peaks are used to detect the presence and generation of dispersed micro-bubbles (<180 μm diameter), and bubbles within porous media that are not readily visualized. Envisioned applications include assessment of the impacts of vibration on reaction, mass transfer, and flow/flow pattern outcomes. This knowledge will inform laboratory and pilot scale process studies, where nuisance vibrations may affect the interpretation of process outcomes, and large scale or in situ processes in aquifers or hydrocarbon reservoirs where imposed vibration may be deployed to improve aspects of process performance. Future work will include miscible interface observation and quantitative measurements in the bulk and in porous media where the roles of micro-bubbles comprise subjects of special interest.

  17. A dynamic pressure view cell for acoustic stimulation of fluids--Micro-bubble generation and fluid movement in porous media.

    PubMed

    Stewart, Robert A; Shaw, J M

    2015-09-01

    The development and baseline operation of an acoustic view cell for observing fluids, and fluid-fluid and fluid-solid interfaces in porous media over the frequency range of 10-5000 Hz is described. This range includes the industrially relevant frequency range 500-5000 Hz that is not covered by existing devices. Pressure waveforms of arbitrary shape are generated in a 17.46 mm ID by 200 mm and 690.5 mm long glass tubes at flow rates up to 200 ml/min using a syringe pump. Peak-to-peak amplitudes exceeding 80 kPa are readily realized at frequencies from 10 to 5000 Hz in bubble free fluids when actuated with 20 Vpp as exemplified using castor oil. At resonant frequencies, peak-to-peak pressure amplitudes exceeding 500 kPa were obtained (castor oil at 2100 Hz when actuated with 20 Vpp). Impacts of vibration on macroscopic liquid-liquid and liquid-vapour interfaces and interface movement are illustrated. Pressure wave transmission and attenuation in a fluid saturated porous medium, randomly packed 250-330 μm spherical silica beads, is also demonstrated. Attenuation differences and frequency shifts in resonant peaks are used to detect the presence and generation of dispersed micro-bubbles (<180 μm diameter), and bubbles within porous media that are not readily visualized. Envisioned applications include assessment of the impacts of vibration on reaction, mass transfer, and flow/flow pattern outcomes. This knowledge will inform laboratory and pilot scale process studies, where nuisance vibrations may affect the interpretation of process outcomes, and large scale or in situ processes in aquifers or hydrocarbon reservoirs where imposed vibration may be deployed to improve aspects of process performance. Future work will include miscible interface observation and quantitative measurements in the bulk and in porous media where the roles of micro-bubbles comprise subjects of special interest.

  18. Measuring the Kuroshio Current with ocean acoustic tomography.

    PubMed

    Taniguchi, Naokazu; Huang, Chen-Fen; Kaneko, Arata; Liu, Cho-Teng; Howe, Bruce M; Wang, Yu-Huai; Yang, Yih; Lin, Ju; Zhu, Xiao-Hua; Gohda, Noriaki

    2013-10-01

    Ocean current profiling using ocean acoustic tomography (OAT) was conducted in the Kuroshio Current southeast of Taiwan from August 20 to September 15, 2009. Sound pulses were transmitted reciprocally between two acoustic stations placed near the underwater sound channel axis and separated by 48 km. Based on the result of ray simulation, the received signals are divided into multiple ray groups because it is difficult to resolve the ray arrivals for individual rays. The average differential travel times from these ray groups are used to reconstruct the vertical profiles of currents. The currents are estimated with respect to the deepest water layer via two methods: An explicit solution and an inversion with regularization. The strong currents were confined to the upper 200 m and rapidly weakened toward 500 m in depth. Both methods give similar results and are consistent with shipboard acoustic Doppler current profiler results in the upper 150 m. The observed temporal variation demonstrates a similar trend to the prediction from the Hybrid Coordinate Ocean Model.

  19. Offshore exposure experiments on cuttlefish indicate received sound pressure and particle motion levels associated with acoustic trauma

    PubMed Central

    Solé, Marta; Sigray, Peter; Lenoir, Marc; van der Schaar, Mike; Lalander, Emilia; André, Michel

    2017-01-01

    Recent findings on cephalopods in laboratory conditions showed that exposure to artificial noise had a direct consequence on the statocyst, sensory organs, which are responsible for their equilibrium and movements in the water column. The question remained about the contribution of the consequent near-field particle motion influence from the tank walls, to the triggering of the trauma. Offshore noise controlled exposure experiments (CEE) on common cuttlefish (Sepia officinalis), were conducted at three different depths and distances from the source and particle motion and sound pressure measurements were performed at each location. Scanning electron microscopy (SEM) revealed injuries in statocysts, which severity was quantified and found to be proportional to the distance to the transducer. These findings are the first evidence of cephalopods sensitivity to anthropogenic noise sources in their natural habitat. From the measured received power spectrum of the sweep, it was possible to determine that the animals were exposed at levels ranging from 139 to 142 dB re 1 μPa2 and from 139 to 141 dB re 1 μPa2, at 1/3 octave bands centred at 315 Hz and 400 Hz, respectively. These results could therefore be considered a coherent threshold estimation of noise levels that can trigger acoustic trauma in cephalopods. PMID:28378762

  20. Offshore exposure experiments on cuttlefish indicate received sound pressure and particle motion levels associated with acoustic trauma.

    PubMed

    Solé, Marta; Sigray, Peter; Lenoir, Marc; van der Schaar, Mike; Lalander, Emilia; André, Michel

    2017-04-05

    Recent findings on cephalopods in laboratory conditions showed that exposure to artificial noise had a direct consequence on the statocyst, sensory organs, which are responsible for their equilibrium and movements in the water column. The question remained about the contribution of the consequent near-field particle motion influence from the tank walls, to the triggering of the trauma. Offshore noise controlled exposure experiments (CEE) on common cuttlefish (Sepia officinalis), were conducted at three different depths and distances from the source and particle motion and sound pressure measurements were performed at each location. Scanning electron microscopy (SEM) revealed injuries in statocysts, which severity was quantified and found to be proportional to the distance to the transducer. These findings are the first evidence of cephalopods sensitivity to anthropogenic noise sources in their natural habitat. From the measured received power spectrum of the sweep, it was possible to determine that the animals were exposed at levels ranging from 139 to 142 dB re 1 μPa(2) and from 139 to 141 dB re 1 μPa(2), at 1/3 octave bands centred at 315 Hz and 400 Hz, respectively. These results could therefore be considered a coherent threshold estimation of noise levels that can trigger acoustic trauma in cephalopods.

  1. Comparison between psycho-acoustics and physio-acoustic measurement to determine optimum reverberation time of pentatonic angklung music concert hall

    NASA Astrophysics Data System (ADS)

    Sudarsono, Anugrah S.; Merthayasa, I. G. N.; Suprijanto

    2015-09-01

    This research tried to compare psycho-acoustics and Physio-acoustic measurement to find the optimum reverberation time of soundfield from angklung music. Psycho-acoustic measurement was conducted using a paired comparison method and Physio-acoustic measurement was conducted with EEG Measurement on T3, T4, FP1, and FP2 measurement points. EEG measurement was conducted with 5 persons. Pentatonic angklung music was used as a stimulus with reverberation time variation. The variation was between 0.8 s - 1.6 s with 0.2 s step. EEG signal was analysed using a Power Spectral Density method on Alpha Wave, High Alpha Wave, and Theta Wave. Psycho-acoustic measurement on 50 persons showed that reverberation time preference of pentatonic angklung music was 1.2 second. The result was similar to Theta Wave measurement on FP2 measurement point. High Alpha wave on T4 measurement gave different results, but had similar patterns with psycho-acoustic measurement

  2. A novel acoustic method for gas flow measurement using correlation techniques

    NASA Astrophysics Data System (ADS)

    Knuuttila, Matti Tapani

    The study demonstrates a new kind of acoustic method for gas flow measurement. The method uses upstream and downstream propagating low frequency plane wave and correlation techniques for volume flow rate determination. The theory of propagating low frequency plane waves in the pipe is introduced and is proved empirically to be applicable for flow measurement. The flow profile dependence of the method is verified and found to be negligible at least in the region of moderate perturbations. The physical principles of the method were applied in practice in the form of a flowmeter with new design concepts. The developed prototype meters were verified against the reference standard of NMI (Nederlands Meetinstituut), which showed that a wide dynamic range of 1:80 is achievable with total expanded uncertainty below 0.3%. Also the requirements used for turbine meters of linearity, weighted mean error and stability were shown to be well fulfilled. A brief comparison with other flowmeter types shows the new flowmeter to be competitive. The advantages it offers are a small pressure drop over the meter, no blockage of flow in possible malfunction, no pulsation to flow, essentially no moving parts, and the possibility for bidirectional measurements. The introduced flowmeter is also capable of using the introduced flowmeter is also capable of using the telephone network or a radio-modem to read the consumption of gas and report its operation to the user.

  3. Verification of Ares I Liftoff Acoustic Environments via the Ares I Scale Model Acoustic Test

    NASA Technical Reports Server (NTRS)

    Counter, Douglas; Houston, Janice

    2012-01-01

    The Ares I Scale Model Acoustic Test (ASMAT) program was implemented to verify the predicted Ares I liftoff acoustic environments and to determine the acoustic reduction gained by using an above deck water sound suppression system. The test article included a 5% scale Ares I vehicle model and Mobile Launcher with tower. Acoustic and pressure data were measured by over 200 instruments. The ASMAT results are compared to Ares I-X flight data.

  4. Measurement Adherence in the Blood Pressure Self-Measurement Room

    PubMed Central

    Buus, Niels Henrik; Jespersen, Bente; Ahrendt, Peter; Bertelsen, Olav W.; Toftegaard, Thomas S.

    2013-01-01

    Abstract Background: Patients with hypertension or receiving blood pressure (BP)-lowering treatment are often required to self-measure their BP in a dedicated self-measurement room before consultation. Current praxis does not guarantee valid measurements, possibly leading to misdiagnoses or inappropriate antihypertensive medication. The aim of this study was to investigate patients' ability to correctly self-report and follow recommendations. Patients and Methods: We used a context-aware system to gather information on BP measurements and relevant context parameters. Patients were not informed that the system automatically collected behavior data and were instructed to self-report their measurements on a paper sheet as usual. We then compared the automatically recorded data with the self-reported data in order to detect any nonadherent reporting behavior. Also, we investigated the patients' ability to adhere to the measurement recommendations. Results: We found that (1) a third of all 113 participating patients failed to self-report measured BP data correctly and (2) none of the 642 measurements obtained adhered fully to the recommendations. Conclusions: Results indicate that context-aware technology may be useful for accurately modeling aspects of nonadherent patient behavior. This may be used to inform staff of the validity of the measurement and pinpoint patients in need of additional training or to design better aids to assist the patients. The developed system is generally applicable to other self-measurement environments, including the home setting and remote outpatient clinics, as it is built using telemedicine technology and thus well suited for remote monitoring and diagnosis. PMID:23631589

  5. Acoustic Measurements of a Large Civil Transport Main Landing Gear Model

    NASA Technical Reports Server (NTRS)

    Ravetta, Patricio A.; Khorrami, Mehdi R.; Burdisso, Ricardo A.; Wisda, David M.

    2016-01-01

    Microphone phased array acoustic measurements of a 26 percent-scale, Boeing 777-200 main landing gear model with and without noise reduction fairings installed were obtained in the anechoic configuration of the Virginia Tech Stability Tunnel. Data were acquired at Mach numbers of 0.12, 0.15, and 0.17 with the latter speed used as the nominal test condition. The fully and partially dressed gear with the truck angle set at 13 degrees toe-up landing configuration were the two most extensively tested configurations, serving as the baselines for comparison purposes. Acoustic measurements were also acquired for the same two baseline configurations with the truck angle set at 0 degrees. In addition, a previously tested noise reducing, toboggan-shaped fairing was re-evaluated extensively to address some of the lingering questions regarding the extent of acoustic benefit achievable with this device. The integrated spectra generated from the acoustic source maps reconfirm, in general terms, the previously reported noise reduction performance of the toboggan fairing as installed on an isolated gear. With the recent improvements to the Virginia Tech tunnel acoustic quality and microphone array capabilities, the present measurements provide an additional, higher quality database to the acoustic information available for this gear model.

  6. Non-invasive method of measuring cerebral spinal fluid pressure

    NASA Technical Reports Server (NTRS)

    Borchert, Mark S. (Inventor); Lambert, James L. (Inventor)

    2000-01-01

    The invention provides a method of non-invasively determining intracranial pressure from measurements of an eye. A parameter of an optic nerve of the eye is determined, along with an intraocular pressure of the eye. The intracranial pressure may be determined from the intraocular pressure and the parameter.

  7. A Methodology to Integrate Magnetic Resonance and Acoustic Measurements for Reservoir Characterization

    SciTech Connect

    Parra, Jorge O.; Hackert, Chris L.; Collier, Hughbert A.; Bennett, Michael

    2002-01-29

    The objective of this project was to develop an advanced imaging method, including pore scale imaging, to integrate NMR techniques and acoustic measurements to improve predictability of the pay zone in hydrocarbon reservoirs. This is accomplished by extracting the fluid property parameters using NMR laboratory measurements and the elastic parameters of the rock matrix from acoustic measurements to create poroelastic models of different parts of the reservoir. Laboratory measurement techniques and core imaging are being linked with a balanced petrographical analysis of the core and theoretical model.

  8. A Methodology to Integrate Magnetic Resonance and Acoustic Measurements for Reservoir Characterization

    SciTech Connect

    Parra, Ph.D., Jorge O.

    2002-06-10

    The objective of the project was to develop an advanced imaging method, including pore scale imaging, to integrate nuclear magnetic resonance (NMR) techniques and acoustic measurements to improve predictability of the pay zone in hydrocarbon reservoirs. This will be accomplished by extracting the fluid property parameters using NMR laboratory measurements and the elastic parameters of the rock matrix from acoustic measurements to create poroelastic models of different parts of the reservoir. Laboratory measurement techniques and core imaging were linked with a balanced petrographical analysis of cores and theoretical modeling.

  9. A Methodology to Integrate Magnetic Resonance and Acoustic Measurements for Reservoir Characterization

    SciTech Connect

    Parra, J.O.

    2001-01-26

    The objective of this project was to develop an advanced imaging method, including pore scale imaging, to integrate magnetic resonance (MR) techniques and acoustic measurements to improve predictability of the pay zone in two hydrocarbon reservoirs. This was accomplished by extracting the fluid property parameters using MR laboratory measurements and the elastic parameters of the rock matrix from acoustic measurements to create poroelastic models of different parts of the reservoir. Laboratory measurements were compared with petrographic analysis results to determine the relative roles of petrographic elements such as porosity type, mineralogy, texture, and distribution of clay and cement in creating permeability heterogeneity.

  10. Comparison of Different Measurement Technologies for the In-Flight Assessment of Radiated Acoustic Intensity

    NASA Technical Reports Server (NTRS)

    Klos, Jacob; Palumbo, Daniel L.; Buehrle, Ralph D.; Williams, Earl G.; Valdivia, Nicolas; Herdic, Peter C.; Sklanka, Bernard

    2005-01-01

    A series of tests was planned and conducted in the Interior Noise Test Facility at Boeing Field, on the NASA Aries 757 flight research aircraft, and in the Structural Acoustic Loads and Transmission Facility at NASA Langley Research Center. These tests were designed to answer several questions concerning the use of array methods in flight. One focus of the tests was determining whether and to what extent array methods could be used to identify the effects of an acoustical treatment applied to a limited portion of an aircraft fuselage. Another focus of the tests was to verify that the arrays could be used to localize and quantify a known source purposely placed in front of the arrays. Thus the issues related to backside sources and flanking paths present in the complicated sound field were addressed during these tests. These issues were addressed through the use of reference transducers, both accelerometers mounted to the fuselage and microphones in the cabin, that were used to correlate the pressure holograms. measured by the microphone arrays using either SVD methods or partial coherence methods. This correlation analysis accepts only energy that is coherent with the sources sensed by the reference transducers, allowing a noise control engineer to only identify and study those vibratory sources of interest. The remainder of this paper will present a detailed description of the test setups that were used in this test sequence and typical results of the NAH/IBEM analysis used to reconstruct the sound fields. Also, a comparison of data obtained in the laboratory environments and during flights of the 757 aircraft will be made.

  11. Laser-induced acoustic desorption/atmospheric pressure chemical ionization mass spectrometry.

    PubMed

    Gao, Jinshan; Borton, David J; Owen, Benjamin C; Jin, Zhicheng; Hurt, Matt; Amundson, Lucas M; Madden, Jeremy T; Qian, Kuangnan; Kenttämaa, Hilkka I

    2011-03-01

    Laser-induced acoustic desorption (LIAD) was successfully coupled to a conventional atmospheric pressure chemical ionization (APCI) source in a commercial linear quadrupole ion trap mass spectrometer (LQIT). Model compounds representing a wide variety of different types, including basic nitrogen and oxygen compounds, aromatic and aliphatic compounds, as well as unsaturated and saturated hydrocarbons, were tested separately and as a mixture. These model compounds were successfully evaporated into the gas phase by using LIAD and then ionized by using APCI with different reagents. From the four APCI reagent systems tested, neat carbon disulfide provided the best results. The mixture of methanol and water produced primarily protonated molecules, as expected. However, only the most basic compounds yielded ions under these conditions. In sharp contrast, using APCI with either neat benzene or neat carbon disulfide as the reagent resulted in the ionization of all the analytes studied to predominantly yield stable molecular ions. Benzene yielded a larger fraction of protonated molecules than carbon disulfide, which is a disadvantage. A similar but minor amount of fragmentation was observed for these two reagents. When the experiment was performed without a liquid reagent (nitrogen gas was the reagent), more fragmentation was observed. Analysis of a known mixture as well as a petroleum cut was also carried out. In summary, the new experiment presented here allows the evaporation of thermally labile compounds, both polar and nonpolar, without dissociation or aggregation, and their ionization to predominantly form stable molecular ions.

  12. Laser-Induced Acoustic Desorption/Atmospheric Pressure Chemical Ionization Mass Spectrometry

    PubMed Central

    Gao, Jinshan; Borton, David J.; Owen, Benjamin C.; Jin, Zhicheng; Hurt, Matt; Amundson, Lucas M.; Madden, Jeremy T.; Qian, Kuangnan; Kenttämaa, Hilkka I.

    2010-01-01

    Laser-induced acoustic desorption (LIAD) was successfully coupled to a conventional atmospheric pressure chemical ionization (APCI) source in a linear quadrupole ion trap mass spectrometer (LQIT). Model compounds representing a wide variety of different types, including basic nitrogen and oxygen compounds, aromatic and aliphatic compounds, as well as unsaturated and saturated hydrocarbons, were tested separately and as a mixture. These model compounds were successfully evaporated into the gas phase by using LIAD and then ionized by using APCI with different reagents. Four APCI reagent systems were tested: the traditionally used mixture of methanol and water, neat benzene, neat carbon disulfide, and nitrogen gas (no liquid reagent). The mixture of methanol and water produced primarily protonated molecules, as expected. However, only the most basic compounds yielded ions under these conditions. In sharp contrast, using APCI with either neat benzene or neat carbon disulfide as the reagent resulted in the ionization of all the analytes studied to predominantly yield stable molecular ions. Benzene yielded a larger fraction of protonated molecules than carbon disulfide, which is a disadvantage. A similar amount of fragmentation was observed for these reagents. When the experiment was performed without a liquid reagent(nitrogen gas was the reagent), more fragmentation was observed. Analysis of a known mixture as well as a petroleum cut was also carried out. In summary, the new experiment presented here allows the evaporation of thermally labile compounds, both polar and nonpolar, without dissociation or aggregation, and their ionization to form stable molecular ions. PMID:21472571

  13. Reduction of peak acoustic pressure and shaping of heated region by use of multifoci sonications in MR-guided high-intensity focused ultrasound mediated mild hyperthermia

    PubMed Central

    Partanen, Ari; Tillander, Matti; Yarmolenko, Pavel S.; Wood, Bradford J.; Dreher, Matthew R.; Köhler, Max O.

    2013-01-01

    Purpose: Ablative hyperthermia (>55 °C) has been used as a definitive treatment for accessible solid tumors not amenable to surgery, whereas mild hyperthermia (40–45 °C) has been shown effective as an adjuvant for both radiotherapy and chemotherapy. An optimal mild hyperthermia treatment is spatially accurate, with precise and homogeneous heating limited to the target region while also limiting the likelihood of unwanted thermal or mechanical bioeffects (tissue damage, vascular shutoff). Magnetic resonance imaging-guided high-intensity focused ultrasound (MR-HIFU) can noninvasively heat solid tumors under image-guidance. In a mild hyperthermia setting, a sonication approach utilizing multiple concurrent foci may provide the benefit of reducing acoustic pressure in the focal region (leading to reduced or no mechanical effects), while providing better control over the heating. The objective of this study was to design, implement, and characterize a multifoci sonication approach in combination with a mild hyperthermia heating algorithm, and compare it to the more conventional method of electronically sweeping a single focus. Methods: Simulations (acoustic and thermal) and measurements (acoustic, with needle hydrophone) were performed. In addition, heating performance of multifoci and single focus sonications was compared using a clinical MR-HIFU platform in a phantom (target = 4–16 mm), in normal rabbit thigh muscle (target = 8 mm), and in a Vx2 tumor (target = 8 mm). A binary control algorithm was used for real-time mild hyperthermia feedback control (target range = 40.5–41 °C). Data were analyzed for peak acoustic pressure and intensity, heating energy efficiency, temperature accuracy (mean), homogeneity of heating (standard deviation [SD], T10 and T90), diameter and length of the heated region, and thermal dose (CEM43). Results: Compared to the single focus approach, multifoci sonications showed significantly lower (67% reduction) peak acoustic

  14. Reproducibility experiments on measuring acoustical properties of rigid-frame porous media (round-robin tests).

    PubMed

    Horoshenkov, Kirill V; Khan, Amir; Bécot, François-Xavier; Jaouen, Luc; Sgard, Franck; Renault, Amélie; Amirouche, Nesrine; Pompoli, Francesco; Prodi, Nicola; Bonfiglio, Paolo; Pispola, Giulio; Asdrubali, Francesco; Hübelt, Jörn; Atalla, Noureddine; Amédin, Celse K; Lauriks, Walter; Boeckx, Laurens

    2007-07-01

    This paper reports the results of reproducibility experiments on the interlaboratory characterization of the acoustical properties of three types of consolidated porous media: granulated porous rubber, reticulated foam, and fiberglass. The measurements are conducted in several independent laboratories in Europe and North America. The studied acoustical characteristics are the surface complex acoustic impedance at normal incidence and plane wave absorption coefficient which are determined using the standard impedance tube method. The paper provides detailed procedures related to sample preparation and installation and it discusses the dispersion in the acoustical material property observed between individual material samples and laboratories. The importance of the boundary conditions, homogeneity of the porous material structure, and stability of the adopted signal processing method are highlighted.

  15. Intramuscular Pressure Measurement During Locomotion in Humans

    NASA Technical Reports Server (NTRS)

    Ballard, Ricard E.

    1996-01-01

    To assess the usefulness of intramuscular pressure (IMP) measurement for studying muscle function during gait, IMP was recorded in the soleus and tibialis anterior muscles of ten volunteers during, treadmill walking, and running using transducer-tipped catheters. Soleus IMP exhibited single peaks during late-stance phase of walking (181 +/- 69 mmHg, mean +/- S.E.) and running (269 +/- 95 mmHg). Tibialis anterior IMP showed a biphasic response, with the largest peak (90 +/- 15 mmHg during walking and 151 +/- 25 mmHg during running) occurring shortly after heel strike. IMP magnitude increased with gait speed in both muscles. Linear regression of soleus IMP against ankle joint torque obtained by a dynamometer in two subjects produced linear relationships (r = 0.97). Application of these relationships to IMP data yielded estimated peak soleus moment contributions of 0.95-165 Nm/Kg during walking, and 1.43-2.70 Nm/Kg during running. IMP results from local muscle tissue deformations caused by muscle force development and thus, provides a direct, practical index of muscle function during locomotion in humans.

  16. Observer error in blood pressure measurement.

    PubMed Central

    Neufeld, P D; Johnson, D L

    1986-01-01

    This paper describes an experiment undertaken to determine observer error in measuring blood pressure by the auscultatory method. A microcomputer was used to display a simulated mercury manometer and play back tape-recorded Korotkoff sounds synchronized with the fall of the mercury column. Each observer's readings were entered into the computer, which displayed a histogram of all readings taken up to that point and thus showed the variation among observers. The procedure, which could easily be adapted for use in teaching, was used to test 311 observers drawn from physicians, nurses, medical students, nursing students and others at nine health care institutions in Ottawa. The results showed a strong bias for even-digit readings and standard deviations of roughly 5 to 6 mm Hg. The standard deviation for the systolic readings was somewhat smaller for the physicians as a group than for the nurses (3.5 v. 5.9 mm Hg). However, the standard deviations for the diastolic readings were roughly equal for these two groups (approximately 5.5 mm Hg). Images Fig. 1 PMID:3756693

  17. Previous blood pressure measurement and associated factors in student adolescents

    PubMed Central

    Magalhães, Marina Gabriella Pereira de Andrada; Farah, Breno Quintella; de Barros, Mauro Virgilio Gomes; Ritti-Dias, Raphael Mendes

    2015-01-01

    Objective To identify prevalence of previous blood pressure measurement and analyze some associated factors in adolescents. Methods This cross-sectional study included 6,077 adolescents aged 14 to 19 years. Demographic characteristics included (sex, age, period of study, region of residence, work, skin color, and economic) status, history of blood pressure measurement within last 12 months, local of blood pressure measurement, and reading obtained. To assess associations between previous blood pressure measurement with demographic characteristics and high blood pressure we used descriptive statistics and logistic regression analysis. Results Out of the adolescents, 56.8% reported no blood pressure measurement within the last 12 months. The health centers and the physician’s office were most mentioned places for blood pressure measurement (28.3% and 36.9%, respectively). Boys (odds ratio of 1.64 95%CI: 1.46-1.84) aged 14 to 16 years (odds ratio of 1.12; 95%CI: 1.01-1.25), whose economic status was unfavorable (odds ratio of 1.48; 95%CI: 1.32-1.67) were significantly associated with no blood pressure measurement. Working was a protective factor for was not blood pressure measurement (odds ratio of 0.84; 95%CI: 0.73-0.97). Conclusion Most of adolescents did not have their blood pressure measured within the last 12 months. Boys aged 14 to 16 years and those with unfavorable economic status had higher chance of not having their blood pressure measured. PMID:26466061

  18. 21 CFR 870.1130 - Noninvasive blood pressure measurement system.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Noninvasive blood pressure measurement system. 870.1130 Section 870.1130 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN... Noninvasive blood pressure measurement system. (a) Identification. A noninvasive blood pressure...

  19. 21 CFR 870.1130 - Noninvasive blood pressure measurement system.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Noninvasive blood pressure measurement system. 870.1130 Section 870.1130 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN... Noninvasive blood pressure measurement system. (a) Identification. A noninvasive blood pressure...

  20. 21 CFR 870.1130 - Noninvasive blood pressure measurement system.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Noninvasive blood pressure measurement system. 870.1130 Section 870.1130 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN... Noninvasive blood pressure measurement system. (a) Identification. A noninvasive blood pressure...

  1. 21 CFR 870.1130 - Noninvasive blood pressure measurement system.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Noninvasive blood pressure measurement system. 870.1130 Section 870.1130 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN... Noninvasive blood pressure measurement system. (a) Identification. A noninvasive blood pressure...

  2. The phase transformation of methane caused by pressure change during its rising from seepage, revealed by acoustic reflection data

    NASA Astrophysics Data System (ADS)

    Aoyama, C.; Aoyama, S.

    2014-12-01

    The objective of this survey is to measure acoustical reflection from the methane plumes at close range by utilizing a remotely-operated vehicle, in order to quantify methane gas flux seeping out from shallow methane hydrates in the sea of japan. In the off-Joetsu area, we conducted acoustic survey for methane plumes distribution using quantitative echo sounder (Simrad EK60) and Multi beam echo sounder (SEABAT 8160) installed on R/V Natsushima, and then conducted underwater survey using ROV Hyper-Dolphin in the following methods, 1) Observing seafloor morphology, 2) Measurement methane discharge with a calibrated collecting equipment , 3) Measuring rising speed of methane bubbles with a ruler, 4) Collecting acoustic reflection data using quantitative echo sounder, 5) Observing rising methane bubbles. All processes in the underwater survey were recorded by a HD camera equipped on ROV, and those videos are used for after-cruise analysis. In the underwater survey by ROV, we found three methane plume points and successfully collected acoustic data which would detect each methane bubble. Based on videos and acoustic data obtained in this survey, detailed analysis conducted.

  3. Visualization and Measurements of Sound Pressure Distribution of Ultrasonic Wave by Stroboscopic Real-Time Holographic Interferometry

    NASA Astrophysics Data System (ADS)

    Hisada, Shigeyoshi; Suzuki, Takahiro; Nakahara, Sumio; Fujita, Takeyoshi

    2002-05-01

    The sound pressure distribution of underwater ultrasonic waves is measured by real-time stroboscope holographic interferometry using bismuth silicon oxide single crystal. Stroboscopic sub-microsecond irradiation of laser light enables the recording of the stationary holographic interferogram of refractive index changes of water by ultrasonic waves for the frame time of a charge coupled device camera. The fringe order distribution is calculated from the interferogram by Fourier transform fringe analysis. The optical path differences caused by sound field along the optical path are converted into local field values of sound pressure, which is displayed as a gray scale distribution image. In the experiment, the sound pressure distributions of ultrasonic waves through rectangular and circular apertures are observed. They are compared with the theoretical sound pressure distribution. The sound pressure values obtained by a hydrophone show good agreement with the measured values obtained by this method. The converging and diverging sound pressure fields realized by an acoustic lens are measured.

  4. Long-term continuous acoustical suspended-sediment measurements in rivers - Theory, application, bias, and error

    USGS Publications Warehouse

    Topping, David J.; Wright, Scott A.

    2016-05-04

    It is commonly recognized that suspended-sediment concentrations in rivers can change rapidly in time and independently of water discharge during important sediment‑transporting events (for example, during floods); thus, suspended-sediment measurements at closely spaced time intervals are necessary to characterize suspended‑sediment loads. Because the manual collection of sufficient numbers of suspended-sediment samples required to characterize this variability is often time and cost prohibitive, several “surrogate” techniques have been developed for in situ measurements of properties related to suspended-sediment characteristics (for example, turbidity, laser-diffraction, acoustics). Herein, we present a new physically based method for the simultaneous measurement of suspended-silt-and-clay concentration, suspended-sand concentration, and suspended‑sand median grain size in rivers, using multi‑frequency arrays of single-frequency side‑looking acoustic-Doppler profilers. The method is strongly grounded in the extensive scientific literature on the incoherent scattering of sound by random suspensions of small particles. In particular, the method takes advantage of theory that relates acoustic frequency, acoustic attenuation, acoustic backscatter, suspended-sediment concentration, and suspended-sediment grain-size distribution. We develop the theory and methods, and demonstrate the application of the method at six study sites on the Colorado River and Rio Grande, where large numbers of suspended-sediment samples have been collected concurrently with acoustic attenuation and backscatter measurements over many years. The method produces acoustical measurements of suspended-silt-and-clay and suspended-sand concentration (in units of mg/L), and acoustical measurements of suspended-sand median grain size (in units of mm) that are generally in good to excellent agreement with concurrent physical measurements of these quantities in the river cross sections at

  5. Measurement of a broadband negative index with space-coiling acoustic metamaterials.

    PubMed

    Xie, Yangbo; Popa, Bogdan-Ioan; Zigoneanu, Lucian; Cummer, Steven A

    2013-04-26

    We report the experimental demonstration of a broadband negative refractive index obtained in a labyrinthine acoustic metamaterial structure. Two different approaches were employed to prove the metamaterial negative index nature: one-dimensional extractions of effective parameters from reflection and transmission measurements and two-dimensional prism-based measurements that convincingly show the transmission angle corresponding to negative refraction. The transmission angles observed in the latter case also agree very well with the refractive index obtained in the one-dimensional measurements and numerical simulations. We expect this labyrinthine metamaterial to become the unit cell of choice for practical acoustic metamaterial devices that require broadband and significantly negative indices of refraction.

  6. [An integrated system of blood pressure measurement with bluetooth communication].

    PubMed

    Wang, Wei; Wang, Jing; Sun, Hongyang; Xu, Zuyang; Chai, Xinyu

    2012-07-01

    The development of the integrated blood pressure system with bluetooth communication function is introduced. Experimental results show that the system can complete blood pressure measurement and data transmission wireless effectively, which can be used in m-Health in future.

  7. Rotor Blade Pressure Measurement in a Rotating Machinery Using Pressure and Temperature Sensitive Paints

    NASA Technical Reports Server (NTRS)

    Torgerson, S.; Liu, T.; Sullivan, J.

    1998-01-01

    Pressure and temperature sensitive paints have been utilized for the measurement of blade surface pressure and temperature distributions in a high speed axial compressor and an Allied Signal F109 gas turbine engine. Alternate blades were painted with temperature sensitive paints and then pressure sensitive paint. This combination allows temperature distributions to be accounted for when determining the blade suction surface pressure distribution. Measurements were taken and pressure maps on the suction surface of a blade were obtained over a range of rotational speeds. Pressure maps of the suction surface show-strong shock waves at the higher speeds.

  8. Noninvasive Measurement of Central Vascular Pressures With Arterial Tonometry: Clinical Revival of the Pulse Pressure Waveform?

    PubMed Central

    Nelson, Matthew R.; Stepanek, Jan; Cevette, Michael; Covalciuc, Michael; Hurst, R. Todd; Tajik, A. Jamil

    2010-01-01

    The arterial pulse has historically been an essential source of information in the clinical assessment of health. With current sphygmomanometric and oscillometric devices, only the peak and trough of the peripheral arterial pulse waveform are clinically used. Several limitations exist with peripheral blood pressure. First, central aortic pressure is a better predictor of cardiovascular outcome than peripheral pressure. Second, peripherally obtained blood pressure does not accurately reflect central pressure because of pressure amplification. Lastly, antihypertensive medications have differing effects on central pressures despite similar reductions in brachial blood pressure. Applanation tonometry can overcome the limitations of peripheral pressure by determining the shape of the aortic waveform from the radial artery. Waveform analysis not only indicates central systolic and diastolic pressure but also determines the influence of pulse wave reflection on the central pressure waveform. It can serve as a useful adjunct to brachial blood pressure measurements in initiating and monitoring hypertensive treatment, in observing the hemodynamic effects of atherosclerotic risk factors, and in predicting cardiovascular outcomes and events. Radial artery applanation tonometry is a noninvasive, reproducible, and affordable technology that can be used in conjunction with peripherally obtained blood pressure to guide patient management. Keywords for the PubMed search were applanation tonometry, radial artery, central pressure, cardiovascular risk, blood pressure, and arterial pulse. Articles published from January 1, 1995, to July 1, 2009, were included in the review if they measured central pressure using radial artery applanation tonometry. PMID:20435839

  9. Wideband Acoustic Immittance: Normative Study and Test-Retest Reliability of Tympanometric Measurements in Adults

    ERIC Educational Resources Information Center

    Sun, Xiao-Ming

    2016-01-01

    Purpose: The purpose of this study was to present normative data of tympanometric measurements of wideband acoustic immittance and to characterize wideband tympanograms. Method: Data were collected in 84 young adults with strictly defined normal hearing and middle ear status. Energy absorbance (EA) was measured using clicks for 1/12-octave…

  10. Acoustic measurement of suspensions of clay and silt particles using single frequency attenuation and backscatter

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The use of ultrasonic acoustic technology to measure the concentration of fine suspended sediments has the potential to greatly increase the temporal and spatial resolution of sediment measurements while reducing the need for personnel to be present at gauging stations during storm events. The conv...

  11. Final Report: Geothermal dual acoustic tool for measurement of rock stress

    SciTech Connect

    Normann, Randy A.

    2014-12-01

    This paper outlines the technology need for a rock formation stress measurement in future EGS wells. This paper reports on the results of work undertaken under a Phase I, DOE/SBIR on the feasibility to build an acoustic well logging tool for measuring rock formation stress.

  12. Final Report. Geothermal Dual Acoustic Tool for Measurement of Rock Stress

    SciTech Connect

    Normann, Randy A

    2014-12-01

    This paper outlines the technology need for a rock formation stress measurement in future EGS wells. This paper reports on the results of work undertaken under a Phase I, DOE/SBIR on the feasibility to build an acoustic well logging tool for measuring rock formation stress.

  13. Measurement Corner: Volume, Temperature and Pressure

    ERIC Educational Resources Information Center

    Teates, Thomas G.

    1977-01-01

    Boyle's Law and basic relationships between volume and pressure of a gas at constant temperature are presented. Suggests two laboratory activities for demonstrating the effect of temperature on the volume of a gas or liquid. (CS)

  14. [Measurement of blood pressure variability and the clinical value].

    PubMed

    Kékes, Ede; Kiss, István

    2014-10-19

    Authors have collected and analyzed literature data on blood pressure variability. They present the methods of blood pressure variability measurement, clinical value and relationships with target organ damages and risk of presence of cardiovascular events. They collect data about the prognostic value of blood pressure variability and the effects of different antihypertensive drugs on blood pressure variability. They underline that in addition to reduction of blood pressure to target value, it is essential to influence blood pressure fluctuation and decrease blood pressure variability, because blood pressure fluctuation presents a major threat for the hypertensive subjects. Data from national studies are also presented. They welcome that measurement of blood pressure variability has been included in international guidelines.

  15. Measurement of Aqueous Foam Rheology by Acoustic Levitation

    NASA Technical Reports Server (NTRS)

    McDaniel, J. Gregory; Holt, R. Glynn; Rogers, Rich (Technical Monitor)

    2000-01-01

    An experimental technique is demonstrated for acoustically levitating aqueous foam drops and exciting their spheroidal modes. This allows fundamental studies of foam-drop dynamics that provide an alternative means of estimating the viscoelastic properties of the foam. One unique advantage of the technique is the lack of interactions between the foam and container surfaces, which must be accounted for in other techniques. Results are presented in which a foam drop with gas volume fraction phi = 0.77 is levitated at 30 kHz and excited into its first quadrupole resonance at 63 +/- 3 Hz. By modeling the drop as an elastic sphere, the shear modulus of the foam was estimated at 75 +/- 3 Pa.

  16. Measuring the speed of light with baryon acoustic oscillations.

    PubMed

    Salzano, Vincenzo; Dąbrowski, Mariusz P; Lazkoz, Ruth

    2015-03-13

    In this Letter, we describe a new method to use baryon acoustic oscillations (BAO) to derive a constraint on the possible variation of the speed of light. The method relies on the fact that there is a simple relation between the angular diameter distance (D(A)) maximum and the Hubble function (H) evaluated at the same maximum-condition redshift, which includes speed of light c. We note the close analogy of the BAO probe with a laboratory experiment: here we have D(A) which plays the role of a standard (cosmological) ruler, and H^{-1}, with the dimension of time, as a (cosmological) clock. We evaluate if current or future missions such as Euclid can be sensitive enough to detect any variation of c.

  17. Studies of acoustical properties of bulk porous flexible materials

    NASA Technical Reports Server (NTRS)

    Lambert, R. F.

    1984-01-01

    Acoustic prediction and measurement of bulk porous materials with flexible frames is investigated. The acoustic properties of Kevlar 29 are examined. Various acoustic tests are employed to determine impedance, sound wave propagation, and wave pressure equations for the highly porous fiber composites. The derivation of design equations and future research goals are included.

  18. Comparison of cosmology and seabed acoustics measurements using statistical inference from maximum entropy

    NASA Astrophysics Data System (ADS)

    Knobles, David; Stotts, Steven; Sagers, Jason

    2012-03-01

    Why can one obtain from similar measurements a greater amount of information about cosmological parameters than seabed parameters in ocean waveguides? The cosmological measurements are in the form of a power spectrum constructed from spatial correlations of temperature fluctuations within the microwave background radiation. The seabed acoustic measurements are in the form of spatial correlations along the length of a spatial aperture. This study explores the above question from the perspective of posterior probability distributions obtained from maximizing a relative entropy functional. An answer is in part that the seabed in shallow ocean environments generally has large temporal and spatial inhomogeneities, whereas the early universe was a nearly homogeneous cosmological soup with small but important fluctuations. Acoustic propagation models used in shallow water acoustics generally do not capture spatial and temporal variability sufficiently well, which leads to model error dominating the statistical inference problem. This is not the case in cosmology. Further, the physics of the acoustic modes in cosmology is that of a standing wave with simple initial conditions, whereas for underwater acoustics it is a traveling wave in a strongly inhomogeneous bounded medium.

  19. a Rayleigh Wave Technique to Measure the Acoustic Nonlinearity Parameter of Materials

    NASA Astrophysics Data System (ADS)

    Shui, G.; Jacobs, L. J.; Qu, J.; Wang, Y. S.; Kim, J.-Y.

    2008-02-01

    Nonlinear ultrasonic techniques have shown great potential for evaluating accumulated damage early in the fatigue life, and ultimately for predicting remaining lifetime of a structural component. The acoustic nonlinearity parameter, a direct measure of the accumulated fatigue damage, is determined from the second harmonic amplitude in finite amplitude sinusoidal ultrasonic waves transmitted through the material. An absolute determination of the acoustic nonlinear parameter is notoriously difficult for several reasons. In this paper, a new experimental technique based on Rayleigh surface waves is presented for determining the absolute acoustic nonlinearity parameter of a relatively thin material specimen. Rayleigh waves are efficiently generated in a specimen by exciting at its edge, and the surface normal velocity of the propagating Rayleigh waves is measured with a laser interferometer system. The high efficiency of the excitation method allows us to drive the transmitting piezoelectric transducer as low as 60 Vpp, and thus to avoid the inherent harmonic distortion from the transducer. The absolute acoustic nonlinearity parameter is then determined from the measured magnitudes of the fundamental and second harmonic surface normal velocities. This technique is applied to determining the acoustic nonlinearity parameters of aluminum alloys 2024 and 6061; the results are compared with those available in the literature. The present technique is especially well-suited for relatively thin components, and much simpler and efficient than the traditional longitudinal wave technique.

  20. Measuring Ultrasonic Acoustic Velocity in a Thin Sheet of Graphite Epoxy Composite

    NASA Technical Reports Server (NTRS)

    2008-01-01

    A method for measuring the acoustic velocity in a thin sheet of a graphite epoxy composite (GEC) material was investigated. This method uses two identical acoustic-emission (AE) sensors, one to transmit and one to receive. The delay time as a function of distance between sensors determines a bulk velocity. A lightweight fixture (balsa wood in the current implementation) provides a consistent method of positioning the sensors, thus providing multiple measurements of the time delay between sensors at different known distances. A linear fit to separation, x, versus delay time, t, will yield an estimate of the velocity from the slope of the line.