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Sample records for acoustic transmission measurements

  1. 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.

  2. 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.

  3. Random and systematic measurement errors in acoustic impedance as determined by the transmission line method

    NASA Technical Reports Server (NTRS)

    Parrott, T. L.; Smith, C. D.

    1977-01-01

    The effect of random and systematic errors associated with the measurement of normal incidence acoustic impedance in a zero-mean-flow environment was investigated by the transmission line method. The influence of random measurement errors in the reflection coefficients and pressure minima positions was investigated by computing fractional standard deviations of the normalized impedance. Both the standard techniques of random process theory and a simplified technique were used. Over a wavelength range of 68 to 10 cm random measurement errors in the reflection coefficients and pressure minima positions could be described adequately by normal probability distributions with standard deviations of 0.001 and 0.0098 cm, respectively. An error propagation technique based on the observed concentration of the probability density functions was found to give essentially the same results but with a computation time of about 1 percent of that required for the standard technique. The results suggest that careful experimental design reduces the effect of random measurement errors to insignificant levels for moderate ranges of test specimen impedance component magnitudes. Most of the observed random scatter can be attributed to lack of control by the mounting arrangement over mechanical boundary conditions of the test sample.

  4. Pneumothorax effects on pulmonary acoustic transmission

    PubMed Central

    Balk, Robert A.; Warren, William H.; Royston, Thomas J.; Dai, Zoujun; Peng, Ying; Sandler, Richard H.

    2015-01-01

    Pneumothorax (PTX) is an abnormal accumulation of air between the lung and the chest wall. It is a relatively common and potentially life-threatening condition encountered in patients who are critically ill or have experienced trauma. Auscultatory signs of PTX include decreased breath sounds during the physical examination. The objective of this exploratory study was to investigate the changes in sound transmission in the thorax due to PTX in humans. Nineteen human subjects who underwent video-assisted thoracic surgery, during which lung collapse is a normal part of the surgery, participated in the study. After subjects were intubated and mechanically ventilated, sounds were introduced into their airways via an endotracheal tube. Sounds were then measured over the chest surface before and after lung collapse. PTX caused small changes in acoustic transmission for frequencies below 400 Hz. A larger decrease in sound transmission was observed from 400 to 600 Hz, possibly due to the stronger acoustic transmission blocking of the pleural air. At frequencies above 1 kHz, the sound waves became weaker and so did their changes with PTX. The study elucidated some of the possible mechanisms of sound propagation changes with PTX. Sound transmission measurement was able to distinguish between baseline and PTX states in this small patient group. Future studies are needed to evaluate this technique in a wider population. PMID:26023225

  5. Pneumothorax effects on pulmonary acoustic transmission.

    PubMed

    Mansy, Hansen A; Balk, Robert A; Warren, William H; Royston, Thomas J; Dai, Zoujun; Peng, Ying; Sandler, Richard H

    2015-08-01

    Pneumothorax (PTX) is an abnormal accumulation of air between the lung and the chest wall. It is a relatively common and potentially life-threatening condition encountered in patients who are critically ill or have experienced trauma. Auscultatory signs of PTX include decreased breath sounds during the physical examination. The objective of this exploratory study was to investigate the changes in sound transmission in the thorax due to PTX in humans. Nineteen human subjects who underwent video-assisted thoracic surgery, during which lung collapse is a normal part of the surgery, participated in the study. After subjects were intubated and mechanically ventilated, sounds were introduced into their airways via an endotracheal tube. Sounds were then measured over the chest surface before and after lung collapse. PTX caused small changes in acoustic transmission for frequencies below 400 Hz. A larger decrease in sound transmission was observed from 400 to 600 Hz, possibly due to the stronger acoustic transmission blocking of the pleural air. At frequencies above 1 kHz, the sound waves became weaker and so did their changes with PTX. The study elucidated some of the possible mechanisms of sound propagation changes with PTX. Sound transmission measurement was able to distinguish between baseline and PTX states in this small patient group. Future studies are needed to evaluate this technique in a wider population. PMID:26023225

  6. Asymmetric acoustic transmission in multiple frequency bands

    SciTech Connect

    Sun, Hong-xiang; Yuan, Shou-qi; Zhang, Shu-yi

    2015-11-23

    We report both experimentally and numerically that the multi-band device of the asymmetric acoustic transmission is realized by placing two periodic gratings with different periods on both sides of two brass plates immersed in water. The asymmetric acoustic transmission can exist in four frequency bands below 1500 kHz, which arises from the interaction between various diffractions from the two gratings and Lamb modes in the brass plates immersed in water. The results indicate that the device has the advantages of multiple band, broader bandwidth, and simpler structure. Our finding should have great potential applications in ultrasonic devices.

  7. Acoustic energy transmission in cast iron pipelines

    NASA Astrophysics Data System (ADS)

    Kiziroglou, Michail E.; Boyle, David E.; Wright, Steven W.; Yeatman, Eric M.

    2015-12-01

    In this paper we propose acoustic power transfer as a method for the remote powering of pipeline sensor nodes. A theoretical framework of acoustic power propagation in the ceramic transducers and the metal structures is drawn, based on the Mason equivalent circuit. The effect of mounting on the electrical response of piezoelectric transducers is studied experimentally. Using two identical transducer structures, power transmission of 0.33 mW through a 1 m long, 118 mm diameter cast iron pipe, with 8 mm wall thickness is demonstrated, at 1 V received voltage amplitude. A near-linear relationship between input and output voltage is observed. These results show that it is possible to deliver significant power to sensor nodes through acoustic waves in solid structures. The proposed method may enable the implementation of acoustic - powered wireless sensor nodes for structural and operation monitoring of pipeline infrastructure.

  8. 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

  9. Impedance matched joined drill pipe for improved acoustic transmission

    DOEpatents

    Moss, William C.

    2000-01-01

    An impedance matched jointed drill pipe for improved acoustic transmission. A passive means and method that maximizes the amplitude and minimize the temporal dispersion of acoustic signals that are sent through a drill string, for use in a measurement while drilling telemetry system. The improvement in signal transmission is accomplished by replacing the standard joints in a drill string with joints constructed of a material that is impedance matched acoustically to the end of the drill pipe to which it is connected. Provides improvement in the measurement while drilling technique which can be utilized for well logging, directional drilling, and drilling dynamics, as well as gamma-ray spectroscopy while drilling post shot boreholes, such as utilized in drilling post shot boreholes.

  10. Acoustic cloaking by extraordinary sound transmission

    NASA Astrophysics Data System (ADS)

    Zhao, Jiajun; Chen, Zhi Ning; Li, Baowen; Qiu, Cheng-Wei

    2015-06-01

    Isotropic acoustic cloaking is proposed using density-near-zero materials for extraordinary sound transmission. The cloaking cell is made by single-piece homogeneous elastic copper, which can be detached and assembled arbitrarily. We theoretically and numerically demonstrate the cloaking performance by deploying density-near-zero cells in various ways in two-dimensional space as well as in acoustic waveguides. The density-near-zero material can make any inside objects imperceptible along undistorted sound paths. Individually and collectively, the cloaking cell maintains both the planar wavefront and the nearly perfect one-dimensional transmission, in presence of any inserted object. The overall cloaked space can be designed by adding cells without the limit of the total cloaked volume.

  11. Acoustic data transmission through a drillstring

    DOEpatents

    Drumheller, Douglas S.

    1992-01-01

    A method and apparatus for acoustically transmitting data along a drillstring is presented. In accordance with one embodiment of the present invention, acoustic data signals are conditioned to counteract distortions caused by the drillstring. Preferably, this conditioning step comprises multiplying each frequency component of the data signal by exp (-ikL) where L is the transmission length of the drillstring, k is the wave number in the drillstring at the frequency of each component and i is (-1).sup.1/2. In another embodiment of this invention, data signals having a frequency content in at least one passband of the drillstring are generated preferably traveling in only one direction (e.g., up the drillstring) while echoes in the drillstring resulting from the data transmission are suppressed.

  12. Acoustic data transmission through a drillstring

    DOEpatents

    Drumheller, D.S.

    1992-07-07

    A method and apparatus for acoustically transmitting data along a drillstring are presented. In accordance with one embodiment of the present invention, acoustic data signals are conditioned to counteract distortions caused by the drillstring. Preferably, this conditioning step comprises multiplying each frequency component of the data signal by exp ([minus]ikL) where L is the transmission length of the drillstring, k is the wave number in the drillstring at the frequency of each component and i is ([minus]1)[sup 1/2]. In another embodiment of this invention, data signals having a frequency content in at least one passband of the drillstring are generated preferably traveling in only one direction (e.g., up the drillstring) while echoes in the drillstring resulting from the data transmission are suppressed. 20 figs.

  13. 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

  14. 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

  15. Acoustic asymmetric transmission based on time-dependent dynamical scattering

    PubMed Central

    Wang, Qing; Yang, Yang; Ni, Xu; Xu, Ye-Long; Sun, Xiao-Chen; Chen, Ze-Guo; Feng, Liang; Liu, Xiao-ping; Lu, Ming-Hui; Chen, Yan-Feng

    2015-01-01

    An acoustic asymmetric transmission device exhibiting unidirectional transmission property for acoustic waves is extremely desirable in many practical scenarios. Such a unique property may be realized in various configurations utilizing acoustic Zeeman effects in moving media as well as frequency-conversion in passive nonlinear acoustic systems and in active acoustic systems. Here we demonstrate a new acoustic frequency conversion process in a time-varying system, consisting of a rotating blade and the surrounding air. The scattered acoustic waves from this time-varying system experience frequency shifts, which are linearly dependent on the blade’s rotating frequency. Such scattering mechanism can be well described theoretically by an acoustic linear time-varying perturbation theory. Combining such time-varying scattering effects with highly efficient acoustic filtering, we successfully develop a tunable acoustic unidirectional device with 20 dB power transmission contrast ratio between two counter propagation directions at audible frequencies. PMID:26038886

  16. Extraordinary acoustic transmission mediated by Helmholtz resonators

    SciTech Connect

    Koju, Vijay; Rowe, Ebony; Robertson, William M.

    2014-07-15

    We demonstrate perfect transmission of sound through a rigid barrier embedded with Helmholtz resonators. The resonators are confined within a waveguide and they are oriented such that one neck protrudes onto each side of the barrier. Perfect sound transmission occurs even though the open area of the necks is less than 3% of the barrier area. Maximum transmission occurs at the resonant frequency of the Helmholtz resonator. Because the dimensions of the Helmholtz resonators are much smaller than the resonant wavelength, the transmission is independent of the direction of sound on the barrier and of the relative placement of the necks. Further, we show that the transmitted sound experiences a continuous phase transition of π radians as a function of frequency through resonance. In simulations of adjacent resonators with slightly offset resonance frequencies, the phase difference leads to destructive interference. By expanding the simulation to a linear array of tuned Helmholtz resonators we show that it is possible to create an acoustic lens. The ability of Helmholtz resonator arrays to manipulate the phase of a plane acoustic wave enables a new class of sonic beam-forming devices analogous to diffractive optics.

  17. Acoustic transmission through compound subwavelength slit arrays

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  18. Comparison of Transmission Line Methods for Surface Acoustic Wave Modeling

    NASA Technical Reports Server (NTRS)

    Wilson, William; Atkinson, Gary

    2009-01-01

    Surface Acoustic Wave (SAW) technology is low cost, rugged, lightweight, extremely low power and can be used to develop passive wireless sensors. For these reasons, NASA is investigating the use of SAW technology for Integrated Vehicle Health Monitoring (IVHM) of aerospace structures. To facilitate rapid prototyping of passive SAW sensors for aerospace applications, SAW models have been developed. This paper reports on the comparison of three methods of modeling SAWs. The three models are the Impulse Response Method (a first order model), and two second order matrix methods; the conventional matrix approach, and a modified matrix approach that is extended to include internal finger reflections. The second order models are based upon matrices that were originally developed for analyzing microwave circuits using transmission line theory. Results from the models are presented with measured data from devices. Keywords: Surface Acoustic Wave, SAW, transmission line models, Impulse Response Method.

  19. Dispersion and mirror transmission characteristics of bulk acoustic wave resonators.

    PubMed

    Kokkonen, Kimmo; Pensala, Tuomas; Kaivola, Matti

    2011-01-01

    A heterodyne laser interferometer is used for a detailed study of the acoustic wave fields excited in a 932-MHz solidly mounted ZnO thin-film BAW resonator. The sample is manufactured on a glass substrate, which also allows direct measurement of the vibration fields from the bottom of the acoustic mirror. Vibration fields are measured both on top of the resonator and at the mirror-substrate interface in a frequency range of 350 to 1200 MHz. Plate wave dispersion diagrams are calculated from the experimental data in both cases and the transmission characteristics of the acoustic mirror are determined as a function of both frequency and lateral wave number. The experimental data are compared with 1-D and 2-D simulations to evaluate the validity of the modeling tools commonly used in mirror design. All the major features observed in the 1-D model are identified in the measured dispersion diagrams, and the mirror transmission characteristics predicted for the longitudinal waves, by both the 1-D and the 2-D models, match the measured values well. PMID:21244989

  20. Acoustic transmission across a roughened fluid-fluid interface.

    PubMed

    Lim, R; Paustian, I C; Lopes, J L

    2001-04-01

    A set of tank experiments was performed to investigate acoustic transmission across a roughened fluid-fluid interface with the intention to test heuristic Bragg scattering predictions used to explain observations of anomalous transmission in field experiments. In the tank experiments, two immiscible fluids (vegetable oil floating on glycerin) formed the layers. Small polystyrene beads were floated at the interface to simulate roughness. An array of hydrophones placed in the bottom layer (glycerin) was used to measure the acoustic levels transmitted across the interface. This array was also employed as a beamformer to determine the apparent angle and sound speed of the scattered signals. Data were acquired at subcritical grazing angles in the frequency range of 100-200 kHz for three different bead diameters and for various configurations in which the locations of the beads floating on the interface were varied. Results of these measurements demonstrated that a significant amount of acoustic energy can be scattered into the bottom layer by beads floating at the interface. The scattered levels increased with increasing bead diameter. However, discrepancies occurred between observed propagation properties and the Bragg predictions. By comparing the processed tank data to a computer simulation of the same it was determined that these discrepancies are a consequence of near-field reception of the scattering by the bead array and ignoring the directionality of the scattering by the beads. Consequences to observations made in field experiments are discussed. PMID:11325108

  1. Acoustic data transmission through a drill string

    DOEpatents

    Drumheller, D.S.

    1988-04-21

    Acoustical signals are transmitted through a drill string by canceling upward moving acoustical noise and by preconditioning the data in recognition of the comb filter impedance characteristics of the drill string. 5 figs.

  2. INSTRUMENTATION FOR SURVEYING ACOUSTIC SIGNALS IN NATURAL GAS TRANSMISSION LINES

    SciTech Connect

    John L. Loth; Gary J. Morris; George M. Palmer; Richard Guiler; Deepak Mehra

    2003-09-01

    In the U.S. natural gas is distributed through more than one million miles of high-pressure transmission pipelines. If all leaks and infringements could be detected quickly, it would enhance safety and U.S. energy security. Only low frequency acoustic waves appear to be detectable over distances up to 60 km where pipeline shut-off valves provide access to the inside of the pipeline. This paper describes a Portable Acoustic Monitoring Package (PAMP) developed to record and identify acoustic signals characteristic of: leaks, pump noise, valve and flow metering noise, third party infringement, manual pipeline water and gas blow-off, etc. This PAMP consists of a stainless steel 1/2 inch NPT plumbing tree rated for use on 1000 psi pipelines. Its instrumentation is designed to measure acoustic waves over the entire frequency range from zero to 16,000 Hz by means of four instruments: (1) microphone, (2) 3-inch water full range differential pressure transducer with 0.1% of range sensitivity, (3) a novel 3 inch to 100 inch water range amplifier, using an accumulator with needle valve and (4) a line-pressure transducer. The weight of the PAMP complete with all accessories is 36 pounds. This includes a remote control battery/switch box assembly on a 25-foot extension chord, a laptop data acquisition computer on a field table and a sun shield.

  3. Broadband enhanced transmission of acoustic waves through serrated metal gratings

    NASA Astrophysics Data System (ADS)

    Qi, Dong-Xiang; Fan, Ren-Hao; Deng, Yu-Qiang; Peng, Ru-Wen; Wang, Mu; Jiangnan University Collaboration

    In this talk, we present our studies on broadband properties of acoustic waves through metal gratings. We have demonstrated that serrated metal gratings, which introduce gradient coatings, can give rise to broadband transmission enhancement of acoustic waves. Here, we have experimentally and theoretically studied the acoustic transmission properties of metal gratings with or without serrated boundaries. The average transmission is obviously enhanced for serrated metal gratings within a wide frequency range, while the Fabry-Perot resonance is significantly suppressed. An effective medium hypothesis with varying acoustic impedance is proposed to analyze the mechanism, which was verified through comparison with finite-element simulation. The serrated boundary supplies gradient mass distribution and gradient normal acoustic impedance, which could efficiently reduce the boundary reflection. Further, by increasing the region of the serrated boundary, we present a broadband high-transmission grating for wide range of incident angle. Our results may have potential applications to broadband acoustic imaging, acoustic sensing and new acoustic devices. References: [1] Dong-Xiang Qi, Yu-Qiang Deng, Di-Hu Xu, Ren-Hao Fan, Ru-Wen Peng, Ze-Guo Chen, Ming-Hui Lu, X. R. Huang and Mu Wang, Appl. Phys. Lett. 106, 011906 (2015); [2] Dong-Xiang Qi, Ren-Hao Fan, Ru-Wen Peng, Xian-Rong Huang, Ming-Hui Lu, Xu Ni, Qing Hu, and Mu Wang, Applied Physics Letters 101, 061912 (2012).

  4. Extraordinary acoustic transmission through annuluses in air and its applications in acoustic beam splitter and concentrator

    NASA Astrophysics Data System (ADS)

    Ge, Yong; Sun, Hong-xiang; Liu, Shu-sen; Yuan, Shou-qi; Xia, Jian-ping; Guan, Yi-jun; Zhang, Shu-yi

    2016-08-01

    We report an extraordinary acoustic transmission through two layer annuluses made of metal cylinders in air both numerically and experimentally. The effect arises from the enhancement and reconstruction of the incident source induced by different Mie-resonance modes of the annuluses. The proposed system takes advantages of the consistency in the waveform between the input and output waves, the high amplitude amplification of output waves, and the easy adjustment of structure. More interestingly, we investigate the applications of the extraordinary acoustic transmission in the acoustic beam splitter and acoustic concentrator. Our finding should have an impact on ultrasonic applications.

  5. Extraordinary acoustic transmission through annuluses in air and its applications in acoustic beam splitter and concentrator.

    PubMed

    Ge, Yong; Sun, Hong-Xiang; Liu, Shu-Sen; Yuan, Shou-Qi; Xia, Jian-Ping; Guan, Yi-Jun; Zhang, Shu-Yi

    2016-08-01

    We report an extraordinary acoustic transmission through two layer annuluses made of metal cylinders in air both numerically and experimentally. The effect arises from the enhancement and reconstruction of the incident source induced by different Mie-resonance modes of the annuluses. The proposed system takes advantages of the consistency in the waveform between the input and output waves, the high amplitude amplification of output waves, and the easy adjustment of structure. More interestingly, we investigate the applications of the extraordinary acoustic transmission in the acoustic beam splitter and acoustic concentrator. Our finding should have an impact on ultrasonic applications. PMID:27587144

  6. Comparison of Computational Aeroacoustics Prediction of Acoustic Transmission Through a 3D Stator With Experiment

    NASA Technical Reports Server (NTRS)

    Hixon, Ray; Envia, Edmane; Dahl, Milo; Sutliff, Daniel L.

    2014-01-01

    In this paper, numerical predictions of acoustic transmission through a 3D stator obtained using the NASA BASS code are compared with experimentally measured data. The influence of vane count and stagger as well as frequency and mode order on the transmission loss is investigated. The data-theory comparisons indicate that BASS can predict all the important trends observed in the experimental data.

  7. Comparison of Computational Aeroacoustics Prediction of Acoustic Transmission Through a 3D Stator with Experiment

    NASA Technical Reports Server (NTRS)

    Hixon, Ray; Envia, Edmane; Dahl, Milo; Sutliff, Daniel

    2014-01-01

    In this paper, numerical predictions of acoustic transmission through a 3D stator obtained using the NASA BASS code are compared with experimentally measured data. The influence of vane count and stagger as well as frequency and mode order on the transmission loss is investigated. The data-theory comparisons indicate that BASS can predict all the important trends observed in the experimental data.

  8. 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.

  9. Transmission Characteristics of Primate Vocalizations: Implications for Acoustic Analyses

    PubMed Central

    Maciej, Peter; Fischer, Julia; Hammerschmidt, Kurt

    2011-01-01

    Acoustic analyses have become a staple method in field studies of animal vocal communication, with nearly all investigations using computer-based approaches to extract specific features from sounds. Various algorithms can be used to extract acoustic variables that may then be related to variables such as individual identity, context or reproductive state. Habitat structure and recording conditions, however, have strong effects on the acoustic structure of sound signals. The purpose of this study was to identify which acoustic parameters reliably describe features of propagated sounds. We conducted broadcast experiments and examined the influence of habitat type, transmission height, and re-recording distance on the validity (deviation from the original sound) and reliability (variation within identical recording conditions) of acoustic features of different primate call types. Validity and reliability varied independently of each other in relation to habitat, transmission height, and re-recording distance, and depended strongly on the call type. The smallest deviations from the original sounds were obtained by a visually-controlled calculation of the fundamental frequency. Start- and end parameters of a sound were most susceptible to degradation in the environment. Because the recording conditions can have appreciable effects on acoustic parameters, it is advisable to validate the extraction method of acoustic variables from recordings over longer distances before using them in acoustic analyses. PMID:21829682

  10. Experimental realization of extraordinary acoustic transmission using Helmholtz resonators

    SciTech Connect

    Crow, Brian C.; Cullen, Jordan M.; McKenzie, William W.; Koju, Vijay; Robertson, William M.

    2015-02-15

    The phenomenon of extraordinary acoustic transmission through a solid barrier with an embedded Helmholtz resonator (HR) is demonstrated. The Helmholtz resonator consists of an embedded cavity and two necks that protrude, one on each side of the barrier. Extraordinary transmission occurs for a narrow spectral range encompassing the resonant frequency of the Helmholtz resonator. We show that an amplitude transmission of 97.5% is achieved through a resonator whose neck creates an open area of 6.25% of the total barrier area. In addition to the enhanced transmission, we show that there is a smooth, continuous phase transition in the transmitted sound as a function of frequency. The frequency dependent phase transition is used to experimentally realize slow wave propagation for a narrow-band Gaussian wave packet centered at the maximum transmission frequency. The use of parallel pairs of Helmholtz resonators tuned to different resonant frequencies is experimentally explored as a means of increasing the transmission bandwidth. These experiments show that because of the phase transition, there is always a frequency between the two Helmholtz resonant frequencies at which destructive interference occurs whether the resonances are close or far apart. Finally, we explain how the phase transition associated with Helmholtz-resonator-mediated extraordinary acoustic transmission can be exploited to produce diffractive acoustic components including sub-wavelength thickness acoustic lenses.

  11. 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.

  12. 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. PMID:12656385

  13. 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.

  14. Time reversal acoustic communication for multiband transmission.

    PubMed

    Song, Aijun; Badiey, Mohsen

    2012-04-01

    In this letter, multiband acoustic communication is proposed to access a relatively wide frequency band. The entire frequency band is divided into multiple separated sub-bands, each of which is several kilohertz in width. Time reversal decision feedback equalizers are used to compensate for inter-symbol interference at each sub-band. The communication scheme was demonstrated in a shallow water acoustic experiment conducted in Kauai, Hawaii during the summer of 2011. Using quadrature phase-shift keying signaling at four sub-bands over the frequency band of 10-32 kHz, a data rate of 32 k bits/s was achieved over a 3 km communication range. PMID:22502482

  15. 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).

  16. Pulsed EMAT (Electromagnetic Acoustic Transducer) acoustic measurements on a horizontal continuous caster for internal temperature determination

    NASA Astrophysics Data System (ADS)

    Boyd, Donald M.

    1989-10-01

    Development of a Pulsed Electromagnetic Acoustic Transducer (EMAT) through transmission system for acoustic measurements on steel billets up to 1300 C was completed. Laboratory measurements of acoustic velocity were made, and used to determine the average internal temperature of hot stainless and carbon steel billets. Following the success of the laboratory system development, the laboratory EMAT system was subsequently tested successfully at the Baltimore Specialty Steel Co. on a horizontal continuous caster. Details of the sensor system development and the steel plant demonstration results are presented. Future directions for the high temperature pulsed EMAT internal temperature concept are discussed for potential material processing applications.

  17. Acoustic measurements of gas density

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

    Sound transmission through gases in an enclosure is considered. Analytical results are given in terms of geometrical parameters, wave numbers, and source type for simple model problems, and are compared with data obtained by Haran (1983). It is concluded that density measurements can be made in a gas contained in an enclosure by measuring the sound pressure level at a receiver located near a dipole source driven at a constant velocity amplitude at low frequencies.

  18. Transport composite fuselage technology: Impact dynamics and acoustic transmission

    NASA Technical Reports Server (NTRS)

    Jackson, A. C.; Balena, F. J.; Labarge, W. L.; Pei, G.; Pitman, W. A.; Wittlin, G.

    1986-01-01

    A program was performed to develop and demonstrate the impact dynamics and acoustic transmission technology for a composite fuselage which meets the design requirements of a 1990 large transport aircraft without substantial weight and cost penalties. The program developed the analytical methodology for the prediction of acoustic transmission behavior of advanced composite stiffened shell structures. The methodology predicted that the interior noise level in a composite fuselage due to turbulent boundary layer will be less than in a comparable aluminum fuselage. The verification of these analyses will be performed by NASA Langley Research Center using a composite fuselage shell fabricated by filament winding. The program also developed analytical methodology for the prediction of the impact dynamics behavior of lower fuselage structure constructed with composite materials. Development tests were performed to demonstrate that the composite structure designed to the same operating load requirement can have at least the same energy absorption capability as aluminum structure.

  19. Call Transmission Efficiency in Native and Invasive Anurans: Competing Hypotheses of Divergence in Acoustic Signals

    PubMed Central

    Llusia, Diego; Gómez, Miguel; Penna, Mario; Márquez, Rafael

    2013-01-01

    Invasive species are a leading cause of the current biodiversity decline, and hence examining the major traits favouring invasion is a key and long-standing goal of invasion biology. Despite the prominent role of the advertisement calls in sexual selection and reproduction, very little attention has been paid to the features of acoustic communication of invasive species in nonindigenous habitats and their potential impacts on native species. Here we compare for the first time the transmission efficiency of the advertisement calls of native and invasive species, searching for competitive advantages for acoustic communication and reproduction of introduced taxa, and providing insights into competing hypotheses in evolutionary divergence of acoustic signals: acoustic adaptation vs. morphological constraints. Using sound propagation experiments, we measured the attenuation rates of pure tones (0.2–5 kHz) and playback calls (Lithobates catesbeianus and Pelophylax perezi) across four distances (1, 2, 4, and 8 m) and over two substrates (water and soil) in seven Iberian localities. All factors considered (signal type, distance, substrate, and locality) affected transmission efficiency of acoustic signals, which was maximized with lower frequency sounds, shorter distances, and over water surface. Despite being broadcast in nonindigenous habitats, the advertisement calls of invasive L. catesbeianus were propagated more efficiently than those of the native species, in both aquatic and terrestrial substrates, and in most of the study sites. This implies absence of optimal relationship between native environments and propagation of acoustic signals in anurans, in contrast to what predicted by the acoustic adaptation hypothesis, and it might render these vertebrates particularly vulnerable to intrusion of invasive species producing low frequency signals, such as L. catesbeianus. Our findings suggest that mechanisms optimizing sound transmission in native habitat can play a

  20. Call transmission efficiency in native and invasive anurans: competing hypotheses of divergence in acoustic signals.

    PubMed

    Llusia, Diego; Gómez, Miguel; Penna, Mario; Márquez, Rafael

    2013-01-01

    Invasive species are a leading cause of the current biodiversity decline, and hence examining the major traits favouring invasion is a key and long-standing goal of invasion biology. Despite the prominent role of the advertisement calls in sexual selection and reproduction, very little attention has been paid to the features of acoustic communication of invasive species in nonindigenous habitats and their potential impacts on native species. Here we compare for the first time the transmission efficiency of the advertisement calls of native and invasive species, searching for competitive advantages for acoustic communication and reproduction of introduced taxa, and providing insights into competing hypotheses in evolutionary divergence of acoustic signals: acoustic adaptation vs. morphological constraints. Using sound propagation experiments, we measured the attenuation rates of pure tones (0.2-5 kHz) and playback calls (Lithobates catesbeianus and Pelophylax perezi) across four distances (1, 2, 4, and 8 m) and over two substrates (water and soil) in seven Iberian localities. All factors considered (signal type, distance, substrate, and locality) affected transmission efficiency of acoustic signals, which was maximized with lower frequency sounds, shorter distances, and over water surface. Despite being broadcast in nonindigenous habitats, the advertisement calls of invasive L. catesbeianus were propagated more efficiently than those of the native species, in both aquatic and terrestrial substrates, and in most of the study sites. This implies absence of optimal relationship between native environments and propagation of acoustic signals in anurans, in contrast to what predicted by the acoustic adaptation hypothesis, and it might render these vertebrates particularly vulnerable to intrusion of invasive species producing low frequency signals, such as L. catesbeianus. Our findings suggest that mechanisms optimizing sound transmission in native habitat can play a less

  1. Analytical models for use in fan inflow control structure design. Inflow distortion and acoustic transmission models

    NASA Technical Reports Server (NTRS)

    Gedge, M. R.

    1979-01-01

    Analytical models were developed to study the effect of flow contraction and screening on inflow distortions to identify qualitative design criteria. Results of the study are that: (1) static testing distortions are due to atmospheric turbulence, nacelle boundary layer, exhaust flow reingestion, flow over stand, ground plane, and engine casing; (2) flow contraction suppresses, initially, turbulent axial velocity distortions and magnifies turbulent transverse velocity distortions; (3) perforated plate and gauze screens suppress axial components of velocity distortions to a degree determined by the screen pressure loss coefficient; (4) honeycomb screen suppress transverse components of velocity distortions to a degree determined by the length to diameter ratio of the honeycomb; (5) acoustic transmission loss of perforated plate is controlled by the reactance of its acoustic impedance; (6) acoustic transmission loss of honeycomb screens is negligible; and (7) a model for the direction change due to a corner between honeycomb panels compares favorably with measured data.

  2. Theoretical vibro-acoustic modeling of acoustic noise transmission through aircraft windows

    NASA Astrophysics Data System (ADS)

    Aloufi, Badr; Behdinan, Kamran; Zu, Jean

    2016-06-01

    In this paper, a fully vibro-acoustic model for sound transmission across a multi-pane aircraft window is developed. The proposed model is efficiently applied for a set of window models to perform extensive theoretical parametric studies. The studied window configurations generally simulate the passenger window designs of modern aircraft classes which have an exterior multi-Plexiglas pane, an interior single acrylic glass pane and a dimmable glass ("smart" glass), all separated by thin air cavities. The sound transmission loss (STL) characteristics of three different models, triple-, quadruple- and quintuple-paned windows identical in size and surface density, are analyzed for improving the acoustic insulation performances. Typical results describing the influence of several system parameters, such as the thicknesses, number and spacing of the window panes, on the transmission loss are then investigated. In addition, a comparison study is carried out to evaluate the acoustic reduction capability of each window model. The STL results show that the higher frequencies sound transmission loss performance can be improved by increasing the number of window panels, however, the low frequency performance is decreased, particularly at the mass-spring resonances.

  3. 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.

  4. Hydrothermal vent flow and turbulence measurements with acoustic scintillation instrumentation

    NASA Astrophysics Data System (ADS)

    di Iorio, D.; Xu, G.

    2009-12-01

    Acoustically derived measurements of hydrothermal vent flow and turbulence were obtained from the active black smoker Dante in the Main Endeavour vent field, using scintillation analysis from one-way transmissions. The scintillation transmitter and receiver array formed a 93 m acoustic path through the buoyant plume 20 m above the structure. The acoustic path was parallel to the valley sidewall where the M2 tidal currents are approximately aligned along ridge due to topographic steering by the valley walls and hence most of the plume displacement is expected to occur along the acoustic path. On one deployment, data were collected for 6.5 weeks and vertical velocities range from 0.1 to 0.2 m/s showing a strong dependence on the spring/neap tidal cycle. The refractive index fluctuations which can be paramaterized in terms of the root-mean-square temperature fluctuations also shows a strong tidal modulation during spring tide.

  5. Refinement and application of acoustic impulse technique to study nozzle transmission characteristics

    NASA Technical Reports Server (NTRS)

    Salikuddin, M.; Brown, W. H.; Ramakrishnan, R.; Tanna, H. K.

    1983-01-01

    An improved acoustic impulse technique was developed and was used to study the transmission characteristics of duct/nozzle systems. To accomplish the above objective, various problems associated with the existing spark-discharge impulse technique were first studied. These included (1) the nonlinear behavior of high intensity pulses, (2) the contamination of the signal with flow noise, (3) low signal-to-noise ratio at high exhaust velocities, and (4) the inability to control or shape the signal generated by the source, specially when multiple spark points were used as the source. The first step to resolve these problems was the replacement of the spark-discharge source with electroacoustic driver(s). These included (1) synthesizing on acoustic impulse with acoustic driver(s) to control and shape the output signal, (2) time domain signal averaging to remove flow noise from the contaminated signal, (3) signal editing to remove unwanted portions of the time history, (4) spectral averaging, and (5) numerical smoothing. The acoustic power measurement technique was improved by taking multiple induct measurements and by a modal decomposition process to account for the contribution of higher order modes in the power computation. The improved acoustic impulse technique was then validated by comparing the results derived by an impedance tube method. The mechanism of acoustic power loss, that occurs when sound is transmitted through nozzle terminations, was investigated. Finally, the refined impulse technique was applied to obtain more accurate results for the acoustic transmission characteristics of a conical nozzle and a multi-lobe multi-tube supressor nozzle.

  6. Characterization of the Reverberation Chamber at the NASA Langley Structural Acoustics Loads and Transmission (SALT) Facility

    NASA Technical Reports Server (NTRS)

    Grosveld, Ferdinand W.

    2013-01-01

    In 2011 the noise generating capabilities in the reverberation chamber of the Structural Acoustic Loads and Transmission (SALT) facility at NASA Langley Research Center were enhanced with two fiberglass reinforced polyester resin exponential horns, each coupled to Wyle Acoustic Source WAS-3000 airstream modulators. This report describes the characterization of the reverberation chamber in terms of the background noise, diffusivity, sound pressure levels, the reverberation times and the related overall acoustic absorption in the empty chamber and with the acoustic horn(s) installed. The frequency range of interest includes the 80 Hz to 8000 Hz one-third octave bands. Reverberation time and sound pressure level measurements were conducted and standard deviations from the mean were computed. It was concluded that a diffuse field could be produced above the Schroeder frequency in the 400 Hz one-third octave band and higher for all applications. This frequency could be lowered by installing panel diffusers or moving vanes to improve the acoustic modal overlap in the chamber. In the 80 Hz to 400 Hz one-third octave bands a successful measurement will be dependent on the type of measurement, the test configuration, the source and microphone locations and the desired accuracy. It is recommended that qualification measurements endorsed in the International Standards be conducted for each particular application.

  7. Directional acoustic measurements by laser Doppler velocimeters

    NASA Technical Reports Server (NTRS)

    Mazumder, M. K.; Overbey, R. L.; Testerman, M. K.

    1976-01-01

    Laser Doppler velocimeters (LDVs) are used as velocity microphones to measure sound pressure level in the range from 90 to 130 dB, spectral components, and two-point correlation functions for acoustic-noise source identification. Close agreement between LDV and microphone data is observed. Directional sensitivity and the ability to measure remotely make LDVs useful tools for acoustic measurement where placement of any physical probe is difficult or undesirable, as in the diagnosis of jet noise.

  8. Recent Enhancements to the NASA Langley Structural Acoustics Loads and Transmission (SALT) Facility

    NASA Technical Reports Server (NTRS)

    Rizzi, Stephen A.; Cabell, Randolph H.; Allen, Albert R.

    2013-01-01

    The Structural Acoustics Loads and Transmission (SALT) facility at the NASA Langley Research Center is comprised of an anechoic room and a reverberant room, and may act as a transmission loss suite when test articles are mounted in a window connecting the two rooms. In the latter configuration, the reverberant room acts as the noise source side and the anechoic room as the receiver side. The noise generation system used for qualification testing in the reverberant room was previously shown to achieve a maximum overall sound pressure level of 141 dB. This is considered to be marginally adequate for generating sound pressure levels typically required for launch vehicle payload qualification testing. Recent enhancements to the noise generation system increased the maximum overall sound pressure level to 154 dB, through the use of two airstream modulators coupled to 35 Hz and 160 Hz horns. This paper documents the acoustic performance of the enhanced noise generation system for a variety of relevant test spectra. Additionally, it demonstrates the capability of the SALT facility to conduct transmission loss and absorption testing in accordance with ASTM and ISO standards, respectively. A few examples of test capabilities are shown and include transmission loss testing of simple unstiffened and built up structures and measurement of the diffuse field absorption coefficient of a fibrous acoustic blanket.

  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. Subwavelength acoustic focusing by surface-wave-resonance enhanced transmission in doubly negative acoustic metamaterials

    SciTech Connect

    Zhou, Xiaoming; Badreddine Assouar, M. Oudich, Mourad

    2014-11-21

    We present analytical and numerical analyses of a yet unseen lensing paradigm that is based on a solid metamaterial slab in which the wave excitation source is attached. We propose and demonstrate sub-diffraction-limited acoustic focusing induced by surface resonant states in doubly negative metamaterials. The enhancement of evanescent waves across the metamaterial slab produced by their resonant coupling to surface waves is evidenced and quantitatively determined. The effect of metamaterial parameters on surface states, transmission, and wavenumber bandwidth is clearly identified. Based on this concept consisting of a wave source attached on the metamaterial, a high resolution of λ/28.4 is obtained with the optimum effective physical parameters, opening then an exciting way to design acoustic metamaterials for ultrasonic focused imaging.

  11. Perturbation measurement of waveguides for acoustic thermometry

    NASA Astrophysics Data System (ADS)

    Lin, H.; Feng, X. J.; Zhang, J. T.

    2013-09-01

    Acoustic thermometers normally embed small acoustic transducers in the wall bounding a gas-filled cavity resonator. At high temperature, insulators of transducers loss electrical insulation and degrade the signal-to-noise ratio. One essential solution to this technical trouble is to couple sound by acoustic waveguides between resonator and transducers. But waveguide will break the ideal acoustic surface and bring perturbations(Δf+ig) to the ideal resonance frequency. The perturbation model for waveguides was developed based on the first-order acoustic theory in this paper. The frequency shift Δf and half-width change g caused by the position, length and radius of waveguides were analyzed using this model. Six different length of waveguides (52˜1763 mm) were settled on the cylinder resonator and the perturbation (Δf+ig) were measured at T=332 K and p=250˜500 kPa. The experiment results agreed with the theoretical prediction very well.

  12. Rotating Microphone Rake Measures Spinning Acoustic Modes

    NASA Technical Reports Server (NTRS)

    Konno, Kevin E.; Hausmann, Clifford R.

    1996-01-01

    Rotating rake of pressure transducers developed for use in experimental studies of sources and propagation of noise generated by subsonic fan engines. Pressure transducers used as microphones to measure acoustic modes generated by, and spin with, fans. Versatility of control software used in rake-drive system enables measurements of acoustic modes on wide range of test-engine configurations. Rake-drive hardware easily adapted to different engines because not mechanically coupled to engine under test.

  13. Acoustic solitons in waveguides with Helmholtz resonators: transmission line approach.

    PubMed

    Achilleos, V; Richoux, O; Theocharis, G; Frantzeskakis, D J

    2015-02-01

    We report experimental results and study theoretically soliton formation and propagation in an air-filled acoustic waveguide side loaded with Helmholtz resonators. We propose a theoretical modeling of the system, which relies on a transmission-line approach, leading to a nonlinear dynamical lattice model. The latter allows for an analytical description of the various soliton solutions for the pressure, which are found by means of dynamical systems and multiscale expansion techniques. These solutions include Boussinesq-like and Korteweg-de Vries pulse-shaped solitons that are observed in the experiment, as well as nonlinear Schrödinger envelope solitons, that are predicted theoretically. The analytical predictions are in excellent agreement with direct numerical simulations and in qualitative agreement with the experimental observations. PMID:25768623

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. Measuring Acoustic-Radiation Stresses in Materials

    NASA Technical Reports Server (NTRS)

    Cantrell, John H.; Yost, W. T.

    1986-01-01

    System measures nonlinearity parameters of materials. Uses static strain generated by acoustic wave propagating in material. Since static strain is effectively "dc" component of waveform distortion, problems associated with phase-cancellation artifacts disappear. Further, sign of nonlinearity parameter obtained by simple inspection of measured signal polarity. These features make this system very amenable to use in field. System expected to become standard for acoustic-radiation-stress measurements for solids and liquids and for characterization of material properties related to strength and residual or applied stresses. Also expected to become standard for transducer calibration.

  19. Measurement of complex acoustic intensity in an acoustic waveguide.

    PubMed

    Duan, Wenbo; Kirby, Ray; Prisutova, Jevgenija; Horoshenkov, Kirill V

    2013-11-01

    Acoustic intensity is normally treated as a real quantity, but in recent years, many articles have appeared in which intensity is treated as a complex quantity where the real (active) part is related to local mean energy flow and the imaginary (reactive) part to local oscillatory transport of energy. This offers the potential to recover additional information about a sound field and then to relate this to the properties of the sound source and the environment that surrounds it. However, this approach is applicable only to multi-modal sound fields, which places significant demands on the accuracy of the intensity measurements. Accordingly, this article investigates the accuracy of complex intensity measurements obtained using a tri-axial Microflown intensity probe by comparing measurement and prediction for sound propagation in an open flanged pipe. Under plane wave conditions, comparison between prediction and experiment reveals good agreement, but when a higher order mode is present, the reactive intensity field becomes complicated and agreement is less successful. It is concluded that the potential application of complex intensity as a diagnostic tool is limited by difficulties in measuring reactive intensity in complex sound fields when using current state of the art acoustic instrumentation. PMID:24180778

  20. WaveQ3D: Fast and accurate acoustic transmission loss (TL) eigenrays, in littoral environments

    NASA Astrophysics Data System (ADS)

    Reilly, Sean M.

    This study defines a new 3D Gaussian ray bundling acoustic transmission loss model in geodetic coordinates: latitude, longitude, and altitude. This approach is designed to lower the computation burden of computing accurate environmental effects in sonar training application by eliminating the need to transform the ocean environment into a collection of Nx2D Cartesian radials. This approach also improves model accuracy by incorporating real world 3D effects, like horizontal refraction, into the model. This study starts with derivations for a 3D variant of Gaussian ray bundles in this coordinate system. To verify the accuracy of this approach, acoustic propagation predictions of transmission loss, time of arrival, and propagation direction are compared to analytic solutions and other models. To validate the model's ability to predict real world phenomena, predictions of transmission loss and propagation direction are compared to at-sea measurements, in an environment where strong horizontal refraction effect have been observed. This model has been integrated into U.S. Navy active sonar training system applications, where testing has demonstrated its ability to improve transmission loss calculation speed without sacrificing accuracy.

  1. Acoustic Phase Measurements from Volume Scatter in the Ocean.

    NASA Astrophysics Data System (ADS)

    Huston, Robert Delmar

    A primary goal of this thesis has been to demonstrate that stable, useful measurements of the orientation of the acoustic signal vector as a function of range and time can be obtained from ocean backscatter, and that this orientation, or acoustic phase, can be related to the local sound speed distribution. Consistent and useful measurement of absolute phase depends upon the positions of individual scatterers, which are normally random and sparse relative to the acoustic wavelength. This difficulty has been overcome by coherent super-position of echoes from successive transmissions, such that the effective density of acoustic targets progressively increases as the summation proceeds. The theoretical basis of this type of coherent processing has been developed and examined in the limiting case, in which it approximates a scatterer continuum for which an analytic expression has been found. The theory provides fundamental insights to the behaviour of both the amplitude and phase of volume scatter. As the ratio of coherent to incoherent signal increases with successive superposition of the echoes (coherent processing), the phase statistics evolve from a uniform to a nearly Gaussian distribution. Once the phase signal is bounded to within +/-45 ^circ, the basic requirement for a coherent 'volume mirror' has been met and reliable interferometric estimates are possible. The experimental work used a bistatic configuration with a multi-beam projector and narrow beam hydrophone operating at 215 kHz. The results confirm the theoretical concepts and demonstrate that within the quite limited range of environmental conditions that were studied, the coherently processed acoustic signals are consistent with independent measurements of the evolving sound speed profile. The main contribution of this thesis has been to lay a firm theoretical and experimental foundation for the use of volume backscatter in acoustic interferometer devices. Based on these results, the potential for new

  2. Acoustic particle palpation for measuring tissue elasticity

    PubMed Central

    Koruk, Hasan; El Ghamrawy, Ahmed

    2015-01-01

    We propose acoustic particle palpation—the use of sound to press a population of acoustic particles against an interface—as a method for measuring the qualitative and quantitative mechanical properties of materials. We tested the feasibility of this method by emitting ultrasound pulses across a tunnel of an elastic material filled with microbubbles. Ultrasound stimulated the microbubble cloud to move in the direction of wave propagation, press against the distal surface, and cause deformations relevant for elasticity measurements. Shear waves propagated away from the palpation site with a velocity that was used to estimate the material's Young's modulus. PMID:26869723

  3. Acoustic particle palpation for measuring tissue elasticity

    NASA Astrophysics Data System (ADS)

    Koruk, Hasan; El Ghamrawy, Ahmed; Pouliopoulos, Antonios N.; Choi, James J.

    2015-11-01

    We propose acoustic particle palpation—the use of sound to press a population of acoustic particles against an interface—as a method for measuring the qualitative and quantitative mechanical properties of materials. We tested the feasibility of this method by emitting ultrasound pulses across a tunnel of an elastic material filled with microbubbles. Ultrasound stimulated the microbubble cloud to move in the direction of wave propagation, press against the distal surface, and cause deformations relevant for elasticity measurements. Shear waves propagated away from the palpation site with a velocity that was used to estimate the material's Young's modulus.

  4. Boundary-Layer Effects on Acoustic Transmission Through Narrow Slit Cavities

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

    We explore the slit-width dependence of the resonant transmission of sound in air through both a slit array formed of aluminum slats and a single open-ended slit cavity in an aluminum plate. Our experimental results accord well with Lord Rayleigh's theory concerning how thin viscous and thermal boundary layers at a slit's walls affect the acoustic wave across the whole slit cavity. By measuring accurately the frequencies of the Fabry-Perot-like cavity resonances, we find a significant 5% reduction in the effective speed of sound through the slits when an individual viscous boundary layer occupies only 5% of the total slit width. Importantly, this effect is true for any airborne slit cavity, with the reduction being achieved despite the slit width being on a far larger scale than an individual boundary layer's thickness. This work demonstrates that the recent prevalent loss-free treatment of narrow slit cavities within acoustic metamaterials is unrealistic.

  5. Acoustic measurements of clay-size particles

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Knowledge of sediment concentration is important in the study of streams and rivers. The work presented explores using high frequency (20 MHz) acoustic signal attenuation to measure the concentration of fine sediment particles (0.2-5.0 microns) in a fluvial environment. A small laboratory tank with...

  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. Surface area measurement utilizing an acoustic bridge

    PubMed

    Torigoe; Ishii

    2000-05-01

    A new method is proposed for measuring the surface area of an object. The acoustic conductance of a cavity is proportional to the surface area of the cavity inner wall. The surface area of an object thus can be known from the measurement of the acoustic impedance of a chamber in which the object is placed. In order to measure the acoustic impedance accurately; the proposed method employs the acoustic bridge technique. The experimental device is composed of the following elements so arranged that their electric equivalents form a bridge circuit: a measuring chamber in which an object under test is placed and whose volume can be adjusted; a reference chamber whose inner surface area can be varied; a loudspeaker (the signal source) mounted between the two chambers; and a bypass channel at the midpoint of which a microphone (the null detector) is installed. This bridge balances when the volume and the inner surface area of each chamber become equal. The surface area of the object can then be known from the inner surface area of the reference chamber. Several experiments were performed with this device and the success of the proposed method was verified. PMID:10830378

  8. Acoustical measurements in ancient Roman theatres

    NASA Astrophysics Data System (ADS)

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

    2001-05-01

    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.

  9. Finite-difference, time-domain analysis of a folded acoustic transmission line.

    PubMed

    Jackson, Charles M

    2005-03-01

    Recently designed, modern versions of renais sance woodwind instruments such as the recorder and serpent use square cross sections and a folded acoustic transmission line. Conventional microwave techniques would expect that this bend would cause unwanted reflections and impedance discontinuities. This paper analyses the folded acoustic transmission line using finite-difference, time-domain techniques and shows that the discontinuity can be compensated with by the use of a manufacturable method. PMID:15857045

  10. Acoustical concept for measuring particle size distributions

    SciTech Connect

    Mahler, D.S.; Kaufman, M.

    1981-02-01

    A new concept is investigated for measuring particle size and distribution for air pollution control applications. This study illustrates that the proposed device--the Acoustic Particulate Monitor (APM)--can measure total mass loading, mean particle diameter, and width of particle size distributions on an in-situ basis. The concept for such an instrument is based upon experimental and theoretical observations that the presence of dust in air causes a reduction in the speed of sound as a function of the transmitted frequency. These percentage reductions in the speed of sound are small and the research results illustrate how the accompanying shift in the acoustical phase is a highly sensitive method for detecting such effects. The magnitudes of the phase shift are related to mass loading. The frequency associated with the maximum phase shift is defined as the acoustic frequency, fA. Experimentally determining fA provides a measure of the mean particle size of the distribution. The detailed shape of the phase shift as a function of frequency is a measure of the spread in the size distribution of the entrained particulate. Experiments were performed using several configurations. Results were verified using direct mass measurements and microphotographs.

  11. Acoustic vs Interferometric Measurements of Lightning

    NASA Astrophysics Data System (ADS)

    Arechiga, R. O.; Erives, H.; Sonnenfeld, R. G.; Stanley, M. A.; Rison, W.; Thomas, R. J.; Edens, H. E.; Lapierre, J. L.; Stock, M.; Jensen, D.; Morris, K.

    2015-12-01

    During the summer of 2015 we acquired acoustic and RF data on severalflashes from thunderstorms over Fort Morgan CO. and Langmuir Laboratoryin the Magdalena mountains of central New Mexico. The acoustic arrayswere located at a distance of roughly 150 m from the interferometers.Lightning mapping array and slow antenna data were also obtained. Theacoustic arrays consist of arrays of five audio-range and six infrasoundmicrophones operating at 50 KHz and 1 KHz respectively. The lightninginterferometer at Fort Morgan CO. consists of three flat-plate, 13" diameterantennas at the vertices of an equilateral 50 m per side triangle. Theinterferometer at Langmuir Laboratory consists of three 13" dishes separatedby about 15 m. Both interferometers, operating at 180 Megasamples persecond, use the analysis software and digitizer hardware pioneered byStanley, Stock et al. The high data rate allows for excellent spatialresolution of high speed (and typically high current) processes such asK-changes, return strokes and dart-leaders. In previous studies, we haveshown the usefulness of acoustic recordings to locate thunder sources aswell as infrasound pulses from lightning. This work will present acomparison of Acoustic and Interferometric measurements from lightning,using some interesting flashes, including a positive cloud to ground,that occurred in these campaigns.

  12. Verification of three-microphone impedance tube method for measurement of transmission loss in aerogels

    NASA Astrophysics Data System (ADS)

    Connick, Robert J.

    Accurate measurement of normal incident transmission loss is essential for the acoustic characterization of building materials. In this research, a method of measuring normal incidence sound transmission loss proposed by Salissou et al. as a complement to standard E2611-09 of the American Society for Testing and Materials [Standard Test Method for Measurement of Normal Incidence Sound Transmission of Acoustical Materials Based on the Transfer Matrix Method (American Society for Testing and Materials, New York, 2009)] is verified. Two sam- ples from the original literature are used to verify the method as well as a Filtros RTM sample. Following the verification, several nano-material Aerogel samples are measured.

  13. Underwater asymmetric acoustic transmission structure using the medium with gradient change of impedance

    NASA Astrophysics Data System (ADS)

    Bo, Hu; Jie, Shi; Sheng-Guo, Shi; Yu, Sun; Zhong-Rui, Zhu

    2016-02-01

    We propose an underwater asymmetric acoustic transmission structure comprised of two media each with a gradient change of acoustic impedance. By gradually increasing the acoustic impedances of the media, the propagating direction of the acoustic wave can be continuously bent, resulting in allowing the acoustic wave to pass through along the positive direction and blocking acoustic waves from the negative one. The main advantages of this structure are that the asymmetric transmission effect of this structure can be realized and enhanced more easily in water. We investigate both numerically and experimentally the asymmetric transmission effect. The experimental results show that a highly efficient asymmetric acoustic transmission can be yielded within a remarkable broadband frequency range, which agrees well with the numerical prediction. It is of potential practical significance for various underwater applications such as reducing vibration and noise. Project supported by the National Natural Science Foundation of China (Grant Nos. 11204049 and 11204050), the Program for Changjiang Scholars and Innovative Research Team in University of Ministry of Education of China (Grant No. IRT1228), and the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant Nos. 20122304120023 and 20122304120011).

  14. Environmentally adaptive acoustic transmission loss prediction in turbulent and nonturbulent atmospheres.

    PubMed

    Wichern, Gordon; Azimi-Sadjadi, Mahmood R; Mungiole, Michael

    2007-05-01

    An environmentally adaptive system for prediction of acoustic transmission loss (TL) in the atmosphere is developed in this paper. This system uses several back propagation neural network predictors, each corresponding to a specific environmental condition. The outputs of the expert predictors are combined using a fuzzy confidence measure and a nonlinear fusion system. Using this prediction methodology the computational intractability of traditional acoustic model-based approaches is eliminated. The proposed TL prediction system is tested on two synthetic acoustic data sets for a wide range of geometrical, source and environmental conditions including both nonturbulent and turbulent atmospheres. Test results of the system showed root mean square (RMS) errors of 1.84 dB for the nonturbulent and 1.36 dB for the turbulent conditions, respectively, which are acceptable levels for near real-time performance. Additionally, the environmentally adaptive system demonstrated improved TL prediction accuracy at high frequencies and large values of horizontal separation between source and receiver. PMID:17521880

  15. Deep Seafloor Acoustic Backscattering Measurements Using Sea Beam

    NASA Astrophysics Data System (ADS)

    de Moustier, Christian

    Multibeam echo-sounders such as Sea Beam allow investigators to carry out detailed bathymetric surveys of large areas of the seafloor. However, bathymetry only reveals the shape of seafloor features to the resolution of the sounding system, and in order to make geological interpretations one needs to characterize the nature of the seafloor surveyed. Because bottom roughness and/or variations in bottom substrate cause fluctuations in the backscattered acoustic signal received by an echo-sounder, such characteristics can be inferred in part by analyzing the structure and the variations of this signal over several transmission cycles. The approach taken has been to record digitally the detected echo envelopes of Sea Beam's 16 narrow beams over a variety of seafloor environments, and process these data to determine whether the acoustics held enough information to differentiate between bottom types. Significant results derived from these acoustic data concern (1) the Sea Beam system's performance (2) its potential for mapping acoustic boundaries and (3) the display of the echoes received in a side looking sonar -like picture. The system was found to work well under most circumstances as a contour mapping tool, but it occasionally suffers echo processing malfunctions producing artifacts in the contoured bathymetric output which can induce the unwary investigator to make geological interpretation errors de Moustier and Kleinrock (1985) J.G.R. in press . Acoustic boundary mapping has been successfully carried out over a manganese nodule mining site in the Northeastern Tropical Pacific where a first order assessment of nodule coverage validated with bottom photographs proved the techniques feasible de Moustier (1985) Geophysics, V .50 p.989-1001 . Comparison of results from environments as diverse as a lava sheet flow on the crest of the East Pacific Rise, a sedimentary basin offshore Southern California, and a manganese nodule field show marked differences in the overall

  16. Gas density does not affect pulmonary acoustic transmission in normal men.

    PubMed

    Mahagnah, M; Gavriely, N

    1995-03-01

    Fremitus, the transmission of sound and vibration from the mouth to the chest wall, has long been used clinically to examine the pulmonary system. Recently, modern technology has become available to measure the acoustic transfer function (TF) and transit times (TT) of the pulmonary system. Because sound speed is inversely proportional to the square root of gas density in free gas, but not in porous media, we measured the effect of air and Heliox (80% He-20% O2) breathing on pulmonary sound transmission in six healthy subjects to investigate the mechanism of sound transmission. Wide-band noise (75-2,000 Hz) was "injected" into the mouth and picked up over the trachea and chest wall. The averaged power spectra, TF, phase, and coherence were calculated using a fast Fourier transform-based algorithm. The phase data were used to calculate TT as a function of frequency. TF was found to consist of a low-pass filter property with essentially flat transmitted energy to 300 Hz and exponential decline to 600 Hz at the anterior right upper lobe (CR) and flat transmission to 100 Hz with exponential decline to 150 Hz at the right posterior base (BR). TF was not affected by breathing Heliox. The average TT values, calculated from the slopes of the averaged phase, were 1.5 +/- 0.5 ms for trachea to CR and 5.2 +/- 0.5 ms for trachea to BR transmission during air breathing. During Heliox breathing, the values of TT were 1.5 +/- 0.5 ms and 4.9 +/- 0.5 ms from the trachea to CR and from the trachea to BR locations, respectively. These results suggest that sound transmission in the respiratory system is dominated by wave propagation through the parenchymal porous structure. PMID:7775338

  17. Information and data real time transmission acoustic underwater system: TRIDENT

    NASA Astrophysics Data System (ADS)

    Trubuil, Joel; Labat, Joel; Lapierre, Gerard

    2001-05-01

    The objective of the Groupe d'Etudes Sous-Marines de l'Atlantique (GESMA) is to develop a robust high data rate acoustic link. A real-time receiver recently developed at ENST Bretagne has just been designed to cope with all perturbations induced by such harsh channels. In order to cope with channel features, a spatio-temporal equalizer introduced by J. Labat et al. [Brevet FT no. 9914844, ``Perfectionnements aux dispositifs d'galisation adaptative pour recepteurs de systemes de communications numriques,'' Nov. 1999] was recently implemented and evaluated. This equalizer is the core of the receiver platform [Trubuil et al., ``Real-time high data rate acoustic link based on spatio temporal blind equalization: the TRIDENT acoustic system,'' OCEANS 2002]. This paper provides an overview of this project. The context of the study and the design of high data rate acoustic link are presented. Last Brest harbor experiments (2002, 2003) are described. The real time horizontal acoustic link performances are evaluated. Two carriers frequencies are available (20, 35 kHz). Acoustic communications for bit rate ranging from 10 to 20 kbps and for channel length (shallow water) ranging from 500 to 4000 m have been conducted successfully over several hours.

  18. Acoustic levitation methods for density measurements

    NASA Astrophysics Data System (ADS)

    Trinh, E. H.; Hsu, C. J.

    1986-12-01

    The capability of ultrasonic levitators operating in air to perform density measurements has been demonstrated. The remote determination of the density of ordinary liquids as well as low density solid metals can be carried out using levitated samples with size on the order of a few millimeters and at a frequency of 20 kHz. Two basic methods may be used. The first one is derived from a previously known technique developed for acoustic levitation in liquid media, and is based on the static equilibrium position of levitated samples in the earth's gravitational field. The second approach relies on the dynamic interaction between a levitated sample and the acoustic field. The first technique appears more accurate (1 percent uncertainty), but the latter method is directly applicable to a near gravity-free environment such as that found in space.

  19. Acoustic levitation methods for density measurements

    NASA Technical Reports Server (NTRS)

    Trinh, E. H.; Hsu, C. J.

    1986-01-01

    The capability of ultrasonic levitators operating in air to perform density measurements has been demonstrated. The remote determination of the density of ordinary liquids as well as low density solid metals can be carried out using levitated samples with size on the order of a few millimeters and at a frequency of 20 kHz. Two basic methods may be used. The first one is derived from a previously known technique developed for acoustic levitation in liquid media, and is based on the static equilibrium position of levitated samples in the earth's gravitational field. The second approach relies on the dynamic interaction between a levitated sample and the acoustic field. The first technique appears more accurate (1 percent uncertainty), but the latter method is directly applicable to a near gravity-free environment such as that found in space.

  20. Multi-band asymmetric acoustic transmission in a bended waveguide with multiple mechanisms

    NASA Astrophysics Data System (ADS)

    Huang, Yu-lei; Sun, Hong-xiang; Xia, Jian-ping; Yuan, Shou-qi; Ding, Xin-lei

    2016-07-01

    We report the realization of a multi-band device of the asymmetric acoustic transmission by placing a phononic crystal inside a bended waveguide immersed in water, as determined both experimentally and numerically. The asymmetric acoustic transmission exists in three frequency bands below 500 kHz induced by multiple mechanisms. Besides the band gap of the phononic crystal, we also introduce the deaf mode and interaction between the phononic crystal and waveguide. More importantly, this asymmetric transmission can be systematically controlled by mechanically rotating the square rods of the phononic crystal. The device has the advantages of multiple band, broader bandwidth, and adjustable property, showing promising applications in ultrasonic devices.

  1. Outdoor measurements of spherical acoustic shock decay.

    PubMed

    Young, Sarah M; Gee, Kent L; Neilsen, Tracianne B; Leete, Kevin M

    2015-09-01

    Prior anechoic measurements of a small acetylene-oxygen balloon explosion were used to study spherical weak-shock decay over short ranges [Muhlestein et al., J. Acoust. Soc. Am. 131, 2422-2430 (2012)]. Here, longer-range measurements conducted at the Bonneville Salt Flats with a larger balloon are described. Waveform and spectral characteristics and comparisons of the peak pressure decay with an analytical weak-shock model are presented. Weak shocks persist to at least 305 m, with an amplitude decay that is predicted reasonably well using the model. Deviations are discussed in the context of atmospheric effects and nonlinear ground reflections. PMID:26428831

  2. Measurements of thermo-acoustic coupling

    NASA Astrophysics Data System (ADS)

    Pun, Winston

    The problem of combustion instabilities has existed since the early 1940s, when they were observed during the development of solid and liquid rocket engines. While various engineering solutions have served well in these fields, the problem is revisited in modern gas-turbine engines. The purpose of this work is to provide experimental measurements of laboratory devices that exhibit thermo-acoustic coupling, similar to the interaction observed during combustion instabilities, which will aid in the design and development of stable systems. Possibly the simplest device which exhibits these characteristics is a Rijke tube. An electrical, horizontally mounted, 1 m long version of the original Rijke tube is presented, with measurements taken during unstable and stable operation. An accurate stability boundary with uncertainty is determined for a heater position of x/L = ¼, as a function of mass flow rate and heater power. Hysteresis, not previously reported, is observed at flow rates above 3 g/s. A one-dimensional model of the stability boundary with linear acoustics is shown to have qualitative agreement with experimental data. A novel technique has also been devised which can provide insight into the local dynamic response of a flame to an acoustic field. In the experiments, a test chamber is acoustically excited by a pair of low-frequency drivers. The response of the flame is visualized by two techniques; chemiluminescence and planar laser-induced fluorescence (PLIF) of the hydroxyl (OH) radical, both of which are well-known indicators for heat release in flames. The resulting images are phase-resolved and averaged to yield a qualitative picture of the fluctuation of the heat release. The images are correlated with a pressure transducer near the flame, which allows stability to be evaluated using Rayleigh's criterion and a combustion response function. This is the first known measurement of the combustion dynamics of a flame over a range of frequencies. Results

  3. Binaural Simulation Experiments in the NASA Langley Structural Acoustics Loads and Transmission Facility

    NASA Technical Reports Server (NTRS)

    Grosveld, Ferdinand W.; Silcox, Richard (Technical Monitor)

    2001-01-01

    A location and positioning system was developed and implemented in the anechoic chamber of the Structural Acoustics Loads and Transmission (SALT) facility to accurately determine the coordinates of points in three-dimensional space. Transfer functions were measured between a shaker source at two different panel locations and the vibrational response distributed over the panel surface using a scanning laser vibrometer. The binaural simulation test matrix included test runs for several locations of the measuring microphones, various attitudes of the mannequin, two locations of the shaker excitation and three different shaker inputs including pulse, broadband random, and pseudo-random. Transfer functions, auto spectra, and coherence functions were acquired for the pseudo-random excitation. Time histories were acquired for the pulse and broadband random input to the shaker. The tests were repeated with a reflective surface installed. Binary data files were converted to universal format and archived on compact disk.

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

    PubMed Central

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

    2014-01-01

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

  5. Acoustic input impedance measurements on brass instruments

    NASA Astrophysics Data System (ADS)

    Pyle, Robert W., Jr.

    2002-11-01

    Measurement of the acoustic input impedance of a brass instrument can reveal something about the instrument's intonation, its reasonable playing range, its tone color, and perhaps whether the mouthpiece used for the impedance measurement is appropriate for the instrument. Such measurements are made at sound-presssure levels much lower than those encountered under playing conditions. Thus, impedance measurements may offer the only feasible way to infer something about the playing characteristics of instruments, typically museum specimens, that are too rare or too fragile to be played. In this paper the effects of some of the available choices of sound source and stimulus signal on measurement accuracy will be explored. Driver-transducer nonlinearity, source impedance, signal-to-noise ratio, and any necessary signal processing will be discussed.

  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. 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.

  8. 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.

  9. Outdoor synthetic aperture acoustic ground target measurements

    NASA Astrophysics Data System (ADS)

    Bishop, Steven; Ngaya, Therese-Ann; Vignola, Joe; Judge, John; Marble, Jay; Gugino, Peter; Soumekh, Mehrdad; Rosen, Erik

    2010-04-01

    A novel outdoor synthetic aperture acoustic (SAA) system consists of a microphone and loudspeaker traveling along a 6.3-meter rail system. This is an extension from a prior indoor laboratory measurement system in which selected targets were insonified while suspended in air. Here, the loudspeaker and microphone are aimed perpendicular to their direction of travel along the rail. The area next to the rail is insonified and the microphone records the reflected acoustic signal, while the travel of the transceiver along the rail creates a synthetic aperture allowing imaging of the scene. Ground surfaces consisted of weathered asphalt and short grass. Several surface-laid objects were arranged on the ground for SAA imaging. These included rocks, concrete masonry blocks, grout covered foam blocks; foliage obscured objects and several spherical canonical targets such as a bowling ball, and plastic and metal spheres. The measured data are processed and ground targets are further analyzed for characteristics and features amenable for discrimination. This paper includes a description of the measurement system, target descriptions, synthetic aperture processing approach and preliminary findings with respect to ground surface and target characteristics.

  10. 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)

  11. Comparison of acoustic and strain gauge techniques for crack closure measurements

    NASA Technical Reports Server (NTRS)

    Buck, O.; Inman, R. V.; Frandsen, J. D.

    1976-01-01

    A quantitative study on the systems performances of the COD gauge and the acoustic transmission techniques to elastic deformation of part-through crack and compact tension specimens has been conducted. It is shown that the two instruments measure two completely different quantities: The COD gauge yields information on the length change of the specimen whereas the acoustic technique is sensitive directly to the amount of contract area between two surfaces, interfering with the acoustic signal. In another series of experiments, compression tests on parts with specifically prepared surfaces were performed so that the surface contact area could be correlated with the transmitted acoustic signal, as well as the acoustic with the COD gauge signal. A linear relation between contact area and COD gauge signal was obtained until full contact had been established.

  12. 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.

  13. Resonant transmission and mode modulation of acoustic waves in H-shaped metallic gratings

    SciTech Connect

    Deng, Yu-Qiang; Fan, Ren-Hao; Zhang, Kun; Peng, Ru-Wen E-mail: dongxiang87@gmail.com; Qi, Dong-Xiang E-mail: dongxiang87@gmail.com

    2015-04-15

    In this work, we demonstrate that resonant full transmission of acoustic waves exists in subwavelength H-shaped metallic gratings, and transmission peaks can be efficiently tuned by adjusting the grating geometry. We investigate this phenomenon through both numerical simulations and theoretical calculations based on rigorous-coupled wave analysis. The transmission peaks are originated from Fabry-Perot resonances together with the couplings between the diffractive wave on the surface and the multiple guided modes in the slits. Moreover, the transmission modes can be efficiently tuned by adjusting the cavity geometry, without changing the grating thickness. The mechanism is analyzed based on an equivalent circuit model and verified by both the theoretical calculations and the numerical simulations. This research has potential application in acoustic-device miniaturization over a wide range of wavelengths.

  14. Analytical modeling of a sandwiched plate piezoelectric transformer-based acoustic-electric transmission channel.

    PubMed

    Lawry, Tristan J; Wilt, Kyle R; Scarton, Henry A; Saulnier, Gary J

    2012-11-01

    The linear propagation of electromagnetic and dilatational waves through a sandwiched plate piezoelectric transformer (SPPT)-based acoustic-electric transmission channel is modeled using the transfer matrix method with mixed-domain two-port ABCD parameters. This SPPT structure is of great interest because it has been explored in recent years as a mechanism for wireless transmission of electrical signals through solid metallic barriers using ultrasound. The model we present is developed to allow for accurate channel performance prediction while greatly reducing the computational complexity associated with 2- and 3-dimensional finite element analysis. As a result, the model primarily considers 1-dimensional wave propagation; however, approximate solutions for higher-dimensional phenomena (e.g., diffraction in the SPPT's metallic core layer) are also incorporated. The model is then assessed by comparing it to the measured wideband frequency response of a physical SPPT-based channel from our previous work. Very strong agreement between the modeled and measured data is observed, confirming the accuracy and utility of the presented model. PMID:23192811

  15. 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.

  16. 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.

  17. 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.

  18. Tunable broadband unidirectional acoustic transmission based on a waveguide with phononic crystal

    NASA Astrophysics Data System (ADS)

    Song, Ailing; Chen, Tianning; Wang, Xiaopeng; Wan, Lele

    2016-08-01

    In this paper, a tunable broadband unidirectional acoustic transmission (UAT) device composed of a bended tube and a superlattice with square columns is proposed and numerically investigated by using finite element method. The UAT is realized in the proposed UAT device within two wide frequency ranges. And the effectiveness of the UAT device is demonstrated by analyzing the sound pressure distributions when the acoustic waves are incident from different directions. The unidirectional band gaps can be effectively tuned by mechanically rotating the square columns, which is a highlight of this paper. Besides, a bidirectional acoustic isolation (BAI) device is obtained by placing two superlattices in the bended tube, in which the acoustic waves cannot propagate along any directions. The physical mechanisms of the proposed UAT device and BAI device are simply discussed. The proposed models show potential applications in some areas, such as unidirectional sonic barrier or noise insulation.

  19. Acoustic transmission enhancement through a soft interlayer with a reactance boundary.

    PubMed

    Quan, Li; Qian, Feng; Liu, Xiaozhou; Gong, Xiufen

    2015-08-01

    Research has shown that acoustic transmission enhancement (ATE) can occur in stiff materials with high acoustic impedance that include a soft interlayer with low acoustic impedance inserted between them without any opening (i.e., without any links between the two stiff materials). Previously, ATE was induced either by coupling acoustic surface waves or Love waves with the Fabry-Perot resonant modes inside the apertures or by the locally resonant modes of the structure. However, in this article ATE is achieved using wave-vector redistribution induced by a reactance boundary. An optimal boundary was designed to adjust the wave vector in the propagation direction, decreasing reflection caused by impedance differences. The role of boundary conditions on ATE was also clarified. PMID:26328694

  20. 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

  1. Gear Transmission Error Measurement System Made Operational

    NASA Technical Reports Server (NTRS)

    Oswald, Fred B.

    2002-01-01

    A system directly measuring the transmission error between the meshing spur or helical gears was installed at the NASA Glenn Research Center and made operational in August 2001. This system employs light beams directed by lenses and prisms through gratings mounted on the two gear shafts. The amount of light that passes through both gratings is directly proportional to the transmission error of the gears. The device is capable of resolution better than 0.1 mm (one thousandth the thickness of a human hair). The measured transmission error can be displayed in a "map" that shows how the transmission error varies with the gear rotation or it can be converted to spectra to show the components at the meshing frequencies. Accurate transmission error data will help researchers better understand the mechanisms that cause gear noise and vibration and will lead to The Design Unit at the University of Newcastle in England specifically designed the new system for NASA. It is the only device in the United States that can measure dynamic transmission error at high rotational speeds. The new system will be used to develop new techniques to reduce dynamic transmission error along with the resulting noise and vibration of aeronautical transmissions.

  2. Measuring Transmission Efficiencies Of Mass Spectrometers

    NASA Technical Reports Server (NTRS)

    Srivastava, Santosh K.

    1989-01-01

    Coincidence counts yield absolute efficiencies. System measures mass-dependent transmission efficiencies of mass spectrometers, using coincidence-counting techniques reminiscent of those used for many years in calibration of detectors for subatomic particles. Coincidences between detected ions and electrons producing them counted during operation of mass spectrometer. Under certain assumptions regarding inelastic scattering of electrons, electron/ion-coincidence count is direct measure of transmission efficiency of spectrometer. When fully developed, system compact, portable, and used routinely to calibrate mass spectrometers.

  3. Cosmological implications of baryon acoustic oscillation measurements

    NASA Astrophysics Data System (ADS)

    Aubourg, Éric; Bailey, Stephen; Bautista, Julian E.; Beutler, Florian; Bhardwaj, Vaishali; Bizyaev, Dmitry; Blanton, Michael; Blomqvist, Michael; Bolton, Adam S.; Bovy, Jo; Brewington, Howard; Brinkmann, J.; Brownstein, Joel R.; Burden, Angela; Busca, Nicolás G.; Carithers, William; Chuang, Chia-Hsun; Comparat, Johan; Croft, Rupert A. C.; Cuesta, Antonio J.; Dawson, Kyle S.; Delubac, Timothée; Eisenstein, Daniel J.; Font-Ribera, Andreu; Ge, Jian; Le Goff, J.-M.; Gontcho, Satya Gontcho A.; Gott, J. Richard; Gunn, James E.; Guo, Hong; Guy, Julien; Hamilton, Jean-Christophe; Ho, Shirley; Honscheid, Klaus; Howlett, Cullan; Kirkby, David; Kitaura, Francisco S.; Kneib, Jean-Paul; Lee, Khee-Gan; Long, Dan; Lupton, Robert H.; Magaña, Mariana Vargas; Malanushenko, Viktor; Malanushenko, Elena; Manera, Marc; Maraston, Claudia; Margala, Daniel; McBride, Cameron K.; Miralda-Escudé, Jordi; Myers, Adam D.; Nichol, Robert C.; Noterdaeme, Pasquier; Nuza, Sebastián E.; Olmstead, Matthew D.; Oravetz, Daniel; Pâris, Isabelle; Padmanabhan, Nikhil; Palanque-Delabrouille, Nathalie; Pan, Kaike; Pellejero-Ibanez, Marcos; Percival, Will J.; Petitjean, Patrick; Pieri, Matthew M.; Prada, Francisco; Reid, Beth; Rich, James; Roe, Natalie A.; Ross, Ashley J.; Ross, Nicholas P.; Rossi, Graziano; Rubiño-Martín, Jose Alberto; Sánchez, Ariel G.; Samushia, Lado; Santos, Ricardo Tanausú Génova; Scóccola, Claudia G.; Schlegel, David J.; Schneider, Donald P.; Seo, Hee-Jong; Sheldon, Erin; Simmons, Audrey; Skibba, Ramin A.; Slosar, Anže; Strauss, Michael A.; Thomas, Daniel; Tinker, Jeremy L.; Tojeiro, Rita; Vazquez, Jose Alberto; Viel, Matteo; Wake, David A.; Weaver, Benjamin A.; Weinberg, David H.; Wood-Vasey, W. M.; Yèche, Christophe; Zehavi, Idit; Zhao, Gong-Bo; BOSS Collaboration

    2015-12-01

    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. In particular, 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 Λ CDM 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 Λ CDM values at ≈1 σ . While the overall χ2 of model fits is satisfactory, the LyaF BAO measurements are in moderate (2 - 2.5 σ ) 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, ∑mν<0.56 eV (95% confidence), improving to ∑mν<0.25 eV if we include the

  4. 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.

  5. Asymmetric acoustic transmission through near-zero-index and gradient-index metasurfaces

    NASA Astrophysics Data System (ADS)

    Shen, Chen; Xie, Yangbo; Li, Junfei; Cummer, Steven A.; Jing, Yun

    2016-05-01

    We present a design of acoustic metasurfaces yielding asymmetric transmission within a certain frequency band. The design consists of a layer of gradient-index metasurface and a layer of low refractive index metasurface. Incident waves are controlled in a wave vector dependent manner to create strong asymmetric transmission. Numerical simulations show that the approach provides high transmission contrast between the two incident directions within the designed frequency band. This is further verified by experiments. Compared to previous designs, the proposed approach yields a compact and planar device. Our design may find applications in various scenarios such as noise control and therapeutic ultrasound.

  6. Proving experiments on an acoustic transmission suite and its reverberation room

    NASA Astrophysics Data System (ADS)

    Plumb, G. D.

    An Acoustic Transmission Suite is a facility used for the laboratory measurement of the airborne sound transmission properties of partitions. It consists of a pair of adjoining rooms, the source room and the receive room, with a hole for the construction of the test partition in their common walls. The building is designed to minimize the sound power flow by paths other than that through the test partition. Such a facility has recently been built at the British Broadcasting Corporation (BBC) Research Department. A double brick cavity wall was built to allow the limiting sound insulation performance between the source and receive rooms in the Transmission Suite to be measured. This performance is effectively equal to that which would be measured with a perfectly isolating partition in place, and limits the maximum insulation that could be measured using the Suite. The actual isolation was shown to be impaired by a rigid bond between the test wall and the receive room walls. A demountable lightweight partition was fitted firstly to the receive and then to the source room side of the test wall. This improved the isolation of the test wall and proved that the rigid bond at its edges had been the cause of the impaired isolation. It also revealed a void above the test wall, and a further weakness through the cavity between the source and receive rooms. The mean limiting sound reduction index between the source and receive rooms was shown to be 65 dB, provided that the cavity between source and receive rooms was sealed. In future, a mechanism must be employed which provides vibration isolation between the test wall and the Transmission Suite building structure. The receive room was designed to meet the specifications detailed in the ISO-Standard for reverberation rooms. Proving tests were carried out on the reverberation room and repeatability tests were carried out to evaluate the minimum number of decays needed in each frequency band for absorption coefficient

  7. 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.

  8. Acoustic transmission matrix of a variable area duct or nozzle carrying a compressible subsonic flow

    NASA Technical Reports Server (NTRS)

    Miles, J. H.

    1980-01-01

    The differential equations governing the propagation of sound in a variable area duct or nozzle carrying a one-dimensional subsonic compressible fluid flow are derived and put in state variable form using acoustic pressure and particle velocity as the state variables. The duct or nozzle is divided into a number of regions. The region size is selected so that in each region the Mach number can be assumed constant and the area variation can be approximated by an exponential area variation. Consequently, the state variable equation in each region has constant coefficients. The transmission matrix for each region is obtained by solving the constant coefficient acoustic state variable differential equation. The transmission matrix for the duct or nozzle is the product of the individual transmission matrices of each region. Solutions are presented for several geometries with and without mean flow.

  9. Acoustic transmission matrix of a variable area duct or nozzle carrying a compressible subsonic flow

    NASA Technical Reports Server (NTRS)

    Miles, J. H.

    1980-01-01

    The differential equations governing the propagation of sound in a variable area duct or nozzle carrying a one dimensional subsonic compressible fluid flow are derived and put in state variable form using acoustic pressure and particle velocity as the state variables. The duct or nozzle is divided into a number of regions. The region size is selected so that in each region the Mach number can be assumed constant and the area variation can be approximated by an exponential area variation. Consequently, the state variable equation in each region has constant coefficients. The transmission matrix for each region is obtained by solving the constant coefficient acoustic state variable differential equation. The transmission matrix for the duct or nozzle is the product of the individual transmission matrices of each region. Solutions are presented for several geometries with and without mean flow.

  10. Angular dependence of fluctuations in acoustic transmissions relative to tidal direction in the SWAT environment

    NASA Astrophysics Data System (ADS)

    George, Jacob; Field, Robert L.

    2003-10-01

    Recently, fluctuations in continuous wave acoustic transmissions through internal tides that are periodic and have a constant amplitude in range have been studied [J. George and R. L. Field, J. Acoust. Soc. Am. 113, 2333 (2003)]. It was demonstrated through WKB/Pekeris calculations that the fluctuations are significantly greater when the transmission is nearly perpendicular to the tidal direction, and decrease when the transmission becomes more parallel to the tidal direction. Testing the validity of the above results in the realistic ocean provided the motivation for the present work. This was done through simulation using the NRL Coastal Ocean Model (NCOM) fitted to experimental data. The NCOM output provided the sound speed profile as a function of space and time. Results of the simulation will be presented. [Work supported by ONR (PE-62435N), and administered by NRL.

  11. Broadband asymmetric acoustic transmission by a plate with quasi-periodic surface ridges

    SciTech Connect

    Li, Chunhui; Ke, Manzhu Ye, Yangtao; Xu, Shengjun; Qiu, Chunyin; Liu, Zhengyou

    2014-07-14

    In this paper, an acoustic system with broadband asymmetric transmission is designed and fabricated, which consists of a water-immersed aluminum plate engraved with quasi-periodically-patterned ridges on single surface. It demonstrates that when the acoustic waves are launched into the system from the structured side, they can couple into the Lamb modes in the plate efficiently and attain a high transmission; on the contrary, when the waves are incident from the opposite flat side, the coupling is weak, and the transmission is low. Superior to systems with periodic patterning, this quasi-periodically-patterned system has a broad working frequency range due to the collective contributions from the multiple diffractions specific to the structure.

  12. Acoustic propagation in the Hudson River Estuary: Analysis of experimental measurements and numerical modeling results

    NASA Astrophysics Data System (ADS)

    Radhakrishnan, Sreeram

    Underwater intrusion detection is an ongoing security concern in port and harbor areas. Of particular interest is to detect SCUBA divers, unmanned underwater vehicles and small boats from their acoustic signature. A thorough understanding of the effects of the shallow water propagating medium on acoustic signals can help develop new technologies and improve the performance of existing acoustic based surveillance systems. The Hudson River Estuary provides us with such a shallow water medium to conduct research and improve our knowledge of shallow water acoustics. Acoustic propagation in the Hudson River Estuary is highly affected by the temporal and spatial variability of salinity and temperature due to tides, freshwater inflows, winds etc. The primary goal of this research is to help develop methodologies to predict the formation of an acoustic field in the realistic environment of the lower Hudson River Estuary. Shallow water high-frequency acoustic propagation experiments were conducted in the Hudson River near Hoboken, New Jersey. Channel Impulse Response (CIR) measurements were carried out in the frequency band from 10 to 100 kHz for distances up to 200 meters in a water depth of 8-10 meters which formed the basis for experimental Transmission Loss (TL). CIR data was also utilized to demonstrate multi-path propagation in shallow water. Acoustic propagation models based on Ray Theory and Parabolic Equation methods were implemented in the frequency band from 10 to 100 kHz and TL was estimated. The sound velocity profiles required as input by acoustic propagation models were calculated from in-situ measurements of temperature, salinity and depth. Surface reflection loss was obtained from CIR data and incorporated into the acoustic propagation models. Experimentally obtained TL was used to validate the acoustic model predictions. An outcome of this research is an operational acoustic transmission loss (TL) forecast system based on the existing, Stevens New York

  13. Progress in Acoustic Transmission of Power through Walls

    NASA Technical Reports Server (NTRS)

    Sherrit,Stewart; Coty, Benjamin; Bao, Xiaoqi; Bar-Cohen, Yoseph; Badescu, Mircea; Chang, Zensheu

    2008-01-01

    A document presents updated information on implementation of the wireless acoustic-electric feed-through (WAEF) concept, which was reported in Using Piezoelectric Devices To Transmit Power Through Walls (NPO-41157), NASA Tech Briefs, Vol. 32, No. 6 (June 2008), page 70. To recapitulate: In a basic WAEF setup, a transmitting piezoelectric transducer on one side of a wall is driven at resonance to excite ultrasonic vibrations in the wall. A receiving piezoelectric transducer on the opposite side of the wall converts the vibrations back to an ultrasonic AC electric signal, which is then detected and otherwise processed in a manner that depends on the modulation (if any) applied to the signal and whether the signal is used to transmit power, data, or both. The present document expands upon the previous information concerning underlying physical principles, advantages, and potential applications of WAEF. It discusses the design and construction of breadboard prototype piezoelectric transducers for WAEF. It goes on to present results of computational simulations of performance and results of laboratory tests of the prototypes. In one notable test, a 100-W light bulb was lit by WAEF to demonstrate the feasibility of powering a realistic load.

  14. 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.

  15. Coherent reflection from surface gravity water waves during reciprocal acoustic transmissions.

    PubMed

    Badiey, Mohsen; Song, Aijun; Smith, Kevin B

    2012-10-01

    During a recent experiment in Kauai, Hawaii, reciprocal transmissions were conducted between two acoustic transceivers mounted on the seafloor at a depth of 100 m. The passage of moving surface wave crests was shown to generate focused and intense coherent acoustic returns, which had increasing or decreasing delay depending on the direction of propagation relative to the direction of surface wave crests. It is shown that a rough surface two-dimensional parabolic equation model with an evolving sea surface can produce qualitative agreement with data for the dynamic surface returns. PMID:23039567

  16. 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

  17. Modal analysis and acoustic transmission through offset-core honeycomb sandwich panels

    NASA Astrophysics Data System (ADS)

    Mathias, Adam Dustin

    The work presented in this thesis is motivated by an earlier research that showed that double, offset-core honeycomb sandwich panels increased thermal resistance and, hence, decreased heat transfer through the panels. This result lead to the hypothesis that these panels could be used for acoustic insulation. Using commercial finite element modeling software, COMSOL Multiphysics, the acoustical properties, specifically the transmission loss across a variety of offset-core honeycomb sandwich panels, is studied for the case of a plane acoustic wave impacting the panel at normal incidence. The transmission loss results are compared with those of single-core honeycomb panels with the same cell sizes. The fundamental frequencies of the panels are also computed in an attempt to better understand the vibrational modes of these particular sandwich-structured panels. To ensure that the finite element analysis software is adequate for the task at hand, two relevant benchmark problems are solved and compared with theory. Results from these benchmark results compared well to those obtained from theory. Transmission loss results from the offset-core honeycomb sandwich panels show increased transmission loss, especially for large cell honeycombs when compared to single-core honeycomb panels.

  18. Transmission profiles from SCIAMACHY solar occultation measurements

    NASA Astrophysics Data System (ADS)

    Zalach, Jacob; Von Savigny, Christian

    Vertical atmospheric transmission profiles contain information about its composition and make it possible to reconstruct the vertical distribution of its components. The measurement of stratospheric aerosol extinction profiles and its size distribution is the goal of the ROMIC-ROSA project for which transmission profiles are the most important precondition. One established method to obtain such profiles are satellite born occultation measurements. For this project SCIAMACHY (EnviSat) solar occultation measurements are analysed. The data set covers a time period of ten years within a wavelength interval between 240 and 2380 nm. Due to different spatial resolution of the measured solar profiles a direct application of existing analysis tools and algorithms is not possible. First they have to be adjusted to the present data. This contribution explains the present data processing and shows the resulting transmission profiles.

  19. 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.

  20. Acoustic Measurement of Suspended Fine Particle Concentrations by Attenuation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Knowledge of sediment concentration is important in the study of streams and rivers. The work presented explores the appropriate frequency and transducer spacing for acoustic measurement of suspended particles in the range of 0.1 – 64 microns. High frequency (20 MHz) acoustic signal attenuation wa...

  1. Stroboscopic and acoustic measures of inspiratory phonation.

    PubMed

    Kelly, C L; Fisher, K V

    1999-09-01

    Inspiratory phonation (IP) is the production of voice as air is taken into the lungs. Although IP is promoted as a laryngeal assessment and voice treatment technique, it has been described quantitatively in very few speakers. This study quantified changes in laryngeal adduction, fundamental frequency, and intensity during IP relative to expiratory phonation (EP). We hypothesized that IP would increase laryngeal abduction and fundamental frequency. The experiment was a within-subjects, repeated measures design with each subject serving as her own control. Participants were 10 females (ages 19-50 years) who underwent simultaneous transoral videostrobolaryngoscopy and acoustic voice recording. We found that membranous vocal fold contact decreased significantly during IP relative to EP, while the trends for change of ventricular fold squeeze during IP varied across individuals. Vocal fundamental frequency increased significantly during IP relative to EP, but intensity did not vary consistently across conditions. Without teaching or coaching, changes that occurred during IP did not carry over to EP produced immediately following IP within the same respiratory cycle. PMID:10498055

  2. Multi-dimensional analysis of subjective acoustical ratings and acoustical measures in existing concert halls

    NASA Astrophysics Data System (ADS)

    Okano, Toshiyuki

    2001-05-01

    Correlations between subjective acoustical ratings and hall-averaged values of acoustical measures are studied among existing worldwide major concert halls. It was shown that the classified acoustical ratings by Beranek [Concert and Opera Halls, How They Sound (ASA, 1996)] are discriminated correctly by combining binaural quality index (BQI) with some other acoustical measures. BQI is determined by the arithmetic average of inter-aural cross correlation coefficient in three octave bands of 500, 1000, and 2000 Hz, subtracted from unity, calculated from the early 80-ms part of binaural impulse response. Considering that the upper limit value of BQI not to cause disturbing image shift is approximately 0.85 at individual seat [Okano, J. Acoust. Soc. Am. 2219-2230 (2000)], the values of 0.6 or higher in hall averaged value of BQI, 0.85 or smaller in individual seat value of BQI, and approximately 5 dB or higher in strength factor at middle frequencies are proposed as design objectives to attain a high acoustical quality. It should be provided that other acoustical measures are also optimized. These target values will be very effective in studying room shape of halls, using scale models or computer models.

  3. Frequency-Preserved Acoustic Diode Model with High Forward-Power-Transmission Rate

    NASA Astrophysics Data System (ADS)

    Liu, Chang; Du, Zongliang; Sun, Zhi; Gao, Huajian; Guo, Xu

    2015-06-01

    The acoustic diode (AD) can provide brighter and clearer ultrasound images by eliminating acoustic disturbances caused by sound waves traveling in two directions at the same time and interfering with each other. Such an AD could give designers new flexibility in making ultrasonic sources like those used in medical imaging or nondestructive testing. However, current AD designs, based on nonlinear effects, only partially fill this role by converting sound to a new frequency and blocking any backward flow of the original frequency. In this work, an AD model that preserves the frequencies of acoustic waves and has a relatively high forward-power-transmission rate is proposed. Theoretical analysis indicates that the proposed AD has forward, reverse, and breakdown characteristics very similar to electrical diodes. The significant rectifying effect of the proposed AD is verified numerically through a one-dimensional example. Possible schemes for experimental realization of this model as well as more complex and efficient AD designs are also discussed.

  4. Serological Measures of Trachoma Transmission Intensity

    PubMed Central

    Martin, Diana L.; Wiegand, Ryan; Goodhew, Brook; Lammie, Patrick; Black, Carolyn M.; West, Sheila; Gaydos, Charlotte A.; Dize, Laura; Mkocha, Harran; Kasubi, Mabula; Gambhir, Manoj

    2015-01-01

    Ocular infection with Chlamydia trachomatis can lead to trachoma, a leading infectious cause of blindness. Trachoma is targeted for elimination by 2020. Clinical grading for ocular disease is currently used for evaluating trachoma elimination programs, but serological surveillance can be a sensitive measure of disease transmission and provide a more objective testing strategy than clinical grading. We calculated the basic reproduction number from serological data in settings with high, medium, and low disease transmission based on clinical disease. The data showed a striking relationship between age seroprevalence and clinical data, demonstrating the proof-of-principle that age seroprevalence predicts transmission rates and therefore could be used as an indicator of decreased transmission of ocular trachoma. PMID:26687891

  5. Serological Measures of Trachoma Transmission Intensity.

    PubMed

    Martin, Diana L; Wiegand, Ryan; Goodhew, Brook; Lammie, Patrick; Black, Carolyn M; West, Sheila; Gaydos, Charlotte A; Dize, Laura; Mkocha, Harran; Kasubi, Mabula; Gambhir, Manoj

    2015-01-01

    Ocular infection with Chlamydia trachomatis can lead to trachoma, a leading infectious cause of blindness. Trachoma is targeted for elimination by 2020. Clinical grading for ocular disease is currently used for evaluating trachoma elimination programs, but serological surveillance can be a sensitive measure of disease transmission and provide a more objective testing strategy than clinical grading. We calculated the basic reproduction number from serological data in settings with high, medium, and low disease transmission based on clinical disease. The data showed a striking relationship between age seroprevalence and clinical data, demonstrating the proof-of-principle that age seroprevalence predicts transmission rates and therefore could be used as an indicator of decreased transmission of ocular trachoma. PMID:26687891

  6. The Effect of Habitat Acoustics on Common Marmoset Vocal Signal Transmission

    PubMed Central

    MORRILL, RYAN J.; THOMAS, A. WREN; SCHIEL, NICOLA; SOUTO, ANTONIO; MILLER, CORY T.

    2013-01-01

    Noisy acoustic environments present several challenges for the evolution of acoustic communication systems. Among the most significant is the need to limit degradation of spectro-temporal signal structure in order to maintain communicative efficacy. This can be achieved by selecting for several potentially complementary processes. Selection can act on behavioral mechanisms permitting signalers to control the timing and occurrence of signal production to avoid acoustic interference. Likewise, the signal itself may be the target of selection, biasing the evolution of its structure to comprise acoustic features that avoid interference from ambient noise or degrade minimally in the habitat. Here, we address the latter topic for common marmoset (Callithrix jacchus) long-distance contact vocalizations, known as phee calls. Our aim was to test whether this vocalization is specifically adapted for transmission in a species-typical forest habitat, the Atlantic forests of northeastern Brazil. We combined seasonal analyses of ambient habitat acoustics with experiments in which pure tones, clicks, and vocalizations were broadcast and rerecorded at different distances to characterize signal degradation in the habitat. Ambient sound was analyzed from intervals throughout the day and over rainy and dry seasons, showing temporal regularities across varied timescales. Broadcast experiment results indicated that the tone and click stimuli showed the typically inverse relationship between frequency and signaling efficacy. Although marmoset phee calls degraded over distance with marked predictability compared with artificial sounds, they did not otherwise appear to be specially designed for increased transmission efficacy or minimal interference in this habitat. We discuss these data in the context of other similar studies and evidence of potential behavioral mechanisms for avoiding acoustic interference in order to maintain effective vocal communication in common marmosets. PMID

  7. Acoustic propagation through anisotropic internal wave fields: transmission loss, cross-range coherence, and horizontal refraction.

    PubMed

    Oba, Roger; Finette, Steven

    2002-02-01

    Results of a computer simulation study are presented for acoustic propagation in a shallow water, anisotropic ocean environment. The water column is characterized by random volume fluctuations in the sound speed field that are induced by internal gravity waves, and this variability is superimposed on a dominant summer thermocline. Both the internal wave field and resulting sound speed perturbations are represented in three-dimensional (3D) space and evolve in time. The isopycnal displacements consist of two components: a spatially diffuse, horizontally isotropic component and a spatially localized contribution from an undular bore (i.e., a solitary wave packet or solibore) that exhibits horizontal (azimuthal) anisotropy. An acoustic field is propagated through this waveguide using a 3D parabolic equation code based on differential operators representing wide-angle coverage in elevation and narrow-angle coverage in azimuth. Transmission loss is evaluated both for fixed time snapshots of the environment and as a function of time over an ordered set of snapshots which represent the time-evolving sound speed distribution. Horizontal acoustic coherence, also known as transverse or cross-range coherence, is estimated for horizontally separated points in the direction normal to the source-receiver orientation. Both transmission loss and spatial coherence are computed at acoustic frequencies 200 and 400 Hz for ranges extending to 10 km, a cross-range of 1 km, and a water depth of 68 m. Azimuthal filtering of the propagated field occurs for this environment, with the strongest variations appearing when propagation is parallel to the solitary wave depressions of the thermocline. A large anisotropic degradation in horizontal coherence occurs under the same conditions. Horizontal refraction of the acoustic wave front is responsible for the degradation, as demonstrated by an energy gradient analysis of in-plane and out-of-plane energy transfer. The solitary wave packet is

  8. Acoustic propagation through anisotropic internal wave fields: Transmission loss, cross-range coherence, and horizontal refraction

    NASA Astrophysics Data System (ADS)

    Oba, Roger; Finette, Steven

    2002-02-01

    Results of a computer simulation study are presented for acoustic propagation in a shallow water, anisotropic ocean environment. The water column is characterized by random volume fluctuations in the sound speed field that are induced by internal gravity waves, and this variability is superimposed on a dominant summer thermocline. Both the internal wave field and resulting sound speed perturbations are represented in three-dimensional (3D) space and evolve in time. The isopycnal displacements consist of two components: a spatially diffuse, horizontally isotropic component and a spatially localized contribution from an undular bore (i.e., a solitary wave packet or solibore) that exhibits horizontal (azimuthal) anisotropy. An acoustic field is propagated through this waveguide using a 3D parabolic equation code based on differential operators representing wide-angle coverage in elevation and narrow-angle coverage in azimuth. Transmission loss is evaluated both for fixed time snapshots of the environment and as a function of time over an ordered set of snapshots which represent the time-evolving sound speed distribution. Horizontal acoustic coherence, also known as transverse or cross-range coherence, is estimated for horizontally separated points in the direction normal to the source-receiver orientation. Both transmission loss and spatial coherence are computed at acoustic frequencies 200 and 400 Hz for ranges extending to 10 km, a cross-range of 1 km, and a water depth of 68 m. Azimuthal filtering of the propagated field occurs for this environment, with the strongest variations appearing when propagation is parallel to the solitary wave depressions of the thermocline. A large anisotropic degradation in horizontal coherence occurs under the same conditions. Horizontal refraction of the acoustic wave front is responsible for the degradation, as demonstrated by an energy gradient analysis of in-plane and out-of-plane energy transfer. The solitary wave packet is

  9. 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.

  10. 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.

  11. Application of High Order Acoustic Finite Elements to Transmission Losses and Enclosure Problems

    NASA Technical Reports Server (NTRS)

    Craggs, A.; Stevenson, G.

    1985-01-01

    A family of acoustic finite elements was developed based on C continuity (acoustic pressure being the nodal variable) and the no-flow condition. The family include triangular, quadrilateral and hexahedral isoparametric elements with linear quadratic and cubic variation in modelling and distortion. Of greatest use in problems with irregular boundaries are the cubic isoparametric elements: the 32 node hexahedral element for three-dimensional systems; and the twelve node quadrilateral and ten node triangular elements for two-dimensional/axisymmetric applications. These elements were applied to problems involving cavity resonances, transmission loss in silencers and the study of end effects, using a Floating Point Systems 164 attached array processor accessed through an Amdahl 5860 mainframe. The elements are presently being used to study the end effects associated with duct terminations within finite enclosures. The transmission losses with various silencers and sidebranches in ducts is also being studied using the same elements.

  12. A study of methods to predict and measure the transmission of sound through the walls of light aircraft. Integration of certain singular boundary element integrals for applications in linear acoustics

    NASA Technical Reports Server (NTRS)

    Zimmerle, D.; Bernhard, R. J.

    1985-01-01

    An alternative method for performing singular boundary element integrals for applications in linear acoustics is discussed. The method separates the integral of the characteristic solution into a singular and nonsingular part. The singular portion is integrated with a combination of analytic and numerical techniques while the nonsingular portion is integrated with standard Gaussian quadrature. The method may be generalized to many types of subparametric elements. The integrals over elements containing the root node are considered, and the characteristic solution for linear acoustic problems are examined. The method may be generalized to most characteristic solutions.

  13. Hydraulic Fracture Propagation through Preexisting Discontinuity Monitored by Acoustic Emission and Ultrasonic Transmission

    NASA Astrophysics Data System (ADS)

    Stanchits, S.; Lund, J.; Surdi, A.; Edelman, E.; Whitney, N.; Eldredge, R.; Suarez-Rivera, R.

    2011-12-01

    Hydraulic fracturing is critical to enhance hydrocarbon production from ultra-low permeability unconventional reservoirs, and is the common completion methodology for tight formations around the world. Unfortunately, these reservoirs are often highly heterogeneous and their heterogeneity imparts a degree of geometrical complexity in hydraulic fractures that is poorly understood. Fracture complexity (e.g. branching) results in higher surface area and could be beneficial to production provided it remains conductive. Understanding the sources and consequences of fracture complexity is thus of high importance to completion and production operations. In this study we postulate that textural complexity in tight heterogeneous formations induces fracture complexity, and that the main sources of textural complexity are associated with veins, bed boundaries, lithologic contacts, and geologic interfaces. We thus study the effect of interfaces on hydraulic fracture propagation under laboratory conditions by Acoustic Emission (AE) and Ultrasonic Transmission (UT) monitoring techniques. The experiments were conducted on low permeability sandstone blocks of 279 x 279 x 381 mm length with saw cut discontinuities oriented orthogonally to the expected direction of fracture propagation. The rock is loaded in a poly-axial test frame to representative effective in-situ stress conditions of normal and deviatoric stress. Hydraulic fracturing was initiated by injection of silicon oil into a borehole drilled off center from the block. Acoustic emission (AE) events were continuously monitored during testing using nineteen P-wave sensors. Additional sensors were installed to periodically monitor ultrasonic transmission (UT) along various directions oblique and perpendicular to the fracture and the interface. The AE and UT data were recorded using a Vallen AMSY-6 system, with 16-bit amplitude resolution and 5 MHz sampling rate. Detailed analysis of AE localizations allowed us to identify

  14. Motion measurement of acoustically levitated object

    NASA Technical Reports Server (NTRS)

    Watkins, John L. (Inventor); Barmatz, Martin B. (Inventor)

    1993-01-01

    A system is described for determining motion of an object that is acoustically positioned in a standing wave field in a chamber. Sonic energy in the chamber is sensed, and variation in the amplitude of the sonic energy is detected, which is caused by linear motion, rotational motion, or drop shape oscillation of the object. Apparatus for detecting object motion can include a microphone coupled to the chamber and a low pass filter connected to the output of the microphone, which passes only frequencies below the frequency of sound produced by a transducer that maintains the acoustic standing wave field. Knowledge about object motion can be useful by itself, can be useful to determine surface tension, viscosity, and other information about the object, and can be useful to determine the pressure and other characteristics of the acoustic field.

  15. 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.

  16. A unique method to study acoustic transmission through ducts using signal synthesis and averaging of acoustic pulses

    NASA Technical Reports Server (NTRS)

    Salikuddin, M.; Ramakrishnan, R.; Ahuja, K. K.; Brown, W. H.

    1981-01-01

    An acoustic impulse technique using a loudspeaker driver is developed to measure the acoustic properties of a duct/nozzle system. A signal synthesis method is used to generate a desired single pulse with a flat spectrum. The convolution of the desired signal and the inverse Fourier transform of the reciprocal of the driver's response are then fed to the driver. A signal averaging process eliminates the jet mixing noise from the mixture of jet noise and the internal noise, thereby allowing very low intensity signals to be measured accurately, even for high velocity jets. A theoretical analysis is carried out to predict the incident sound field; this is used to help determine the number and locations of the induct measurement points to account for the contributions due to higher order modes present in the incident tube method. The impulse technique is validated by comparing experimentally determined acoustic characteristics of a duct-nozzle system with similar results obtained by the impedance tube method. Absolute agreement in the comparisons was poor, but the overall shapes of the time histories and spectral distributions were much alike.

  17. Transmission line icing measurement on photogrammetry method

    NASA Astrophysics Data System (ADS)

    Huang, Huan; Ma, Xiaohong; Zhao, Lijin; Du, Hao; Luo, Hong; Mao, Xianyin; Tang, Min; Liu, Yawen

    2015-12-01

    Icing thickness parameter is the basic data for power sector to make decision for icing accident prevention. In this paper, a transmission line icing measurement method is proposed. It used the photogrammetry method to realize icing parameters measurement through the integration of high resolution camera, laser range finder and inertial measurement unit. Compared with traditional icing measurement method, this method is flexible and is the effective supplement of the fixed icing detection terminal. And its high accuracy measurement guarantees the reliability of the icing thickness parameters.

  18. A Numerical Investigation of Turbine Noise Source Hierarchy and Its Acoustic Transmission Characteristics: Proof-of-Concept Progress

    NASA Technical Reports Server (NTRS)

    VanZante, Dale; Envia, Edmane

    2008-01-01

    A CFD-based simulation of single-stage turbine was done using the TURBO code to assess its viability for determining acoustic transmission through blade rows. Temporal and spectral analysis of the unsteady pressure data from the numerical simulations showed the allowable Tyler-Sofrin modes that are consistent with expectations. This indicated that high-fidelity acoustic transmission calculations are feasible with TURBO.

  19. New Gear Transmission Error Measurement System Designed

    NASA Technical Reports Server (NTRS)

    Oswald, Fred B.

    2001-01-01

    The prime source of vibration and noise in a gear system is the transmission error between the meshing gears. Transmission error is caused by manufacturing inaccuracy, mounting errors, and elastic deflections under load. Gear designers often attempt to compensate for transmission error by modifying gear teeth. This is done traditionally by a rough "rule of thumb" or more recently under the guidance of an analytical code. In order for a designer to have confidence in a code, the code must be validated through experiment. NASA Glenn Research Center contracted with the Design Unit of the University of Newcastle in England for a system to measure the transmission error of spur and helical test gears in the NASA Gear Noise Rig. The new system measures transmission error optically by means of light beams directed by lenses and prisms through gratings mounted on the gear shafts. The amount of light that passes through both gratings is directly proportional to the transmission error of the gears. A photodetector circuit converts the light to an analog electrical signal. To increase accuracy and reduce "noise" due to transverse vibration, there are parallel light paths at the top and bottom of the gears. The two signals are subtracted via differential amplifiers in the electronics package. The output of the system is 40 mV/mm, giving a resolution in the time domain of better than 0.1 mm, and discrimination in the frequency domain of better than 0.01 mm. The new system will be used to validate gear analytical codes and to investigate mechanisms that produce vibration and noise in parallel axis gears.

  20. Evaluation of the transmission line model for couplant layer corrections in pulse-echo measurements.

    PubMed

    Sturtevant, Blake; Pantea, Cristian; Sinha, Dipen

    2013-05-01

    An acoustic couplant layer plays an integral role in many ultrasonic nondestructive testing and material characterization applications. It is important to account for this layer for accurate time-delay measurements. In pulse-echo measurements, the couplant layer can be accounted for by modeling the frequency dependence of phase delay. In this paper, two such models are evaluated for robustness in determining an accurate phase velocity: a simple linear relationship and the acoustic transmission line with its associated nonlinear expression. For this evaluation, measurements of acoustic phase delay in an aluminum sample were made by the pulse-echo method using tone bursts of 1800 different carrier frequencies between 35 and 125 MHz. The transmission line model was fit to the measured data using an unconstrained nonlinear least squares fitting routine with two free parameters: the acoustic phase velocity in the sample and the couplant thickness. It was found that this nonlinear model was extremely sensitive to the initial parameter guesses and could not unambiguously determine both the couplant layer thickness and acoustic phase velocity. In contrast, the faster and simpler linear least squares fit to the delay data determines a unique phase velocity in agreement with resonant ultrasound spectroscopy, an independent measurement technique. PMID:23661128

  1. Material Property Measurement in Hostile Environments using Laser Acoustics

    SciTech Connect

    Ken L. Telschow

    2004-08-01

    Acoustic methods are well known and have been used to measure various intrinsic material properties, such as, elastic coefficients, density, crystal axis orientation, microstructural texture, and residual stress. Extrinsic properties, such as, dimensions, motion variables or temperature are also readily determined from acoustic methods. Laser acoustics, employing optical generation and detection of elastic waves, has a unique advantage over other acoustic methods—it is noncontacting, uses the sample surface itself for transduction, requires no couplant or invasive sample surface preparation and can be utilized in any hostile environment allowing optical access to the sample surface. In addition, optical generation and detection probe beams can be focused to the micron scale and/or shaped to alter the transduction process with a degree of control not possible using contact transduction methods. Laser methods are amenable to both continuous wave and pulse-echo measurements and have been used from Hz to 100’s of GHz (time scales from sec to psec) and with amplitudes sufficient to fracture materials. This paper shall review recent applications of laser acoustic methods to determining material properties in hostile environments that preclude the use of contacting transduction techniques. Example environments include high temperature (>1000C) sintering and molten metal processing, thin film deposition by plasma techniques, materials moving at high velocity during the fabrication process and nuclear high radiation regions. Recent technological advances in solid-state lasers and telecommunications have greatly aided the development and implementation of laser acoustic methods, particularly at ultra high frequencies. Consequently, laser acoustic material property measurements exhibit high precision and reproducibility today. In addition, optical techniques provide methods of imaging acoustic motion that is both quantitative and rapid. Possible future directions for

  2. One-dimensional pressure transfer models for acoustic-electric transmission channels

    NASA Astrophysics Data System (ADS)

    Wilt, K. R.; Lawry, T. J.; Scarton, H. A.; Saulnier, G. J.

    2015-09-01

    A method for modeling piezoelectric-based ultrasonic acoustic-electric power and data transmission channels is presented. These channels employ piezoelectric disk transducers to convey signals across a series of physical layers using ultrasonic waves. This model decomposes the mechanical pathway of the signal into individual ultrasonic propagation layers which are generally independent of the layer's adjacent domains. Each layer is represented by a two-by-two traveling pressure wave transfer matrix which relates the forward and reverse pressure waves on one side of the layer to the pressure waves on the opposite face, where each face is assumed to be in contact with a domain of arbitrary reference acoustic impedance. A rigorous implementation of ultrasonic beam spreading is introduced and implemented within applicable domains. Compatible pressure-wave models for piezoelectric transducers are given, which relate the electric voltage and current interface of the transducer to the pressure waves on one mechanical interface while also allowing for passive acoustic loading of the secondary mechanical interface. It is also shown that the piezoelectric model's electrical interface is compatible with transmission line parameters (ABCD-parameters), allowing for connection of electronic components and networks. The model is shown to be capable of reproducing the behavior of realistic physical channels.

  3. Taking advantage of acoustic inhomogeneities in photoacoustic measurements

    NASA Astrophysics Data System (ADS)

    Da Silva, Anabela; Handschin, Charles; Riedinger, Christophe; Piasecki, Julien; Mensah, Serge; Litman, Amélie; Akhouayri, Hassan

    2016-03-01

    Photoacoustic offers promising perspectives in probing and imaging subsurface optically absorbing structures in biological tissues. The optical uence absorbed is partly dissipated into heat accompanied with microdilatations that generate acoustic pressure waves, the intensity which is related to the amount of fluuence absorbed. Hence the photoacoustic signal measured offers access, at least potentially, to a local monitoring of the absorption coefficient, in 3D if tomographic measurements are considered. However, due to both the diffusing and absorbing nature of the surrounding tissues, the major part of the uence is deposited locally at the periphery of the tissue, generating an intense acoustic pressure wave that may hide relevant photoacoustic signals. Experimental strategies have been developed in order to measure exclusively the photoacoustic waves generated by the structure of interest (orthogonal illumination and detection). Temporal or more sophisticated filters (wavelets) can also be applied. However, the measurement of this primary acoustic wave carries a lot of information about the acoustically inhomogeneous nature of the medium. We propose a protocol that includes the processing of this primary intense acoustic wave, leading to the quantification of the surrounding medium sound speed, and, if appropriate to an acoustical parametric image of the heterogeneities. This information is then included as prior knowledge in the photoacoustic reconstruction scheme to improve the localization and quantification.

  4. Acoustic beamforming through a thin plate using vibration measurements.

    PubMed

    Leclère, Quentin; Picard, Christophe

    2015-06-01

    The aim of this paper is to propose a methodology to localize acoustic sources from the measurement of airborne induced vibrations of a thin structure. Targeted applications are the identification of acoustic sources through a thin wall, with a potential filtration of the incident field, which may be of practical interest, for instance, when identifying exterior acoustic sources from the inside of a moving vehicle. Two methods are coupled here to achieve this purpose: the Force Analysis Technique (FAT), used to identify the parietal pressure field exciting the thin structure from vibration measurements, and beamforming, used for the localization of acoustic sources from the (FAT-)identified parietal pressure. The coupling of the two methods is studied first from a theoretical point of view, and an experimental proof of concept is then presented, showing the feasibility and relevance of the proposed approach. PMID:26093428

  5. Experimental study using nearfield acoustic holography of sound transmission through fuselage sidewall structures

    NASA Technical Reports Server (NTRS)

    Maynard, J. D.

    1986-01-01

    The reduction of cabin noise in lightweight, propeller-driven aircraft is an especially difficult problem in noise control. Nearfield Acoustic Holography (NAH) was used to determine the mode of vibration and acoustic intensity for panels which differed in: construction (number of stiffening ribs, size of stifening ribs, construction material, and panel surface curvature); boundary support condition (free edge condition or clamped edge condition); and mode of excitation (structural-borne forces or airborne forces). The different samples of aircraft panels are described and the measurement of the natural response frequencies was discussed under various boundary support and excitation conditions. The results of the NAH measurements are presented.

  6. An Enhanced Energy Balanced Data Transmission Protocol for Underwater Acoustic Sensor Networks

    PubMed Central

    Javaid, Nadeem; Shah, Mehreen; Ahmad, Ashfaq; Imran, Muhammad; Khan, Majid Iqbal; Vasilakos, Athanasios V.

    2016-01-01

    This paper presents two new energy balanced routing protocols for Underwater Acoustic Sensor Networks (UASNs); Efficient and Balanced Energy consumption Technique (EBET) and Enhanced EBET (EEBET). The first proposed protocol avoids direct transmission over long distance to save sufficient amount of energy consumed in the routing process. The second protocol overcomes the deficiencies in both Balanced Transmission Mechanism (BTM) and EBET techniques. EBET selects relay node on the basis of optimal distance threshold which leads to network lifetime prolongation. The initial energy of each sensor node is divided into energy levels for balanced energy consumption. Selection of high energy level node within transmission range avoids long distance direct data transmission. The EEBET incorporates depth threshold to minimize the number of hops between source node and sink while eradicating backward data transmissions. The EBET technique balances energy consumption within successive ring sectors, while, EEBET balances energy consumption of the entire network. In EEBET, optimum number of energy levels are also calculated to further enhance the network lifetime. Effectiveness of the proposed schemes is validated through simulations where these are compared with two existing routing protocols in terms of network lifetime, transmission loss, and throughput. The simulations are conducted under different network radii and varied number of nodes. PMID:27070605

  7. An Enhanced Energy Balanced Data Transmission Protocol for Underwater Acoustic Sensor Networks.

    PubMed

    Javaid, Nadeem; Shah, Mehreen; Ahmad, Ashfaq; Imran, Muhammad; Khan, Majid Iqbal; Vasilakos, Athanasios V

    2016-01-01

    This paper presents two new energy balanced routing protocols for Underwater Acoustic Sensor Networks (UASNs); Efficient and Balanced Energy consumption Technique (EBET) and Enhanced EBET (EEBET). The first proposed protocol avoids direct transmission over long distance to save sufficient amount of energy consumed in the routing process. The second protocol overcomes the deficiencies in both Balanced Transmission Mechanism (BTM) and EBET techniques. EBET selects relay node on the basis of optimal distance threshold which leads to network lifetime prolongation. The initial energy of each sensor node is divided into energy levels for balanced energy consumption. Selection of high energy level node within transmission range avoids long distance direct data transmission. The EEBET incorporates depth threshold to minimize the number of hops between source node and sink while eradicating backward data transmissions. The EBET technique balances energy consumption within successive ring sectors, while, EEBET balances energy consumption of the entire network. In EEBET, optimum number of energy levels are also calculated to further enhance the network lifetime. Effectiveness of the proposed schemes is validated through simulations where these are compared with two existing routing protocols in terms of network lifetime, transmission loss, and throughput. The simulations are conducted under different network radii and varied number of nodes. PMID:27070605

  8. Acoustic levitator for containerless measurements on low temperature liquids

    SciTech Connect

    Benmore, Chris J; Weber, Richard; Neuefeind, Joerg C; Rey, Charles A A

    2009-01-01

    A single-axis acoustic levitator was constructed and used to levitate liquid and solid drops at temperatures from -40 to +40 C. The levitator consisted of: (i) two acoustic transducers mounted on a rigid vertical support that was bolted to an optical breadboard, (ii) a acoustic power supply that controlled acoustic intensity, relative phase of the drive to the transducers, and could modulate the acoustic forces at frequencies up to 1kHz, (iii) a video camera, and (iv) a system for providing a stream of controlled temperature gas flow over the sample. The acoustic transducers were operated at their resonant frequency of ~ 22 kHz and could produce sound pressure levels up to 160 dB. The force applied by the acoustic field could be modulated using a frequency generator to excite oscillations in the sample. Sample temperature was controlled using a modified Cryostream Plus and measured using thermocouples and an infrared thermal imager. The levitator was installed at x-ray beamline 11 ID-C at the Advanced Photon Source and used to investigate the structure of supercooled liquids.

  9. Acoustic levitator for structure measurements on low temperature liquid droplets.

    PubMed

    Weber, J K R; Rey, C A; Neuefeind, J; Benmore, C J

    2009-08-01

    A single-axis acoustic levitator was constructed and used to levitate liquid and solid drops of 1-3 mm in diameter at temperatures in the range -40 to +40 degrees C. The levitator comprised (i) two acoustic transducers mounted on a rigid vertical support that was bolted to an optical breadboard, (ii) an acoustic power supply that controlled acoustic intensity, relative phase of the drive to the transducers, and could modulate the acoustic forces at frequencies up to 1 kHz, (iii) a video camera, and (iv) a system for providing a stream of controlled temperature gas flow over the sample. The acoustic transducers were operated at their resonant frequency of approximately 22 kHz and could produce sound pressure levels of up to 160 dB. The force applied by the acoustic field could be modulated to excite oscillations in the sample. Sample temperature was controlled using a modified Cryostream Plus and measured using thermocouples and an infrared thermal imager. The levitator was installed at x-ray beamline 11 ID-C at the Advanced Photon Source and used to investigate the structure of supercooled liquids. PMID:19725664

  10. 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.

  11. Measurement of magnetic moment via optical transmission

    NASA Astrophysics Data System (ADS)

    Heidsieck, Alexandra; Schmid, Daniel; Gleich, Bernhard

    2016-03-01

    The magnetic moment of nanoparticles is an important property for drug targeting and related applications as well as for the simulation thereof. However, the measurement of the magnetic moment of nanoparticles, nanoparticle-virus-complexes or microspheres in solution can be difficult and often yields unsatisfying or incomparable results. To measure the magnetic moment, we designed a custom measurement device including a magnetic set-up to observe nanoparticles indirectly via light transmission in solution. We present a simple, cheap device of manageable size, which can be used in any laboratory as well as a novel evaluation method to determine the magnetic moment of nanoparticles via the change of the optical density of the particle suspension in a well-defined magnetic gradient field. In contrast to many of the established measurement methods, we are able to observe and measure the nanoparticle complexes in their natural state in the respective medium. The nanoparticles move along the magnetic gradient and thereby away from the observation point. Due to this movement, the optical density of the fluid decreases and the transmission increases over time at the measurement location. By comparing the measurement with parametric simulations, we can deduce the magnetic moment from the observed behavior.

  12. Analogy between the one-dimensional acoustic waveguide and the electrical transmission line in the cases of nonlinearity and relaxation

    NASA Astrophysics Data System (ADS)

    Yang, Desen; Zhang, Haoyang; Shi, Shengguo; Li, Di; Shi, Jie; Hu, Bo

    2015-10-01

    The propagation of plane acoustic waves can be investigated by taking advantage of the electro-acoustical analogy between the one-dimensional acoustic waveguide and the electrical transmission line, because they share the same type of equation. This paper follow the previous studies and expand the analogy into the cases of quadratic nonlinearity and dispersion produced by relaxation process. From the basic equations relating acoustic pressure, density fluctuation and velocity, which are valid for the nonlinear and relaxing media, the equivalent travelling-wave circuits of one-dimensional acoustic waveguide with the consideration of nonlinearity and relaxation processes are obtained. Furthermore, we also discuss the analogy relationship of parameters which exist in the acoustical and electrical systems.

  13. Sound Transmission Loss Through a Corrugated-Core Sandwich Panel with Integrated Acoustic Resonators

    NASA Technical Reports Server (NTRS)

    Schiller, Noah H.; Allen, Albert R.; Zalewski, Bart F; Beck, Benjamin S.

    2014-01-01

    The goal of this study is to better understand the effect of structurally integrated resonators on the transmission loss of a sandwich panel. The sandwich panel has facesheets over a corrugated core, which creates long aligned chambers that run parallel to the facesheets. When ports are introduced through the facesheet, the long chambers within the core can be used as low-frequency acoustic resonators. By integrating the resonators within the structure they contribute to the static load bearing capability of the panel while also attenuating noise. An analytical model of a panel with embedded resonators is derived and compared with numerical simulations. Predictions show that acoustic resonators can significantly improve the transmission loss of the sandwich panel around the natural frequency of the resonators. In one configuration with 0.813 m long internal chambers, the diffuse field transmission loss is improved by more than 22 dB around 104 Hz. The benefit is achieved with no added mass or volume relative to the baseline structure. The embedded resonators are effective because they radiate sound out-of-phase with the structure. This results in destructive interference, which leads to less transmitted sound power.

  14. A radial transmission line material measurement apparatus

    SciTech Connect

    Warne, L.K.; Moyer, R.D.; Koontz, T.E.; Morris, M.E.

    1993-05-01

    A radial transmission line material measurement sample apparatus (sample holder, offset short standards, measurement software, and instrumentation) is described which has been proposed, analyzed, designed, constructed, and tested. The purpose of the apparatus is to obtain accurate surface impedance measurements of lossy, possibly anisotropic, samples at low and intermediate frequencies (vhf and low uhf). The samples typically take the form of sections of the material coatings on conducting objects. Such measurements thus provide the key input data for predictive numerical scattering codes. Prediction of the sample surface impedance from the coaxial input impedance measurement is carried out by two techniques. The first is an analytical model for the coaxial-to-radial transmission line junction. The second is an empirical determination of the bilinear transformation model of the junction by the measurement of three full standards. The standards take the form of three offset shorts (and an additional lossy Salisbury load), which have also been constructed. The accuracy achievable with the device appears to be near one percent.

  15. Transmission Grating Measurements of Undulator K

    SciTech Connect

    Bionta, R. M.

    2010-12-01

    This study was undertaken to understand the practicalities of determine K differences in the undulator modules by measuring single-shot x-ray spectra of the spontaneous radiation with a transmissive grating spectrometer under development to measure FEL spectra. Since the quality of the FEL is dependent on a uniform K value in all the undulator modules, being able to measure the relative undulator K values is important. Preliminary results were presented in a presentation, 'Use of FEL Off-Axis Zone Plate Spectrometer to Measure Relative K by the Pinhole/Centroid Method', at the 'LCLS Beam-Based Undulator K Measurements Workshop' on November 14, 2005 (UCRL-PRES-217281). This study applies equally well to reflective gratings of the appropriate period and inclinations.

  16. Transmission two-modulator generalized ellipsometry measurements.

    PubMed

    Jellison, Gerald E; Griffiths, C Owen; Holcomb, David E; Rouleau, Christopher M

    2002-11-01

    The two-modulator generalized ellipsometer has been used to measure samples in transmission. In this configuration, the instrument can completely characterize a linear diattenuator and retarder, measuring birefringence, diattenuation, the angle of the principal axis, and the sample depolarization simultaneously and accurately. This instrument can be operated in two modes: (1) spectroscopic, in which measurements are made through the entire sample aperture as a function of wavelength, and (2) spatially resolved, in which measurements are made at a single wavelength and a birefringence picture is made of the sample. Current spatially resolved measurements have been made at a resolution of approximately 40 microm. Four samples have been examined with this instrument: (1) a mica plate, (2) a Polaroid polarizer, and (3) two quartz plates. PMID:12412646

  17. Transmission two-modulator generalized ellipsometry measurements

    NASA Astrophysics Data System (ADS)

    Jellison, Gerald E., Jr.; Griffiths, C. Owen; Holcomb, David E.; Rouleau, Christopher M.

    2002-11-01

    The two-modulator generalized ellipsometer has been used to measure samples in transmission. In this configuration, the instrument can completely characterize a linear diattenuator and retarder, measuring birefringence, diattenuation, the angle of the principal axis, and the sample depolarization simultaneously and accurately. This instrument can be operated in two modes: (1) spectroscopic, in which measurements are made through the entire sample aperture as a function of wavelength, and (2) spatially resolved, in which measurements are made at a single wavelength and a birefringence picture is made of the sample. Current spatially resolved measurements have been made at a resolution of approx40 mum. Four samples have been examined with this instrument: (1) a mica plate, (2) a Polaroid polarizer, and (3) two quartz plates.

  18. Non-ossicular signal transmission in human middle ears: Experimental assessment of the “acoustic route” with perforated tympanic membranes

    PubMed Central

    Voss, Susan E.; Rosowski, John J.; Merchant, Saumil N.; Peake, William T.

    2008-01-01

    Direct acoustic stimulation of the cochlea by the sound-pressure difference between the oval and round windows (called the “acoustic route”) has been thought to contribute to hearing in some pathological conditions, along with the normally dominant “ossicular route.” To determine the efficacy of this acoustic route and its constituent mechanisms in human ears, sound pressures were measured at three locations in cadaveric temporal bones [with intact and perforated tympanic membranes (TMs)]: (1) in the external ear canal lateral to the TM, PTM; (2) in the tympanic cavity lateral to the oval window, POW; and (3) near the round window, PRW. Sound transmission via the acoustic route is described by two concatenated processes: (1) coupling of sound pressure from ear canal to middle-ear cavity, HPCAV≡PCAV/PTM, where PCAV represents the middle-ear cavity pressure, and (2) sound-pressure difference between the windows, HWPD≡(POW−PRW)/PCAV. Results show that: HPCAV depends on perforation size but not perforation location; HWPD depends on neither perforation size nor location. The results (1) provide a description of the window pressures based on measurements, (2) refute the common otological view that TM perforation location affects the “relative phase of the pressures at the oval and round windows,” and (3) show with an intact ossicular chain that acoustic-route transmission is substantially below ossicular-route transmission except for low frequencies with large perforations. Thus, hearing loss from TM perforations results primarily from reduction in sound coupling via the ossicular route. Some features of the frequency dependence of HPCAV and HWPD can be interpreted in terms of a structure-based lumped-element acoustic model of the perforation and middle-ear cavities. PMID:17902851

  19. Radiation Transmission Measurements for Demron Fabric

    SciTech Connect

    Friedman, H; Singh, M S

    2003-01-07

    Radiation Shield Technologies has requested a measurement survey of its Demron fabric to determine the shielding properties in the x-ray, gamma ray and beta particle emissions in the range of energies relevant to clinical and Homeland Security applications. It is important to perform a detailed measurement program in order to sort out the shielding properties of this material in light of the often-times complex spectra emitted by standard radio-nuclides and x-ray generators. Low energy portions of the spectra are shielded more easily by this fabric than are the higher energy components and a simple single-layer test can lead to misleading results. This concept of ''spectral hardening'' was investigated by measuring the transmission factors for many layers and extracting information from the slopes of the transmission curves thereby obtaining a true picture of the shielding properties of the material as a function of energy. After the initial measurement program was completed, the mass attenuation coefficients were calculated using the LLNL cross section data, TART code, RST supplied weight fractions and the measured density of the fabric. This code is used for the Monte Carlo simulation of coupled neutron-photon transport in 3-D geometry for shielding and other applications. With such a design tool, it is possible to ''tune'' the characteristics of the Demron fabric to meet the specific needs for a given radiation environment.

  20. Quantitative measurement of acoustic pressure in the focal zone of acoustic lens-line focusing using the Schlieren method.

    PubMed

    Jiang, Xueping; Cheng, Qian; Xu, Zheng; Qian, Menglu; Han, Qingbang

    2016-04-01

    This paper proposes a theory and method for quantitative measurement of the acoustic lens-line focusing ultrasonic (ALLFU) field in its focal spot size and acoustic pressure using the Schlieren imaging technique. Using Fourier transformation, the relationship between the brightness of the Schlieren image and the acoustic pressure was introduced. The ALLFU field was simulated using finite element method and compared with the Schlieren acoustic field image. The measurement of the focal spot size was performed using the Schlieren method. The acoustic pressure in the focal zone of the ALLFU field and the transducer-transmitting voltage response were quantitatively determined by measuring the diffraction light fringe intensity. The results show that the brightness of the Schlieren image is a linear function of the acoustic intensity when the acousto-optic interaction length remains constant and the acoustic field is weak. PMID:27139646

  1. Field-Deployable Acoustic Digital Systems for Noise Measurement

    NASA Technical Reports Server (NTRS)

    Shams, Qamar A.; Wright, Kenneth D.; Lunsford, Charles B.; Smith, Charlie D.

    2000-01-01

    Langley Research Center (LaRC) has for years been a leader in field acoustic array measurement technique. Two field-deployable digital measurement systems have been developed to support acoustic research programs at LaRC. For several years, LaRC has used the Digital Acoustic Measurement System (DAMS) for measuring the acoustic noise levels from rotorcraft and tiltrotor aircraft. Recently, a second system called Remote Acquisition and Storage System (RASS) was developed and deployed for the first time in the field along with DAMS system for the Community Noise Flight Test using the NASA LaRC-757 aircraft during April, 2000. The test was performed at Airborne Airport in Wilmington, OH to validate predicted noise reduction benefits from alternative operational procedures. The test matrix was composed of various combinations of altitude, cutback power, and aircraft weight. The DAMS digitizes the acoustic inputs at the microphone site and can be located up to 2000 feet from the van which houses the acquisition, storage and analysis equipment. Digitized data from up to 10 microphones is recorded on a Jaz disk and is analyzed post-test by microcomputer system. The RASS digitizes and stores acoustic inputs at the microphone site that can be located up to three miles from the base station and can compose a 3 mile by 3 mile array of microphones. 16-bit digitized data from the microphones is stored on removable Jaz disk and is transferred through a high speed array to a very large high speed permanent storage device. Up to 30 microphones can be utilized in the array. System control and monitoring is accomplished via Radio Frequency (RF) link. This paper will present a detailed description of both systems, along with acoustic data analysis from both systems.

  2. Tunability of acoustic phonon transmission and thermal conductance in three dimensional quasi-periodically stubbed waveguides

    NASA Astrophysics Data System (ADS)

    Xie, Zhong-Xiang; Liu, Jing-Zhong; Yu, Xia; Wang, Hai-Bin; Deng, Yuan-Xiang; Li, Ke-Min; Zhang, Yong

    2015-03-01

    We investigate acoustic phonon transmission and thermal conductance in three dimensional (3D) quasi-periodically stubbed waveguides according to the Fibonacci sequence. Results show that the transmission coefficient exhibits the periodic oscillation upon varying the length of stub/waveguide at low frequency, and the period of such oscillation is tunably decreased with increasing the Fibonacci number N. Interestingly, there also exist some anti-resonant dips that gradually develop into wide stop-frequency gaps with increasing N. As the temperature goes up, a transition of the thermal conductance from the decrease to the increase occurs in these systems. When N is increased, the thermal conductance is approximately decreased with a linear trend. Moreover, the decreasing degree sensitively depends on the variation of temperature. A brief analysis of these results is given.

  3. The application of finite element techniques to acoustic transmission in lined ducts with flow

    NASA Technical Reports Server (NTRS)

    Astley, R. J.; Eversman, W.

    1979-01-01

    The finite element method (FEM) is used to analyze the propagation of sound in two-dimensional nonuniform ducts carrying a compressible subsonic mean flow. Galerkin and residual least squares (RLS) methods with natural and forced boundary conditions are considered. The accuracy of FEM results for the eigenvalue and transmission problems is assessed by comparison with alternative numerical schemes for nonuniform ducts. The results presented and those from associated investigations indicate that modal coupling is a significant feature of the acoustic field, especially at high Mach numbers. A multimodal model therefore appears to be essential if any reliable conclusions are to be drawn in the context of turbofan inlet regions. Improvements to the eigenvalue scheme following the implementation of higher-order Hermitian elements indicate a similar modification for the transmission problem.

  4. Multiplex transmission system for gate drive signals of inverter circuit using surface acoustic wave filters

    NASA Astrophysics Data System (ADS)

    Suzuki, Akifumi; Ueda, Kensuke; Goka, Shigeyoshi; Wada, Keiji; Kakio, Shoji

    2016-07-01

    We propose and fabricate a multiplexed transmission system based on frequency-division multiple access (FDMA) with surface acoustic wave (SAW) filters. SAW filters are suitable for use in wide-gap switching devices and multilevel inverters because of their capability to operate at high temperatures, good electrical isolation, low cost, and high reliability. Our proposed system reduces the number of electrical signal wires needed to control each switching device and eliminates the need for isolation circuits, simplifying the transmission system and gate drive circuits. We successfully controlled two switching devices with a single coaxial line and confirmed the operation of a single-phase half-bridge inverter at a supply voltage of 100 V, and the total delay time to control the switching devices was less than 2.5 µs. Our experimental results validated our proposed system.

  5. Acoustical transmission-line model of the middle-ear cavities and mastoid air cells

    PubMed Central

    Keefe, Douglas H.

    2015-01-01

    An acoustical transmission line model of the middle-ear cavities and mastoid air cell system (MACS) was constructed for the adult human middle ear with normal function. The air-filled cavities comprised the tympanic cavity, aditus, antrum, and MACS. A binary symmetrical airway branching model of the MACS was constructed using an optimization procedure to match the average total volume and surface area of human temporal bones. The acoustical input impedance of the MACS was calculated using a recursive procedure, and used to predict the input impedance of the middle-ear cavities at the location of the tympanic membrane. The model also calculated the ratio of the acoustical pressure in the antrum to the pressure in the middle-ear cavities at the location of the tympanic membrane. The predicted responses were sensitive to the magnitude of the viscothermal losses within the MACS. These predicted input impedance and pressure ratio functions explained the presence of multiple resonances reported in published data, which were not explained by existing MACS models. PMID:25920840

  6. Vibro-acoustic response and sound transmission loss analysis of functionally graded plates

    NASA Astrophysics Data System (ADS)

    Chandra, N.; Raja, S.; Nagendra Gopal, K. V.

    2014-10-01

    This paper presents analytical studies on the vibro-acoustic and sound transmission loss characteristics of functionally graded material (FGM) plates using a simple first-order shear deformation theory. The material properties of the plate are assumed to vary according to power law distribution of the constituent materials in terms of volume fraction. The sound radiation due to sinusoidally varying point load, uniformly distributed load and obliquely incident sound wave is computed by solving the Rayleigh integral with a primitive numerical scheme. Displacement, velocity, acceleration, radiated sound power level, radiated sound pressure level and radiation efficiency of FGM plate for varying power law index are examined. The sound transmission loss of the FGM plate for several incidence angles and varying power law index is studied in detail. It has been found that, for the plate being considered, the sound power level increases monotonically with increase in power law index at lower frequency range (0-500 Hz) and a non-monotonic trend is appeared towards higher frequencies for both point and distributed force excitations. Increased vibration and acoustic response is observed for ceramic-rich FGM plate at higher frequency band; whereas a similar trend is seen for metal-rich FGM plate at lower frequency band. The dBA values are found to be decreasing with increase in power law index. The radiation efficiency of ceramic-rich FGM plate is noticed to be higher than that of metal and metal-rich FGM plates. The transmission loss below the first resonance frequency is high for ceramic-rich FGM plate and low for metal-rich FGM plate and further depends on the specific material property. The study has found that increased transmission loss can be achieved at higher frequencies with metal-rich FGM plates.

  7. Deep seafloor acoustic backscattering measurements using sea beam

    NASA Astrophysics Data System (ADS)

    Demoustier, C.

    Multibeam echo-sounders such as Sea Beam allow detailed bathymetric surveys of large areas of the seafloor. However, bathymetry only reveals the shape of seafloor features to the resolution of the sounding system, and in order to make geological interpretations the nature of the seafloor surveyed needs to be characterized. Because bottom roughness and/or variations in bottom substrate cause fluctuations in the backscattered acoustic signal received by an echo-sounder, such characteristics can be inferred in part by analyzing the structure and the variations of this signal over several transmission cycles. The approach taken was to record digitally the detected echo envelopes of the Sea Beam's 16 narrow beams over a variety of seafloor environments, and process these data to determine whether the acoustics held enough information to differentiate between bottom types. Significant results derived from these acoustic data concern the Sea Beam system's performance, its potential for mapping acoustic boundaries, and the display of the echoes received in a side looking sonar-like picture.

  8. Transmission Electron Microscope Measures Lattice Parameters

    NASA Technical Reports Server (NTRS)

    Pike, William T.

    1996-01-01

    Convergent-beam microdiffraction (CBM) in thermionic-emission transmission electron microscope (TEM) is technique for measuring lattice parameters of nanometer-sized specimens of crystalline materials. Lattice parameters determined by use of CBM accurate to within few parts in thousand. Technique developed especially for use in quantifying lattice parameters, and thus strains, in epitaxial mismatched-crystal-lattice multilayer structures in multiple-quantum-well and other advanced semiconductor electronic devices. Ability to determine strains in indivdual layers contributes to understanding of novel electronic behaviors of devices.

  9. 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.

  10. Acoustical measurement of the Salt Lake Mormon Tabernacle

    NASA Astrophysics Data System (ADS)

    Rollins, Sarah; Leishman, Timothy W.

    2001-05-01

    An acoustical survey of the Salt Lake Mormon Tabernacle has been performed to assess the behavior of the hall in its current state. The tabernacle is a well-known historical building with a large elongated dome ceiling. This paper discusses the measurements used to characterize the hall. Several parameters derived from omnidirectional, directional, and binaural impulse response measurements are presented. Color maps of the parameters over audience seating areas reveal their spatial variations. These maps and the statistical properties of the parameters aid in clarifying the acoustical characteristics and anomalies of the hall.

  11. Measurement of thin films using very long acoustic wavelengths

    NASA Astrophysics Data System (ADS)

    Clement, G. T.; Nomura, H.; Adachi, H.; Kamakura, T.

    2013-12-01

    A procedure for measuring material thickness by means of necessarily long acoustic wavelengths is examined. The approach utilizes a temporal phase lag caused by the impulse time of wave momentum transferred through a thin layer that is much denser than its surrounding medium. In air, it is predicted that solid or liquid layers below approximately 1/2000 of the acoustic wavelength will exhibit a phase shift with an arctangent functional dependence on thickness and layer density. The effect is verified for thin films on the scale of 10 μm using audible frequency sound (7 kHz). Soap films as thin as 100 nm are then measured using 40 kHz air ultrasound. The method's potential for imaging applications is demonstrated by combining the approach with near-field holography, resulting in reconstructions with sub-wavelength resolution in both the depth and lateral directions. Potential implications at very high and very low acoustic frequencies are discussed.

  12. 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.

  13. Measurement of Neutron Transmission Through Iron Spheres

    SciTech Connect

    Massey, T.N.; Grimes, S.M.; Wenner, M.T.; Haghighat, Alireza; Adams, James M.; Carlson, Allan D.

    2005-05-24

    We have measured the transmission of neutrons through iron spheres with several different neutron sources. The D(d,n) reaction and the 15N(n,p) reaction were found to be the best candidates for nearly monoenergetic sources at energies below 11 MeV. We have used a quasi monoenergetic source with 3.0-, 5.0-, and 7.0-MeV deuterons incident on a deuteron gas cell and 5.1-MeV protons incident on a 15N gas cell. The Ohio University Beam Swinger Facility was used in these measurements. This allowed a single fixed detector in a well-shielded time-of-flight (TOF) tunnel to be used for measurements at all angles. This allows a great reduction in the background from room scattered neutrons. The detector, either NE-213 or lithium glass, was calibrated relative to the neutron spectrum from the B(d,n) or the Al(d,n) source reaction. These spectra have been measured relative to the primary neutron standard, 235U(n, f). The transmitted neutrons have been measured for all source reactions at several angles. The data will be reported as the number of neutrons versus time-of-flight since multiple scattering does not allow the energy to be determined accurately by time-of-flight. We have also measured the source reaction at several angles to enhance the modeling of the source spectrum.

  14. A collimated focused ultrasound beam of high acoustic transmission and minimum diffraction achieved by using a lens with subwavelength structures

    SciTech Connect

    Lin, Zhou; Tu, Juan; Cheng, Jianchun; Guo, Xiasheng E-mail: dzhang@nju.edu.cn; Wu, Junru; Huang, Pingtong; Zhang, Dong E-mail: dzhang@nju.edu.cn

    2015-09-14

    An acoustic focusing lens incorporated with periodically aligned subwavelength grooves corrugated on its spherical surface has been developed. It is demonstrated theoretically and experimentally that acoustic focusing achieved by using the lens can suppress the relative side-lobe amplitudes, enhance the focal gain, and minimize the shifting of the focus. Use of the lens coupled with a planar ultrasound transducer can generate an ultrasound beam with enhanced acoustic transmission and collimation effect, which offers the capability of improving the safety, efficiency, and accuracy of targeted surgery implemented by high intensity focused ultrasound.

  15. Measuring Transmission Spectra from the Ground

    NASA Astrophysics Data System (ADS)

    Jordan, Andres; Espinoza, Nestor; Eyheramendy, Susana

    2015-08-01

    Transmission spectroscopy allows study of the atmospheres of exoplanets without the need of spatially resolving them from their parent stars and is one of the most valuable follow-up possibilities offered by transiting systems. The measurement of a transmission spectrum, i.e. the apparent planetary size in units in the stellar radius as a function of wavelength, is conceptually simple, but the expected features that need to be discerned are on the order of one part in a thousand or less, and need to be extracted against a background of (potentially correlated) noise and systematic effects with amplitudes greatly exceeding that of the sought signal. In this talk I will describe how we have tackled the estimation of transmission spectra in a ground based survey we are carrying out with IMACS at Las Campanas Observatory, the Arizona-CfA-Catolica Exoplanet Spectroscopy Survey. Our treatment assumes an additive model consisting of the signal, common systematics and one of a set of stochastic processes with different memory characteristics for the noise. Common systematics are estimated from comparison stars using principal component analysis and the model parameter posterior distributions are estimated using MCMC. Model comparison is used to let the data select the model with the most appropriate noise component. I will illustrate the performance of our approach, and discuss possible avenues of improvement. I will also illustrate the importance of potential biases arising from our incomplete knowledge of stellar properties. In particular, I will show that limb darkening assumptions can limit the accuracy of our estimates of planetary radii above the achievable precisions in regimes currently being probed.

  16. Velocity and rotation measurements in acoustically levitated droplets

    NASA Astrophysics Data System (ADS)

    Saha, Abhishek; Basu, Saptarshi; Kumar, Ranganathan

    2012-10-01

    The velocity scale inside an acoustically levitated droplet depends on the levitator and liquid properties. Using Particle Imaging Velocimetry (PIV), detailed velocity measurements have been made in a levitated droplet of different diameters and viscosity. The maximum velocity and rotation are normalized using frequency and amplitude of acoustic levitator, and droplet viscosity. The non-dimensional data are fitted for micrometer- and millimeter-sized droplets levitated in different levitators for different viscosity fluids. It is also shown that the rotational speed of nanosilica droplets at an advanced stage of vaporization compares well with that predicted by exponentially fitted parameters.

  17. PROGRESS IN ACOUSTIC SUSPENDED-SEDIMENT MEASUREMENT RESEARCH

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An automatic acoustic pulse-echo distance measuring device (Field SedBed Monitor) was developed to collect bed height records in the Goodwin Creek Experimental Watershed. The bed material at the study site is composed of a mixture of sand and gravel with a median size of 8.3 mm. Using bed height re...

  18. SUSPENDED-SEDIMENT MEASUREMENTS IN LABORATORY FLUMES USING ACOUSTIC TECHNIQUES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Automated measurement of suspended sediments is crucial to the study of sediment transport. The short duration, high-intensity flows that are responsible for a large fraction of sediment movement are best observed by continuous monitoring systems. Acoustic systems are ideal for continuous monitori...

  19. 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.

  20. Acoustical Measurements of Selected Intonation Contours of French.

    ERIC Educational Resources Information Center

    Howie, John M.

    Recent studies of rising intonation contours in French, in particular the acoustical differences that serve to distinguish Yes/No questions from other rising intonations are reviewed. The preliminary results of a pilot study of rising intonations in French, in which average curves were obtained from spectrographic measurements of fundamental…

  1. 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.

  2. 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…

  3. Phase behaviour and phase separation kinetics measurement using acoustic arrays

    NASA Astrophysics Data System (ADS)

    Khammar, M.; Shaw, J. M.

    2011-10-01

    Speed of sound and acoustic wave attenuation are sensitive to fluid phase composition and to the presence of liquid-liquid interfaces. In this work, the use of an acoustic array comprising 64 elements as a non-intrusive sensor for liquid-liquid interface, phase separation kinetics measurement in bulk fluids, and local composition measurement in porous media is illustrated. Three benchmark examples: the phase behaviour of methanol + mixed hexanes and methanol + heptane mixtures at 25.0 °C and 1 bar, and Athabasca bitumen + heptane in a synthetic silica porous medium at 22.5 °C and 1 bar, illustrate the accuracy of liquid-liquid interface and potential research and industrial applications of the technique. Liquid-liquid interfaces can be detected independently using both speed of sound and acoustic wave attenuation measurements. The precision of the interface location measurement is 300 μm. As complete scans can be performed at a rate of 1 Hz, phase separation kinetics and diffusion of liquids within porous media are readily tracked. The technique is expected to find application where the fluids or porous media are opaque to visible light and where other imaging techniques are not readily applied, or are too costly. A current limitation is that the acoustic probes must be cooled to less than 315 K in order for them to operate.

  4. A field-deployable digital acoustic measurement system

    NASA Technical Reports Server (NTRS)

    Gray, David L.; Wright, Kenneth D., II; Rowland, Wayne D.

    1991-01-01

    A field deployable digital acoustic measurement system was developed to support acoustic research programs at the Langley Research Center. The system digitizes the acoustic inputs at the microphone, which can be located up to 1000 feet from the van which houses the acquisition, storage, and analysis equipment. Digitized data from up to 12 microphones is recorded on high density 8mm tape and is analyzed post-test by a microcomputer system. Synchronous and nonsynchronous sampling is available with maximum sample rates of 12,500 and 40,000 samples per second respectively. The high density tape storage system is capable of storing 5 gigabytes of data at transfer rates up to 1 megabyte per second. System overall dynamic range exceeds 83 dB.

  5. A Numerical Investigation of Turbine Noise Source Hierarchy and Its Acoustic Transmission Characteristics

    NASA Technical Reports Server (NTRS)

    VanZante, Dale; Envia, Edmane

    2008-01-01

    Understanding the relative importance of the various turbine noise generation mechanisms and the characteristics of the turbine acoustic transmission loss are essential ingredients in developing robust reduced-order models for predicting the turbine noise signature. A computationally based investigation has been undertaken to help guide the development of a turbine noise prediction capability that does not rely on empiricism. The investigation relies on highly detailed numerical simulations of the unsteady flowfield inside a modern high-pressure turbine (HPT). The simulations are developed using TURBO, which is an unsteady Reynolds-averaged Navier-Stokes (URANS) code capable of multi-stage simulations. The purpose of this study is twofold. First, to determine an estimate of the relative importance of the contributions to the coherent part of the acoustic signature of a turbine from the three potential sources of turbine noise generation, namely, blade-row viscous interaction, potential field interaction, and entropic source associated with the interaction of the blade rows with the temperature nonuniformities caused by the incomplete mixing of the hot fluid and the cooling flow. Second, to develop an understanding of the turbine acoustic transmission characteristics and to assess the applicability of existing empirical and analytical transmission loss models to realistic geometries and flow conditions for modern turbine designs. The investigation so far has concentrated on two simulations: (1) a single-stage HPT and (2) a two-stage HPT and the associated inter-turbine duct/strut segment. The simulations are designed to resolve up to the second harmonic of the blade passing frequency tone in accordance with accepted rules for second order solvers like TURBO. The calculations include blade and vane cooling flows and a radial profile of pressure and temperature at the turbine inlet. The calculation can be modified later to include the combustor pattern factor at the

  6. Broadband acoustic scattering measurements of underwater unexploded ordnance (UXO).

    PubMed

    Bucaro, J A; Houston, B H; Saniga, M; Dragonette, L R; Yoder, T; Dey, S; Kraus, L; Carin, L

    2008-02-01

    In order to evaluate the potential for detection and identification of underwater unexploded ordnance (UXO) by exploiting their structural acoustic response, we carried out broadband monostatic scattering measurements over a full 360 degrees on UXO's (two mortar rounds, an artillery shell, and a rocket warhead) and false targets (a cinder block and a large rock). The measurement band, 1-140 kHz, includes a low frequency structural acoustics region in which the wavelengths are comparable to or larger than the target characteristic dimensions. In general, there are aspects that provide relatively high target strength levels ( approximately -10 to -15 dB), and from our experience the targets should be detectable in this structural acoustics band in most acoustic environments. The rigid body scattering was also calculated for one UXO in order to highlight the measured scattering features involving elastic responses. The broadband scattering data should be able to support feature-based separation of UXO versus false targets and identification of various classes of UXO as well. PMID:18247878

  7. Volumetric measurements of a spatially growing dust acoustic wave

    SciTech Connect

    Williams, Jeremiah D.

    2012-11-15

    In this study, tomographic particle image velocimetry (tomo-PIV) techniques are used to make volumetric measurements of the dust acoustic wave (DAW) in a weakly coupled dusty plasma system in an argon, dc glow discharge plasma. These tomo-PIV measurements provide the first instantaneous volumetric measurement of a naturally occurring propagating DAW. These measurements reveal over the measured volume that the measured wave mode propagates in all three spatial dimensional and exhibits the same spatial growth rate and wavelength in each spatial direction.

  8. Direct-Sequence Spread-Spectrum Modulation for Utility Packet Transmission in Underwater Acoustic Communication Networks

    NASA Astrophysics Data System (ADS)

    Duke, Peter S.

    2002-09-01

    This thesis investigates the feasibility and performance of using Direct-Sequence Spread-Spectrum (DSSS) modulation for utility-packet transmission in Seaweb underwater wireless acoustic communications networks, Seaweb networks require robust channel-tolerant utility packets having a low probability of detection (LPD) and allowing for multi-user access, MATLAB code simulated the DSSS transmitter and receiver structures and a modeled channel impulse response represented the underwater environment, The specific modulation scheme implemented is direct-sequence, differentially encoded binary phase-shift keying (DS-DBPSK) with quadrature spreading, Performance is examined using Monte Carlo simulation Bit error rates and packet error rates for various signal-to-noise ratios and channel conditions are presented and the use of a RAKE receiver, forward error-correction coding and symbol interleaving are examined for improving system performance.

  9. Cascading multi-hop reservation and transmission in underwater acoustic sensor networks.

    PubMed

    Lee, Jae-Won; Cho, Ho-Shin

    2014-01-01

    The long propagation delay in an underwater acoustic channel makes designing an underwater media access control (MAC) protocol more challenging. In particular, handshaking-based MAC protocols widely used in terrestrial radio channels have been known to be inappropriate in underwater acoustic channels, because of the inordinately large latency involved in exchanging control packets. Furthermore, in the case of multi-hop relaying in a hop-by-hop handshaking manner, the end-to-end delay significantly increases. In this paper, we propose a new MAC protocol named cascading multi-hop reservation and transmission (CMRT). In CMRT, intermediate nodes between a source and a destination may start handshaking in advance for the next-hop relaying before handshaking for the previous node is completed. By this concurrent relaying, control packet exchange and data delivery cascade down to the destination. In addition, to improve channel utilization, CMRT adopts a packet-train method where multiple data packets are sent together by handshaking once. Thus, CMRT reduces the time taken for control packet exchange and accordingly increases the throughput. The performance of CMRT is evaluated and compared with that of two conventional MAC protocols (multiple-access collision avoidance for underwater (MACA-U) and MACA-U with packet trains (MACA-UPT)). The results show that CMRT outperforms other MAC protocols in terms of both throughput and end-to-end delay. PMID:25275349

  10. Acoustic measurements of a large cavity in a wind tunnel

    NASA Technical Reports Server (NTRS)

    Scheiman, J.

    1978-01-01

    Acoustic measurements were made with inside and far-field microphones. Correlation of measured frequencies with available theories indicates that existing theories are applicable over a broader range than previously shown. The cavity configuration with a partial covering downstream amplified tonal intensities. The frequency of the tones depended on cavity size, not on cavity open area. Introducing upstream disturbances decreased the amplitude of the cavity tones.

  11. 49 CFR 192.485 - Remedial measures: Transmission lines.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 3 2011-10-01 2011-10-01 false Remedial measures: Transmission lines. 192.485... Control § 192.485 Remedial measures: Transmission lines. (a) General corrosion. Each segment of transmission line with general corrosion and with a remaining wall thickness less than that required for...

  12. 49 CFR 192.485 - Remedial measures: Transmission lines.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 3 2010-10-01 2010-10-01 false Remedial measures: Transmission lines. 192.485... Control § 192.485 Remedial measures: Transmission lines. (a) General corrosion. Each segment of transmission line with general corrosion and with a remaining wall thickness less than that required for...

  13. 49 CFR 192.485 - Remedial measures: Transmission lines.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 3 2012-10-01 2012-10-01 false Remedial measures: Transmission lines. 192.485... Control § 192.485 Remedial measures: Transmission lines. (a) General corrosion. Each segment of transmission line with general corrosion and with a remaining wall thickness less than that required for...

  14. 49 CFR 192.485 - Remedial measures: Transmission lines.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 3 2014-10-01 2014-10-01 false Remedial measures: Transmission lines. 192.485... Control § 192.485 Remedial measures: Transmission lines. (a) General corrosion. Each segment of transmission line with general corrosion and with a remaining wall thickness less than that required for...

  15. 49 CFR 192.485 - Remedial measures: Transmission lines.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 3 2013-10-01 2013-10-01 false Remedial measures: Transmission lines. 192.485... Control § 192.485 Remedial measures: Transmission lines. (a) General corrosion. Each segment of transmission line with general corrosion and with a remaining wall thickness less than that required for...

  16. Mass flow rate measurement in abrasive jets using acoustic emission

    NASA Astrophysics Data System (ADS)

    Ivantsiv, V.; Spelt, J. K.; Papini, M.

    2009-09-01

    The repeatability of abrasive jet machining operations is presently limited by fluctuations in the mass flow rate due to powder compaction, stratification and humidity effects. It was found that the abrasive mass flow rate for a typical abrasive jet micromachining setup could be determined by using data from the acoustic emission of the abrasive jet impacting a flat plate. Two methods for extracting the mass flow rate from the acoustic emission were developed and compared. In the first method, the number of particle impacts per unit time was determined by a direct count of peaks in the acoustic emission signal. The second method utilizes the power spectrum density of the acoustic emission in a specific frequency range. Both measures were found to correlate strongly with the mass flow rate measured by weighing samples of blasted powder for controlled time periods. It was found that the peak count method permits measurement of the average frequency of the impacts and the mass flow rate, but can only be applied to flow rates in which the impact frequency is approximately one order of magnitude less than the frequency of the target plate ringing. The power spectrum density method of signal processing is applicable to relatively fine powders and to flow rates at which the average impact frequency is of the same order of magnitude as that of the ringing due to the impact. The acoustic emission technique can be used to monitor particle flow variations over a wide range of time periods and provides a straightforward and accurate means of process control.

  17. A high transmission broadband gradient index lens using elastic shell acoustic metamaterial elements.

    PubMed

    Titovich, Alexey S; Norris, Andrew N; Haberman, Michael R

    2016-06-01

    The use of cylindrical elastic shells as elements in acoustic metamaterial devices is demonstrated through simulations and underwater measurements of a cylindrical-to-plane wave lens. Transformation acoustics of a circular region to a square dictate that the effective density in the lens remain constant and equal to that of water. Piecewise approximation to the desired effective compressibility is achieved using a square array with elements based on the elastic shell metamaterial concept developed by Titovich and Norris [J. Acoust. Soc. Am. 136(4), 1601-1609 (2014)]. The sizes of the elements are chosen based on availability of shells, minimizing fabrication difficulties. The tested device is neutrally buoyant comprising 48 elements of nine different types of commercial shells made from aluminum, brass, copper, and polymers. Simulations indicate a broadband range in which the device acts as a cylindrical to plane wave lens. The experimental findings confirm the broadband quadropolar response from approximately 20 to 40 kHz, with positive gain of the radiation pattern in the four plane wave directions. PMID:27369162

  18. Evaluation of moving-coil loudspeaker and passive radiator parameters using normal-incidence sound transmission measurements: theoretical developments.

    PubMed

    Leishman, Timothy W; Anderson, Brian E

    2013-07-01

    The parameters of moving-coil loudspeaker drivers are typically determined using direct electrical excitation and measurement. However, as electro-mechano-acoustical devices, their parameters should also follow from suitable mechanical or acoustical evaluations. This paper presents the theory of an acoustical method of excitation and measurement using normal-incidence sound transmission through a baffled driver as a plane-wave tube partition. Analogous circuits enable key parameters to be extracted from measurement results in terms of open and closed-circuit driver conditions. Associated tools are presented that facilitate adjacent field decompositions and derivations of sound transmission coefficients (in terms of driver parameters) directly from the circuits. The paper also clarifies the impact of nonanechoic receiving tube terminations and the specific benefits of downstream field decompositions. PMID:23862800

  19. 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.

  20. Development of large-scale acoustic waveguides for liquid-level measurements

    SciTech Connect

    Kirkpatrick, J.F.; Kuzniak, W.C.

    1987-01-01

    Large-scale magnetostrictive ultrasonic waveguides are being developed and tested for liquid-level measurement. The use of inexpensive, commercially available, nickel tubing provides a homogeneous waveguide with nondispersive transmission properties and good independence of torsional and extensional wave modes. Because the entire waveguide is magnetostrictive, acoustic excitation and sensing is possible at any point along the length of the waveguide. The problems of establishing and maintaining circumferential fields for torsional wave generation have been solved by electromagnetic field generation. Prototype devices have been built and tested which exhibit a linear relationship between either torsional amplitude or phase velocity and depth of immersion.

  1. Acoustic Reflection and Transmission of 2-Dimensional Rotors and Stators, Including Mode and Frequency Scattering Effects

    NASA Technical Reports Server (NTRS)

    Hanson, Donald B.

    1999-01-01

    A reduced order modeling scheme has been developed for the unsteady acoustic and vortical coupling between blade rows of a turbomachine. The essential behavior of the system is governed by modal scattering coefficients (i.e., reflection and transmission coefficients) of the rotor, stator, inlet and nozzle, which are calculated as if they were connected to non-reflecting ducts. The objective of this report is to identify fundamental behavior of these scattering coefficients for a better understanding of the role of blade row reflection and transmission in noise generation. A 2D flat plate unsteady cascade model is used for the analysis with the expectation that the general behavior presented herein will carry over to models that include more realistic flow and geometry. It is shown that stators scatter input waves into many modes at the same frequency whereas rotors scatter on frequency, or harmonic order. Important cases are shown here the rotor reflection coefficient is greater than unity; a mode at blade passing frequency (BPF) traveling from the stator with unit sound power is reflected by the rotor with more than unit power at 2xBPF and 3xBPE Analysis is presented to explain this unexpected phenomenon. Scattering curves are presented in a format chosen for design use and for physical interpretation. To aid in interpretation of the curves, formulas are derived for special condition where waveforms are parallel to perpendicular to the rotor.

  2. Acoustic isolation vessel for measurement of the background noise in microphones

    NASA Technical Reports Server (NTRS)

    Ngo, Kim C. T.; Zuckerwar, Allan J.

    1993-01-01

    An acoustic isolation vessel has been developed to measure the background noise in microphones. The test microphone is installed in an inner vessel, which is suspended within an outer vessel, and the intervening air space is evacuated to a high vacuum. An analytical expression for the transmission coefficient is derived, based on a five-media model, and compared to experiment. At an isolation vacuum of 5 x 10 exp -6 Torr the experimental transmission coefficient was found to be lower than -155 dB at frequencies ranging from 40 to 1200 Hz. Measurements of the A-weighted noise levels of commercial condenser microphones of four different sizes show good agreement with published values.

  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. Acoustic temperature profile measurement technique for large combustion chambers

    SciTech Connect

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

    1989-05-01

    Measurement of times of flight of sound waves can be used to determinetemperatures in a gas. This paper describes a system, based on this principle,that is capable of giving the temperature profile in a nonisothermal gasvolume, for example, prevalent in a large furnace. The apparatus is simple,rugged, accurate, and capable of being automated for process controlapplications. It is basically an acoustic waveguide where the outsidetemperature profile is tranferred to a chosen gas contained inside theguide.

  5. 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.

  6. Optical and acoustical measuring techniques. [for Doppler measurement of flow velocities

    NASA Technical Reports Server (NTRS)

    Cliff, W. C.

    1977-01-01

    The paper reviews the techniques of laser and acoustic Doppler measurement of fluid velocities in confined and free flows. The main mathematical relations are presented, and some systems are studied. Resolution properties of coaxial, bistatic, and pulsed CO2 laser Doppler velocimeter systems are compared. Schematics for pulsed and continuous wave acoustic Doppler systems are discussed. Both of these types of systems benefit from using a bistatic configuration instead of a coaxial system. The pulsed systems avoid contamination of source noise by not sampling until after the source noise has passed the receiver. Comparison of wind velocity measured with a pulsed acoustic Doppler and with a boundary layer profile is made.

  7. Measurements of acoustic pressure at high amplitudes and intensities

    NASA Astrophysics Data System (ADS)

    Crum, L. A.; Bailey, M. R.; Kaczkowski, P.; McAteer, J. A.; Pishchalnikov, Y. A.; Sapozhnikov, O. A.

    2004-01-01

    In our research group, we desire measurements of the large pressure amplitudes generated by the shock waves used in shock wave lithotripsy (SWL) and the large acoustic intensities used in High Intensity Focused Ultrasound (HIFU). Conventional piezoelectric or PVDF hydrophones can not be used for such measurements as they are damaged either by cavitation, in SWL applications, or heat, in HIFU applications. In order to circumvent these difficulties, we have utilized optical fiber hydrophones in SWL that do not cavitate, and small glass probes and a scattering technique for measurements of large HIFU intensities. Descriptions of these techniques will be given as well as some typical data.

  8. 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.

  9. Flow velocity measurement with the nonlinear acoustic wave scattering

    NASA Astrophysics Data System (ADS)

    Didenkulov, Igor; Pronchatov-Rubtsov, Nikolay

    2015-10-01

    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.

  10. In-situ physical properties measurements using crosswell acoustic data

    SciTech Connect

    Johnson, P.A.; Albright, J.N.

    1985-01-01

    Crosswell acoustic surveys enable the in-situ measurements of elastic moduli, Poisson's ratio, porosity, and apparent seismic Q of gas-bearing low-permeability formations represented at the Department of Energy Multi-Well Experiment (MWX) site near Rifle, Colorado. These measurements, except for Q, are compared with laboratory measurements on core taken from the same depths at which the crosswell measurements are made. Seismic Q determined in situ is compared to average values for sandstone. Porosity was determined from crosswell data using the empirical relationship between acoustic velocity, porosity, and effective pressure developed by Domenico. Domenico, S.N., ''Rock Lithology and Porosity Determination from Shear and compressional Wave Velocity,'' Geophysics, Vol. 49, No. 9, Aug. 1984, pp. 1188-1195. In-situ porosities are significantly greater than the core-derived values. Sources of the discrepancy may arise from (i) the underestimation of porosity that can result when Boyle's Law measurements are made on low-permeability core and (ii) the application of Dominico's relationship, which is developed for clean sands, to the mixed sandstone and shale lithologies represented at the MWX site. Values for Young's modulus and Poisson's ratio derived from crosswell measurements are comparable to values obtained from core. Apparent seismic Q measured in situ between wells is lower than Q measured on core and clearly shows the heterogeneity of sandstone deposited in a fluvial environment. 16 refs., 4 figs., 2 tabs.

  11. 1KW Power Transmission Using Wireless Acoustic-Electric Feed-Through (WAEF)

    NASA Technical Reports Server (NTRS)

    Sherrit, S.; Bao, X.; Badescu, M.; Aldrich, J.; Bar-Cohen, Y.; Biederman, W.

    2008-01-01

    A variety of space applications require the delivery of power into sealed structures. Since the structural integrity can be degraded by holes for cabling we present an alternative method of delivering power and information using stress waves to the internal space of a sealed structure. One particular application of this technology is in sample return missions where it is critical to preserve the sample integrity and to prevent earth contamination. Therefore, the container has to be hermetically sealed and the integrity of the seal must be monitored in order to insure to a high degree of reliability the integrity of the sample return vessel. In this study we investigated the use of piezoelectric acoustic-electric power feed-through devices to transfer electric power wirelessly through a solid wall by using elastic or acoustic waves. The technology is applicable to a range of space and terrestrial applications where power is required by electronic equipment inside sealed containers, vacuum or pressure vessels, etc., where holes in the wall are prohibitive or may result in significant structural performance degradation or unnecessarily complex designs. To meet requirements of higher power applications, the feasibility to transfer kilowatts level power was investigated. Pre-stressed longitudinal piezoelectric feed-through devices were analyzed by finite element models and an equivalent circuit model was developed to predict the power transfer characteristics to different electric loads. Based on the results of the analysis a prototype device was designed, fabricated and a demonstration of the transmission of electric power up to 1.068-kW was successfully conducted. Efficiencies in the 80-90% range were also demonstrated and methods to increase the efficiency further are currently being considered.

  12. Acoustic waveguide technique for sensing incipient faults in underground power-transmission cables: including acousto-optic techniques. Final report

    SciTech Connect

    Harrold, R.T.

    1981-09-01

    The feasibility of using acoustic waveguide techniques for sensing incipient faults in underground power transmission cables was determined. Theoretical and practical studies were made of both the acoustic emission spectrum signatures associated with cable incipient faults, and the attenuation of acoustic waves in waterfilled metal tubes used as waveguides. Based on critical data, it can be estimated that in favorable circumstances, the acoustic waveguide system would only be useful for sensing incipient faults in underground cables of approx. 800 meters (approx. 0.5 miles) or less in length. As underground power transmission cables are often several kilometers in length, it was clear at this stage of the study, that simple acoustic waveguide sensing techniques would not be adequate, and some modification would be needed. With DOE approval it was decided to investigate acousto-optic sensing techniques in order to extend the detection range. In particular, a system in which acoustic emissions from cable incipient faults impinge on a fiber-optic lightguide and locally change its refractive indes, and as a consequence, modulate laser light transmitted along the light guide. Experiments based on this concept were successful, and it has been demonstrated that it is possible to sense acoustic emissions with energy levels below one micro-joule. A practical test of this system in the laboratory using a section of compressed gas-insulated cable with an internal flashover was successfully carried out. Long distance fault sensing with this technique should be feasible as laser light can be transmitted several kilometers in fiber optic lightguides. It is believed that laser-acousto-optic fault sensing is a viable technique which, with development, could be applied for fault sensing in power cables and other apparatus.

  13. Three-dimensional broadband intensity probe for measuring acoustical parameters

    NASA Astrophysics Data System (ADS)

    Miah, Khalid Hossain

    Measuring different acoustical properties have been the key in reducing noise and improving the sound quality from various sources. In this report, a broadband (200 Hz -- 6.5 kHz) three-dimensional seven-microphone intensity probe system is developed to measure the sound intensity, and total energy density in different acoustical environments. Limitations of most commercial intensity probes in measuring the three-dimensional intensity for a broadband sound field was the main motivation in developing this probe. The finite-difference error and the phase mismatch error which are the two main errors associated with the intensity measurements are addressed in this report. As for the physical design, seven microphones were arranged in a two-concentric arrays with one microphone located at the center of the probe. The outer array is for low-frequencies (200 Hz -- 1.0 kHz), and the inner one is for high-frequencies (1.0 kHz -- 6.5 kHz). The screw adjustable center microphone is used for the microphone calibration, and as the reference microphone of the probe. The simultaneous calibrations of all the microphones in the probe were done in the anechoic room. Theories for the intensity and the energy densities calculations for the probe were derived from the existing four-microphone probe configuration. Reflection and diffraction effects on the intensity measurements due to the presence of the microphones, and the supporting structures were also investigated in this report. Directivity patterns of the calculated intensity showed the omnidirectional nature of the probe. The intensity, and total energy density were calculated and compared with the ideal values in the anechoic room environment. Characterization of sound fields in a reverberant enclosed space, and sound source identification are some applications that were investigated using this probe. Results of different measurements showed effectiveness of the probe as a tool to measure key acoustical properties in many

  14. Nonintrusive Monitoring and Control of Metallurgical Processes by Acoustic Measurements

    NASA Astrophysics Data System (ADS)

    Yu, Hao-Ling; Khajavi, Leili Tafaghodi; Barati, Mansoor

    2011-06-01

    The feasibility of developing a new online monitoring technique based on the characteristic acoustic response of gas bubbles in a liquid has been investigated. The method is intended to monitor the chemistry of the liquid through its relation to the bubble sound frequency. A low-temperature model consisting of water and alcohol mixtures was established, and the frequency of bubbles rising under varying concentrations of methanol was measured. It was shown that the frequency of the sound created by bubble pulsation varies with the percentage of alcohol in water. The frequency drops sharply with the increase in methanol content up to 20 wt pct, after which the decreases is gradual. Surface tension seems to be a critical liquid property affecting the sound frequency through its two-fold effects on the bubble size and the pulsation domain. The dependence between the frequency and the liquid composition suggests the feasibility of developing an acoustic-based technique for process control purposes.

  15. 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. PMID:21361436

  16. Acoustic plethysmography measures breathing in unrestrained neonatal mice.

    PubMed

    Daubenspeck, J Andrew; Li, Aihua; Nattie, Eugene E

    2008-01-01

    Measurement of breathing volumes in neonatal mice is of growing importance in order to characterize the influence of development and genetic modifications on respiratory control to evaluate hypotheses concerned with human infant deficits that may affect sudden infant death syndrome, for example. Current techniques require undesirable physical constraints or incur possible artifacts specific to very small animals. We have examined the utility of a recently proposed approach using an acoustic resonance procedure that does not require undue physical constraint beyond placement in the acoustic plethysmograph. We show here that this approach can be applied to baby mice 5 days after birth and that it can be accurately calibrated. In addition, this approach should be useful to study unrestrained neonatal mice under conditions where body temperature approaches environmental temperature and barometric plethysmography cannot be used. PMID:17962574

  17. Reliability of Phase Velocity Measurements of Flexural Acoustic Waves in the Human Tibia In-Vivo

    PubMed Central

    2016-01-01

    Purpose Axial-transmission acoustics have shown to be a promising technique to measure individual bone properties and detect bone pathologies. With the ultimate goal being the in-vivo application of such systems, quantification of the key aspects governing the reliability is crucial to bring this method towards clinical use. Materials and Methods This work presents a systematic reliability study quantifying the sources of variability and their magnitudes of in-vivo measurements using axial-transmission acoustics. 42 healthy subjects were measured by an experienced operator twice per week, over a four-month period, resulting in over 150000 wave measurements. In a complementary study to assess the influence of different operators performing the measurements, 10 novice operators were trained, and each measured 5 subjects on a single occasion, using the same measurement protocol as in the first part of the study. Results The estimated standard error for the measurement protocol used to collect the study data was ∼ 17 m/s (∼ 4% of the grand mean) and the index of dependability, as a measure of reliability, was Φ = 0.81. It was shown that the method is suitable for multi-operator use and that the reliability can be improved efficiently by additional measurements with device repositioning, while additional measurements without repositioning cannot improve the reliability substantially. Phase velocity values were found to be significantly higher in males than in females (p < 10−5) and an intra-class correlation coefficient of r = 0.70 was found between the legs of each subject. Conclusions The high reliability of this non-invasive approach and its intrinsic sensitivity to mechanical properties opens perspectives for the rapid and inexpensive clinical assessment of bone pathologies, as well as for monitoring programmes without any radiation exposure for the patient. PMID:27015093

  18. Generation of Acoustic Gravity Waves by Periodic Radio Transmissions from a High-Power Ionospheric Heater

    NASA Astrophysics Data System (ADS)

    Frolov, Vladimir; Chernogor, Leonid; Rozumenko, Victor

    The Radiophysical Research Institute (Nizhny Novgorod, Russia) and Kharkiv V. N. Karazin National University (Kharkiv, Ukraine) have studied opportunities for the effective generation of acoustic gravity waves (AGWs) in 3 - 180-min period range. The excitation of such waves was conducted for the last several years using the SURA heating facility (Nizhny Novgorod). The detection of the HF-induced AGWs was carried out in the Radiophysical Observatory located near Kharkiv City at a distance of about 960 km from the SURA. A coherent radar for vertical sounding, an ionosonde, and magnetometer chains were used in our measurements. The main results are the following (see [1-5]): 1. Infrasound oscillation trains with a period of 6 min are detected during periodic SURA heater turn-on and -off. Similar oscillation trains are detected after long time pumping, during periodic transmissions with a period of 20 s, as well as after pumping turn-off. The train recordings begin 28 - 54 min after the heater turn-on or -off, and the train propagation speeds are about 300 - 570 m/s, the value of which is close to the sound speed at upper atmospheric altitudes. The amplitude of the Doppler shift frequency is of 10 - 40 mHz, which fits to the 0.1 - 0.3% electron density disturbances at ionospheric altitudes. The amplitude of the infrasound oscillations depends on the SURA mode of operation and the state of the upper atmosphere and ionosphere. 2. High-power radio transmissions stimulate the generation (or enhancement) of waves at ionospheric altitudes in the range of internal gravity wave periods. The HF-induced waves propagate with speeds of 360 - 460 m/s and produce changes in electron density with amplitudes of 2 - 3%. The generation of such periodic perturbations is more preferable with periods of 10 - 60 minutes. Their features depend significantly on the heater mode of operation. It should be stressed that perturbation intensity increases when a pumping wave frequency approaches

  19. Transmission (forward) mode, transcranial, noninvasive optoacoustic measurements for brain monitoring, imaging, and sensing

    NASA Astrophysics Data System (ADS)

    Petrov, Irene Y.; Petrov, Yuriy; Prough, Donald S.; Richardson, C. Joan; Fonseca, Rafael A.; Robertson, Claudia S.; Asokan, C. Vasantha; Agbor, Adaeze; Esenaliev, Rinat O.

    2016-03-01

    We proposed to use transmission (forward) mode for cerebral, noninvasive, transcranial optoacoustic monitoring, imaging, and sensing in humans. In the transmission mode, the irradiation of the tissue of interest and detection of optoacoustic signals are performed from opposite hemispheres, while in the reflection (backward) mode the irradiation of the tissue of interest and detection of optoacoustic signals are performed from the same hemisphere. Recently, we developed new, transmission-mode optoacoustic probes for patients with traumatic brain injury (TBI) and for neonatal patients. The transmission mode probes have two major parts: a fiber-optic delivery system and an acoustic transducer (sensor). To obtain optoacoustic signals in the transmission mode, in this study we placed the sensor on the forehead, while light was delivered to the opposite side of the head. Using a medical grade, multi-wavelength, OPObased optoacoustic system tunable in the near infrared spectral range (680-950 nm) and a novel, compact, fiber-coupled, multi-wavelength, pulsed laser diode-based system, we recorded optoacoustic signals generated in the posterior part of the head of adults with TBI and neonates. The optoacoustic signals had two distinct peaks: the first peak from the intracranial space and the second peak from the scalp. The first peak generated by cerebral blood was used to measure cerebral blood oxygenation. Moreover, the transmission mode measurements provided detection of intracranial hematomas in the TBI patients. The obtained results suggest that the transmission mode can be used for optoacoustic brain imaging, tomography, and mapping in humans.

  20. Estimating suspended solids concentrations from backscatter intensity measured by acoustic Doppler current profiler in San Francisco Bay, California

    USGS Publications Warehouse

    Gartner, J.W.

    2004-01-01

    The estimation of mass concentration of suspended solids is one of the properties needed to understand the characteristics of sediment transport in bays and estuaries. However, useful measurements or estimates of this property are often problematic when employing the usual methods of determination from collected water samples or optical sensors. Analysis of water samples tends to undersample the highly variable character of suspended solids, and optical sensors often become useless from biological fouling in highly productive regions. Acoustic sensors, such as acoustic Doppler current profilers that are now routinely used to measure water velocity, have been shown to hold promise as a means of quantitatively estimating suspended solids from acoustic backscatter intensity, a parameter used in velocity measurement. To further evaluate application of this technique using commercially available instruments, profiles of suspended solids concentrations are estimated from acoustic backscatter intensity recorded by 1200- and 2400-kHz broadband acoustic Doppler current profilers located at two sites in San Francisco Bay, California. ADCP backscatter intensity is calibrated using optical backscatterance data from an instrument located at a depth close to the ADCP transducers. In addition to losses from spherical spreading and water absorption, calculations of acoustic transmission losses account for attenuation from suspended sediment and correction for nonspherical spreading in the near field of the acoustic transducer. Acoustic estimates of suspended solids consisting of cohesive and noncohesive sediments are found to agree within about 8-10% (of the total range of concentration) to those values estimated by a second optical backscatterance sensor located at a depth further from the ADCP transducers. The success of this approach using commercially available Doppler profilers provides promise that this technique might be appropriate and useful under certain conditions in

  1. Determination of the elastic modulus of snow via acoustic measurements

    NASA Astrophysics Data System (ADS)

    Gerling, Bastian; van Herwijnen, Alec; Löwe, Henning

    2016-04-01

    The elastic modulus of snow is a key quantity from the viewpoint of avalanche research and forecasting, snow engineering or materials science in general. Since it is a fundamental property, many measurements have been reported in the literature. Due to differences in measurement methods, there is a lot of variation in the reported values. Especially values derived via computer tomography (CT) based numerical calculations using finite element methods are not corresponding to the results of other methods. The central issue is that CT based moduli are purely elastic whereas other methods may include viscoelastic deformation. In order to avoid this discrepancy we derived the elastic modulus of snow via wave propagation measurements and compared our results with CT based calculations. We measured the arrival times of acoustic pulses propagating through the snow samples to determine the P-wave velocity and in turn derive the elastic modulus along the direction of wave propagation. We performed a series of laboratory experiments to derive the P-wave modulus of snow in relation to density. The P-wave modulus ranged from 10 to 280 MPa for a snow density between 150 and 370 kg/m³. The moduli derived from the acoustic measurements correlated well with the CT-based values and both exhibited a power law trend over the entire density range. Encouraged by these results we used the acoustic method to investigate the temporal evolution of the elastic modulus. The rate of increase was very close to values mentioned in literature on the sintering rate of snow. Overall, our results are a first but important step towards a new measurement method to attain the elastic properties of snow.

  2. Acoustics

    NASA Astrophysics Data System (ADS)

    The acoustics research activities of the DLR fluid-mechanics department (Forschungsbereich Stroemungsmechanik) during 1988 are surveyed and illustrated with extensive diagrams, drawings, graphs, and photographs. Particular attention is given to studies of helicopter rotor noise (high-speed impulsive noise, blade/vortex interaction noise, and main/tail-rotor interaction noise), propeller noise (temperature, angle-of-attack, and nonuniform-flow effects), noise certification, and industrial acoustics (road-vehicle flow noise and airport noise-control installations).

  3. 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. PMID:8552975

  4. Predicting the intelligibility of deaf children's speech from acoustic measures

    NASA Astrophysics Data System (ADS)

    Uchanski, Rosalie M.; Geers, Ann E.; Brenner, Christine M.; Tobey, Emily A.

    2001-05-01

    A weighted combination of speech-acoustic measures may provide an objective assessment of speech intelligibility in deaf children that could be used to evaluate the benefits of sensory aids and rehabilitation programs. This investigation compared the accuracy of two different approaches, multiple linear regression and a simple neural net. These two methods were applied to identical sets of acoustic measures, including both segmental (e.g., voice-onset times of plosives, spectral moments of fricatives, second formant frequencies of vowels) and suprasegmental measures (e.g., sentence duration, number and frequency of intersentence pauses). These independent variables were obtained from digitized recordings of deaf children's imitations of 11 simple sentences. The dependent measure was the percentage of spoken words from the 36 McGarr Sentences understood by groups of naive listeners. The two predictive methods were trained on speech measures obtained from 123 out of 164 8- and 9-year-old deaf children who used cochlear implants. Then, predictions were obtained using speech measures from the remaining 41 children. Preliminary results indicate that multiple linear regression is a better predictor of intelligibility than the neural net, accounting for 79% as opposed to 65% of the variance in the data. [Work supported by NIH.

  5. 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

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

    PubMed

    Brunker, Joanna; Beard, Paul

    2016-07-01

    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

  7. A pseudo-inverse algorithm for simultaneous measurements using multiple acoustical sources.

    PubMed

    Xiang, Ning; Li, Shu

    2007-03-01

    Simultaneous multiple acoustical sources measurement (SMASM) has been proposed for more effective and reliable identification of acoustical systems under critical conditions [N. Xiang and M. R. Schroeder, J. Acoust. Soc. Am. 113, 2754-2761 (2003); N. Xiang, J. N. Daigle, and M. Kleiner, J. Acoust. Soc. Am. 117, 1889-1894 (2005)]. This paper presents a pseudo-inverse algorithm for the SMASM correlation technique as an alternative way of extracting impulse responses of acoustical channels. Simulations and room acoustics experiments are carried out and the results prove the feasibility of the proposed algorithm. PMID:17407864

  8. 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

  9. Experimental study using Nearfield Acoustical Holography of sound transmission fuselage sidewall structures

    NASA Technical Reports Server (NTRS)

    Maynard, J. D.

    1983-01-01

    This project involves the development of the Nearfield Acoustic Holography (NAH) technique (in particular its extension from single frequency to wideband noise measurement) and its application in a detailed study of the noise radiation characteristics of several samples of aircraft sidewall panels. With the extensive amount of information provided by the NAH technique, the properties of the sound field radiated by the panels may be correlated with their structure, mounting, and excitation (single frequency or wideband, spatially correlated or uncorrelated, structure-borne). The work accomplished at the beginning of this grant period included: (1) Calibration of the 256 microphone array and test of its accuracy. (2) extension of the facility to permit measurements on wideband noise sources. The extensions incuded the addition of high-speed data acquisition hardware and an array processor, and the development of new software. (3) Installation of motion picture graphics for correlating panel motion with structure, mounting, radiation, etc. (4) Development of new holographic data processing techniques.

  10. Acoustic Techniques for Thin Film Thickness Measurement in Semiconductor Processing

    NASA Astrophysics Data System (ADS)

    Bhardwaj, Sanjay

    In modern semiconductor manufacturing, process monitoring and control are important issues limited at the present time by a lack of sensors and instrumentation capable of measuring process parameters like film thickness. In order to address this problem, two novel systems for thin film thickness measurement in semiconductor processing based upon contacting acoustic techniques have been developed. Both of these systems couple acoustic energy into the wafer via a nondestructive Hertzian contact and achieve high resolution by exciting and receiving ultrasonic signals from a ZnO transducer with microwave frequency electronics. The basic physical mechanism for film thickness determination is to analyze reflected waves due to acoustic impedance mismatches between various material layers on a silicon substrate. The first system requires frontside contacting of a sapphire buffer rod to an opaque film deposited on a silicon wafer and involves the use of broadband, high frequency pulse-echo electronics in the 0.5-5 GHz range. With this system, ex-situ measurements of aluminum and gold thin films on a silicon substrate have been done in the 0.25-2.5 mum. range with 3-6% accuracy as compared to surface profilometer measurements. Possible applications for this system include using it as a post -deposition process monitor, generating film thickness contour maps, or examining multilayer structures. The second system requires backside contacting of a sapphire buffer rod to a silicon wafer, which is in a vacuum station, and involves monitoring the changes in phase of CW 1-2 GHz acoustic waves as a function of frontside film growth. Using this technique, in-situ indium and aluminum film thickness monitoring has been done in both evaporator and sputtering environments with a resolution of 40 A. Temperature experiments in an oven have shown a resolution of 0.05 K for the sapphire buffer rod. Finally, multistep processing has been done and a multilayer film structure has been measured

  11. Measurement of the volume of weights using an acoustic volumeter and the reliability of such measurement

    NASA Astrophysics Data System (ADS)

    Kobata, T.; Ueki, M.; Ooiwa, A.; Ishii, Y.

    2004-04-01

    For the precise measurement of the mass of a weight, buoyancy correction of air for the volume of a weight is necessary. Although hydrostatic weighing is the most accurate method currently used in determining volume, it is a relatively complicated process requiring the weight to be wetted in a reference fluid. Since more weights with high accuracy of mass are being used, a more sophisticated method of determining volume that satisfies uncertainty requirements has been demanded to improve the efficiency of calibration. In this paper, an acoustic volumeter is proposed for the measurement of the volume of weights. An acoustic volumeter can measure volume in atmosphere in a simple manner. Consequently, it is not necessary to consider the contamination and mass change due to the liquid used in the hydrostatic weighing method. In practical applications, a procedure for measuring the volume of weights ranging from 100 g to 10 kg using an acoustic volumeter is proposed. The volumes obtained using an acoustic volumeter were compared with those obtained by the hydrostatic weighing method, and the reliability of the measurement was evaluated with a relative uncertainty below the order of 1 × 10-3. From the measurement results, it was shown that the use of an acoustic volumeter is effective for the measurement of the volume of weights.

  12. a Modeling and Measurement Study of Acoustic Horns

    NASA Astrophysics Data System (ADS)

    Post, John Theodore

    Although acoustic horns have been in use for thousands of years, formal horn design only began approximately 80 years ago with the pioneering effort of A. G. Webster. In this dissertation, the improvements to Webster's original horn model are reviewed and the lack of analytical progress since Webster is noted. In an attempt to augment the traditional methods of analysis, a semi-analytical technique presented by Rayleigh is extended. Although Rayleigh's method is not based on one-dimensional wave propagation, it is found not to offer significant improvement over Webster's model. In order to be free of the limitations associated with analytical techniques, a numerical method based on boundary elements has been developed. It is suitable for solving radiation problems that can be modeled as a source in an infinite bafffe. The exterior boundary element formulation is exchanged for an interior formulation by placing a hemisphere over the baffled source and using an analytical expansion of the field in the exterior half space. The boundary element method is demonstrated by solving the baffled piston problem, and is then used to obtain the acoustic throat impedance and far-field directivity of axisymmetric horns having exponential and tractrix contours. Experiments are performed to measure the throat impedance and the far-field directivity of two axisymmetric horns mounted in a rigid baffle. An exponential horn and a tractrix horn with equal throat radius (2.54 cm), length (55.9 cm), and mouth radius (27.1 cm) are critically examined. A modern implementation of the "reaction on the source" method is compared with a new implementation of the two-microphone method for measuring acoustic impedance. The modified two-microphone method is found to be extremely simple and accurate, but the "reaction on the source" method has the advantage of in situ measurements. The far-field directivity is measured by a new technique that allows the far-field pressure to be calculated from the

  13. The contamination of acoustic pressure measurements by sensor oscillations

    SciTech Connect

    Surry, J.; Kezele, D.; Risley, C.

    1996-04-01

    The significance of micromotion (sensor) noise contamination of low frequency, low level, ambient ocean acoustic measurements has been pursued experimentally and analytically. Oceanographic hydrophones are subject to small motions resulting from various phenomena; the present study focussed on a pressure-sensitive hydrophone exposed to vertical oscillations. While under such imposed motion, the responses from a pressure-sensitive hydrophone and a collocated accelerometer were analyzed relative to a stationary reference hydrophone. The imposed motion was vertical, colored noise (1 to 50 Hz) of various acceleration amplitudes (10 {mu}g to 10 mg), transmitted through an elastic isolation suspension. Formation of Frequency Response Functions between the measured transducer signals, demonstrated that a three component model of the hydrophone signal predicts the response-to-motion contamination of the acoustic signal. In the lower frequency range, the vertical motion through the static head gradient generates a signal similar to the response-to-acoustic signal, while in the upper frequency range, the hydrophone responds inertially to the motion. For acceleration greater than 30 {mu}g, these components masked the laboratory ambient sound, except in a narrow frequency band where the two motion related components canceled each other. The in-water acceleration sensitivity of the hydrophone was found to be higher than the measured in-air value, apparently due to two hydrodynamic effects: water mass loading predicted by a classical added-mass term and a greatly magnifying effect from an adjacent moving body. Extrapolating the results to a deep ocean environment, the hydrophone signals would be contaminated below 5 Hz. A spectral technique is demonstrated to remove both forms of motion contamination from laboratory data. {copyright} {ital 1996 American Institute of Physics.}

  14. 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

  15. 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.

  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. PMID:26936543

  17. Lens transmission measurement for an absolute radiation thermometer

    SciTech Connect

    Hao, X.; Yuan, Z.; Lu, X.

    2013-09-11

    The lens transmission for the National Institute of Metrology of China absolute radiation thermometer is measured by a hybrid method. The results of the lens transmission measurements are 99.002% and 86.792% for filter radiometers with center wavelengths 633 nm and 900 nm, respectively. These results, after correcting for diffraction factors and the size-of-source effect when the lens is incorporated within the radiometer, can be used for measurement of thermodynamic temperature. The expanded uncertainty of the lens transmission measurement system has been evaluated. It is 1.3×10{sup −3} at 633 nm and 900 nm, respectively.

  18. 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.

  19. Preliminary measurements of thermal effects in the dust acoustic wave

    NASA Astrophysics Data System (ADS)

    Williams, Jeremiah

    2009-11-01

    A complex (dusty) plasma (CDP) is a four-component system composed of ions, electrons, neutral particles and charged microparticles. The presence of the microparticles gives rise to new plasma phenomena, including collective modes such as the dust acoustic wave. Recent measurements of the dispersion relationship of this wave mode [E. Thomas, Jr., et. al., Phys. Plasmas 14, 123701 (2007), J.D. Williams, et. al., Phys. Plasmas 15, 043704 (2008)] have shown that, over a range of neutral gas pressures, it is necessary to include thermal effects to accurately fit the measured dispersion relations. In this work, initial measurements of the dispersion relation in a new dusty plasma experiment, the Wittenberg University DUsty Plasma Experiment (WUDUPE), will be presented. In particular, the dependence of the kinetic dust temperature on the neutral gas pressure will be presented.

  20. Effects of microphone type on acoustic measures of voice.

    PubMed

    Parsa, V; Jamieson, D G; Pretty, B R

    2001-09-01

    Acoustic measures provide an objective means to describe pathological voices and are a routine component of the clinical voice examination. Because the voice sample is obtained using a microphone, microphone characteristics have the potential to influence the values of parameters obtained from a voice sample. This project examined how the choice of microphone affects key voice parameters and investigated how one might compensate for such microphone effects through filtering or by including additional parameters in the decision process. A database of 53 normal voice samples and 100 pathological voice samples was used in four experiments conducted in an anechoic chamber using four different microphones. One omnidirectional microphone and three cardioid microphones were used in these experiments. The original voice samples were presented to each microphone through a speaker located in an anechoic chamber, and the output of each microphone sampled to computer disk. Each microphone modified the frequency spectrum of the voice signal; this, in turn, affected the values of the voice parameters obtained. These microphone effects reduced the accuracy with which acoustic measures of voice could be used to discriminate pathological from normal voices. Discrimination performance improved when the microphone output was filtered to compensate for microphone frequency response. Performance also improved when spectral moment coefficient parameters were added to the vocal function parameters already in use. PMID:11575630

  1. 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.

  2. Measuring the Acoustic Impedance of Pipes and Musical Instruments

    NASA Astrophysics Data System (ADS)

    Jaeger, Herbert

    2007-05-01

    Using a small electret microphone and a piezo-buzzer we have constructed a simple impedance transducer to measure the input impedance of air columns, such as cylindrical pipes, as well as musical instruments. The input impedance of an air column is given as the ratio of the pressure to the volume flow of air at the input of the air column. The microphone serves as the pressure transducer, while the piezo-buzzer is controlled to provide a constant velocity amplitude. Therefore the microphone signal is proportional to the acoustical impedance and, if required, can be calibrated using a simple air column for which the impedance can be calculated. This impedance transducer is currently in use as demonstration equipment for a physical acoustics class. It is simple to use and robust, so that it is well-suited for an undergraduate introductory laboratory environment. This talk will discuss the function of the impedance transducer and show examples of the type of measurements that can be performed. To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2007.OSS07.C1.1

  3. Noise suppression in curved glass shells using macro-fiber-composite actuators studied by the means of digital holography and acoustic measurements

    NASA Astrophysics Data System (ADS)

    Mokrý, P.; Psota, P.; Steiger, K.; Václavík, J.; Doleček, R.; Lédl, V.; Šulc, M.

    2015-02-01

    The paper presents methods and experimental results of the semi-active control of noise transmission in a curved glass shell with attached piezoelectric macro fiber composite (MFC) actuators. The semi-active noise control is achieved via active elasticity control of piezoelectric actuators by connecting them to an active electric shunt circuit that has a negative effective capacitance. Using this approach, it is possible to suppress the vibration of the glass shell in the normal direction with respect to its surface and to increase the acoustic transmission loss of the piezoelectric MFC-glass composite structure. The effect of the MFC actuators connected to the negative capacitance shunt circuit on the surface distribution of the normal vibration amplitude is studied using frequency-shifted digital holography (FSDH). The principle of the used FSDH method is described in the paper. The frequency dependence of the acoustic transmission loss through the piezoelectric MFC-glass composite structure is estimated using measurements of the specific acoustic impedance of the curved glass shell. The specific acoustic impedance is measured using two microphones and a laser Doppler vibrometer (LDV). The results from the LDV measurements are compared with the FSDH data. The results of the experiments show that using this approach, the acoustic transmission loss in a glass shell can be increased by 36 dB in the frequency range around 247 Hz and by 25 dB in the frequency range around 258 Hz. The experiments indicate that FSDH measurements provide an efficient tool that can be used for fast and accurate measurements of the acoustic transmission loss in large planar structures.

  4. 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.

  5. Acoustic measurement of the surface tension of levitated drops

    NASA Astrophysics Data System (ADS)

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

    1988-07-01

    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.

  6. 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.

  7. 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.

  8. Simultaneous backward data transmission and power harvesting in an ultrasonic transcutaneous energy transfer link employing acoustically dependent electric impedance modulation.

    PubMed

    Ozeri, Shaul; Shmilovitz, Doron

    2014-09-01

    The advancement and miniaturization of body implanted medical devices pose several challenges to Ultrasonic Transcutaneous Energy Transfer (UTET), such as the need to reduce the size of the piezoelectric resonator, and the need to maximize the UTET link power-transfer efficiency. Accordingly, the same piezoelectric resonator that is used for energy harvesting at the body implant, may also be used for ultrasonic backward data transfer, for instance, through impedance modulation. This paper presents physical considerations and design guidelines of the body implanted transducer of a UTET link with impedance modulation for a backward data transfer. The acoustic matching design procedure was based on the 2×2 transfer matrix chain analysis, in addition to the Krimholtz Leedom and Matthaei KLM transmission line model. The UTET power transfer was carried out at a frequency of 765 kHz, continuous wave (CW) mode. The backward data transfer was attained by inserting a 9% load resistance variation around its matched value (550 Ohm), resulting in a 12% increase in the acoustic reflection coefficient. A backward data transmission rate of 1200 bits/s was experimentally demonstrated using amplitude shift keying, simultaneously with an acoustic power transfer of 20 mW to the implant. PMID:24861424

  9. Radiation Transmission Measurements for a Lightweight Fabric

    SciTech Connect

    Friedman, H; Singh, M S; DeMeo, R F

    2003-01-17

    Radiation Shield Technologies has developed a lightweight fabric, shown in Fig. 1, with radiation shielding properties for X ray, gamma ray and beta particle emissions in the range of energies relevant to clinical and Homeland Security applications. Detailed measurements were done to measure the shielding properties of this material against the spectra of standard radionuclides and x-ray generators. The mass attenuation coefficients were calculated using LLNL cross section data, a 3-D photon transport code, elemental weight fractions and the measured density of the fabric.

  10. Enhancing active and passive remote sensing in the ocean using broadband acoustic transmissions and coherent hydrophone arrays

    NASA Astrophysics Data System (ADS)

    Tran, Duong Duy

    The statistics of broadband acoustic signal transmissions in a random continental shelf waveguide are characterized for the fully saturated regime. The probability distribution of broadband signal energies after saturated multi-path propagation is derived using coherence theory. The frequency components obtained from Fourier decomposition of a broadband signal are each assumed to be fully saturated, where the energy spectral density obeys the exponential distribution with 5.6 dB standard deviation and unity scintillation index. When the signal bandwidth and measurement time are respectively larger than the correlation bandwidth and correlation time of its energy spectral density components, the broadband signal energy obtained by integrating the energy spectral density across the signal bandwidth then follows the Gamma distribution with standard deviation smaller than 5.6 dB and scintillation index less than unity. The theory is verified with broadband transmissions in the Gulf of Maine shallow water waveguide in the 300-1200 Hz frequency range. The standard deviations of received broadband signal energies range from 2.7 to 4.6 dB for effective bandwidths up to 42 Hz, while the standard deviations of individual energy spectral density components are roughly 5.6 dB. The energy spectral density correlation bandwidths of the received broadband signals are found to be larger for signals with higher center frequency. Sperm whales in the New England continental shelf and slope were passively localized, in both range and bearing using a single low-frequency (< 2500 Hz), densely sampled, towed horizontal coherent hydrophone array system. Whale bearings were estimated using time-domain beamforming that provided high coherent array gain in sperm whale click signal-to-noise ratio. Whale ranges from the receiver array center were estimated using the moving array triangulation technique from a sequence of whale bearing measurements. The dive profile was estimated for a sperm

  11. Ultrasonic Measurement of Microdisplacement Induced by Acoustic Radiation Force

    NASA Astrophysics Data System (ADS)

    Nagaoka, Ryo; Izumi, Takuya; Komatsu, Yosuke; Kobayashi, Kazuto; Saijo, Yoshifumi

    2013-07-01

    Quantitative evaluation of human skin aging is achieved by measuring the viscoelasticity of the skin. In the present study, microdisplacement induced by acoustic radiation force (ARF) is quantitatively measured by high-frequency ultrasonography (HFUS) and the result is confirmed by laser-Doppler velocimetry (LDV). Poly(vinyl alcohol) (PVA) with 1% cellulose particles was used as the biological phantom. A concave piezoelectric zirconate titanate (PZT) transducer with a diameter and focal length of 3 cm was used as an applicator to generate ARF. Microdisplacement at each depth of PVA was measured by the phased tracking method at 100 MHz of ultrasound with a repetition rate of 2000 Hz. When 80 tone-burst pulses were applied, the displacement measured by HFUS was 9 µm and the same result was obtained by LDV. As the displacement at each depth of PVA is measurable using ARF and the HFUS system, the system could be applied to measuring the viscoelasticity of the layered structure of the human skin.

  12. 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.

  13. Noninvasive Measurement of Acoustic Properties of Fluids Using Ultrasonic Interferometry Technique

    SciTech Connect

    Han, W.; Sinha, D.N.; Springer, K.N.; Lizon, D.C.

    1997-06-15

    A swept-frequency ultrasonic interferometry technique is used for noninvasively determining acoustic properties of fluids inside containers. Measurements over a frequency range 1-15 MHz on six liquid chemicals are presented. Measurements were made with the liquid inside standard rectangular optical glass cells and stainless steel cylindrical shells. A theoretical model based on one-dimensional planar acoustic wave propagation through multi-layered media is employed for the interpretation of the observed resonance (interference) spectrum. Two analytical methods, derived from the transmission model are used for determination of sound speed, sound attenuation coefficient, and density of liquids from the relative amplitude and half-power peak width of the observed resonance peaks. Effects of the container material and geometrical properties, path-length, wall thickness are also studied. This study shows that the interferometry technique and the experimental method developed are capable of accurate determination of sound speed, sound attenuation, and density in fluids completely noninvasively. It is a capable and versatile fluid characterization technique and has many potential NDE applications.

  14. Radiated microwave power transmission system efficiency measurements

    NASA Technical Reports Server (NTRS)

    Dickinson, R. M.; Brown, W. C.

    1975-01-01

    The measured and calculated results from determining the operating efficiencies of a laboratory version of a system for transporting electric power from one point to another via a wireless free space radiated microwave beam are reported. The system's overall end-to-end efficiency as well as intermediated conversion efficiencies were measured. The maximum achieved end-to-end dc-to-ac system efficiency was 54.18% with a probable error of + or - 0.94%. The dc-to-RF conversion efficiency was measured to be 68.87% + or - 1.0% and the RF-to-dc conversion efficiency was 78.67 + or - 1.1%. Under these conditions a dc power of 495.62 + or - 3.57 W was received with a free space transmitter antenna receiver antenna separation of 170.2 cm (67 in).

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.}

  1. 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.

  2. 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.

  3. Wireless acoustic-electric feed-through for power and signal transmission

    NASA Technical Reports Server (NTRS)

    Sherrit, Stewart (Inventor); Bar-Cohen, Yoseph (Inventor); Bao, Xiaoqi (Inventor); Doty, Benjamin (Inventor); Badescu, Mircea (Inventor); Chang, Zensheu (Inventor)

    2011-01-01

    An embodiment provides electrical energy from a source on one side of a medium to a load on the other side of the medium, the embodiment including a first piezoelectric to generate acoustic energy in response to electrical energy from the source, and a second piezoelectric to convert the received acoustic energy to electrical energy used by the load. Other embodiments are described and claimed.

  4. 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…

  5. An acoustic method for the remote measurement of seagrass metrics

    NASA Astrophysics Data System (ADS)

    Paul, M.; Lefebvre, A.; Manca, E.; Amos, C. L.

    2011-05-01

    Seagrass meadows are ecosystems of great ecological and economical value and their monitoring is an important task within coastal environmental management. In this paper, an acoustic mapping technique is presented using a profiling sonar. The method has been applied to three different sites with meadows of Zostera marina, Zostera noltii and Posidonia oceanica respectively, with the aim to test the method's applicability. From the backscatter data the seabed could be identified as the strongest scatterer along an acoustic beam. The presented algorithm was used to compute water depth, seagrass canopy height and seagrass coverage and to produce maps of the survey areas. Canopy height was estimated as the distance between the bed and the point where backscatter values decrease to water column values. The algorithm was extended from previous methods to account for a variety of meadow types. Seagrass coverage was defined as the percentage of beams in a sweep where the backscatter 5-10 cm above the bed was higher than a threshold value. This threshold value is dynamic and depends on the average backscatter value throughout the water column. The method is therefore applicable in a range of turbidity conditions. Comparison with results from other survey techniques (i.e. dive surveys, underwater videos) yielded a high correlation which indicates that the method is suited to measure seagrass coverage and height. Analysis of the data showed that each seagrass species has a characteristic canopy height and spatial coverage distribution. These differences were used to undertake a preliminary species identification, as each species has a typical canopy height and preferred depth range. Furthermore, the results show that these differences can be used to track boundaries between species remotely. Finally, the application of the meadow distribution pattern to the health of a meadow is discussed.

  6. 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.

  7. 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

  8. Infrared transmission measurements of highly curved optical components

    NASA Astrophysics Data System (ADS)

    Tiszauer, Detlev H.; Morrow, Howard E.

    Fourier Transform Infrared Spectrometer (FTIR) measurements on flat witness samples are combined with ray trace results of transmission through a 1/8 inch, 12 mill focal length lens to estimate the net transmission of that lens as it is used in the Geostationary Operational Environmental Satellite (GOES I) Sounder optical train. The ray trace code uses a 'double random' ray method allowing radiometry to be done with a standard ray propagation algorithm.

  9. 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.

  10. Cosmological implications of baryon acoustic oscillation (BAO) measurements

    NASA Astrophysics Data System (ADS)

    Vazquez, Jose; BOSS Collaboration

    2015-04-01

    We present constraints on cosmological parameters and tests of dark models from the combination of baryon acoustic oscillation (BAO) with cosmic microwave background (CMB) data and a reanalysis of Type Ia supernova (SN) data. In particular, we take of high-precision BAO measurements from galaxy clustering the Lyman-a forest (LyaF) in the SDSS-III Baryon Oscillation Survey (BOSS). show that the flat LCDM model, that best describes the CMB data alone, is discrepant at 95% with the LyaF measurements. Hence, in order to reconcile them we consider models with more unusual histories of the dark energy, matter, or radiation components. In part we want to know what our combined data can place on interesting physical, such as neutrino masses, extra relativistic species, or dark energy that is dynamically significant at early times. But we also want to see whether any of these alternative models can resolve the discrepancy with the LyaF measurements at z = 2.34.

  11. 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.

  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. Acoustic fatigue and sound transmission characteristics of a ram composite panel design

    NASA Technical Reports Server (NTRS)

    Cockburn, J. A.; Chang, K. Y.; Kao, G. C.

    1972-01-01

    An experimental study to determine the acoustic fatigue characteristics of a flat multi-layered structural panel is described. The test panel represented a proposed design for the outer skin of a research application module to be housed within the space shuttle orbiter vehicle. The test specimen was mounted in one wall of the Wyle 100,000 cu ft reverberation room and exposed to a broadband acoustic environment having an overall level of 145 db. The test panel was exposed to nine separate applications of the acoustic environment, each application consisting of 250 seconds duration. Upon completion of the ninth test run, the specimen was exposed to a simulated micrometeoroid impact near the panel center. One additional test run of 250 seconds duration was then performed to complete the overall simulation of 50 flight missions. The experimental results show that no significant fatigue damage occurred until the test specimen was exposed to a simulated micrometeoroid impact. The intermediate foam layer forming the core of the test specimen suffered considerable damage due to this impact, causing a marked variation in the dynamic characteristics of the overall test panel. During the final application of the acoustic environment, the strain and acceleration response spectra showed considerable variation from those spectra obtained prior to impact of the panel. Fatigue damage from acoustic loading however, was limited to partial de-bonding around the edges of the composite panel.

  14. 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

  15. Studies of acoustic-electric feed-throughs for power transmission through structures

    NASA Technical Reports Server (NTRS)

    Sherrit, Stewart; Doty, Benjamin; Badescu, Mircea; Bao, Xiaoqi; Bar-Cohen, Yoseph; Aldrich, Jack; Chang, Zensheu

    2006-01-01

    There are numerous engineering design problems where the use of wires to transfer power and communicate data thru the walls of a structure is prohibitive or significantly difficult that it may require a complex design. Using physical feedthroughs in such systems may make them susceptible to leakage of chemicals or gasses, loss of pressure or vacuum, as well as difficulties in providing adequate thermal or electrical insulation. Moreover, feeding wires thru a wall of a structure reduces the strength of the structure and makes the structure prone to cracking due to fatigue that can result from cyclic loading and stress concentrations. One area that has already been identified to require a wireless alternative to electrical feedthroughs is the container of the Mars Sample Return Mission, which will need wireless sensors to sense a pressure leak and to avoid potential contamination. The idea of using elastic or acoustic waves to transfer power was suggested recently by [Y. Hu, et al., July 2003]. This system allows for the avoidance of cabling or wiring. The technology is applicable to the transfer of power for actuation, sensing and other tasks inside any sealed container or vacuum/pressure vessel. An alternative approach to the modeling presented previously [Sherrit et a., 2005] used network analysis to solve the same problem in a clear and expandable manner. Experimental tests on three different designs of these devices were performed. The three designs used different methods of coupling the piezoelectric element to the wall. In the first test the piezoelectric material was bolted using a backing structure. In the second test the piezoelectric was clamped after the application of grease and finally the piezoelectric element was attached using a conductive epoxy. The mechanical clamp with grease produced the highest measured efficiency of 53% however this design was the least practical from a fabrication viewpoint. The power transfer efficiency of conductive epoxy

  16. Automated acoustic intensity measurements and the effect of gear tooth profile on noise

    NASA Technical Reports Server (NTRS)

    Atherton, William J.; Pintz, Adam; Lewicki, David G.

    1987-01-01

    Acoustic intensity measurements were made at NASA Lewis Research Center on a spur gear test apparatus. The measurements were obtained with the Robotic Acoustic Intensity Measurement System developed by Cleveland State University. This system provided dense spatial positioning, and was calibrated against a high quality acoustic intensity system. The measured gear noise compared gearsets having two different tooth profiles. The tests evaluated the sound field of the different gears for two speeds and three loads. The experimental results showed that gear tooth profile had a major effect on measured noise. Load and speed were found to have an effect on noise also.

  17. 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.

  18. Analysis of Measured and Simulated Supraglottal Acoustic Waves.

    PubMed

    Fraile, Rubén; Evdokimova, Vera V; Evgrafova, Karina V; Godino-Llorente, Juan I; Skrelin, Pavel A

    2016-09-01

    To date, although much attention has been paid to the estimation and modeling of the voice source (ie, the glottal airflow volume velocity), the measurement and characterization of the supraglottal pressure wave have been much less studied. Some previous results have unveiled that the supraglottal pressure wave has some spectral resonances similar to those of the voice pressure wave. This makes the supraglottal wave partially intelligible. Although the explanation for such effect seems to be clearly related to the reflected pressure wave traveling upstream along the vocal tract, the influence that nonlinear source-filter interaction has on it is not as clear. This article provides an insight into this issue by comparing the acoustic analyses of measured and simulated supraglottal and voice waves. Simulations have been performed using a high-dimensional discrete vocal fold model. Results of such comparative analysis indicate that spectral resonances in the supraglottal wave are mainly caused by the regressive pressure wave that travels upstream along the vocal tract and not by source-tract interaction. On the contrary and according to simulation results, source-tract interaction has a role in the loss of intelligibility that happens in the supraglottal wave with respect to the voice wave. This loss of intelligibility mainly corresponds to spectral differences for frequencies above 1500 Hz. PMID:26377510

  19. Concentration measurements with Laser-Induced Thermal Acoustics

    NASA Astrophysics Data System (ADS)

    Schlamp, Stefan; Sobota, Thomas H.

    2001-03-01

    Laser-induced thermal acoustics (LITA) is used to measure the concentration of iodine vapor (40-150 ppm) in air instantaneously (1 μs), remotely, and non-intrusively. Two focused, pulsed intersecting laser beams inscribe a density grating in the fluid. A cw interrogation beam directed at the Bragg angle on the grating is scattered into a coherent signal beam whose intensity depends on the instantaneous density grating magnitude. The signal beam is detected by a photomultiplier tube and its history recorded by a digital storage oscilloscope. The species in question (e.g., I_2) and the dilution species are excited resonantly (by thermalization) and non-resonantly (by electrostriction), respectively. The signals show oscillations at (twice) the grating's Brillouin frequency for the case of thermalization (electrostriction). The ratio of the thermalization to the electrostriction grating magnitudes is proportional to the resonant species concentration. They are extracted by a least-squares fitting scheme. For good accuracy, the ratio must be of order unity. For this case, the standard error is 5%. The speed of sound (error <1%) and flow velocity (error <1%) can be measured simultaneously.

  20. CT scanner x-ray spectrum estimation from transmission measurements

    PubMed Central

    Duan, Xinhui; Wang, Jia; Yu, Lifeng; Leng, Shuai; McCollough, Cynthia H.

    2011-01-01

    Purpose: In diagnostic CT imaging, multiple important applications depend on the knowledge of the x-ray spectrum, including Monte Carlo dose calculations and dual-energy material decomposition analysis. Due to the high photon flux involved, it is difficult to directly measure spectra from the x-ray tube of a CT scanner. One potential method for indirect measurement involves estimating the spectrum from transmission measurements. The expectation maximization (EM) method is an accurate and robust method to solve this problem. In this article, this method was evaluated in a commercial CT scanner. Methods: Two step-wedges (polycarbonate and aluminum) were used to produce different attenuation levels. Transmission measurements were performed on the scanner and the measured data from the scanner were exported to an external computer to calculate the spectra. The EM method was applied to solve the equations that represent the attenuation processes of polychromatic x-ray photons. Estimated spectra were compared to the spectra simulated using a software provided by the manufacturer of the scanner. To test the accuracy of the spectra, a verification experiment was performed using a phantom containing different depths of water. The measured transmission data were compared to the transmission values calculated using the estimated spectra. Results: Spectra of 80, 100, 120, and 140 kVp from a dual-source CT scanner were estimated. The estimated and simulated spectra were well matched. The differences of mean energies were less than 1 keV. In the verification experiment, the measured and calculated transmission values were in excellent agreement. Conclusions: Spectrum estimation using transmission data and the EM method is a quantitatively accurate and robust technique to estimate the spectrum of a CT system. This method could benefit studies relying on accurate knowledge of the x-ray spectra from CT scanner. PMID:21452736

  1. 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

  2. A novel transmission line characterisation based on measurement data reconfirmation

    NASA Astrophysics Data System (ADS)

    Kim, Dongchul; Kim, Hyewon; Eo, Yungseon

    2014-04-01

    Due to inherent resonance effects and frequency-variant dielectric properties, it is very difficult to experimentally determine the stable and accurate circuit model parameters of thin film transmission line structures over a broad frequency band. In this article, a new, simple and straightforward frequency-variant transmission line circuit model parameter determination method is presented. Experimental test patterns for high-frequency transmission line characterisations are designed and fabricated using a package process. The S-parameters for the test patterns are measured using a vector network analyzer (VNA) from 100 MHz to 26.5 GHz. The parasitic effects due to contact pads are de-embedded. The frequency-variant complex permittivity and resonance-effect-free transmission line parameters (i.e., the propagation constant and characteristic impedance) are then determined in a broad frequency band.

  3. A study of methods of prediction and measurement of the transmission of sound through the walls of light aircraft

    NASA Technical Reports Server (NTRS)

    Forssen, B.; Wang, Y. S.; Raju, P. K.; Crocker, M. J.

    1981-01-01

    The acoustic intensity technique was applied to the sound transmission loss of panel structures (single, composite, and stiffened). A theoretical model of sound transmission through a cylindrical shell is presented.

  4. 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.

  5. Use of an acoustic helium analyzer for measuring lung volumes.

    PubMed

    Krumpe, P E; MacDannald, H J; Finley, T N; Schear, H E; Hall, J; Cribbs, D

    1981-01-01

    We have evaluated the use of an acoustic gas analyzer (AGA) for the measurement of total lung capacity (TLC) by single-breath helium dilution. The AGA has a rapid response time (0-90% response = 160 ms for 10% He), is linear for helium concentration of 0.1-10%, is stable over a wide range of ambient temperatures, and is small and portable. We plotted the output of the AGA vs. expired lung volume after a vital capacity breath of 10% He. However, since the AGA is sensitive to changes in speed of sound relative to air, the AGA output signal also reports an artifact due to alveolar gases. We corrected for this artifact by replotting a single-breath expiration after a vital capacity breath of room air. Mean alveolar helium concentration (HeA) was then measured by planimetry, using this alveolar gas curve as the base line. TLC was calculated using the HeA from the corrected AGA output and compared with TLC calculated from HeA simultaneously measured using a mass spectrometer (MS). In 12 normal subjects and 9 patients with chronic obstructive pulmonary disease (COPD) TLC-AGA and TLC-MS were compared by linear regression analysis; correlation coefficient (r) was 0.973 for normals and 0.968 for COPD patients (P less than 0.001). This single-breath; estimation of TLC using the corrected signal of the AGA vs. Expired volume seems ideally suited for the measurement of subdivisions of lung volume in field studies. PMID:7204187

  6. 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

  7. 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.

  8. Toward Standardized Acoustic Radiation Force (ARF)-Based Ultrasound Elasticity Measurements With Robotic Force Control

    PubMed Central

    Kumar, Shalki; Lily, Kuo; Sen, H. Tutkun; Iordachita, Iulian; Kazanzides, Peter

    2016-01-01

    Objective Acoustic radiation force (ARF)-based approaches to measure tissue elasticity require transmission of a focused high-energy acoustic pulse from a stationary ultrasound probe and ultrasound-based tracking of the resulting tissue displacements to obtain stiffness images or shear wave speed estimates. The method has established benefits in biomedical applications such as tumor detection and tissue fibrosis staging. One limitation, however, is the dependence on applied probe pressure, which is difficult to control manually and prohibits standardization of quantitative measurements. To overcome this limitation, we built a robot prototype that controls probe contact forces for shear wave speed quantification. Methods The robot was evaluated with controlled force increments applied to a tissue-mimicking phantom and in vivo abdominal tissue from three human volunteers. Results The root-mean-square error between the desired and measured forces was 0.07 N in the phantom and higher for the fatty layer of in vivo abdominal tissue. The mean shear wave speeds increased from 3.7 to 4.5 m/s in the phantom and 1.0 to 3.0 m/s in the in vivo fat for compressive forces ranging from 2.5 to 30 N. The standard deviation of shear wave speeds obtained with the robotic approach were low in most cases (< 0.2 m/s) and comparable to that obtained with a semiquantitative landmark-based method. Conclusion Results are promising for the introduction of robotic systems to control the applied probe pressure for ARF-based measurements of tissue elasticity. Significance This approach has potential benefits in longitudinal studies of disease progression, comparative studies between patients, and large-scale multidimensional elasticity imaging. PMID:26552071

  9. Transmission of wave energy in curved ducts. [acoustic propagation within rigid walls

    NASA Technical Reports Server (NTRS)

    Rostafinski, W.

    1974-01-01

    Investigation of the ability of circular bends to transmit acoustic energy flux. A formulation of wave-energy flow is developed for motion in curved ducts. A parametric study over a range of frequencies shows the ability of circular bends to transmit energy in the case of perfectly rigid walls.

  10. Optical transmission measurements on monocrystalline and polycrystalline cesium iodide

    NASA Technical Reports Server (NTRS)

    Viehmann, W.; Arens, J. F.; Simon, M.

    1973-01-01

    A summary is presented of optical measurements performed on a variety of cesium iodide samples to characterize quantitatively the optical quality of the materials, and to define and measure parameters which determine its suitability as a detector material for high energy cosmic ray experiments on HEAO-A. The general case of light transmission through a long rectangular slab under multiple internal reflections is discussed along with transmission and scattering as a function of wavelength at normal incidence. Scattering parameters are tabulated for encapsulated single crystal CsI and polyscin.

  11. Generation and Propagation of a Picosecond Acoustic Pulse at a Buried Interface: Time-Resolved X-Ray Diffraction Measurements

    SciTech Connect

    Lee, S.H.; Cavalieri, A.L.; Fritz, D.M.; Swan, M.C.; Reis, D.A.; Hegde, R.S.; Reason, M.; Goldman, R.S.

    2005-12-09

    We report on the propagation of coherent acoustic wave packets in (001) surface oriented Al{sub 0.3}Ga{sub 0.7}As/GaAs heterostructure, generated through localized femtosecond photoexcitation of the GaAs. Transient structural changes in both the substrate and film are measured with picosecond time-resolved x-ray diffraction. The data indicate an elastic response consisting of unipolar compression pulses of a few hundred picosecond duration traveling along [001] and [001] directions that are produced by predominately impulsive stress. The transmission and reflection of the strain pulses are in agreement with an acoustic mismatch model of the heterostructure and free-space interfaces.

  12. Precision evaluation for intensive GPS acoustic measurements along Japan trench

    NASA Astrophysics Data System (ADS)

    Kido, M.; Fujimoto, H.; Osada, Y.; Ohta, Y.; Tadokoro, K.; Watanabe, T.; Nagai, S.; Yasuda, K.; Okuda, T.; Yamamoto, J.

    2013-12-01

    After the Tohoku-oki earthquake in 2011, researchers recognized the importance of the state of inter-plate coupling close to the trench for giant earthquakes, in where seafloor geodetic surveys were few or not available. To overcome this limitation, we have developed GPS/acoustic instrument for greater depth up to 6000m, which can cover the region close to the trench for most subduction zones. MEXT, Japan promotes to construct a network of GPS/acoustic survey sites along the Japan trench to elucidate post-seismic behavior after the giant earthquake. In 2012, research group in Tohoku and Nagoya Universities constructed 20 new survey sites along the Japan trench and started their initial positioning. Three to six transponders were installed for each site, which were 86 transponders in total. The network covers large portion of the Japan trench, mainly along the deep land-side of the trench, covering the region of expected significant afterslip as well as of the large coseismic slip. In this year second phase surveys are planned to detect displacement of roughly 1-yesr since the last survey. These are the first intensive surveys that we have never been experienced, and with new survey style. Therefore, in advance to the second phase survey, we summarize the first phase survey in 2012 in the presentation. As one of the most important key to obtain precise positioning of seafloor transponders is how to estimate horizontal variation of sound speed in ocean, which are neglected in the past analysis. For this purpose, some of the sites consist of six transponders, with which such variation can be potentially estimated. For this context, in the second phase surveys, we are going to introduce automatic surface vehicle to enable simultaneous measurement from two points from sea surface, which will provide information of the horizontal variation in sound speed even for three or four transponders. In addition we have made both moving and stationary surveys, in which we can

  13. Acoustic signature of violins based on bridge transfer mobility measurements.

    PubMed

    Elie, Benjamin; Gautier, François; David, Bertrand

    2014-09-01

    This paper is an attempt to solve two problems related to musical acoustics. The first one consists in defining a signature of an instrument, namely, summarizing its vibroacoustical behavior. The second one deals with the existing relationship between the musical sound and the vibroacoustic properties of the instrument body. The violin is the application of this paper. A proposed solution for the first problem consists in an estimation of the bridge transfer mobility and the mean-value of the lateral bridge transfer mobility. The second problem is studied via the comparison between the amplitudes of harmonics, extracted from a glissando audio signal, and the lateral bridge transfer mobility: Both curves exhibit similar features. This is the main result of the paper. This is evidenced by studying the effect of a violin mute on both the lateral bridge transfer mobility and the produced sound. Finally, this is evidenced by successfully identifying which violin is played in an audio recording, using the computation of the Pearson distance between the distribution of the amplitude of harmonics and a database of measured mobilities. PMID:25190411

  14. 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.

  15. 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

  16. Measuring Large Optical Transmission Matrices of Disordered Media

    NASA Astrophysics Data System (ADS)

    Yu, Hyeonseung; Hillman, Timothy R.; Choi, Wonshik; Lee, Ji Oon; Feld, Michael S.; Dasari, Ramachandra R.; Park, YongKeun

    2013-10-01

    We report a measurement of the large optical transmission matrix (TM) of a complex turbid medium. The TM is acquired using polarization-sensitive, full-field interferometric microscopy equipped with a rotating galvanometer mirror. It is represented with respect to input and output bases of optical modes, which correspond to plane wave components of the respective illumination and transmitted waves. The modes are sampled so finely in angular spectrum space that their number exceeds the total number of resolvable modes for the illuminated area of the sample. As such, we investigate the singular value spectrum of the TM in order to detect evidence of open transmission channels, predicted by random-matrix theory. Our results comport with theoretical expectations, given the experimental limitations of the system. We consider the impact of these limitations on the usefulness of transmission matrices in optical measurements.

  17. Measuring large optical transmission matrices of disordered media.

    PubMed

    Yu, Hyeonseung; Hillman, Timothy R; Choi, Wonshik; Lee, Ji Oon; Feld, Michael S; Dasari, Ramachandra R; Park, YongKeun

    2013-10-11

    We report a measurement of the large optical transmission matrix (TM) of a complex turbid medium. The TM is acquired using polarization-sensitive, full-field interferometric microscopy equipped with a rotating galvanometer mirror. It is represented with respect to input and output bases of optical modes, which correspond to plane wave components of the respective illumination and transmitted waves. The modes are sampled so finely in angular spectrum space that their number exceeds the total number of resolvable modes for the illuminated area of the sample. As such, we investigate the singular value spectrum of the TM in order to detect evidence of open transmission channels, predicted by random-matrix theory. Our results comport with theoretical expectations, given the experimental limitations of the system. We consider the impact of these limitations on the usefulness of transmission matrices in optical measurements. PMID:24160602

  18. Modeling the measurement of ultrasonic beams transmitted through a penetrable acoustic cone.

    PubMed

    Huthwaite, Peter; Simonetti, Francesco

    2012-10-01

    The interaction of ultrasonic beams with conical scatterers is governed by a combination of diffraction effects occurring at the aperture of the acoustic source/receiver and refraction through the cone. Accordingly, the outcome of a transmission experiment is dependent upon the many physical parameters characterizing the transducers and the cone. We develop a simplified model which describes the deflection caused by refraction through the cone using ray theory, then uses Huygens' summation to calculate the transducer response from this deflection. The model's accuracy is verified by comparison to simulated data. The model shows that transmission occurs in two different regimes, depending on the parameters of the particular problem. In the first regime, the cone alters the spatial phase distribution of the incident field along the receiver's aperture, whereas its amplitude remains almost unchanged. Because the receiver integrates the field over the aperture, the phasing affects the measurements via constructive and destructive interference. In the second regime, the phase alteration is accompanied by large amplitude variations around an average value that is significantly smaller than the amplitude observed in the first regime. The approximation will aid the design of ultrasound tomography arrays, such as those being developed for breast cancer detection. PMID:23143578

  19. Application of an acoustic noise removal method to aircraft-based atmospheric temperature measurements.

    PubMed

    Hugo, Ronald J; Nowlin, Scott R; Hahn, Ila L; Eaton, Frank D; McCrae, Kim A

    2003-01-01

    An acoustic noise removal method is used to reject engine acoustical disturbances from aircraft-based atmospheric temperature measurements. Removal of engine noise from atmospheric temperature measurements allows a larger wave number range to be fit while quantifying the magnitude of atmospheric temperature turbulence. The larger wave number range was found to result in a more statistically certain spectral slope estimate, with up to a 50% reduction in the standard deviation of measured spectral slopes. The noise removal technique was found to break down under conditions of weak atmospheric temperature turbulence where the engine acoustical disturbance can be several orders of magnitude larger than atmospheric temperature turbulence. PMID:12558258

  20. Application of an acoustic noise removal method to aircraft-based atmospheric temperature measurements

    NASA Astrophysics Data System (ADS)

    Hugo, Ronald J.; Nowlin, Scott R.; Hahn, Ila L.; Eaton, Frank D.; McCrae, Kim A.

    2003-01-01

    An acoustic noise removal method is used to reject engine acoustical disturbances from aircraft-based atmospheric temperature measurements. Removal of engine noise from atmospheric temperature measurements allows a larger wave number range to be fit while quantifying the magnitude of atmospheric temperature turbulence. The larger wave number range was found to result in a more statistically certain spectral slope estimate, with up to a 50% reduction in the standard deviation of measured spectral slopes. The noise removal technique was found to break down under conditions of weak atmospheric temperature turbulence where the engine acoustical disturbance can be several orders of magnitude larger than atmospheric temperature turbulence.

  1. Analysis of Particle Image Velocimetry (PIV) Data for Acoustic Velocity Measurements

    NASA Technical Reports Server (NTRS)

    Blackshire, James L.

    1997-01-01

    Acoustic velocity measurements were taken using Particle Image Velocimetry (PIV) in a Normal Incidence Tube configuration at various frequency, phase, and amplitude levels. This report presents the results of the PIV analysis and data reduction portions of the test and details the processing that was done. Estimates of lower measurement sensitivity levels were determined based on PIV image quality, correlation, and noise level parameters used in the test. Comparison of measurements with linear acoustic theory are presented. The onset of nonlinear, harmonic frequency acoustic levels were also studied for various decibel and frequency levels ranging from 90 to 132 dB and 500 to 3000 Hz, respectively.

  2. Directional acoustic measurements by laser Doppler velocimeters. [for jet aircraft noise

    NASA Technical Reports Server (NTRS)

    Mazumder, M. K.; Overbey, R. L.; Testerman, M. K.

    1976-01-01

    Laser Doppler velocimeters (LDVs) were used as velocity microphones to measure sound pressure level in the range of 90-130 db, spectral components, and two-point cross correlation functions for acoustic noise source identification. Close agreement between LDV and microphone data is observed. It was concluded that directional sensitivity and the ability to measure remotely make LDVs useful tools for acoustic measurement where placement of any physical probe is difficult or undesirable, as in the diagnosis of jet aircraft noise.

  3. Neodymium neutron transmission and capture measurements and development of a new transmission detector

    NASA Astrophysics Data System (ADS)

    Barry, Devin P.

    Neodymium is a 235U fission product and is important in reactor neutronic calculations. The aim of this thesis is to improve upon the existing neutron cross section data of neodymium. Neutron capture and transmission measurements were performed by the time-of-flight technique at the Rensselaer Polytechnic Institute LINAC using metallic neodymium samples. The capture measurements were made at the 25-m flight station with a 16-segment Nal multiplicity detector, and the transmission measurements were performed at 15-m and 25-m flight stations, respectively, with 6Li glass scintillation detectors. After the data were collected and reduced, resonance parameters were determined by simultaneously fitting the transmission and capture data with the multilevel R-matrix Bayesian code SAMMY. The resonance parameters for all naturally occurring neodymium isotopes were deduced within the energy range of 1.0 eV to 500 eV. The resulting resonance parameters were used to calculate the capture resonance integral with this energy region and were compared to calculations obtained when using the resonance parameters from ENDF-B/VI. The RPI parameters gave a resonance integral value of 32 +/- 1 barns that is approximately 7% lower than that obtained with the ENDF-B/VI parameters. The current measurements significantly reduce the statistical uncertainties on the resonance parameters when compared with previously published parameters. This thesis also explains the resolution function in detail and discusses its importance when fitting experimental data to extract resonance parameters. More accurate resolution function parameters were determined for epithermal transmission and capture measurements by fitting well known resonances in Uranium-238. Improved transmission bare-bounce target in-beam photomultiplier tube (PMT) resolution function parameters were found and compared to those used previously at the RPI LINAC and a marked improvement in the quality of the fits is shown. In addition

  4. 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.

  5. Transmission measurements of selected liquids in the far infrared

    NASA Astrophysics Data System (ADS)

    Walker, M. A.; Richards, R. K.; Hutchinson, D. P.

    1985-11-01

    Measurements were taken of the transmission of 0.119 mm radiation through 22 liquids using a variable length absorption cell. Seven of these liquids were then selected to be tested at wavelengths of 0.185 mm, 0.307 mm, and 0.447 mm. It was found that a light grade of mineral oil proved to have excellent transmission in the far-infrared (FIR) spectrum. We were able, from the data collected, to estimate the index of refraction of these liquids at wavelengths longer than 0.3 mm.

  6. Measurement of the speed of sound in trabecular bone by using a time reversal acoustics focusing system

    NASA Astrophysics Data System (ADS)

    Lee, Kang Il; Choi, Bok Kyoung

    2014-10-01

    A new method for measuring the speed of sound (SOS) in trabecular bone by using a time reversal acoustics (TRA) focusing system was proposed and validated with measurements obtained by using the conventional pulse-transmission technique. The SOS measured in 14 bovine femoral trabecular bone samples by using the two methods was highly correlated each other, although the SOS measured by using the TRA focusing system was slightly lower by an average of 2.2 m/s. The SOS measured by using the two methods showed high correlation coefficients of r = 0.92 with the apparent bone density, consistent with the behavior in human trabecular bone in vitro. These results prove the efficacy of the new method based on the principle of TRA to measure the SOS in trabecular bone.

  7. 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

    2016-04-01

    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 dependency 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 1,000 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.

  8. Acoustic Radiation Force Impulse Measurement in Renal Transplantation

    PubMed Central

    Lee, Juhan; Oh, Young Taik; Joo, Dong Jin; Ma, Bo Gyoung; Lee, A-lan; Lee, Jae Geun; Song, Seung Hwan; Kim, Seung Up; Jung, Dae Chul; Chung, Yong Eun; Kim, Yu Seun

    2015-01-01

    Abstract Interstitial fibrosis and tubular atrophy (IF/TA) is a common cause of kidney allograft loss. Several noninvasive techniques developed to assess tissue fibrosis are widely used to examine the liver. However, relatively few studies have investigated the use of elastographic methods to assess transplanted kidneys. The aim of this study was to explore the clinical implications of the acoustic radiation force impulse (ARFI) technique in renal transplant patients. A total of 91 patients who underwent living donor renal transplantation between September 2010 and January 2013 were included in this prospective study. Shear wave velocity (SWV) was measured by ARFI at baseline and predetermined time points (1 week and 6 and 12 months after transplantation). Protocol biopsies were performed at 12 months. Instead of reflecting IF/TA, SWVs were found to be related to time elapsed after transplantation. Mean SWV increased continuously during the first postoperative year (P < 0.001). In addition, mixed model analysis showed no correlation existed between SWV and serum creatinine (r = −0.2426, P = 0.0771). There was also no evidence of a relationship between IF/TA and serum creatinine (odds ratio [OR] = 1.220, P = 0.7648). Furthermore, SWV temporal patterns were dependent on the kidney weight to body weight ratio (KW/BW). In patients with a KW/BW <3.5 g/kg, mean SWV continuously increased for 12 months, whereas it decreased after 6 months in those with a KW/BW ≥3.5 g/kg. No significant correlation was observed between SWV and IF/TA or renal dysfunction. However, SWV was found to be related to the time after transplantation. Renal hemodynamics influenced by KW/BW might impact SWV values. PMID:26426636

  9. 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.

  10. 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.

  11. New technology for transmission measurements in process pipes.

    PubMed

    Moss, C E; Favalli, A; Goda, J M; Ianakiev, K D; Lombardi, M; McCluskey, C W; Paffett, M T; Swinhoe, M T

    2013-02-01

    Transmission measurements of radiation through process pipes provide a non-intrusive method of determining the amount of product present in the pipes. The product could be a liquid, a slurry, or a gas, which is the most challenging because of the low density. Traditionally, these techniques have used a radioactive source that has to be replaced periodically. We have developed a transmission technique based on an X-ray tube instead of a decaying source. A notch filter is used to provide a narrow transmission line, and a thin silicon transmission detector is used to monitor the X-ray tube output. The transmitted X-rays are measured with a high-throughput gamma spectrometer that consists of a NaI(Tl) detector and an MCA with precise dead time correction. This spectrometer provides stable transmission measurements with an accuracy of a fraction of a percent. The shielding and collimator are made of machinable tungsten for thermal mechanical stability, as well low-cost, low-weight tungsten powder in polymer castings. We describe two methods of measuring the pipe wall thickness without evacuating the pipe. Our particular application was for enrichment monitors for UF(6) in process pipes. Enrichment monitors that are independent of the plant data require two measurements: a transmission measurement to determine the total amount of uranium in the pipe and a measurement of the 186-keV gamma-ray line to determine the amount of (235)U present. The ratio of these values gives the enrichment. Previous designs used a decaying radioactive source such as (57)Co (122 keV, T(½)=272 days) or (109)Cd (22 keV, T(½)=1.2 years). A major effort was required to access and periodically replace these sources in operating plants. In this report, we describe the use of an X-ray tube, which eliminated the source problem, and other innovations. Then we present data from an enrichment monitor that incorporates these innovations. PMID:23208237

  12. FTIR measurements of thermal infrared sky radiance and transmission

    SciTech Connect

    Bennett, C.L.

    1994-07-01

    Precise relative measurements of sky continuum and line emission and absorption have been made using FTIR spectroscopy. During conditions of horizontally uniform air composition, measurements of the variation of the spectral radiance with elevation angle sample an air column that varies simply as the cosecant of the elevation angle. In spectral regions that are optically thin, an extrapolation to zero air mass can be used to accurately determine instrumental background. An ambient temperature black body reference furnishes an accurate measurement of the instrumental spectral response. The excess sky emission above instrumental background relative to the local black body reference spectrum thus provides a calibrated sky radiance spectrum. This spectrum can be used to calculate the atmospheric transmission. As a test, transmission spectra have been directly obtained with the full moon as a backlighting source, and are in excellent agreement with the sky radiance derived transmission spectra. For spectral regions dominated by water, the continuum emission has been measured for paths involving the entire atmospheric column. Reasonable agreement with previous laboratory measurement of the continuum strength is obtained.

  13. A broadband toolbox for scanning microwave microscopy transmission measurements

    NASA Astrophysics Data System (ADS)

    Lucibello, Andrea; Sardi, Giovanni Maria; Capoccia, Giovanni; Proietti, Emanuela; Marcelli, Romolo; Kasper, Manuel; Gramse, Georg; Kienberger, Ferry

    2016-05-01

    In this paper, we present in detail the design, both electromagnetic and mechanical, the fabrication, and the test of the first prototype of a Scanning Microwave Microscope (SMM) suitable for a two-port transmission measurement, recording, and processing the high frequency transmission scattering parameter S21 passing through the investigated sample. The S21 toolbox is composed by a microwave emitter, placed below the sample, which excites an electromagnetic wave passing through the sample under test, and is collected by the cantilever used as the detector, electrically matched for high frequency measurements. This prototype enhances the actual capability of the instrument for a sub-surface imaging at the nanoscale. Moreover, it allows the study of the electromagnetic properties of the material under test obtained through the measurement of the reflection (S11) and transmission (S21) parameters at the same time. The SMM operates between 1 GHz and 20 GHz, current limit for the microwave matching of the cantilever, and the high frequency signal is recorded by means of a two-port Vector Network Analyzer, using both contact and no-contact modes of operation, the latter, especially minded for a fully nondestructive and topography-free characterization. This tool is an upgrade of the already established setup for the reflection mode S11 measurement. Actually, the proposed setup is able to give richer information in terms of scattering parameters, including amplitude and phase measurements, by means of the two-port arrangement.

  14. A broadband toolbox for scanning microwave microscopy transmission measurements.

    PubMed

    Lucibello, Andrea; Sardi, Giovanni Maria; Capoccia, Giovanni; Proietti, Emanuela; Marcelli, Romolo; Kasper, Manuel; Gramse, Georg; Kienberger, Ferry

    2016-05-01

    In this paper, we present in detail the design, both electromagnetic and mechanical, the fabrication, and the test of the first prototype of a Scanning Microwave Microscope (SMM) suitable for a two-port transmission measurement, recording, and processing the high frequency transmission scattering parameter S21 passing through the investigated sample. The S21 toolbox is composed by a microwave emitter, placed below the sample, which excites an electromagnetic wave passing through the sample under test, and is collected by the cantilever used as the detector, electrically matched for high frequency measurements. This prototype enhances the actual capability of the instrument for a sub-surface imaging at the nanoscale. Moreover, it allows the study of the electromagnetic properties of the material under test obtained through the measurement of the reflection (S11) and transmission (S21) parameters at the same time. The SMM operates between 1 GHz and 20 GHz, current limit for the microwave matching of the cantilever, and the high frequency signal is recorded by means of a two-port Vector Network Analyzer, using both contact and no-contact modes of operation, the latter, especially minded for a fully nondestructive and topography-free characterization. This tool is an upgrade of the already established setup for the reflection mode S11 measurement. Actually, the proposed setup is able to give richer information in terms of scattering parameters, including amplitude and phase measurements, by means of the two-port arrangement. PMID:27250429

  15. Studies of the acoustic transmission characteristics of coaxial nozzles with inverted velocity profiles: Comprehensive data report. [nozzle transfer functions

    NASA Technical Reports Server (NTRS)

    Dean, P. D.; Salikuddin, M.; Ahuja, K. K.; Plumblee, H. E.; Mungur, P.

    1979-01-01

    The efficiency of internal noise radiation through a coannular exhaust nozzle with an inverted velocity profile was studied. A preliminary investigation was first undertaken (1) to define the test parameters which influence the internal noise radiation; (2) to develop a test methodology which could realistically be used to examine the effects of the test parameters; and (3) to validate this methodology. The result was the choice of an acoustic impulse as the internal noise source in the jet nozzles. Noise transmission characteristics of a coannular nozzle system were then investigated. In particular, the effects of fan convergence angle, core extension length to annulus height ratio and flow Mach numbers and temperatures were studied. Relevant spectral data only is presented in the form of normalized nozzle transfer function versus nondimensional frequency.

  16. Frequency modulation at a moving material interface and a conservation law for wave number. [acoustic wave reflection and transmission

    NASA Technical Reports Server (NTRS)

    Kleinstein, G. G.; Gunzburger, M. D.

    1976-01-01

    An integral conservation law for wave numbers is considered. In order to test the validity of the proposed conservation law, a complete solution for the reflection and transmission of an acoustic wave impinging normally on a material interface moving at a constant speed is derived. The agreement between the frequency condition thus deduced from the dynamic equations of motion and the frequency condition derived from the jump condition associated with the integral equation supports the proposed law as a true conservation law. Additional comparisons such as amplitude discontinuities and Snells' law in a moving media further confirm the stated proposition. Results are stated concerning frequency and wave number relations across a shock front as predicted by the proposed conservation law.

  17. 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.

  18. NEMS With Broken T Symmetry: Graphene Based Unidirectional Acoustic Transmission Lines

    PubMed Central

    Zanjani, Mehdi B.; Davoyan, Arthur R.; Engheta, Nader; Lukes, Jennifer R.

    2015-01-01

    In this work we discuss the idea of one-way acoustic signal isolation in low dimensional nanoelectromechanical oscillators. We report a theoretical study showing that one-way conversion between in-phase and anti-phase vibrational modes of a double layer graphene nanoribbon is achieved by introducing spatio-temporal modulation of system properties. The required modulation length in order to reach full conversion between the two modes is subsequently calculated. Generalization of the method beyond graphene nanoribbons and realization of a NEMS signal isolator are also discussed. PMID:25993637

  19. Measuring the acoustic absorption coefficient in biological tissue specimens using ultrasonic phase conjugation

    NASA Astrophysics Data System (ADS)

    Smagin, N. V.; Krutyansky, L. M.; Zelenova, Z. V.; Brysev, A. P.

    2014-03-01

    Acoustic absorption has been measured in a series of biological tissue specimens—porcine muscle, renal and fat tissues—by the standard insert-substitution method, as well as by ultrasonic phase conjugation. Comparison of the experimental results and revealed differences confirm the promise of using phase conjugate waves to measure acoustic losses in biological objects. It is demonstrated that in inhomogeneous tissues, the phase conjugation method makes it possible to obtain a more reliable estimate of dissipative losses.

  20. 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.

  1. 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...

  2. 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 ...

  3. Transmission and reflection of acoustic and entropy waves through a stator-rotor stage

    NASA Astrophysics Data System (ADS)

    Bauerheim, Michael; Duran, Ignacio; Livebardon, Thomas; Wang, Gaofeng; Moreau, Stéphane; Poinsot, Thierry

    2016-07-01

    The propagation of acoustic, entropy and vorticity waves through turbine stages is of significant interest in the field of core noise. In particular, entropy spots have been shown to generate significant noise when accelerated through turbine stages: the so-called indirect combustion noise. Analytical models for the propagation of acoustic, vorticity and entropy waves through a stator vane, developed since the seventies, are generally based on restrictive assumptions such as low frequency waves. In order to analyze such assumptions, the theory of Cumpsty and Marble is extended to rotating rows and applied to a 2D stator-rotor turbine stage. The theoretical transfer functions are then compared with numerical predictions from forced compressible Large-Eddy Simulations of a 2D stator-rotor configuration, using a fluid-fluid coupling strategy with an overset-grid method. The comparisons between the analytical model and the simulations are in good agreement. To improve the analytical predictions, the attenuation due to the entropy spot deformation through the stator vane or the rotor blade is then included, modeled either analytically or extracted from the mean flow of the simulations. The complete analytical model reveals a good agreement with 2D simulations, which allows the prediction and minimization of both direct and indirect noise at the design-stage without computation.

  4. 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.

  5. Field quality measurements of a 2-Tesla transmission line magnet

    SciTech Connect

    Velev, G.V.; Foster, W.; Kashikhin, V.; Mazur, P.; Oleck, A.; Piekarz, H.; Schlabach, P.; Sylvester, C.; Wake, M.; /KEK, Tsukuba

    2005-09-01

    A prototype 2-Tesla superconducting transmission line magnet for future hadron colliders was designed, built and tested at Fermilab. The 1.5 m long, combined-function gradient-dipole magnet has a vertical pole aperture of 20 mm. To measure the magnetic field quality in such a small magnet aperture, a specialized rotating coil of 15.2 mm diameter, 0.69 m long was fabricated. Using this probe, a program of magnetic field quality measurements was successfully performed. Results of the measurements are presented and discussed.

  6. A study of methods to predict and measure the transmission of sound through the walls of light aircraft

    NASA Technical Reports Server (NTRS)

    Bernhard, R. J.; Bolton, J. S.

    1988-01-01

    The objectives are: measurement of dynamic properties of acoustical foams and incorporation of these properties in models governing three-dimensional wave propagation in foams; tests to measure sound transmission paths in the HP137 Jetstream 3; and formulation of a finite element energy model. In addition, the effort to develop a numerical/empirical noise source identification technique was completed. The investigation of a design optimization technique for active noise control was also completed. Monthly progress reports which detail the progress made toward each of the objectives are summarized.

  7. Gated photon correlation spectroscopy for acoustical particle velocity measurements in free-field conditions.

    PubMed

    Koukoulas, Triantafillos; Piper, Ben; Theobald, Pete

    2013-03-01

    The measurement of acoustic pressure at a point in space using optical methods has been the subject of extensive research in airborne acoustics over the last four decades. The main driver is to reliably establish the acoustic pascal, thus allowing the calibration of microphones with standard and non-standard dimensions to be realized in an absolute and direct manner. However, the research work so far has mostly been limited to standing wave tubes. This Letter reports on the development of an optical system capable of measuring acoustic particle velocities in free-field conditions; agreement within less than 0.6 dB was obtained with standard microphone measurements during these initial experiments. PMID:23464122

  8. Turbine engine exhaust gas measurements using in-situ FT-IR emission/transmission spectroscopy

    NASA Astrophysics Data System (ADS)

    Marran, David F.; Cosgrove, Joseph E.; Neira, Jorge; Markham, James R.; Rutka, Ronald; Strange, Richard R.

    2001-02-01

    12 An advanced multiple gas analyzer based on in-situ Fourier transform infrared spectroscopy has been used to successfully measure the exhaust plume composition and temperature of an operating gas turbine engine at a jet engine test stand. The sensor, which was optically coupled to the test cell using novel broadband hollow glass waveguides, performed well in this harsh environment (high acoustical noise and vibration, considerable temperature swings in the ambient with engine operation), providing quantitative gas phase information. Measurements were made through the diameter of the engine's one meter exhaust plume, about 0.7 meters downstream of the engine exit plane. The sensor performed near simultaneous infrared transmission and infrared emission measurements through the centerline of the plume. Automated analysis of the emission and transmission spectra provided the temperature and concentration information needed for engine tuning and control that will ensure optimal engine operation and reduced emissions. As a demonstration of the utility and accuracy of the technique, carbon monoxide, nitric oxide, water, and carbon dioxide were quantified in spite of significant variations in the exhaust gas temperature. At some conditions, unburned fuel, particulates (soot/fuel droplets), methane, ethylene and aldehydes were identified, but not yet quantified.

  9. Large area planar fiber optic accelerometers for measurement of acoustic velocity

    SciTech Connect

    Bucaro, J.A.; Lagakos, N.; Houston, B.H.; Kraus, L.

    1996-04-01

    Large area, flexible planar fiber optic accelerometers have been developed for use as acoustic velocity sensors in underwater applications. The devices use a specially designed optical fiber with specific jackets which suppress the fiber sensor{close_quote}s response to acoustic pressure. The sensor has been subjected to a variety of tests including direct acceleration response, direct pressure response, and response to flexural wave excitation when mounted to a {open_quote}{open_quote}hull simulator{close_quote}{close_quote} backing structure. A thorough analysis has been carried out to understand the dynamic responses and limitations of these sensor types. This work is motivated by the desire to measure spatially averaged acoustic velocity while suppressing higher wavenumber mechanical excitations. In conjunction with existing large area pressure sensors (or with suitable structural models), these devices would provide a powerful capability for the measurement and detection of acoustic fields near structures having general impedance properties. This would allow, for example, the decomposition of the acoustic field into backward and forward propagating waves near such a boundary, the determination of acoustic intensity, the detection of the acoustic field with high signal-to-noise ratios even near a soft, pressure release boundary, and determination of the impedance of the structure itself. {copyright} {ital 1996 American Institute of Physics.}

  10. 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.

  11. Acoustic echo cancellation for full-duplex voice transmission on fading channels

    NASA Technical Reports Server (NTRS)

    Park, Sangil; Messer, Dion D.

    1990-01-01

    This paper discusses the implementation of an adaptive acoustic echo canceler for a hands-free cellular phone operating on a fading channel. The adaptive lattice structure, which is particularly known for faster convergence relative to the conventional tapped-delay-line (TDL) structure, is used in the initialization stage. After convergence, the lattice coefficients are converted into the coefficients for the TDL structure which can accommodate a larger number of taps in real-time operation due to its computational simplicity. The conversion method of the TDL coefficients from the lattice coefficients is derived and the DSP56001 assembly code for the lattice and TDL structure is included, as well as simulation results and the schematic diagram for the hardware implementation.

  12. Assessing responses of humpback whales to North Pacific Acoustic Laboratory (NPAL) transmissions: results of 2001--2003 aerial surveys north of Kauai.

    PubMed

    Mobley, Joseph R

    2005-03-01

    Eight aerial surveys were flown north of the Hawaiian island of Kauai during 2001 when the North Pacific Acoustic Laboratory (NPAL) source was not transmitting, and during 2002 and 2003 when it was. All surveys were performed during the period of peak residency of humpback whales (Feb-Mar). During 2002 and 2003, surveys commenced immediately upon cessation of a 24-h cycle of transmissions. Numbers and distribution of whales observed within 40 km of the NPAL source during 2001 (source off) were compared with those observed during 2002 and 2003 (source on). A total of 75 sightings was noted during 2001, as compared with 81 and 55 during 2002 and 2003, respectively. Differences in sighting rates (sightings/km) across years were not statistically significant. Assessment of distributional changes relied upon comparisons of three measures: (a) location depths; (b) distance from the NPAL source; and (c) distance offshore. None of the distributional comparisons revealed statistically significant differences across years. Several possible interpretations are examined: (a) whales have habituated to the NPAL signal; (b) insufficient statistical power exists in the present design to detect any effects; and (c) the effects are short-lived and become undetectable shortly after the cessation of transmissions. PMID:15810697

  13. 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.

  14. 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.

  15. 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. PMID:24116522

  16. Plasma absorption evidence via chirped pulse spectral transmission measurements

    SciTech Connect

    Jedrkiewicz, Ottavia; Minardi, Stefano; Couairon, Arnaud; Jukna, Vytautas; Selva, Marco; Di Trapani, Paolo

    2015-06-08

    This work aims at highlighting the plasma generation dynamics and absorption when a Bessel beam propagates in glass. We developed a simple diagnostics allowing us to retrieve clear indications of the formation of the plasma in the material, thanks to transmission measurements in the angular and wavelength domains. This technique featured by the use of a single chirped pulse having the role of pump and probe simultaneously leads to results showing the plasma nonlinear absorption effect on the trailing part of the pulse, thanks to the spectral-temporal correspondence in the measured signal, which is also confirmed by numerical simulations.

  17. 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

  18. Assessing the integrity of structural adhesive bonds by the measurement of acoustic properties

    NASA Technical Reports Server (NTRS)

    Jagasivamani, V.; Smith, A. C.

    1992-01-01

    Results are reported of an experimental study tracing the influence of externally applied shear stresses on the acoustic properties in the bondline region. The changes in the acoustic properties with a change in the temperature of the test samples are measured. The results of these tests are employed to evaluate the quality of the adhesive bonds. The dependence of time-of-flight on the temperature of plain steel and of steel adhesively bonded to rubber is illustrated in graphic form.

  19. Feasibility of using an acoustic velocity meter to measure flow in the Chipps Island channel, Suisun Bay, California

    USGS Publications Warehouse

    Hoffard, Stuart H.

    1980-01-01

    Tests were conducted in 1978 to determine the feasibility of using an acoustic velocity meter to measure the Sacramento-San Joaquin Delta outflow in the Chipps Island Channel, Suisun Bay, Calif. Three parts of transducers with frequencies of 100, 40, and 24 kilohertz were installed on a cross-channel test path and operated at three elevations, 15.5, 8.0, and 4.0 feet below mean lower low water, to test signal transmission at varying depths. Transmission was most reliable at the lowest depth, and the 24-kilohertz transducers at the 7-millivolt threshold of signal strength met the study 's criterion of no persistent signal loss of more than one hour 's duration in any phase of the tidal cycle. Signal strength was statistically correlated with the environmental factors of wind velocity, wind direction, solar insolation, electrical conductivity, water temperature, water velocity, stage, rate of change in stage, and the acceleration of the rate of change in stage. All correlations were weak. Signal strength is apparently a function of the interaction of several environmental factors. A 32-day test to observe if aquatic growth on the transducers would affect signal transmission showed no reduction in signal strength. Suspended-sediment samples indicated that both the size and concentration of particles are greater than presumed in earlier studies. According to the results of this study, chances are good for reliable transmission of acoustic velocity meter signals. Usually some signals were much stronger than the average 20-second signal strength at 15-minute intervals used for correlation and the frequency analysis. Superior equipment is now being developed specifically for the Chipps Island site to transmit signals several times stronger than the signals analyzed in these tests. (USGS)

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Microfluidic acoustic trapping force and stiffness measurement using viscous drag effect

    PubMed Central

    Lee, Jungwoo; Jeong, Jong Seob; Shung, K. Kirk

    2013-01-01

    It has recently been demonstrated that it was possible to individually trap 70 μm droplets flowing within a 500 μm wide microfluidic channel by a 24 MHz single element piezo-composite focused transducer. In order to further develop this non-invasive approach as a microfluidic particle manipulation tool of high precision, the trapping force needs to be calibrated to a known force, i.e., viscous drag force arising from the fluid flow in the channel. However, few calibration studies based on fluid viscosity have been carried out with focused acoustic beams for moving objects in microfluidic environments. In this paper, the acoustic trapping force (Ftrapping) and the trap stiffness (or compliance k) are experimentally determined for a streaming droplet in a microfluidic channel. Ftrapping is calibrated to viscous drag force produced from syringe pumps. Chebyshev-windowed chirp coded excitation sequences sweeping the frequency range from 18 MHz to 30 MHz is utilized to drive the transducer, enabling the beam transmission through the channel/fluid interface for interrogating the droplets inside the channel. The minimum force (Fmin,trapping) required for initially immobilizing drifting droplets is determined as a function of pulse repetition frequency (PRF), duty factor (DTF), and input voltage amplitude (Vin) to the transducer. At PRF = 0.1 kHz and DTF = 30%, Fmin,trapping is increased from 2.2 nN for Vin = 22 Vpp to 3.8 nN for Vin = 54 Vpp. With a fixed Vin = 54 Vpp and DTF = 30%, Fmin,trapping can be varied from 3.8 nN at PRF = 0.1 kHz to 6.7 nN at PRF = 0.5 kHz. These findings indicate that both higher driving voltage and more frequent beam transmission yield stronger traps for holding droplets in motion. The stiffness k can be estimated through linear regression by measuring the trapping force (Ftrapping) corresponding to the displacement (x) of a droplet from the trap center. By plotting Ftrapping – x curves for certain values of Vin (22/38/54 Vpp) at DTF = 10

  6. Static and oscillatory response measurements of acoustically levitated foam drops

    NASA Astrophysics Data System (ADS)

    Liu, Li; McDaniel, J. Gregory; Holt, R. Glynn

    2002-11-01

    Small samples of aqueous foam of varying gas volume fraction are acoustically levitated in an ultrasonic field. The drops are subjected to both static and time-varying pressures. Normal mode frequencies and inferred rheological properties (yield stress, shear modulus) for foams as a function of gas volume fraction will be presented. We compare the experimental results to recent theoretical descriptions of such modal oscillations [McDaniel and Holt, Phys. Rev. E 61, 2204 (2000); McDaniel, Akhatov, and Holt, Phys Fluids 14, 1886 (2002)]. [Work supported by NASA.

  7. 48 CFR 1552.211-80 - Data standards for the transmission of laboratory measurement results.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... transmission of laboratory measurement results. 1552.211-80 Section 1552.211-80 Federal Acquisition Regulations... Texts of Provisions and Clauses 1552.211-80 Data standards for the transmission of laboratory... Transmission of Laboratory Measurement Results (OCT 2000) This contract requires the transmission...

  8. 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

  9. Analyzing excitation forces acting on a plate based on measured acoustic pressure.

    PubMed

    Wu, Sean F; Zhou, Pan

    2016-07-01

    This paper presents a theoretical study on "seeing" through an elastic structure to uncover the root cause of sound and vibration by using nearfield acoustical holography (NAH) and normal modes expansion. This approach is of generality because vibro-acoustic responses on the surface of a vibrating structure can always be reconstructed, exactly or approximately. With these vibro-acoustic responses, excitation forces acting on the structure can always be determined, analytically or numerically, given any set of boundary conditions. As an example, the explicit formulations for reconstructing time-harmonic excitation forces, including point, line and surface forces, and their arbitrary combinations acting on a rectangular thin plate in vacuum mounted on an infinite baffle are presented. The reason for choosing this example is that the analytic solutions to vibro-acoustic responses are available, and in-depth analyses of results are possible. Results demonstrate that this approach allows one to identify excitation forces based on measured acoustic pressures and reveal their characteristics such as locations, types and amplitudes, as if one could "see" excitation forces acting behind the plate based on acoustic pressure measured on the opposite side. This approach is extendable to general elastic structures, except that in such circumstance numerical results must be sought. PMID:27475174

  10. Acoustic Techniques for Measuring Surface Sealing and Crusting of Agricultural Soils

    NASA Astrophysics Data System (ADS)

    Hickey, C. J.; Leary, D.; Dicarlo, D. A.

    2004-12-01

    The microtopography of soils is an important surface characteristic that effects water ponding, infiltration, and consequently soil erosion. During a rainstorm event the surface microtopography and soil matrix evolve, thereby altering the erosion and runoff dynamics. The impact of raindrops cause the breakdown of soil aggregates into smaller particles, which can then be deposited into the smaller depressions. The redistribution of soil particles on the surface during rainfall produce a thin surface layer often referred to as surface sealing or crusting. For the purpose of this presentation, surface sealing will be used to describe a reduction in the ability of fluid to flow across the surface. Surface crusting will be associated with the formation of a thin layer of higher stiffness or larger mechanical strength. The sensitivity of acoustics to the effects of sealing and crusting was examined by measuring the acoustic-to seismic (A/S) transfer function and acoustic reflectivity on two different soils in a dry, wetted and rained-on state. The A/S transfer function measurement involves the use of a suspended loud speaker to impinge acoustic energy from the air onto the sample and a laser Doppler vibrometer (LDV) is used to measure the induced surface particle velocity. Therefore, the A/S transfer function is a measure of the seismic energy that has been transferred into the soil from the airborne wave. The acoustic surface reflectivity is a measurement of the amount of acoustic energy reflected from the surface and requires the use of a microphone suspended above the surface. Results suggests that the seismic energy transferred (A/S transfer function) is sensitive to crust formation but is not as sensitive to sealing. The amount of reflected acoustic energy appears to be more sensitive to sealing than crusting.

  11. Long-term continuous acoustical suspended-sediment measurements in rivers - Theory, application, bias, and error

    USGS Publications Warehouse

    Topping, David J.; Wright, Scott A.

    2016-01-01

    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

  12. Measuring malaria endemicity from intense to interrupted transmission

    PubMed Central

    Hay, Simon I; Smith, David L; Snow, Robert W

    2008-01-01

    Summary The quantification of malaria transmission for the classification of malaria risk has long been a concern for epidemiologists. During the era of the Global Malaria Eradication Programme, measurements of malaria endemicity were institutionalised by their incorporation into rules outlining defined action points for malaria control programmes. We review the historical development of these indices and their contemporary relevance. This is at a time when many malaria-endemic countries are scaling-up their malaria control activities and reconsidering their prospects for elimination. These considerations are also important to an international community that has recently been challenged to revaluate the prospects for malaria eradication. PMID:18387849

  13. Shear wave transmissivity measurement by color Doppler shear wave imaging

    NASA Astrophysics Data System (ADS)

    Yamakoshi, Yoshiki; Yamazaki, Mayuko; Kasahara, Toshihiro; Sunaguchi, Naoki; Yuminaka, Yasushi

    2016-07-01

    Shear wave elastography is a useful method for evaluating tissue stiffness. We have proposed a novel shear wave imaging method (color Doppler shear wave imaging: CD SWI), which utilizes a signal processing unit in ultrasound color flow imaging in order to detect the shear wave wavefront in real time. Shear wave velocity is adopted to characterize tissue stiffness; however, it is difficult to measure tissue stiffness with high spatial resolution because of the artifact produced by shear wave diffraction. Spatial average processing in the image reconstruction method also degrades the spatial resolution. In this paper, we propose a novel measurement method for the shear wave transmissivity of a tissue boundary. Shear wave wavefront maps are acquired by changing the displacement amplitude of the shear wave and the transmissivity of the shear wave, which gives the difference in shear wave velocity between two mediums separated by the boundary, is measured from the ratio of two threshold voltages required to form the shear wave wavefronts in the two mediums. From this method, a high-resolution shear wave amplitude imaging method that reconstructs a tissue boundary is proposed.

  14. Enhanced Hygiene Measures and Norovirus Transmission during an Outbreak

    PubMed Central

    Teunis, Peter; Morroy, Gabriella; Wijkmans, Clementine; Oostveen, Sandy; Duizer, Erwin; Kretzschmar, Mirjam; Wallinga, Jacco

    2009-01-01

    Control of norovirus outbreaks relies on enhanced hygiene measures, such as handwashing, surface cleaning, using disposable paper towels, and using separate toilets for sick and well persons. However, little is known about their effectiveness in limiting further spread of norovirus infections. We analyzed norovirus outbreaks in 7 camps at an international scouting jamboree in the Netherlands during 2004. Implementation of hygiene measures coincided with an 84.8% (95% predictive interval 81.2%–86.6%) reduction in reproduction number. This reduction was unexpectedly large but still below the reduction needed to contain a norovirus outbreak. Even more stringent control measures are required to break the chain of transmission of norovirus. PMID:19116045

  15. Research on temperature measurement by X-ray transmission intensity

    NASA Astrophysics Data System (ADS)

    Chen, Shuyue; Cheng, Rong

    2013-02-01

    The relationship between temperature and X-ray transmission intensity was researched and analyzed by inspecting material density change, which is caused by thermal expansion. A digital radiographic system was employed to obtain the images. On this basis, we deduced the temperature formula based on the average gray level of the captured images. The measured temperatures were obtained from the experiments and the errors were analyzed. We concluded that when X-rays pass through an object, the X-ray strength and the gray level of the image under high temperatures are greater than those under lower temperatures and the image gray level error has great impact on the accuracy of the measured temperature. The presented approach allowed the non-contact temperature measurement of material.

  16. The influence of oceanic internal waves on the phase stability of broadband acoustic transmission at long range

    NASA Astrophysics Data System (ADS)

    Viechnicki, John Thomas

    1999-12-01

    Instantaneous phase stability in acoustic wavefields measured during the 1994 Acoustic Engineering Test (AET) is examined. AET is one of several preliminary Acoustic Thermometry of Ocean Climate (ATOC) experiments conducted in the past several years. Internal waves are assumed to be the mechanism responsible for phase decorrelation over time scales of ten to thirty minutes. The AET experiment had a center frequency of 75 Hz and a 3 megameter path length. Comparison of numerical simulations to experimental results provide insight into how internal waves scatter sound and can be used to constrain statistical descriptors of realistic deep ocean internal wave fields. Ray-based wavefield simulations are performed using both Deterministic Ray Theory (DRT) and Stochastic Ray Theory (SRT), while full wave simulations are performed using the co insensitive parabolic equation model. This work complements recent similar inference studies of Colosi et al. (1994) and Heaney (1997) on other preliminary ATOC experiments. Working within the framework of the Garrett- Munk internal wave spectrum, phase coherence time, which was observed to be roughly ten to fifteen minutes in the AET experiment, is found to be dependent on the vertically integrated potential energy density, ɛ, and the bounds on the horizontal wavenumber spectrum, k min and kmax. Results suggest that phase coherence is insensitive to mode number cutoff, jmax . Two manifestations of the phase decorrelation observed in simulations are studied. Temporal wavefront wander as defined by Flatté et al. (1979) is examined over the decorrelation period as a function of the horizontal wavenumber spectrum. Intermittent structure that appears and disappears throughout the wavefront on time scales of ten to thirty minutes is examined. This intermittent structure is observed in both full wave modeling and DRT but not SRT.

  17. Measurement of acoustic velocity in the stack of a thermoacoustic refrigerator using particle image velocimetry

    NASA Astrophysics Data System (ADS)

    Berson, Arganthaël; Michard, Marc; Blanc-Benon, Philippe

    2008-06-01

    Thermoacoustic refrigeration systems generate cooling power from a high-amplitude acoustic standing wave. There has recently been a growing interest in this technology because of its simple and robust architecture and its use of environmentally safe gases. With the prospect of commercialization, it is necessary to enhance the efficiency of thermoacoustic cooling systems and more particularly of some of their components such as the heat exchangers. The characterization of the flow field at the end of the stack plates is a crucial step for the understanding and optimization of heat transfer between the stack and the heat exchangers. In this study, a specific particle image velocimetry measurement is performed inside a thermoacoustic refrigerator. Acoustic velocity is measured using synchronization and phase-averaging. The measurement method is validated inside a void resonator by successfully comparing experimental data with an acoustic plane wave model. Velocity is measured inside the oscillating boundary layers, between the plates of the stack, and compared to a linear model. The flow behind the stack is characterized, and it shows the generation of symmetric pairs of counter-rotating vortices at the end of the stack plates at low acoustic pressure level. As the acoustic pressure level increases, detachment of the vortices and symmetry breaking are observed.

  18. Acoustic Cluster Therapy: In Vitro and Ex Vivo Measurement of Activated Bubble Size Distribution and Temporal Dynamics.

    PubMed

    Healey, Andrew John; Sontum, Per Christian; Kvåle, Svein; Eriksen, Morten; Bendiksen, Ragnar; Tornes, Audun; Østensen, Jonny

    2016-05-01

    Acoustic cluster technology (ACT) is a two-component, microparticle formulation platform being developed for ultrasound-mediated drug delivery. Sonazoid microbubbles, which have a negative surface charge, are mixed with micron-sized perfluoromethylcyclopentane droplets stabilized with a positively charged surface membrane to form microbubble/microdroplet clusters. On exposure to ultrasound, the oil undergoes a phase change to the gaseous state, generating 20- to 40-μm ACT bubbles. An acoustic transmission technique is used to measure absorption and velocity dispersion of the ACT bubbles. An inversion technique computes bubble size population with temporal resolution of seconds. Bubble populations are measured both in vitro and in vivo after activation within the cardiac chambers of a dog model, with catheter-based flow through an extracorporeal measurement flow chamber. Volume-weighted mean diameter in arterial blood after activation in the left ventricle was 22 μm, with no bubbles >44 μm in diameter. After intravenous administration, 24.4% of the oil is activated in the cardiac chambers. PMID:26831341

  19. 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.

  20. Broadband electrostatic acoustic transducer for ultrasonic measurements in liquids

    NASA Technical Reports Server (NTRS)

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

    1979-01-01

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

  1. Measuring baryon acoustic oscillations with future SKA surveys

    NASA Astrophysics Data System (ADS)

    Bull, P.; Camera, S.; Raccanelli, A.; Blake, C.; Ferreira, P.; Santos, M.; Schwarz, D. J.

    2015-04-01

    The imprint of baryon acoustic oscillations (BAO) in large-scale structure can be used as a standard ruler for mapping out the cosmic expansion history, and hence for testing cosmological models. In this article we briefly describe the scientific background to the BAO technique, and forecast the potential of the Phase 1 and 2 SKA telescopes to perform BAO surveys using both galaxy catalogues and intensity mapping, assessing their competitiveness with current and future optical galaxy surveys. We find that a 25,000 sq. deg. intensity mapping survey on a Phase 1 array will preferentially constrain the radial BAO, providing a highly competitive 2% constraint on the expansion rate at z ~ 2. A 30,000 sq. deg. galaxy redshift survey on SKA2 will outperform all other planned experiments for z < 1.4.

  2. 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. PMID:25815922

  3. 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...

  4. Improvements to the methods used to measure bubble attenuation using an underwater acoustical resonator.

    PubMed

    Czerski, Helen; Vagle, Svein; Farmer, David M; Hall-Patch, Nick

    2011-11-01

    Active acoustic techniques are commonly used to measure oceanic bubble size distributions, by inverting the bulk acoustical properties of the water (usually the attenuation) to infer the bubble population. Acoustical resonators have previously been used to determine attenuation over a wide range of frequencies (10-200 kHz) in a single measurement, corresponding to the simultaneous measurement of a wide range of bubble sizes (20-300 μm radii). However, there is now also considerable interest in acquiring measurements of bubbles with radii smaller than 16 μm, since these are thought to be important for ocean optics and as tracers for near-surface flow. To extend the bubble population measurement to smaller radii, it is necessary to extend the attenuation measurements to higher frequencies. Although the principles of resonator operation do not change as the frequency increases, the assumptions previously made during the spectral analysis may no longer be valid. In order to improve the methods used to calculate attenuation from acoustical resonator outputs, a more complete analysis of the resonator operation is presented here than has been published previously. This approach allows for robust attenuation measurements over a much wider frequency range and enables accurate measurements from lower-quality spectral peaks. PMID:22088016

  5. 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.

  6. 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.

  7. Measurement of the NP Elastic Cross Section by Neutron Transmission

    NASA Astrophysics Data System (ADS)

    Daub, Brian; Kovash, Michael; Henzl, Vladimir; Shoniyozov, Khayrullo

    2010-11-01

    There are very few previous measurements of the cross section for neutron-proton elastic scattering at energies between 200 and 500 keV. To improve this situation, we used a pulsed proton beam from the Van de Graaff accelerator at the University of Kentucky to produce 200-800 keV neutrons via the ^7Li(p,n)^7Be reaction. We determined the total n-p elastic cross section by measuring the transmission of the neutron beam in samples of CH2 and carbon, using a BC501 liquid scintillator. The cross section obtained by taking ratios between normalized sample-in and sample-out yields is independent of both detector efficiency and dead time.

  8. Active transmission isolation/rotor loads measurement system

    NASA Technical Reports Server (NTRS)

    Kenigsberg, I. J.; Defelice, J. J.

    1973-01-01

    Modifications were incorporated into a helicopter active transmission isolation system to provide the capability of utilizing the system as a rotor force measuring device. These included; (1) isolator redesign to improve operation and minimize friction, (2) installation of pressure transducers in each isolator, and (3) load cells in series with each torque restraint link. Full scale vibration tests performed during this study on a CH-53A helicopter airframe verified that these modifications do not degrade the systems wide band isolation characteristics. Bench tests performed on each isolator unit indicated that steady and transient loads can be measured to within 1 percent of applied load. Individual isolator vibratory load measurement accuracy was determined to be 4 percent. Load measurement accuracy was found to be independent of variations in all basic isolator operating characteristics. Full scale system load calibration tests on the CH-53A airframe established the feasibility of simultaneously providing wide band vibration isolation and accurate measurement of rotor loads. Principal rotor loads (lift, propulsive force, and torque) were measured to within 2 percent of applied load.

  9. Non-Destructive Measurement of Vascular Tissue Development in Stems of Miniature Tomato Using Acoustic Method

    NASA Astrophysics Data System (ADS)

    Kageyama, Kensuke; Watanabe, Eiko; Kato, Hiroshi

    The guided wave effect resembling that of annual rings found in woods and the cortical region of bones is believed to be observable in vascular tissues of herbaceous plants. The properties of acoustic waves traveling through the vascular tissue in the stem of a miniature tomato were measured using a piezoelectric pulser and receiver. The thickness of the vascular tissues and the stem's water content were measured. The detected acoustic waves showed a guided wave effect. The apparent sound velocity, va, was related to the vascular tissue thickness, tv. These results reveal that the detected acoustic waves traveled along the vascular tissues in stems. The maximum peak intensity of the detected acoustic waves, Imax was also related to t. Furthermore, wilting of the examined plants decreased the Imax, although va was not changed. The decrease in Imax might result from cavitations and embolisms with a subsequent increase in air pores in xylem tissues. These results demonstrate that the measurement of acoustic waves traveling through vascular tissue is a useful tool for the non-destructive evaluation of vascular tissue development and embolism density in xylem tissues.

  10. Use of Acoustic Doppler Instruments for Measuring Discharge in Streams with Appreciable Sediment Transport

    USGS Publications Warehouse

    Mueller, D.S.

    2002-01-01

    The use of Acoustic Doppler current profilers (ADCP) for measuring discharge in streams with sediment transport was discussed. The studies show that the acoustic frequency of an ADCP in combination with the sediment transport characteristics in a river causes the ADCP bottom-tracking algorithms to detect a moving bottom. A moving bottom causes bottom-tracking-referenced water velocities and discharges to be biased low. The results also show that the use of differential global positioning system (DGPS) data allows accurate measurement of water velocities and discharges in such cases.

  11. 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.

  12. Beam distortion detection and deflectometry measurements of gigahertz surface acoustic waves.

    PubMed

    Higuet, Julien; Valier-Brasier, Tony; Dehoux, Thomas; Audoin, Bertrand

    2011-11-01

    Gigahertz acoustic waves propagating on the surface of a metal halfspace are detected using different all-optical detection schemes, namely, deflectometry and beam distortion detection techniques. Both techniques are implemented by slightly modifying a conventional reflectometric setup. They are then based on the measurement of the reflectivity change but unlike reflectometric measurements, they give access to the sample surface displacement. A semi-analytical model, taking into account optical, thermal, and mechanical processes responsible for acoustic waves generation, allows analyzing the physical content of the detected waveforms. PMID:22129002

  13. Electron density measurement in gas discharge plasmas by optical and acoustic methods

    NASA Astrophysics Data System (ADS)

    Biagioni, A.; Anania, M. P.; Bellaveglia, M.; Chiadroni, E.; Cianchi, A.; Di Giovenale, D.; Di Pirro, G.; Ferrario, M.; Filippi, F.; Mostacci, A.; Pompili, R.; Shpakov, V.; Vaccarezza, C.; Villa, F.; Zigler, A.

    2016-08-01

    Plasma density represents a very important parameter for both laser wakefield and plasma wakefield acceleration, which use a gas-filled capillary plasma source. Several techniques can be used to measure the plasma density within a capillary discharge, which are mainly based on optical diagnostic methods, as for example the well-known spectroscopic method using the Stark broadening effect. In this work, we introduce a preliminary study on an alternative way to detect the plasma density, based on the shock waves produced by gas discharge in a capillary. Firstly, the measurements of the acoustic spectral content relative to the laser-induced plasmas by a solid target allowed us to understand the main properties of the acoustic waves produced during this kind of plasma generation; afterwards, we have extended such acoustic technique to the capillary plasma source in order to calibrate it by comparison with the stark broadening method.

  14. Acoustic speed and attenuation coefficient in sheep aorta measured at 5-9 MHz.

    PubMed

    Fraser, Katharine H; Poepping, Tamie L; McNeilly, Alan; Megson, Ian L; Hoskins, Peter R

    2006-06-01

    B-mode ultrasound (US) images from blood vessels in vivo differ significantly from vascular flow phantom images. Phantoms with acoustic properties more closely matched to those of in vivo arteries may give better images. A method was developed for measuring the speed and attenuation coefficient of US over the range 5 to 9 MHz in samples of sheep aorta using a pulse-echo technique. The times-of-flight method was used with envelope functions to identify the reference points. The method was tested with samples of tissue-mimicking material of known acoustic properties. The tissue samples were stored in Krebs physiologic buffer solution and measured over a range of temperatures. At 37 degrees C, the acoustic speed and attenuation coefficient as a function of frequency in MHz were 1600 +/- 50 ms(-1) and 1.5 +/- 4f(0.94 +/- 1.3) dB cm(-1), respectively. PMID:16785018

  15. Acoustic detection of pneumothorax

    NASA Astrophysics Data System (ADS)

    Mansy, Hansen A.; Royston, Thomas J.; Balk, Robert A.; Sandler, Richard H.

    2003-04-01

    This study aims at investigating the feasibility of using low-frequency (<2000 Hz) acoustic methods for medical diagnosis. Several candidate methods of pneumothorax detection were tested in dogs. In the first approach, broadband acoustic signals were introduced into the trachea during end-expiration and transmitted waves were measured at the chest surface. Pneumothorax was found to consistently decrease pulmonary acoustic transmission in the 200-1200-Hz frequency band, while less change was observed at lower frequencies (p<0.0001). The ratio of acoustic energy between low (<220 Hz) and mid (550-770 Hz) frequency bands was significantly different in the control (healthy) and pneumothorax states (p<0.0001). The second approach measured breath sounds in the absence of an external acoustic input. Pneumothorax was found to be associated with a preferential reduction of sound amplitude in the 200- to 700-Hz range, and a decrease of sound amplitude variation (in the 300 to 600-Hz band) during the respiration cycle (p<0.01 for each). Finally, chest percussion was implemented. Pneumothorax changed the frequency and decay rate of percussive sounds. These results imply that certain medical conditions may be reliably detected using appropriate acoustic measurements and analysis. [Work supported by NIH/NHLBI #R44HL61108.

  16. Measured and calculated acoustic attenuation rates of tuned resonator arrays for two surface impedance distribution models with flow

    NASA Technical Reports Server (NTRS)

    Parrott, Tony L.; Abrahamson, A. Louis; Jones, Michael G.

    1988-01-01

    An experiment was performed to validate two analytical models for predicting low frequency attenuation of duct liner configurations built from an array of seven resonators that could be individually tuned via adjustable cavity depths. These analytical models had previously been developed for high frequency aero-engine inlet duct liner design. In the low frequency application, the liner surface impedance distribution is unavoidably spatially varying by virtue of available fabrication techniques. The characteristic length of this spatial variation may be a significant fraction of the acoustic wavelength. Comparison of measured and predicted attenuation rates and transmission losses for both modal decomposition and finite element propagation models were in good to excellent agreement for a test frequency range that included the first and second cavity resonance frequencies. This was true for either of two surface impedance distribution modeling procedures used to simplify the impedance boundary conditions. In the presence of mean flow, measurements revealed a fine scale structure of acoustic hot spots in the attenuation and phase profiles. These details were accurately predicted by the finite element model. Since no impedance changes due to mean flow were assumed, it is concluded that this fine scale structure was due to convective effects of the mean flow interacting with the surface impedance nonuniformities.

  17. A Decade of Ocean Acoustic Measurements from R/P FLIP

    NASA Astrophysics Data System (ADS)

    D'Spain, G. L.

    2002-12-01

    Studies of the properties of low frequency acoustic fields in the ocean continue to benefit from the use of manned, stable offshore platforms such as R/P FLIP. A major benefit is providing the at-sea stability required for deployment of extremely large aperture line arrays, line arrays composed of both acoustic motion and acoustic pressure sensors, and arrays that provide measurements in all 3 spatial dimensions. In addition, FLIP provides a high-profile (25 m) observation post with 360 deg coverage for simultaneous visual observations of marine mammals. A few examples of the scientific results that have been achieved over this past decade with ocean acoustic data collected on FLIP are presented. These results include the normal mode decomposition of earthquake T phases to study their generation and water/land coupling characteristics using a 3000 m vertical aperture hydrophone array, simultaneous vertical and horizontal directional information on the underwater sound field from line arrays of hydrophones and geophones, the strange nightime chorusing behavior of fish measured by 3D array aperture, the mirage effect caused by bathymetry changes in inversions for source location in shallow water, and the diving behavior of blue whales determined from 1D recordings of their vocalizations. Presently, FLIP serves as the central data recording platform in ocean acoustic studies using AUV's.

  18. Picosecond acoustics in vegetal cells: non invasive in vitro measurements at a sub-cell scale

    NASA Astrophysics Data System (ADS)

    Audoin, Bertrand; Rossignol, Clément; Chigarev, Nikolay; Ducousso, Mathieu; Forget, Guillaume; Guillemot, Fabien; Durrieu, Marie-Christine

    2010-01-01

    A 100 fs laser pulse passes through a single transparent cell and is absorbed at the surface of a metallic substrate. Picosecond acoustic waves are generated and propagate through the cell in contact with the metal. Interaction of the high frequency acoustic pulse with a probe laser light gives rise to stimulated Brillouin oscillations. The measurements are thus made with lasers for both the opto-acoustic generation and the acousto-optic detection. The technique offers perspectives for single cell imaging. The in plane resolution is limited by the pump and probe spot sizes, i.e ˜1 μm, and the in depth resolution is provided by the acoustic frequencies, typically in the GHz range. The effect of the technique on cell safety is discussed. Experiments achieved in vegetal cells illustrate reproducibility and sensitivity of the measurements. The acoustic responses of cell organelles are significantly different. The results support the potentialities of the hypersonic non invasive technique in the fields of bio-engineering and medicine.

  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. Spatial-heterodyne interferometry for transmission (SHIFT) measurements

    DOEpatents

    Bingham, Philip R.; Hanson, Gregory R.; Tobin, Ken W.

    2006-10-10

    Systems and methods are described for spatial-heterodyne interferometry for transmission (SHIFT) measurements. A method includes digitally recording a spatially-heterodyned hologram including spatial heterodyne fringes for Fourier analysis using a reference beam, and an object beam that is transmitted through an object that is at least partially translucent; Fourier analyzing the digitally recorded spatially-heterodyned hologram, by shifting an original origin of the digitally recorded spatially-heterodyned hologram to sit on top of a spatial-heterodyne carrier frequency defined by an angle between the reference beam and the object beam, to define an analyzed image; digitally filtering the analyzed image to cut off signals around the original origin to define a result; and performing an inverse Fourier transform on the result.

  1. OASIS in the sea: Measurement of the acoustic reflectivity of zooplankton with concurrent optical imaging

    NASA Astrophysics Data System (ADS)

    Jaffe, J. S.; Ohman, M. D.; De Robertis, A.

    A new instrument Optical-Acoustic Submersible Imaging System (OASIS) has been developed for three-dimensional acoustic tracking of zooplankton with concurrent optical imaging to verify the identity of the insonified organisms. OASIS also measures in situ target strengths (TS) of freely swimming zooplankton and nekton of known identity and 3-D orientation. The system consists of a three-dimensional acoustic imaging system (FishTV), a sensitive optical CCD camera with red-filtered strobe illumination, and ancillary oceanographic sensors. The sonar triggers the acquisition of an optical image when it detects the presence of a significant target in the precise location where the camera, strobe and sonar are co-registered. Acoustic TS can then be related to the optical image, which permits identification of the animal and its 3-D aspect. The system was recently deployed (August 1996) in Saanich Inlet, B.C., Canada. Motile zooplankton and nekton were imaged with no evidence of reaction to or avoidance of the OASIS instrument package. Target strengths of many acoustic reflectors were recorded in parallel with the optical images, triggered by the presence of an animal in the correct location of the sonar system. Inspection of the optical images, corroborated with zooplankton sampling with a MOCNESS net, revealed that the joint optically and acoustically sensed taxa at the site were the euphausiid Euphausia pacifica, the gammarid amphipod Orchomene obtusa, and a gadid fish. The simultaneous optical and acoustic images permitted an exact correlation of TS and taxa. Computer simulations from a model of the backscattered strength from euphausiids are in good agreement with the observed data.

  2. On measurement of the acoustic nonlinearity parameter using the finite amplitude insertion substitution (FAIS) technique

    NASA Astrophysics Data System (ADS)

    Zeqiri, Bajram; Cook, Ashley; Rétat, Lise; Civale, John; ter Haar, Gail

    2015-04-01

    The acoustic nonlinearity parameter, B/A, is an important parameter which defines the way a propagating finite amplitude acoustic wave progressively distorts when travelling through any medium. One measurement technique used to determine its value is the finite amplitude insertion substitution (FAIS) method which has been applied to a range of liquid, tissue and tissue-like media. Importantly, in terms of the achievable measurement uncertainties, it is a relative technique. This paper presents a detailed study of the method, employing a number of novel features. The first of these is the use of a large area membrane hydrophone (30 mm aperture) which is used to record the plane-wave component of the acoustic field. This reduces the influence of diffraction on measurements, enabling studies to be carried out within the transducer near-field, with the interrogating transducer, test cell and detector positioned close to one another, an attribute which assists in controlling errors arising from nonlinear distortion in any intervening water path. The second feature is the development of a model which estimates the influence of finite-amplitude distortion as the acoustic wave travels from the rear surface of the test cell to the detector. It is demonstrated that this can lead to a significant systematic error in B/A measurement whose magnitude and direction depends on the acoustic property contrast between the test material and the water-filled equivalent cell. Good qualitative agreement between the model and experiment is reported. B/A measurements are reported undertaken at (20 ± 0.5) °C for two fluids commonly employed as reference materials within the technical literature: Corn Oil and Ethylene Glycol. Samples of an IEC standardised agar-based tissue-mimicking material were also measured. A systematic assessment of measurement uncertainties is presented giving expanded uncertainties in the range ±7% to ±14%, expressed at a confidence level close to 95

  3. Verification of an acoustic transmission matrix analysis of sound propagation in a variable area duct without flow

    NASA Technical Reports Server (NTRS)

    Miles, J. H.

    1981-01-01

    A predicted standing wave pressure and phase angle profile for a hard wall rectangular duct with a region of converging-diverging area variation is compared to published experimental measurements in a study of sound propagation without flow. The factor of 1/2 area variation used is sufficient magnitude to produce large reflections. The prediction is based on a transmission matrix approach developed for the analysis of sound propagation in a variable area duct with and without flow. The agreement between the measured and predicted results is shown to be excellent.

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

    NASA Technical Reports Server (NTRS)

    Kenny, Jeremy; Hobbs, Chris; Plotkin, Ken; Pilkey, Debbie

    2009-01-01

    Lift-off acoustic environments generated by the future Ares I launch vehicle are assessed by the NASA Marshall Space Flight Center (MSFC) acoustics team using several prediction tools. This acoustic environment is directly caused by the Ares I First Stage booster, powered by the five-segment Reusable Solid Rocket Motor (RSRMV). The RSRMV is a larger-thrust derivative design from the currently used Space Shuttle solid rocket motor, the Reusable Solid Rocket Motor (RSRM). Lift-off acoustics is an integral part of the composite launch vibration environment affecting the Ares launch vehicle and must be assessed to help generate hardware qualification levels and ensure structural integrity of the vehicle during launch and lift-off. Available prediction tools that use free field noise source spectrums as a starting point for generation of lift-off acoustic environments are described in the monograph NASA SP-8072: "Acoustic Loads Generated by the Propulsion System." This monograph uses a reference database for free field noise source spectrums which consist of subscale rocket motor firings, oriented in horizontal static configurations. The phrase "subscale" is appropriate, since the thrust levels of rockets in the reference database are orders of magnitude lower than the current design thrust for the Ares launch family. Thus, extrapolation is needed to extend the various reference curves to match Ares-scale acoustic levels. This extrapolation process yields a subsequent amount of uncertainty added upon the acoustic environment predictions. As the Ares launch vehicle design schedule progresses, it is important to take every opportunity to lower prediction uncertainty and subsequently increase prediction accuracy. Never before in NASA s history has plume acoustics been measured for large scale solid rocket motors. Approximately twice a year, the RSRM prime vendor, ATK Launch Systems, static fires an assembled RSRM motor in a horizontal configuration at their test facility

  5. Acoustic measurements of F-4E 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 primary 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-4E aircraft to ensure that aircraft structural acoustic design limits were not exceeded. The acoustic measurements showed that sonic fatigue problems are anticipated with the F-4E aircraft aft fuselage structure during operation in the hush house. The measured acoustic levels were less than those measured in an F-4E aircraft water cooled hush house at Hill AFB in the lower frequencies, but were increased over that measured during ground run up on some areas of the aircraft. 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. Recommendations were also made to increase the fatigue life of the aft fuselage.

  6. Anharmonic properties of solids from measurements of the stress acoustic constant

    NASA Technical Reports Server (NTRS)

    Cantrell, J. H., Jr.

    1982-01-01

    The equations of elastic motion and their solutions are generalized in order to include nonzero homogeneous initial stresses and redefine the stress acoustic constants to include the effect of initial stress. In deriving the relationship between the stress acoustic constants and the strain-generalized Gruneisen parameters, implications in material anharmonicity and nonlinear thermoelasticity are discovered. It is found that the linear change in velocity obtained from these measurements is a nonlinear process resulting from anharmonicity in the interatomic potential. In addition, the thermal expansion coefficient can also be expressed in terms of linear combinations.

  7. A Void Fraction Characterisation by Low Frequency Acoustic Velocity Measurements in Microbubble Clouds

    NASA Astrophysics Data System (ADS)

    Cavaro, Matthieu

    Low frequency acoustic velocity measurements have been applied for the characterization of microbubble clouds generated in water. This method, based on the Wood's model (1941) links the acoustic velocity throughout a two-phase medium to its void fraction value. Low frequency means below resonance frequencies of the bubbles inside the cloud. An original bench was developed to allow the qualification of this method. The experiments conducted allowed us to characterize void fraction values between 10-3 and 10-7. The radii of the studied microbubbles are between a few micrometers and a hundred micrometers.

  8. NASA powered lift facility internally generated noise and its transmission to the acoustic far field

    NASA Technical Reports Server (NTRS)

    Huff, Ronald G.

    1988-01-01

    Noise tests of NASA Lewis Research Center's Powered Lift Facility (PLF) were performed to determine the frequency content of the internally generated noise that reaches the far field. The sources of the internally generated noise are the burner, elbows, valves, and flow turbulence. Tests over a range of nozzle pressure ratios from 1.2 to 3.5 using coherence analysis revealed that low frequency noise below 1200 Hz is transmitted through the nozzle. Broad banded peaks at 240 and 640 Hz were found in the transmitted noise. Aeroacoustic excitation effects are possible in this frequency range. The internal noise creates a noise floor that limits the amount of jet noise suppression that can be measured on the PLF and similar facilities.

  9. Molecular recognition in gas sensing: Results from acoustic wave and in-situ FTIR measurements

    SciTech Connect

    Hierlemann, A.; Ricco, A.J.; Bodenhoefer, K.; Goepel, W.

    1998-06-01

    Surface acoustic wave (SAW) measurements were combined with direct, in-situ molecular spectroscopy to understand the interactions of surface-confined sensing films with gas-phase analytes. This was accomplished by collecting Fourier-transform infrared external-reflectance spectra (FTIR-ERS) on operating SAW devices during dosing of their specifically coated surfaces with key analytes.

  10. A Multidimensional Investigation of Children's /r/ Productions: Perceptual, Ultrasound, and Acoustic Measures

    ERIC Educational Resources Information Center

    Klein, Harriet B.; McAllister Byun, Tara; Davidson, Lisa; Grigos, Maria I.

    2013-01-01

    Purpose: This study explored relationships among perceptual, ultrasound, and acoustic measurements of children's correct and misarticulated /r/ sounds. Longitudinal data documenting changes across these parameters were collected from 2 children who acquired /r/ over a period of intervention and were compared with data from children with…

  11. A thickness mode acoustic wave sensor for measuring interface stiffness between two elastic materials.

    PubMed

    Chen, Jiankang; Wang, Wencai; Wang, Ji; Yang, Zengtao; Yang, Jiashi

    2008-08-01

    We studied thickness vibration of 2 elastic layers with an elastic interface mounted on a plate piezoelectric resonator. The effect of the interface elasticity on resonant frequencies was examined. The result obtained suggests an acoustic wave sensor for measuring the elastic property of an interface between 2 materials. PMID:18986911

  12. Effect of Foreshortening on Center-to-Limb Variations of Measured Acoustic Travel Times

    NASA Astrophysics Data System (ADS)

    Zhao, Junwei; Stejko, Andrey; Chen, Ruizhu

    2016-03-01

    We use data observed near the solar disk center by the Solar Dynamics Observatory/Helioseismic and Magnetic Imager (SDO/HMI) to mimic observations at high-latitude areas after applying geometric transform and projection. These data are then used to study how foreshortening affects the time-distance measurements of acoustic travel times. We find that foreshortening reduces the measured mean travel-times through altering the acoustic-power weighting in different harmonic degrees, but the level of reduction and the latitude dependence are not as strong as those measured from the observation data at the same latitude. Foreshortening is not found to be accountable for the systematic center-to-limb effect in the measured acoustic travel-time differences, which is an essential factor for a reliable inference of the Sun's meridional-circulation profile. The differences in the acoustic power spectrum between the mimicked data and the observation data in high-latitude areas suggest that the optical spectrum-line formation height or convection cells in these areas may be the primary cause of the center-to-limb effect in helioseismic analyses.

  13. Relation of perceived breathiness to laryngeal kinematics and acoustic measures based on computational modeling

    PubMed Central

    Samlan, Robin A.; Story, Brad H.; Bunton, Kate

    2014-01-01

    Purpose To determine 1) how specific vocal fold structural and vibratory features relate to breathy voice quality and 2) the relation of perceived breathiness to four acoustic correlates of breathiness. Method A computational, kinematic model of the vocal fold medial surfaces was used to specify features of vocal fold structure and vibration in a manner consistent with breathy voice. Four model parameters were altered: vocal process separation, surface bulging, vibratory nodal point, and epilaryngeal constriction. Twelve naïve listeners rated breathiness of 364 samples relative to a reference. The degree of breathiness was then compared to 1) the underlying kinematic profile and 2) four acoustic measures: cepstral peak prominence (CPP), harmonics-to-noise ratio, and two measures of spectral slope. Results Vocal process separation alone accounted for 61.4% of the variance in perceptual rating. Adding nodal point ratio and bulging to the equation increased the explained variance to 88.7%. The acoustic measure CPP accounted for 86.7% of the variance in perceived breathiness, and explained variance increased to 92.6% with the addition of one spectral slope measure. Conclusions Breathiness ratings were best explained kinematically by the degree of vocal process separation and acoustically by CPP. PMID:23785184

  14. Deriving content-specific measures of room acoustic perception using a binaural, nonlinear auditory model.

    PubMed

    van Dorp Schuitman, Jasper; de Vries, Diemer; Lindau, Alexander

    2013-03-01

    Acousticians generally assess the acoustic qualities of a concert hall or any other room using impulse response-based measures such as the reverberation time, clarity index, and others. These parameters are used to predict perceptual attributes related to the acoustic qualities of the room. Various studies show that these physical measures are not able to predict the related perceptual attributes sufficiently well under all circumstances. In particular, it has been shown that physical measures are dependent on the state of occupation, are prone to exaggerated spatial fluctuation, and suffer from lacking discrimination regarding the kind of acoustic stimulus being presented. Accordingly, this paper proposes a method for the derivation of signal-based measures aiming at predicting aspects of room acoustic perception from content specific signal representations produced by a binaural, nonlinear model of the human auditory system. Listening tests were performed to test the proposed auditory parameters for both speech and music. The results look promising; the parameters correlate with their corresponding perceptual attributes in most cases. PMID:23464027

  15. Feasibility of using nonlinear guided waves to measure acoustic nonlinearity of aluminum

    NASA Astrophysics Data System (ADS)

    Matlack, Kathryn H.; Kim, Jin-Yeon; Jacobs, Laurence J.; Qu, Jianmin

    2011-04-01

    This research investigates the feasibility of measuring acoustic nonlinearity in aluminum with different ultrasonic guided wave modes. Acoustic nonlinearity is manifested by generation of a second harmonic component in an originally monochromatic ultrasonic wave signal, and previous research has shown this correlates to an intrinsic material property. This parameter has been shown to increase with accumulated material damage - specifically in low- and high-cycle fatigue - prior to crack initiation, whereas other ultrasonic nondestructive evaluation (NDE) techniques measuring linear parameters are unable to detect damage prior to crack initiation. In structural components such as jet engines and aircraft structures subjected to fatigue damage, crack initiation does not occur until ~80% of a component's life. Thus, there is a need for structural health monitoring (SHM) techniques that can characterize material damage state prior to crack initiation, and therefore nonlinear ultrasonic techniques have the potential to be powerful NDE and SHM tools. Experimental results using Rayleigh and Lamb guided wave modes to measure acoustic nonlinearity in undamaged aluminum 6061 samples are presented, and a comparison of the efficiency of these modes to measure acoustic nonlinearity is given.

  16. Profiles of Material Properties in Induction-Hardened Steel Determined through Inversion of Resonant Acoustic Measurements

    SciTech Connect

    Johnson, W.L.; Kim, S.A.; Norton, S.J.

    2005-04-09

    Electromagnetic-acoustic measurements of resonant frequencies of induction-hardened steel shafts were used in an inverse calculation to determine parameters of the radial variations in the shear constant and density, including the effects of material variations and residual stress. Parameters determined for the profile of the shear constant were consistent with independent measurements on cut specimens and estimates of the acoustoelastic contribution. The profiles determined for material variations were close to those of the measured hardness.

  17. Effect of tank liquid acoustic velocity on Doppler string phantom measurements.

    PubMed

    Goldstein, A

    1991-03-01

    The quantitative effects of degassed water in string phantom tank Doppler measurements are derived theoretically. The Doppler parameter measurements considered are range gate registration, range gate profile, image flow angle measurements, and velocity calculation. The equipment velocity calculation is demonstrated to have an appreciable error which is due to the water acoustic velocity and the transducer acquisition geometry. A velocity calibration technique is proposed that only needs a simple multiplicative factor to compensate for the water in the tank. PMID:2027185

  18. Measurement and modeling of the acoustic field near an underwater vehicle and implications for acoustic source localization.

    PubMed

    Lepper, Paul A; D'Spain, Gerald L

    2007-08-01

    The performance of traditional techniques of passive localization in ocean acoustics such as time-of-arrival (phase differences) and amplitude ratios measured by multiple receivers may be degraded when the receivers are placed on an underwater vehicle due to effects of scattering. However, knowledge of the interference pattern caused by scattering provides a potential enhancement to traditional source localization techniques. Results based on a study using data from a multi-element receiving array mounted on the inner shroud of an autonomous underwater vehicle show that scattering causes the localization ambiguities (side lobes) to decrease in overall level and to move closer to the true source location, thereby improving localization performance, for signals in the frequency band 2-8 kHz. These measurements are compared with numerical modeling results from a two-dimensional time domain finite difference scheme for scattering from two fluid-loaded cylindrical shells. Measured and numerically modeled results are presented for multiple source aspect angles and frequencies. Matched field processing techniques quantify the source localization capabilities for both measurements and numerical modeling output. PMID:17672639

  19. Effect of orientation of euphausiids and copepods on acoustic target strength: Implications for measurements from down-looking and side-looking acoustic systems

    NASA Astrophysics Data System (ADS)

    Sutor, Malinda; Cowles, Timothy J.

    2001-05-01

    Multifrequency acoustics is a potentially useful tool for zooplankton ecologists to rapidly map distributional patterns and determine taxonomic and size composition of scatterers. This is typically done with down-looking or side-looking acoustic systems. The ability to estimate taxonomic and size composition acoustically depends upon accurate models of scattering from zooplankton. In this study, distorted wave Born approximation (DWBA) models of individual zooplankton were used to illustrate that the frequency dependence of expected scattering is different for down-looking and side-looking acoustic systems due to the differences in orientation of scatters within the sampled volume. The results show that peaks and nulls occur at different frequencies for each system with maximum target strength differences of 30 dB. The models were used to predict volume scattering (SV) based on zooplankton collected from MOCNESS tows. Predicted SV was compared to SV measured by both a down-looking HTI acoustic system and a side-looking TAPS. The results showed that changes in orientation can have large effects on predicted total SV, particularly at higher frequencies, and demonstrate that choice of orientation parameters is important and different parameters should be used when comparing predicted SV with measured SV from down-looking or side-looking acoustic systems.

  20. Acoustic signal propagation and measurement in natural stream channels for application to surrogate bed load measurements: Halfmoon Creek, Colorado.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Monitoring sediment-generated noise using submerged hydrophones is a surrogate method for measuring bed load transport in streams with the potential for improving estimates of bed load transport through widespread, inexpensive monitoring. Understanding acoustic signal propagation in natural stream e...

  1. Transmission Measurement of the Third-Order Susceptibility of Gold

    NASA Technical Reports Server (NTRS)

    Smith, David D.; Yoon, Youngkwon; Boyd, Robert W.; Crooks, Richard M.; George, Michael

    1999-01-01

    Gold nanoparticle composites are known to display large optical nonlinearities. In order to assess the validity of generalized effective medium theories (EMT's) for describing the linear and nonlinear optical properties of metal nanoparticle composites, knowledge of the linear and nonlinear susceptibilities of the constituent materials is a prerequisite. In this study the inherent nonlinearity of the metal is measured directly (rather than deduced from a suitable EMT) using a very thin gold film. Specifically, we have used the z-scan technique at a wavelength near the transmission window of bulk gold to measure the third-order susceptibility of a continuous thin gold film deposited on a quartz substrate surface-modified with a self-assembled monolayer to promote adhesion and uniformity without affecting the optical properties. We compare our results with predictions which ascribe the nonlinear response to a Fermi-smearing mechanism. Further, we note that the sign of the nonlinear susceptibility is reversed from that of gold nanoparticle composites.

  2. Dielectric loss measurements using an embedded transmission line resonator

    NASA Astrophysics Data System (ADS)

    Sarabi, Bahman; Stoutimore, M. J. A.; Khalil, Moe; Gladchenko, Sergiy; Kozen, Alexander; Rubloff, Gary; Wellstood, F. C.; Lobb, J. C.; Osborn, K. D.

    2011-03-01

    Lossy dielectrics are a major source of decoherence in superconducting qubits. Superconducting linear resonators have proven to be ideally suited for measuring loss in different dielectrics due to their versatility and relative simplicity in design, fabrication, and measurement. We will present data from samples where the low-loss coplanar resonators are fabricated on top of AlOx dielectric films grown using atomic layer deposition (ALD). Although the low-power loss can be extracted from this geometry, embedding the dielectric under study between metal films has advantages that we will discuss. In addition, ALD films can be grown conformally and without pinholes to small thicknesses in comparison to conventional PECVD films. This allows us to make lumped-element resonators with a relatively small footprint, which can easily be embedded within the transmission line. This research was supported by the Intelligence Advanced Research Projects Activity through the U.S. Army Research Office award No. W911NF-09-1-0351.

  3. New approach in subjective and objective speech transmission quality measurement in TCP/IP networks

    NASA Astrophysics Data System (ADS)

    Souček, Pavel; Slavata, Oldřich; Holub, Jan

    2015-02-01

    This paper deals with problems of speech transmission quality measurement in modern telecommunication networks. It focuses on problems caused by specific types of distortions and errors caused present in transmissions using TCP/IP networks.

  4. 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.

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

    PubMed Central

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

    2013-01-01

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

  6. Acoustic waveguide technique for sensing incipient faults in underground power-transmission cables: Including acousto-optic techniques

    NASA Astrophysics Data System (ADS)

    Harrold, R. T.

    1981-09-01

    Theoretical and practical studies were made of both the acoustic emission, spectrum signatures associated with underground cable incipient faults, and the attenuation of acoustic waves in waterfilled metal tubes used as waveguided. Based on critical data, it can be estimated that in favorable circumstances, the acoustic waveguide system would only be useful for sensing incipient faults in underground cables of approx. 800 meters of less in length. A system were investigated which acoustic emissions from cable incipient faults impinge on a fiber-optic lightguide and locally change its refractive index and modulate laser light transmitted along the light guide. Experiments based on this concept show that is is possible t sense acoustic emissions with energy levels below on micro-joule. A test of this system using a section of compressed gas-insulated cable with an internal flashover was successfully carried out.

  7. 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

  8. Acoustic Measurements in Opera Houses: Comparison Between Different Techniques and Equipment

    NASA Astrophysics Data System (ADS)

    FAUSTI, P.; FARINA, A.

    2000-04-01

    In room acoustics, many objective parameters to quantify subjective impressions have been introduced. These quantities can be measured by using a wide variety of powerful tools and equipment. The results can be influenced by the measurement techniques and instruments used. Furthermore, the results also depend on the measurement positions and on the condition of the hall (full, empty, etc.). The aim of this work is to define a tightly standardized measurement procedure for the collection of a complete objective description of an opera house's acoustics. In this paper some of the results obtained by the authors after measurements made in three different halls are presented. Comparisons were made both between different hardware and software tools (real-time analyzer, DAT, PC-board, source, microphones, post-processing software) and between different measurement methods (interrupted stationary noise, true-impulse, pseudo-random white noise with impulse-response doconvolution, sine sweep) as well as between different positions in the halls, with and without the presence of musicians and audience. The results have shown that the differences obtained when using different measurement techniques and equipment are not of significant importance. The only effective differences were found regarding the recording techniques, as the monaural measurements give appreciably different results from the average of left and right channel of binaural measurements. Slightly different results were alsofound between true impulsive sources (pistol shots, balloons) and omni-directional (dodecahedral) loudspeakers. Attention must be paid to the signal-to-noise ratio, as this can influence the correct calculation of some acoustical parameters. Some differences, not as great as expected, were found in the results with and without the musicians in the orchestra shell and with and without the audience in the hall. This is probably due to the high sound absorption that is typical in Italian opera

  9. 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.

  10. Surface acoustical intensity measurements on a diesel engine

    NASA Technical Reports Server (NTRS)

    Mcgary, M. C.; Crocker, M. J.

    1980-01-01

    The use of surface intensity measurements as an alternative to the conventional selective wrapping technique of noise source identification and ranking on diesel engines was investigated. A six cylinder, in line turbocharged, 350 horsepower diesel engine was used. Sound power was measured under anechoic conditions for eight separate parts of the engine at steady state operating conditions using the conventional technique. Sound power measurements were repeated on five separate parts of the engine using the surface intensity at the same steady state operating conditions. The results were compared by plotting sound power level against frequency and noise source rankings for the two methods.

  11. A Comparison of Measured and Predicted XV-15 Tiltrotor Surface Acoustic Pressures

    NASA Technical Reports Server (NTRS)

    Lyle, Karen H.; Burley, Casey L.; Prichard, Devon S.

    1997-01-01

    Predicted XV-15 exterior surface acoustic pressures are compared with previously published experimental data. Surface acoustic pressure transducers were concentrated near the tip-path-plane of the rotor in airplane mode. The comparison emphasized cruise conditions which are of interest for tiltrotor interior noise - level flight for speeds ranging from 72 m/s to 113 m/s. The predictions were produced by components of the NASA Langley Tiltrotor Aeroacoustic Code (TRAC) system of computer codes. Comparisons between measurements and predictions were made in both the time and frequency domains, as well as overall sound pressure levels. In general, the predictions replicated the measured data well. Discrepancies between measurements and predictions were noted. Some of the discrepancies were due to poor correlation of the measured data with the rotor tach signal. In other cases limitations of the predictive methodology have been indicated.

  12. Acoustic Measurement of Surface Wave Damping by a Meniscus

    NASA Astrophysics Data System (ADS)

    Michel, Guillaume; Pétrélis, François; Fauve, Stéphan

    2016-04-01

    We investigate the reflection of gravity-capillary surface waves by a plane vertical barrier. The size of the meniscus is found to strongly affect reflection: the energy of the reflected wave with a pinned contact line is around twice the one corresponding to a fully developed meniscus. To perform these measurements, a new experimental setup similar to an acousto-optic modulator is developed and offers a simple way to measure the amplitude, frequency and direction of propagation of surface waves.

  13. The acoustic environment of intensive care wards based on long period nocturnal measurements.

    PubMed

    Xie, Hui; Kang, Jian

    2012-01-01

    The patients in the Intensive Care Units are often exposed to excessive levels of noise and activities. They can suffer from sleep disturbance, especially at night, but they are often too ill to cope with the poor environment. This article investigates the acoustic environment of typical intensive care wards in the UK, based on long period nocturnal measurements, and examines the differences between singlebed and multibed wards, using statistical analysis. It has been shown that the acoustic environment differs significantly every night. There are also significant differences between the noise levels in the singlebed and multibed wards, where acoustic ceilings are present. Despite the similar background noises in both ward types, more intrusive noises tend to originate from the multibed wards, while more extreme sounds are likely to occur in the single wards. The sound levels in the measured wards for each night are in excess of the World Health Organization's (WHO) guide levels by at least 20 dBA, dominantly at the middle frequencies. Although the sound level at night varies less than that in the daytime, the nocturnal acoustic environment is not dependant on any specific time, thus neither the noisiest nor quietest period can be determined. It is expected that the statistical analysis of the collected data will provide essential information for the development of relevant guidelines and noise reduction strategies. PMID:23117538

  14. Hydrophone arrays for instantaneous measurement of high-pressure acoustic fields

    NASA Astrophysics Data System (ADS)

    Ketterling, Jeffrey A.; Kracht, Jonathan M.; Cleveland, Robin O.

    2010-03-01

    Electrohydraulic lithotripter acoustic fields are measured with single-element hydrophones even though the acoustic fields are not highly repeatable. The ability to obtain an instantaneous "snapshot" of the sound field would have broad implications for advancing the understanding of how lithotripters fragment stones and damage kidney tissue. To better characterize the acoustic field of lithotripters, linear hydrophone arrays were fabricated by bonding a 9 μm piezopolymer film to a copper-clad polyimide which had an array pattern etched on the copper layer. After bonding, the devices were backed with an epoxy plug in order to provide structural support. The array elements were each 0.5 by 0.5 mm, spaced 1.25 mm center to center, and there were 20 elements. The relative sensitivity of each hydrophone element was measured at 5.25 MHz for an acoustic pressure of 4.5 kPa and the elements were found to vary by ≈ 6%. The arrays were then placed in the focus of a piezoelectric lithotripter and were found to maintain their sensitivity for roughly 500 shock waves before gradually losing sensitivity.

  15. Integration of acoustic radiation force and optical imaging for blood plasma clot stiffness measurement.

    PubMed

    Wang, Caroline W; Perez, Matthew J; Helmke, Brian P; Viola, Francesco; Lawrence, Michael B

    2015-01-01

    Despite the life-preserving function blood clotting serves in the body, inadequate or excessive blood clot stiffness has been associated with life-threatening diseases such as stroke, hemorrhage, and heart attack. The relationship between blood clot stiffness and vascular diseases underscores the importance of quantifying the magnitude and kinetics of blood's transformation from a fluid to a viscoelastic solid. To measure blood plasma clot stiffness, we have developed a method that uses ultrasound acoustic radiation force (ARF) to induce micron-scaled displacements (1-500 μm) on microbeads suspended in blood plasma. The displacements were detected by optical microscopy and took place within a micro-liter sized clot region formed within a larger volume (2 mL sample) to minimize container surface effects. Modulation of the ultrasound generated acoustic radiation force allowed stiffness measurements to be made in blood plasma from before its gel point to the stage where it was a fully developed viscoelastic solid. A 0.5 wt % agarose hydrogel was 9.8-fold stiffer than the plasma (platelet-rich) clot at 1 h post-kaolin stimulus. The acoustic radiation force microbead method was sensitive to the presence of platelets and strength of coagulation stimulus. Platelet depletion reduced clot stiffness 6.9 fold relative to platelet rich plasma. The sensitivity of acoustic radiation force based stiffness assessment may allow for studying platelet regulation of both incipient and mature clot mechanical properties. PMID:26042775

  16. Integration of Acoustic Radiation Force and Optical Imaging for Blood Plasma Clot Stiffness Measurement

    PubMed Central

    Wang, Caroline W.; Perez, Matthew J.; Helmke, Brian P.; Viola, Francesco; Lawrence, Michael B.

    2015-01-01

    Despite the life-preserving function blood clotting serves in the body, inadequate or excessive blood clot stiffness has been associated with life-threatening diseases such as stroke, hemorrhage, and heart attack. The relationship between blood clot stiffness and vascular diseases underscores the importance of quantifying the magnitude and kinetics of blood’s transformation from a fluid to a viscoelastic solid. To measure blood plasma clot stiffness, we have developed a method that uses ultrasound acoustic radiation force (ARF) to induce micron-scaled displacements (1-500 μm) on microbeads suspended in blood plasma. The displacements were detected by optical microscopy and took place within a micro-liter sized clot region formed within a larger volume (2 mL sample) to minimize container surface effects. Modulation of the ultrasound generated acoustic radiation force allowed stiffness measurements to be made in blood plasma from before its gel point to the stage where it was a fully developed viscoelastic solid. A 0.5 wt % agarose hydrogel was 9.8-fold stiffer than the plasma (platelet-rich) clot at 1 h post-kaolin stimulus. The acoustic radiation force microbead method was sensitive to the presence of platelets and strength of coagulation stimulus. Platelet depletion reduced clot stiffness 6.9 fold relative to platelet rich plasma. The sensitivity of acoustic radiation force based stiffness assessment may allow for studying platelet regulation of both incipient and mature clot mechanical properties. PMID:26042775

  17. Analysis of In-Flight Vibration Measurements from Helicopter Transmissions

    NASA Technical Reports Server (NTRS)

    Mosher, Marianne; Huff, Ed; Barszcz

    2004-01-01

    In-flight vibration measurements from the transmission of an OH-58C KIOWA are analyzed. In order to understand the effect of normal flight variation on signal shape, the first gear mesh components of the planetary gear system and bevel gear are studied in detail. Systematic patterns occur in the amplitude and phase of these signal components with implications for making time synchronous averages and interpreting gear metrics in flight. The phase of the signal component increases as the torque increases; limits on the torque range included in a time synchronous average may now be selected to correspond to phase change limits on the underlying signal. For some sensors and components, an increase in phase variation and/or abrupt change in the slope of the phase dependence on torque are observed in regions of very low amplitude of the signal component. A physical mechanism for this deviation is postulated. Time synchronous averages should not be constructed in torque regions with wide phase variation.

  18. Microwave transmission measurements through wire array photonic crystals

    NASA Astrophysics Data System (ADS)

    Dewar, Graeme; Souther, Nathan; Johnson, Michael

    2008-03-01

    We have measured the microwave transmission between 12.4 and 18.0 GHz through wire arrays formed into two dimensional square lattices. One array made of copper wire 0.16 mm in radius consisted of five rows by 21 columns having a lattice constant of 5.15 mm. This array exhibited a pass band above 15 GHz, in good agreement with the calculated plasma frequency found from an expression for the permittivity^1 derived in the long wavelength limit. A second array was made with wire of radius 18 microns and lattice constant 0.8 mm. This array was filled with dielectric loaded with powdered magnetite. A sample of this metamaterial 5.8 mm thick and with no externally applied magnetic field exhibited a pass band above 16 GHz. Implications for creating metamaterials with a negative index of refraction from wire arrays embedded in a magnetic host will be discussed. ^1G. Dewar, in Complex Mediums III: Beyond Linear Isotropic Dielectrics, Akhlesh Lakhtakai, Graeme Dewar, Martin W. McCall, Editors, Proceedings of SPIE Vol. 4806, 156-166 (2002).

  19. Precision electron flow measurements in a disk transmission line.

    SciTech Connect

    Clark, Waylon T.; Pelock, Michael D.; Martin, Jeremy Paul; Jackson, Daniel Peter Jr.; Savage, Mark Edward; Stoltzfus, Brian Scott; Mendel, Clifford Will, Jr.; Pointon, Timothy David

    2008-01-01

    An analytic model for electron flow in a system driving a fixed inductive load is described and evaluated with particle in cell simulations. The simple model allows determining the impedance profile for a magnetically insulated transmission line given the minimum gap desired, and the lumped inductance inside the transition to the minimum gap. The model allows specifying the relative electron flow along the power flow direction, including cases where the fractional electron flow decreases in the power flow direction. The electrons are able to return to the cathode because they gain energy from the temporally rising magnetic field. The simulations were done with small cell size to reduce numerical heating. An experiment to compare electron flow to the simulations was done. The measured electron flow is {approx}33% of the value from the simulations. The discrepancy is assumed to be due to a reversed electric field at the cathode because of the inductive load and falling electron drift velocity in the power flow direction. The simulations constrain the cathode electric field to zero, which gives the highest possible electron flow.

  20. Acoustic Measurement of Surface Wave Damping by a Meniscus.

    PubMed

    Michel, Guillaume; Pétrélis, François; Fauve, Stéphan

    2016-04-29

    We investigate the reflection of gravity-capillary surface waves by a plane vertical barrier. The size of the meniscus is found to strongly affect reflection: the energy of the reflected wave with a pinned contact line is around twice the one corresponding to a fully developed meniscus. To perform these measurements, a new experimental setup similar to an acousto-optic modulator is developed and offers a simple way to measure the amplitude, frequency and direction of propagation of surface waves. PMID:27176523

  1. Acoustical measurement separates core noise and jet noise

    NASA Technical Reports Server (NTRS)

    Parthasarathy, S. P.

    1980-01-01

    Measuring technique discriminates between jet noise and core noise of jet engine. Results of experimentation confirmed that core noise and jet noise can be separated by examining cross-correlation of far-field microphone signals and that crossover point between core noise and jet noise moves toward higher velocities at higher angles with respect to jet axis.

  2. Acoustic method for measuring air temperature and humidity in rooms

    NASA Astrophysics Data System (ADS)

    Kanev, N. G.

    2014-05-01

    A method is proposed to determine air temperature and humidity in rooms with a system of sound sources and receivers, making it possible to find the sound velocity and reverberation time. Nomograms for determining the air temperature and relative air humidity are constructed from the found sound velocity and time reverberation values. The required accuracy of measuring these parameters is estimated.

  3. The effect of artificial rain on backscattered acoustic signal: first measurements

    NASA Astrophysics Data System (ADS)

    Titchenko, Yuriy; Karaev, Vladimir; Meshkov, Evgeny; Goldblat, Vladimir

    The problem of rain influencing on a characteristics of backscattered ultrasonic and microwave signal by water surface is considered. The rain influence on backscattering process of electromagnetic waves was investigated in laboratory and field experiments, for example [1-3]. Raindrops have a significant impact on backscattering of microwave and influence on wave spectrum measurement accuracy by string wave gauge. This occurs due to presence of raindrops in atmosphere and modification of the water surface. For measurements of water surface characteristics during precipitation we propose to use an acoustic system. This allows us obtaining of the water surface parameters independently on precipitation in atmosphere. The measurements of significant wave height of water surface using underwater acoustical systems are well known [4, 5]. Moreover, the variance of orbital velocity can be measure using these systems. However, these methods cannot be used for measurements of slope variance and the other second statistical moments of water surface that required for analyzing the radar backscatter signal. An original design Doppler underwater acoustic wave gauge allows directly measuring the surface roughness characteristics that affect on electromagnetic waves backscattering of the same wavelength [6]. Acoustic wave gauge is Doppler ultrasonic sonar which is fixed near the bottom on the floating disk. Measurements are carried out at vertically orientation of sonar antennas towards water surface. The first experiments were conducted with the first model of an acoustic wave gauge. The acoustic wave gauge (8 mm wavelength) is equipped with a transceiving antenna with a wide symmetrical antenna pattern. The gauge allows us to measure Doppler spectrum and cross section of backscattered signal. Variance of orbital velocity vertical component can be retrieved from Doppler spectrum with high accuracy. The result of laboratory and field experiments during artificial rain is presented

  4. Acoustic method for measuring the sound speed of gases over small path lengths.

    PubMed

    Olfert, J S; Checkel, M D; Koch, C R

    2007-05-01

    Acoustic "phase shift" methods have been used in the past to accurately measure the sound speed of gases. In this work, a phase shift method for measuring the sound speed of gases over small path lengths is presented. We have called this method the discrete acoustic wave and phase detection (DAWPD) method. Experimental results show that the DAWPD method gives accurate (+/-3.2 ms) and predictable measurements that closely match theory. The sources of uncertainty in the DAWPD method are examined and it is found that ultrasonic reflections and changes in the frequency ratio of the transducers (the ratio of driving frequency to resonant frequency) can be major sources of error. Experimentally, it is shown how these sources of uncertainty can be minimized. PMID:17552851

  5. Acoustical studies of the steelpan and HANG: Phase-sensitive holography and sound intensity measurements

    NASA Astrophysics Data System (ADS)

    Morrison, Andrew C. H.

    The Caribbean steelpan and an instrument closely related, the HANG, are two of the most, interesting acoustic musical instruments developed in the last century. Although simple in design, the acoustic properties of the steelpan and HANG are surprisingly complicated. Holographic interferometry was used to determine the resonances of a low tenor steelpan and a pentatonic HANG. Placement of a vibrating mirror in the optical path of the reference beam expands the capabilities of the holography system to include phase measurements. Phase maps and phase response curves of several low resonances of notes on a steelpan and HANG are shown. Sound intensity measurements were acquired to explore the relationship between the resonances and the radiated sound field. The instruments were placed in an anechoic chamber, and selected notes were excited electromagnetically with a swept sinusoid signal. A two-microphone probe was used to gather sound intensity measurements. Sound intensity reaps of the first three harmonics are shown for notes on both instruments.

  6. Measurements of Acoustic Properties of Porous and Granular Materials and Application to Vibration Control

    NASA Technical Reports Server (NTRS)

    Park, Junhong; Palumbo, Daniel L.

    2004-01-01

    For application of porous and granular materials to vibro-acoustic controls, a finite dynamic strength of the solid component (frame) is an important design factor. The primary goal of this study was to investigate structural vibration damping through this frame wave propagation for various poroelastic materials. A measurement method to investigate the vibration characteristics of the frame was proposed. The measured properties were found to follow closely the characteristics of the viscoelastic materials - the dynamic modulus increased with frequency and the degree of the frequency dependence was determined by its loss factor. The dynamic stiffness of hollow cylindrical beams containing porous and granular materials as damping treatment was measured also. The data were used to extract the damping materials characteristics using the Rayleigh-Ritz method. The results suggested that the acoustic structure interaction between the frame and the structure enhances the dissipation of the vibration energy significantly.

  7. Acoustic device and method for measuring gas densities

    NASA Technical Reports Server (NTRS)

    Shakkottai, Parthasarathy (Inventor); Kwack, Eug Y. (Inventor); Back, Lloyd (Inventor)

    1992-01-01

    Density measurements can be made in a gas contained in a flow through enclosure by measuring the sound pressure level at a receiver or microphone located near a dipole sound source which is driven at constant velocity amplitude at low frequencies. Analytical results, which are provided in terms of geometrical parameters, wave numbers, and sound source type for systems of this invention, agree well with published data. The relatively simple designs feature a transmitter transducer at the closed end of a small tube and a receiver transducer on the circumference of the small tube located a small distance away from the transmitter. The transmitter should be a dipole operated at low frequency with the kL value preferable less that about 0.3.

  8. Acoustic input impedance of the avian inner ear measured in ostrich (Struthio camelus).

    PubMed

    Muyshondt, Pieter G G; Aerts, Peter; Dirckx, Joris J J

    2016-09-01

    In both mammals and birds, the mechanical behavior of the middle ear structures is affected by the mechanical impedance of the inner ear. In this study, the aim was to quantify the acoustic impedance of the avian inner ear in the ostrich, which allows us to determine the effect on columellar vibrations and middle ear power flow in future studies. To determine the inner ear impedance, vibrations of the columella were measured for both the quasi-static and acoustic stimulus frequencies. In the frequency range of 0.3-4 kHz, we used electromagnetic stimulation of the ossicle and a laser Doppler vibrometer to measure the vibration response. At low frequencies, harmonic displacements were imposed on the columella using piezo stimulation and the resulting force response was measured with a force sensor. From these measurement data, the acoustic impedance of the inner ear could be determined. A simple RLC model in series of the impedance measurements resulted in a stiffness reactance of KIE = 0.20·10(12) Pa/m³, an inertial impedance of MIE = 0.652·10(6) Pa s(2)/m³, and a resistance of RIE = 1.57·10(9) Pa s/m. We found that values of the inner ear impedance in the ostrich are one to two orders in magnitude smaller than what is found in mammal ears. PMID:27473506

  9. Objective Measures and Musician Preference for Concert Stage Acoustics

    NASA Astrophysics Data System (ADS)

    Bruck, Daniel C.

    The purpose of this research was to examine musician preference for various stage enclosures in an actual concert hall setting and to determine the extent to which preference relates to objective measures of reflected energy and on -stage sound pressure levels. Twelve string and brass trios performed standard musical selections in four stage shell configurations and gave preference ratings for the configurations based on Ease of Ensemble, Ability to Hear Oneself, and Ability to Hear the Other Players. The judgments indicate differences in preference between string and brass players for Ease of Ensemble, and a stage preference across all subjects for Ability to Hear Oneself. Objective measurements of reflected energy ratios conducted in the performance spaces indicate relatively low degrees of correlation with subjective preference, with approximately 29% as the highest level of subjective variance accounted for by the ratios. Stage shell configuration had minimal effect on sound pressure levels within the four stages. It was determined that, in terms of the influence of stage shell configuration, reflected energy ratios are preferred over measures of sound pressure level as indicators of musician preference.

  10. 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.

  11. Acoustic containerless experiment system: A non-contact surface tension measurement

    NASA Technical Reports Server (NTRS)

    Elleman, D. D.; Wang, T. G.; Barmatz, M.

    1988-01-01

    The Acoustic Containerless Experiment System (ACES) was flown on STS 41-B in February 1984 and was scheduled to be reflown in 1986. The primary experiment that was to be conducted with the ACES module was the containerless melting and processing of a fluoride glass sample. A second experiment that was to be conducted was the verification of a non-contact surface tension measurement technique using the molten glass sample. The ACES module consisted of a three-axis acoustic positioning module that was inside an electric furnace capable of heating the system above the melting temperature of the sample. The acoustic module is able to hold the sample with acoustic forces in the center of the chamber and, in addition, has the capability of applying a modulating force on the sample along one axis of the chamber so that the molten sample or liquid drop could be driven into one of its normal oscillation modes. The acoustic module could also be adjusted so that it could place a torque on the molten drop and cause the drop to rotate. In the ACES, a modulating frequency was applied to the drop and swept through a range of frequencies that would include the n = 2 mode. A maximum amplitude of the drop oscillation would indicate when resonance was reached and from that data the surface tension could be calculated. For large viscosity samples, a second technique for measuring surface tension was developed. The results of the ACES experiment and some of the problems encountered during the actual flight of the experiment will be discussed.

  12. Digital stroboscopic holographic interferometry for power flow measurements in acoustically driven membranes

    NASA Astrophysics Data System (ADS)

    Keustermans, William; Pires, Felipe; De Greef, Daniël; Vanlanduit, Steve J. A.; Dirckx, Joris J. J.

    2016-06-01

    Despite the importance of the eardrum and the ossicles in the hearing chain, it remains an open question how acoustical energy is transmitted between them. Identifying the transmission path at different frequencies could lead to valuable information for the domain of middle ear surgery. In this work a setup for stroboscopic holography is combined with an algorithm for power flow calculations. With our method we were able to accurately locate the power sources and sinks in a membrane. The setup enabled us to make amplitude maps of the out-of-plane displacement of a vibrating rubber membrane at subsequent instances of time within the vibration period. From these, the amplitude maps of the moments of force and velocities are calculated. The magnitude and phase maps are extracted from this amplitude data, and form the input for the power flow calculations. We present the algorithm used for the measurements and for the power flow calculations. Finite element models of a circular plate with a local energy source and sink allowed us to test and optimize this algorithm in a controlled way and without the present of noise, but will not be discussed below. At the setup an earphone was connected with a thin tube which was placed very close to the membrane so that sound impinges locally on the membrane, hereby acting as a local energy source. The energy sink was a little piece of foam carefully placed against the membrane. The laser pulses are fired at selected instants within the vibration period using a 30 mW HeNe continuous wave laser (red light, 632.8 nm) in combination with an acousto-optic modulator. A function generator controls the phase of these illumination pulses and the holograms are recorded using a CCD camera. We present the magnitude and phase maps as well as the power flow measurements on the rubber membrane. Calculation of the divergence of this power flow map provides a simple and fast way of identifying and locating an energy source or sink. In conclusion

  13. A measure of acoustic noise generated from transcranial magnetic stimulation coils.

    PubMed

    Dhamne, Sameer C; Kothare, Raveena S; Yu, Camilla; Hsieh, Tsung-Hsun; Anastasio, Elana M; Oberman, Lindsay; Pascual-Leone, Alvaro; Rotenberg, Alexander

    2014-01-01

    The intensity of sound emanating from the discharge of magnetic coils used in repetitive transcranial magnetic stimulation (rTMS) can potentially cause acoustic trauma. Per Occupational Safety and Health Administration (OSHA) standards for safety of noise exposure, hearing protection is recommended beyond restricted levels of noise and time limits. We measured the sound pressure levels (SPLs) from four rTMS coils with the goal of assessing if the acoustic artifact levels are of sufficient amplitude to warrant protection from acoustic trauma per OSHA standards. We studied the SPLs at two frequencies (5 and 10 Hz), three machine outputs (MO) (60, 80 and 100%), and two distances from the coil (5 and 10 cm). We found that the SPLs were louder at closer proximity from the coil and directly dependent on the MO. We also found that in all studied conditions, SPLs were lower than the OSHA permissible thresholds for short (<15 min) acoustic exposure, but at extremes of use, may generate sufficient noise to warrant ear protection with prolonged (>8 h) exposure. PMID:24582370

  14. The acoustical cues to sound location in the rat: Measurements of directional transfer functions

    PubMed Central

    Koka, Kanthaiah; Read, Heather L.; Tollin, Daniel J.

    2008-01-01

    The acoustical cues for sound location are generated by spatial- and frequency-dependent filtering of propagating sound waves by the head and external ears. Although rats have been a common model system for anatomy, physiology, and psychophysics of localization, there have been few studies of the acoustical cues available to rats. Here, directional transfer functions (DTFs), the directional components of the head-related transfer functions, were measured in six adult rats. The cues to location were computed from the DTFs. In the frontal hemisphere, spectral notches were present for frequencies from ∼16 to 30 kHz; in general, the frequency corresponding to the notch increased with increases in source elevation and in azimuth toward the ipsilateral ear. The maximum high-frequency envelope-based interaural time differences (ITDs) were 130 μs, whereas low-frequency (<3.5 kHz) fine-structure ITDs were 160 μs; both types of ITDs were larger than predicted from spherical head models. Interaural level differences (ILDs) strongly depended on location and frequency. Maximum ILDs were <10 dB for frequencies <8 kHz and were as large as 20–40 dB for frequencies >20 kHz. Removal of the pinna eliminated the spectral notches, reduced the acoustic gain and ILDs, altered the acoustical axis, and reduced the ITDs. PMID:18537381

  15. Estimation of acoustical streaming: theoretical model, Doppler measurements and optical visualisation.

    PubMed

    Nowicki, A; Kowalewski, T; Secomski, W; Wójcik, J

    1998-02-01

    An approximate solution for the streaming velocity generated by flat and weakly focused transducers was derived by directly solving the Dirichlet boundary conditions for the Poisson equation, the solution of the Navier-Stokes equation for the axial components of the streaming velocity. The theoretical model was verified experimentally using a 32 MHz pulsed Doppler unit. The experimental acoustical fields were produced by three different 4 mm diameter flat and focused transducers driven by the transmitter generating the average acoustic power within the range from 1 microW to 6 mW. The streaming velocity was measured along the ultrasonic beam from 0 to 2 cm. Streaming was induced in a solution of water and corn starch. The experimental results showed that for a given acoustic power the streaming velocity was independent of the starch density in water, changed from 0.3 to 40 grams of starch in 1 l of distilled water. For applied acoustic powers, the streaming velocity changed linearly from 0.2 to 40 mm/s. Both, the theoretical solutions for plane and focused waves and the experimental results were in good agreement. The streaming velocity field was also visualised using the particle image velocimetry (PIV) and two different evaluation methods. The first based on the FFT-based cross-correlation analysis between small sections for each pair of images and the second employing the algorithm of searching for local displacements between several images. PMID:9614292

  16. The acoustical cues to sound location in the rat: measurements of directional transfer functions.

    PubMed

    Koka, Kanthaiah; Read, Heather L; Tollin, Daniel J

    2008-06-01

    The acoustical cues for sound location are generated by spatial- and frequency-dependent filtering of propagating sound waves by the head and external ears. Although rats have been a common model system for anatomy, physiology, and psychophysics of localization, there have been few studies of the acoustical cues available to rats. Here, directional transfer functions (DTFs), the directional components of the head-related transfer functions, were measured in six adult rats. The cues to location were computed from the DTFs. In the frontal hemisphere, spectral notches were present for frequencies from approximately 16 to 30 kHz; in general, the frequency corresponding to the notch increased with increases in source elevation and in azimuth toward the ipsilateral ear. The maximum high-frequency envelope-based interaural time differences (ITDs) were 130 mus, whereas low-frequency (<3.5 kHz) fine-structure ITDs were 160 mus; both types of ITDs were larger than predicted from spherical head models. Interaural level differences (ILDs) strongly depended on location and frequency. Maximum ILDs were <10 dB for frequencies <8 kHz and were as large as 20-40 dB for frequencies >20 kHz. Removal of the pinna eliminated the spectral notches, reduced the acoustic gain and ILDs, altered the acoustical axis, and reduced the ITDs. PMID:18537381

  17. Dual differential interferometer for measurements of broadband surface acoustic waves

    NASA Technical Reports Server (NTRS)

    Turner, T. M.; Claus, R. O.

    1981-01-01

    A simple duel interferometer which uses two pairs of orthogonally polarized optical beams to measure both the amplitude and direction of propagation of broadband ultrasonic surface waves is described. Each pair of focused laser probe beams is used in a separate wideband differential interferometer to independently detect the component of surface wave motion along one direction on the surface. By combining the two output signals corresponding to both components, the two dimensional surface profile and its variation as a function of time is determined.

  18. Sub-Microsecond Temperature Measurement in Liquid Water Using Laser Induced Thermal Acoustics

    NASA Technical Reports Server (NTRS)

    Alderfer, David W.; Herring, G. C.; Danehy, Paul M.; Mizukaki, Toshiharu; Takayama, Kazuyoshi

    2005-01-01

    Using laser-induced thermal acoustics, we demonstrate non-intrusive and remote sound speed and temperature measurements over the range 10 - 45 C in liquid water. Averaged accuracy of sound speed and temperature measurements (10 s) are 0.64 m/s and 0.45 C respectively. Single-shot precisions based on one standard deviation of 100 or greater samples range from 1 m/s to 16.5 m/s and 0.3 C to 9.5 C for sound speed and temperature measurements respectively. The time resolution of each single-shot measurement was 300 nsec.

  19. Measurement of the flow velocity in unmagnetized plasmas by counter propagating ion-acoustic waves

    SciTech Connect

    Ma, J.X.; Li Yangfang; Xiao Delong; Li Jingju; Li Yiren

    2005-06-15

    The diffusion velocity of an inhomogeneous unmagnetized plasma is measured by means of the phase velocities of ion-acoustic waves propagating along and against the direction of the plasma flow. Combined with the measurement of the plasma density distributions by usual Langmuir probes, the method is applied to measure the ambipolar diffusion coefficient and effective ion collision frequency in inhomogeneous plasmas formed in an asymmetrically discharged double-plasma device. Experimental results show that the measured flow velocities, diffusion coefficients, and effective collision frequencies are in agreement with ion-neutral collision dominated diffusion theory.

  20. Acoustic Experiment to Measure the Bulk Viscosity of Near-Critical Xenon in Microgravity

    NASA Technical Reports Server (NTRS)

    Gillis, K. A.; Shinder, I.; Moldover, M. R.; Zimmerli, G. A.

    2002-01-01

    We plan a rigorous test of the theory of dynamic scaling by accurately measuring the bulk viscosity of xenon in microgravity 50 times closer to the critical temperature T(sub c) than previous experiments. The bulk viscosity zeta (or "second viscosity" or "dilational viscosity") will be determined by measuring the attenuation length of sound alpha lambda and also measuring the frequency-dependence of the speed of sound. For these measurements, we developed a unique Helmholtz resonator and specialized electro-acoustic transducers. We describe the resonator, the transducers, their performance on Earth, and their expected performance in microgravity.

  1. Non-Destructive Evaluation Method and Apparatus for Measuring Acoustic Material Nonlinearity

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

    An acoustic non-linearity parameter (beta) measurement method and system for Non-Destructive Evaluation (NDE) of materials and structural members obviates the need for electronic calibration of the measuring equipment. Unlike known substitutional measuring techniques requiring elaborate calibration procedures, the electrical outputs of the capacitive detector of a sample with known beta and the test sample of unknown beta are compared to determine the unknown beta. In order to provide the necessary stability of the present-inventive reference-based approach, the bandpass filters of the measurement system are maintained in a temperature-controlled environment, and the line voltage supplied to said amplifiers is well-regulated.

  2. Voice acoustic measures of depression severity and treatment response collected via interactive voice response (IVR) technology

    PubMed Central

    Mundt, James C.; Snyder, Peter J.; Cannizzaro, Michael S.; Chappie, Kara; Geralts, Dayna S.

    2011-01-01

    Efforts to develop more effective depression treatments are limited by assessment methods that rely on patient-reported or clinician judgments of symptom severity. Depression also affects speech. Research suggests several objective voice acoustic measures affected by depression can be obtained reliably over the telephone. Thirty-five physician-referred patients beginning treatment for depression were assessed weekly, using standard depression severity measures, during a six-week observational study. Speech samples were also obtained over the telephone each week using an IVR system to automate data collection. Several voice acoustic measures correlated significantly with depression severity. Patients responding to treatment had significantly greater pitch variability, paused less while speaking, and spoke faster than at baseline. Patients not responding to treatment did not show similar changes. Telephone standardization for obtaining voice data was identified as a critical factor influencing the reliability and quality of speech data. This study replicates and extends previous research with a larger sample of patients assessing clinical change associated with treatment. The feasibility of obtaining voice acoustic measures reflecting depression severity and response to treatment using computer-automated telephone data collection techniques is also established. Insight and guidance for future research needs are also identified. PMID:21253440

  3. The determination of the acoustic parameters of volcanic rocks from compressional velocity measurements

    USGS Publications Warehouse

    Carroll, R.D.

    1969-01-01

    A statistical analysis was made of the relationship of various acoustic parameters of volcanic rocks to compressional wave velocities for data obtained in a volcanic region in Nevada. Some additional samples, chiefly granitic rocks, were also included in the study to extend the range of parameters and the variety of siliceous rock types sampled. Laboratory acoustic measurements obtained on 62 dry core samples were grouped with similar measurements obtained from geophysical logging devices at several depth intervals in a hole from which 15 of the core samples had been obtained. The effects of lithostatic and hydrostatic load on changing the rock acoustic parameters measured in the hole were noticeable when compared with the laboratory measurements on the same core. The results of the analyses determined by grouping all of the data, however, indicate that dynamic Young's, shear and bulk modulus, shear velocity, shear and compressional characteristic impedance, as well as amplitude and energy reflection coefficients may be reliably estimated on the basis of the compressional wave velocities of the rocks investigated. Less precise estimates can be made of density based on the rock compressional velocity. The possible extension of these relationships to include many siliceous rocks is suggested. ?? 1969.

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

    PubMed

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

    2013-08-01

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

  5. Overview of hydro-acoustic current-measurement applications by the U.S. geological survey in Indiana

    USGS Publications Warehouse

    Morlock, Scott E.; Stewart, James A.

    1999-01-01

    The U.S. Geological Survey (USGS) maintains a network of 170 streamflow-gaging stations in Indiana to collect data from which continuous records of river discharges are produced. Traditionally, the discharge record from a station is produced by recording river stage and making periodic discharge measurements through a range of stage, then developing a relation between stage and discharge. Techniques that promise to increase data collection accuracy and efficiency include the use of hydro-acoustic instrumentation to measure river velocities. The velocity measurements are used to compute river discharge. In-situ applications of hydro-acoustic instruments by the USGS in Indiana include acoustic velocity meters (AVM's) at six streamflow-gaging stations and newly developed Doppler velocity meters (DVM's) at two stations. AVM's use reciprocal travel times of acoustic signals to measure average water velocities along acoustic paths, whereas DVM's use the Doppler shift of backscattered acoustic signals to compute water velocities. In addition to the in-situ applications, three acoustic Doppler current profilers (ADCP's) are used to make river-discharge measurements from moving boats at streamflow-gaging stations in Indiana. The USGS has designed and is testing an innovative unmanned platform from which to make ADCP discharge measurements.

  6. In-situ optical and acoustical measurements of the buoyant cyanobacterium p. Rubescens: spatial and temporal distribution patterns.

    PubMed

    Hofmann, Hilmar; Peeters, Frank

    2013-01-01

    Optical (fluorescence) and acoustic in-situ techniques were tested in their ability to measure the spatial and temporal distribution of plankton in freshwater ecosystems with special emphasis on the harmful and buoyant cyanobacterium P. rubescens. Fluorescence was measured with the multi-spectral FluoroProbe (Moldaenke FluoroProbe, MFP) and a Seapoint Chlorophyll Fluorometer (SCF). In-situ measurements of the acoustic backscatter strength (ABS) were conducted with three different acoustic devices covering multiple acoustic frequencies (614 kHz ADCP, 2 MHz ADP, and 6 MHz ADV). The MFP provides a fast and reliable technique to measure fluorescence at different wavelengths in situ, which allows discriminating between P. rubescens and other phytoplankton species. All three acoustic devices are sensitive to P. rubescens even if other scatterers, e.g., zooplankton or suspended sediment, are present in the water column, because P. rubescens containing gas vesicles has a strong density difference and hence acoustic contrast to the ambient water and other scatterers. After calibration, the combination of optical and acoustical measurements not only allows qualitative and quantitative observation of P. rubescens, but also distinction between P. rubescens, other phytoplankton, and zooplankton. As the measuring devices can sample in situ at high rates they enable assessment of plankton distributions at high temporal (minutes) and spatial (decimeters) resolution or covering large temporal (seasonal) and spatial (basin scale) scales. PMID:24303028

  7. In-Situ Optical and Acoustical Measurements of the Buoyant Cyanobacterium P. Rubescens: Spatial and Temporal Distribution Patterns

    PubMed Central

    Hofmann, Hilmar; Peeters, Frank

    2013-01-01

    Optical (fluorescence) and acoustic in-situ techniques were tested in their ability to measure the spatial and temporal distribution of plankton in freshwater ecosystems with special emphasis on the harmful and buoyant cyanobacterium P. rubescens. Fluorescence was measured with the multi-spectral FluoroProbe (Moldaenke FluoroProbe, MFP) and a Seapoint Chlorophyll Fluorometer (SCF). In-situ measurements of the acoustic backscatter strength (ABS) were conducted with three different acoustic devices covering multiple acoustic frequencies (614 kHz ADCP, 2 MHz ADP, and 6 MHz ADV). The MFP provides a fast and reliable technique to measure fluorescence at different wavelengths in situ, which allows discriminating between P. rubescens and other phytoplankton species. All three acoustic devices are sensitive to P. rubescens even if other scatterers, e.g., zooplankton or suspended sediment, are present in the water column, because P. rubescens containing gas vesicles has a strong density difference and hence acoustic contrast to the ambient water and other scatterers. After calibration, the combination of optical and acoustical measurements not only allows qualitative and quantitative observation of P. rubescens, but also distinction between P. rubescens, other phytoplankton, and zooplankton. As the measuring devices can sample in situ at high rates they enable assessment of plankton distributions at high temporal (minutes) and spatial (decimeters) resolution or covering large temporal (seasonal) and spatial (basin scale) scales. PMID:24303028

  8. Measurement of Turbulence with Acoustic Doppler Current Profilers - Sources of Error and Laboratory Results

    USGS Publications Warehouse

    Nystrom, E.A.; Oberg, K.A.; Rehmann, C.R.

    2002-01-01

    Acoustic Doppler current profilers (ADCPs) provide a promising method for measuring surface-water turbulence because they can provide data from a large spatial range in a relatively short time with relative ease. Some potential sources of errors in turbulence measurements made with ADCPs include inaccuracy of Doppler-shift measurements, poor temporal and spatial measurement resolution, and inaccuracy of multi-dimensional velocities resolved from one-dimensional velocities measured at separate locations. Results from laboratory measurements of mean velocity and turbulence statistics made with two pulse-coherent ADCPs in 0.87 meters of water are used to illustrate several of inherent sources of error in ADCP turbulence measurements. Results show that processing algorithms and beam configurations have important effects on turbulence measurements. ADCPs can provide reasonable estimates of many turbulence parameters; however, the accuracy of turbulence measurements made with commercially available ADCPs is often poor in comparison to standard measurement techniques.

  9. Measurement of acoustic particle motion in shallow water and its application to geoacoustic inversion.

    PubMed

    Dall'Osto, David R; Choi, Jee Woong; Dahl, Peter H

    2016-01-01

    Within an underwater acoustic waveguide, the interference among multipath arrivals causes a phase difference in orthogonal components of the particle velocity. When two components of the particle velocity are not in phase, the fluid particles follow an elliptical trajectory. This property of the acoustic field can be readily detected by a vector sensor. A non-dimensional vector quantity, the degree of circularity, is used to quantify how much the trajectory resembles a circle. In this paper, vector sensor measurements collected during the 2013 Target and Reverberation Experiment are used to demonstrate the effect of multipath interference on the degree of circularity. Finally, geoacoustic properties representing the sandy sediment at the experimental site are inverted by minimization of a cost function, which quantifies the deviation between the measured and modeled degree of circularity. PMID:26827027

  10. Design and Implementation of an Acoustic X-ray Detector to Measure the LCLS Beam Energy

    SciTech Connect

    Loos, Jennifer L.; /San Jose State U. /SLAC

    2010-08-25

    On April 11, 2009, first light was seen from LCLS. The present apparatus being used to measure the x-ray beam energy is the Total Energy Sensor which uses a suite of thermal sensors. Another device is needed to cross-check the energy measurements. This new diagnostic tool utilizes radiation acoustic phenomena to determine the x-ray beam energy. A target is hit by the x-rays from the beam, and a voltage is generated in two piezoelectric sensors attached to the target in response to the consequent deformation. Once the voltage is known, the power can be obtained. Thermal sensors will also be attached to the target for calibration purposes. Material selection and design were based on: durability, ultra-high vacuum compatibility, safety and thermal properties. The target material was also chosen for its acoustic properties which were determined from tests using a frequency generator and laser. Initial tests suggest the device will function as anticipated.

  11. Acoustical measurements of expression devices in pipe organs.

    PubMed

    Braasch, Jonas

    2008-03-01

    In this investigation, three different swell systems known in pipe organs, the swell box, the crescendo wheel, and the historic wind swell were measured and compared to each other. The dynamic range of the crescendo wheel was found to be most effective, and for frequencies near 2 kHz the increase in sound pressure level could be up to 50 dB between the softest and the loudest adjustment. The maximum dynamic range for the wind swell and the swell box were found to be 10-20 dB in the same frequency range. With its step-wise crescendo procedure, the crescendo wheel simulates the type of orchestra crescendo which is reached by successively adding further musical instruments. In contrast, the swell box and the wind swell produce a crescendo effect similar to the crescendo in which individual musical instruments perform a dynamic movement. This type of crescendo requires a continuous level increase but allows a smaller dynamic range. The disappearance of the wind swell is not surprising because it offers no advantage over the swell box, while being restricted to stops with free reeds. PMID:18345856

  12. Local Measurement of Electron Density and Temperature in High Temperature Laser Plasma Using the Ion-Acoustic Dispersion

    SciTech Connect

    Froula, D H; Davis, P; Ross, S; Meezan, N; Divol, L; Price, D; Glenzer, S H; Rousseaux, C

    2005-09-20

    The dispersion of ion-acoustic fluctuations has been measured using a novel technique that employs multiple color Thomson-scattering diagnostics to measure the frequency spectrum for two separate thermal ion-acoustic fluctuations with significantly different wave vectors. The plasma fluctuations are shown to become dispersive with increasing electron temperature. We demonstrate that this technique allows a time resolved local measurement of electron density and temperature in inertial confinement fusion plasmas.

  13. Discharge measurements using a broad-band acoustic Doppler current profiler

    USGS Publications Warehouse

    Simpson, Michael R.

    2002-01-01

    The measurement of unsteady or tidally affected flow has been a problem faced by hydrologists for many years. Dynamic discharge conditions impose an unreasonably short time constraint on conventional current-meter discharge-measurement methods, which typically last a minimum of 1 hour. Tidally affected discharge can change more than 100 percent during a 10-minute period. Over the years, the U.S. Geological Survey (USGS) has developed moving-boat discharge-measurement techniques that are much faster but less accurate than conventional methods. For a bibliography of conventional moving-boat publications, see Simpson and Oltmann (1993, page 17). The advent of the acoustic Doppler current profiler (ADCP) made possible the development of a discharge-measurement system capable of more accurately measuring unsteady or tidally affected flow. In most cases, an ADCP discharge-measurement system is dramatically faster than conventional discharge-measurement systems, and has comparable or better accuracy. In many cases, an ADCP discharge-measurement system is the only choice for use at a particular measurement site. ADCP systems are not yet ?turnkey;? they are still under development, and for proper operation, require a significant amount of operator training. Not only must the operator have a rudimentary knowledge of acoustic physics, but also a working knowledge of ADCP operation, the manufacturer's discharge-measurement software, and boating techniques and safety.

  14. Integrated measurements of acoustical and optical thin layers II: Horizontal length scales

    NASA Astrophysics Data System (ADS)

    Moline, Mark A.; Benoit-Bird, Kelly J.; Robbins, Ian C.; Schroth-Miller, Maddie; Waluk, Chad M.; Zelenke, Brian

    2010-01-01

    The degree of layered organization of planktonic organisms in coastal systems impacts trophic interactions, the vertical availability of nutrients, and many biological rate processes. While there is reasonable characterization of the vertical structure of these phenomena, the extent and horizontal length scale of variation has rarely been addressed. Here we extend the examination of the vertical scale in the first paper of the series to the horizontal scale with combined shipboard acoustic measurements and bio-optic measurements taken on an autonomous underwater vehicle. Measurements were made in Monterey Bay, CA from 2002 to 2008 for the bio-optical parameters and during 2006 for acoustic scattering measurements. The combined data set was used to evaluate the horizontal decorrelation length scales of the bio-optical and acoustic scattering layers themselves. Because biological layers are often decoupled from the physical structure of the water column, assessment of the variance within identified layers was appropriate. This differs from other studies in that physical parameters were not used as a basis for the layer definition. There was a significant diel pattern to the decorrelation length scale for acoustic layers with the more abundant nighttime layers showing less horizontal variability despite their smaller horizontal extent. A significant decrease in the decorrelation length scale was found in bio-optical parameters over six years of study, coinciding with a documented shift in the plankton community. Results highlight the importance of considering plankton behavior and time of day with respect to scale when studying layers, and the challenges of sampling these phenomena.

  15. Application of Wavelet Packet Analysis to the Measurement of the Baryon Acoustic Oscillation

    NASA Astrophysics Data System (ADS)

    Kadowaki, Kevin; Garcia, Noel; Ford, Taurean; Pando, Jesus; SDSS-FAST Collaboration

    2016-03-01

    We develop a method of wavelet packet analysis to measure the Baryon Acoustic Oscillation (BAO) peak and apply this method to the CMASS galaxy catalog from the SDSS Baryon Oscillation Spectroscopic Survey (BOSS) collaboration. We compare our results to a fiducial ?CDM flat cosmological model and detect a BAO signature in the power spectrum comparable to the previous consensus results of the BOSS collaboration. We find DA = 1365rd /rd , fid at z = . 54 . Member ID Forthcoming.

  16. Breath air measurement using wide-band frequency tuning IR laser photo-acoustic spectroscopy

    NASA Astrophysics Data System (ADS)

    Kistenev, Yury V.; Borisov, Alexey V.; Kuzmin, Dmitry A.; Bulanova, Anna A.; Boyko, Andrey A.; Kostyukova, Nadezhda Y.; Karapuzikov, Alexey A.

    2016-03-01

    The results of measuring of biomarkers in breath air of patients with broncho-pulmonary diseases using wide-band frequency tuning IR laser photo-acoustic spectroscopy and the methods of data mining are presented. We will discuss experimental equipment and various methods of intellectual analysis of the experimental spectra in context of above task. The work was carried out with partial financial support of the FCPIR contract No 14.578.21.0082 (ID RFMEFI57814X0082).

  17. 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.

  18. Development of explicit diffraction corrections for absolute measurements of acoustic nonlinearity parameters in the quasilinear regime.

    PubMed

    Jeong, Hyunjo; Zhang, Shuzeng; Cho, Sungjong; Li, Xiongbing

    2016-08-01

    In absolute measurements of acoustic nonlinearity parameters, amplitudes of harmonics must be corrected for diffraction effects. In this study, we develop explicit multi-Gaussian beam (MGB) model-based diffraction corrections for the first three harmonics in weakly nonlinear, axisymmetric sound beams. The effects of making diffraction corrections on nonlinearity parameter estimation are investigated by defining "total diffraction correction (TDC)". The results demonstrate that TDC cannot be neglected even for harmonic generation experiments in the nearfield region. PMID:27186964

  19. Accuracy of acoustic velocity metering systems for measurement of low velocity in open channels

    USGS Publications Warehouse

    Laenen, Antonius; Curtis, R.E., Jr.

    1989-01-01

    Acoustic velocity meter (AVM) accuracy depends on equipment limitations, the accuracy of acoustic-path length and angle determination, and the stability of the mean velocity to acoustic-path velocity relation. Equipment limitations depend on path length and angle, transducer frequency, timing oscillator frequency, and signal-detection scheme. Typically, the velocity error from this source is about +or-1 to +or-10 mms/sec. Error in acoustic-path angle or length will result in a proportional measurement bias. Typically, an angle error of one degree will result in a velocity error of 2%, and a path-length error of one meter in 100 meter will result in an error of 1%. Ray bending (signal refraction) depends on path length and density gradients present in the stream. Any deviation from a straight acoustic path between transducer will change the unique relation between path velocity and mean velocity. These deviations will then introduce error in the mean velocity computation. Typically, for a 200-meter path length, the resultant error is less than one percent, but for a 1,000 meter path length, the error can be greater than 10%. Recent laboratory and field tests have substantiated assumptions of equipment limitations. Tow-tank tests of an AVM system with a 4.69-meter path length yielded an average standard deviation error of 9.3 mms/sec, and the field tests of an AVM system with a 20.5-meter path length yielded an average standard deviation error of a 4 mms/sec. (USGS)

  20. Granular Shear Zone Formation: Acoustic Emission Measurements and Fiber-bundle Models

    NASA Astrophysics Data System (ADS)

    Michlmayr, Gernot; Or, Dani

    2013-04-01

    We couple the acoustic emissions method with conceptual models of granular material behavior for investigation of granular shear zone formation and to assess eminence of landslide hazard. When granular materials are mechanically loaded or sheared, they tend to produce discrete events of force network restructuring, and frictional interaction at grain contacts. Such abrupt perturbations within the granular lattice release part of the elastic energy stored in the strained material. Elastic waves generated by such events can be measured as acoustic emissions (AE) and may be used as surrogates for intermittent structural transitions associated with shear zone formation. To experimentally investigate the connection between granular shearing and acoustic signals we performed an array of strain-controlled shear-frame tests using glass beads. AE were measured with two different systems operating at two frequency ranges. High temporal resolution measurements of the shear stresses revealed the presence of small fluctuations typically associated with low-frequency (< 20 kHz) acoustic bursts. Shear stress jumps and linked acoustic signals give account of discrete events of grain network rearrangements and obey characteristic exponential frequency-size distributions. We found that statistical features of force jumps and AE events depend on mechanical boundary conditions and evolve during the straining process. Activity characteristics of high-frequency (> 30 kHz) AE events is linked to friction between grains. To interpret failure associated AE signals, we adapted a conceptual fiber-bundle model (FBM) that describes some of the salient statistical features of failure and associated energy production. Using FBMs for the abrupt mechanical response of the granular medium and an associated grain and force chain AE generation model provides us with a full description of the mechanical-acoustical granular shearing process. Highly resolved AE may serve as a diagnostic tool not only

  1. Acoustical measurements during Erbium:YAG laser ablation of porcine calcified tissues

    NASA Astrophysics Data System (ADS)

    Saaf, Randall R.; Wong, Brian J.; Milner, Thomas E.; Peavy, George M.; Anvari, Bahman

    1998-07-01

    The Erbium:YAG laser ((lambda) equals 2.94 micrometer) has been suggested for use in dental, orthopedic, and middle ear surgery due to decreased thermal trauma, precise ablation characteristics, and potential fiber optic delivery. While there has been much focus on the thermal and photoacoustic events that occur during pulsed laser ablation of hard tissue, there are few studies that examine the acoustic energy generated by these devices during ablation from an audiologic standpoint. In this study, the porcine otic capsule, nasal bone, and teeth were irradiated with an Erbium:YAG laser. Frequencies of 5 and 10 Hz shot repetition rate were used with .5 to 4 W average power. Additionally, a burst mode consisting of three pulses was used with .2 to 1.4 J total energy. During ablation, acoustic measurements were made using a sound level meter held 20 mm away from the target site. A constant spot size of 500 micrometer was maintained for each laser blast. With each set of laser parameters, the sound intensity (dB SPL) exceeded 70 dB. Peak intensity measurements of 95 dB were measured. The clinical significance of these findings is discussed and the acoustical aspects of middle ear function and noise trauma are reviewed.

  2. The Application of Acoustic Measurements and Audio Recordings for Diagnosis of In-Flight Hardware Anomalies

    NASA Technical Reports Server (NTRS)

    Welsh, David; Denham, Samuel; Allen, Christopher

    2011-01-01

    In many cases, an initial symptom of hardware malfunction is unusual or unexpected acoustic noise. Many industries such as automotive, heating and air conditioning, and petro-chemical processing use noise and vibration data along with rotating machinery analysis techniques to identify noise sources and correct hardware defects. The NASA/Johnson Space Center Acoustics Office monitors the acoustic environment of the International Space Station (ISS) through periodic sound level measurement surveys. Trending of the sound level measurement survey results can identify in-flight hardware anomalies. The crew of the ISS also serves as a "detection tool" in identifying unusual hardware noises; in these cases the spectral analysis of audio recordings made on orbit can be used to identify hardware defects that are related to rotating components such as fans, pumps, and compressors. In this paper, three examples of the use of sound level measurements and audio recordings for the diagnosis of in-flight hardware anomalies are discussed: identification of blocked inter-module ventilation (IMV) ducts, diagnosis of abnormal ISS Crew Quarters rack exhaust fan noise, and the identification and replacement of a defective flywheel assembly in the Treadmill with Vibration Isolation (TVIS) hardware. In each of these examples, crew time was saved by identifying the off nominal component or condition that existed and in directing in-flight maintenance activities to address and correct each of these problems.

  3. Acoustical measurements of DOE/NASA MOD-0 wind turbine at Plum Brook Station, Ohio

    SciTech Connect

    Etter, C.L.; Kelley, N.D.; McKenna, H.E.; Linn, C.; Garrelts, R.

    1983-06-01

    This report documents the evaluation of low-frequency acoustic emissions associated with the operation of the DOE/NASA MOD-0 wind turbine generator located at Plum Brook Station, Ohio. These measurements were taken as part of a joint SERI/NASA Brook Station, Ohio. These measurements were taken as part of a joint SERI/NASA effort to study acoustic noise generation by utility-sized wind turbines. The machine-operating conditions closely simulated the operation of the larger DOE/NASA MOD-1 wind turbine installed near Boone, NC, in both its design downwind configuration and theoretical upwind mode. Measurement results indicated that acoustic impulses characteristic of the MOD-1 turbine were detectable only with a downwind configuration and a 35-rpm rotor speed, a situation which parallels a 23-rpm rotor speed operation on the MOD-1. Under the available meteorological conditions, no impulses were detected during downwind 23 rpm or by wind-induced noise, indicating a severe limitation of the microphone configuration used in these tests.

  4. Optimizing stepwise rotation of dodecahedron sound source to improve the accuracy of room acoustic measures.

    PubMed

    Martellotta, Francesco

    2013-09-01

    Dodecahedron sound sources are widely used for acoustical measurement purposes as they produce a good approximation of omnidirectional radiation. Evidence shows that such an assumption is acceptable only in the low-frequency range (namely below 1 kHz), while at higher frequencies sound radiation is far from being uniform. In order to improve the accuracy of acoustical measurements obtained from dodecahedron sources, international standard ISO 3382 suggests an averaging of results after a source rotation. This paper investigates the effects of such rotations, both in terms of variations in acoustical parameters and spatial distribution of sound reflections. Taking advantage of a spherical microphone array, the different reflection patterns were mapped as a function of source rotation, showing that some reflections may be considerably attenuated for different aiming directions. This paper investigates the concept of averaging results while changing rotation angles and the minimum number of rotations required to improve the accuracy of the average value. Results show that averages of three measurements carried out at 30° angular steps are closer to actual values and show much less fluctuation. In addition, an averaging of the directional intensity components of the selected responses stabilizes the spatial distribution of the reflections. PMID:23967936

  5. Design and Instrumentation of a Measurement and Calibration System for an Acoustic Telemetry System

    SciTech Connect

    Deng, Zhiqun; Weiland, Mark A.; Carlson, Thomas J.; Eppard, M. B.

    2010-03-31

    The Juvenile Salmon Acoustic Telemetry System (JSATS) is an active sensing technology developed by Portland District, the U.S. Army Corps of Engineers for detecting and tracking small fish. It is used at hydroelectric projects and in the laboratory for evaluating behavior and survival of juvenile salmonids migrating through the Federal Columbia River Power System to the Pacific Ocean. It provides critical data for salmon protection and development of more “fish-friendly” hydroelectric facilities. The objective of this study was to design and build a measurement and calibration system for evaluating the JSATS component, because the JSATS requires comprehensive acceptance and performance testing in a controlled environment before it is deployed in the field. The system consists of a reference transducer, a water test tank lined with anechoic material, a motion control unit, a reference receiver, a signal conditioner and amplifier unit, a data acquisition board, MATLAB control and analysis interface, and a computer. The fully integrated system has been evaluated successfully at various simulated distances and using different encoded signals at frequencies within the bandwidth of the JSATS transmitter. It provides accurate acoustic mapping capability in a controlled environment and automates the process that allows real-time measurements and evaluation of the piezoelectric transducers, sensors, or the acoustic fields. The measurement and calibration system has been in use since 2009 for acceptance and performance testing of, and further improvements to, the JSATS.

  6. Complete velocity distribution in river cross-sections measured by acoustic instruments

    USGS Publications Warehouse

    Cheng, R.T.; Gartner, J.W.

    2003-01-01

    To fully understand the hydraulic properties of natural rivers, velocity distribution in the river cross-section should be studied in detail. The measurement task is not straightforward because there is not an instrument that can measure the velocity distribution covering the entire cross-section. Particularly, the velocities in regions near the free surface and in the bottom boundary layer are difficult to measure, and yet the velocity properties in these regions play the most significant role in characterizing the hydraulic properties. To further characterize river hydraulics, two acoustic instruments, namely, an acoustic Doppler current profiler (ADCP), and a "BoogieDopp" (BD) were used on fixed platforms to measure the detailed velocity profiles across the river. Typically, 20 to 25 stations were used to represent a river cross-section. At each station, water velocity profiles were measured independently and/or concurrently by an ADCP and a BD. The measured velocity properties were compared and used in computation of river discharge. In a tow-tank evaluation of a BD, it has been confirmed that BD is capable of measuring water velocity at about 11 cm below the free-surface. Therefore, the surface velocity distribution across the river was extracted from the BD velocity measurements and used to compute the river discharge. These detailed velocity profiles and the composite velocity distribution were used to assess the validity of the classic theories of velocity distributions, conventional river discharge measurement methods, and for estimates of channel bottom roughness.

  7. Measuring discharge with acoustic Doppler current profilers from a moving boat

    USGS Publications Warehouse

    Mueller, David S.; Wagner, Chad R.; Rehmel, Michael S.; Oberg, Kevin A.; Rainville, Francois

    2013-01-01

    The use of acoustic Doppler current profilers (ADCPs) from a moving boat is now a commonly used method for measuring streamflow. The technology and methods for making ADCP-based discharge measurements are different from the technology and methods used to make traditional discharge measurements with mechanical meters. Although the ADCP is a valuable tool for measuring streamflow, it is only accurate when used with appropriate techniques. This report presents guidance on the use of ADCPs for measuring streamflow; this guidance is based on the experience of U.S. Geological Survey employees and published reports, papers, and memorandums of the U.S. Geological Survey. The guidance is presented in a logical progression, from predeployment planning, to field data collection, and finally to post processing of the collected data. Acoustic Doppler technology and the instruments currently (2013) available also are discussed to highlight the advantages and limitations of the technology. More in-depth, technical explanations of how an ADCP measures streamflow and what to do when measuring in moving-bed conditions are presented in the appendixes. ADCP users need to know the proper procedures for measuring discharge from a moving boat and why those procedures are required, so that when the user encounters unusual field conditions, the procedures can be adapted without sacrificing the accuracy of the streamflow-measurement data.

  8. Measurement of the acoustic characteristics of the concert hall at the Sydney Opera House

    NASA Astrophysics Data System (ADS)

    Bassett, John; Cabrera, Densil

    2003-04-01

    The Sydney Opera House Trust is considering making changes to its Concert Hall. Prior to any alteration, the Acoustics group at the University of Sydney has sought to document the hall. The main measurements were made for 48 receiver locations and 6 source locations, using omnidirectional measurement microphones, B-format (Soundfield) microphones and dummy head microphones in every receiver position. The measurements included impulse responses, anechoic music recordings, and recordings of a calibrated sound power source. Results documented by previous practitioners and researchers are described and comparison is made with the recent results.

  9. Decontamination measures to prevent mechanical transmission of viroids

    Technology Transfer Automated Retrieval System (TEKTRAN)

    With seed-borne and ease in mechanical transmission, an increasing number of viroid outbreaks have been reported in recent years. Such major surge in viroid epidemics is likely enhanced by the intensive ‘hands-on’ activities in greenhouse tomato production. Although viroids are resilient to heat tre...

  10. Acoustic measurement method of the volume flux of a seafloor hydrothermal plume

    NASA Astrophysics Data System (ADS)

    Xu, G.; Jackson, D. R.; Bemis, K. G.; Rona, P. A.

    2011-12-01

    Measuring fluxes (volume, chemical, heat, etc.) of the deep sea hydrothermal vents has been a crucial but challenging task faced by the scientific community since the discovery of the vent systems. However, the great depths and complexities of the hydrothermal vents make traditional sampling methods laborious and almost daunting missions. Furthermore, the samples, in most cases both sparse in space and sporadic in time, are hardly enough to provide a result with moderate uncertainty. In September 2010, our Cabled Observatory Vent Imaging Sonar System (COVIS, http://vizlab.rutgers.edu/AcoustImag/covis.html) was connected to the Neptune Canada underwater ocean observatory network (http://www.neptunecanada.ca) at the Main Endeavour vent field on the Endeavour segment of the Juan de Fuca Ridge. During the experiment, the COVIS system produced 3D images of the buoyant plume discharged from the vent complex Grotto by measuring the back-scattering intensity of the acoustic signal. Building on the methodology developed in our previous work, the vertical flow velocity of the plume is estimated from the Doppler shift of the acoustic signal using geometric correction to compensate for the ambient horizontal currents. A Gaussian distribution curve is fitted to the horizontal back-scattering intensity profile to determine the back-scattering intensity at the boundary of the plume. Such a boundary value is used as the threshold in a window function for separating the plume from background signal. Finally, the volume flux is obtained by integrating the resulting 2D vertical velocity profile over the horizontal cross-section of the plume. In this presentation, we discuss preliminary results from the COVIS experiment. In addition, several alternative approaches are applied to determination of the accuracy of the estimated plume vertical velocity in the absence of direct measurements. First, the results from our previous experiment (conducted in 2000 at the same vent complex using a

  11. Measurement of bioelectric and acoustic profile of breast tissue using hybrid magnetoacoustic method for cancer detection.

    PubMed

    Salim, M I Mohamad; Supriyanto, E; Haueisen, J; Ariffin, I; Ahmad, A H; Rosidi, B

    2013-04-01

    This paper proposes a novel hybrid magnetoacoustic measurement (HMM) system aiming at breast cancer detection. HMM combines ultrasound and magnetism for the simultaneous assessment of bioelectric and acoustic profiles of breast tissue. HMM is demonstrated on breast tissue samples, which are exposed to 9.8 MHz ultrasound wave with the presence of a 0.25 Tesla static magnetic field. The interaction between the ultrasound wave and the magnetic field in the breast tissue results in Lorentz Force that produces a magnetoacoustic voltage output, proportional to breast tissue conductivity. Simultaneously, the ultrasound wave is sensed back by the ultrasound receiver for tissue acoustic evaluation. Experiments are performed on gel phantoms and real breast tissue samples harvested from laboratory mice. Ultrasound wave characterization results show that normal breast tissue experiences higher attenuation compared with cancerous tissue. The mean magnetoacoustic voltage results for normal tissue are lower than that for the cancerous tissue group. In conclusion, the combination of acoustic and bioelectric measurements is a promising approach for breast cancer diagnosis. PMID:23238828

  12. 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.

  13. Coupling of acoustic emission and electrochemical noise measurement techniques in slurry erosion-corrosion studies

    SciTech Connect

    Oltra, R.; Chapey, B.; Huet, F.; Renaud, L.

    1996-12-31

    This study deals with the measurement and the subsequent signal analysis of acoustic emission and current noise recorded during continuous slurry erosion of a metallic target in a corrosive environment. According to a phenomenologic model, the localized corrosion results from the repetitive damage caused by particle impacts. The fluctuations of the acoustic signal and of the electrochemical signal both can be modeled as a shot-noise-like process. The main purpose of this work is to compare two processing techniques for the fluctuating signals: time analysis (mean value) and spectral analysis (power spectral density [PSD] spectrum) to determine the more suitable signal treatment. Another purpose is also to quantify the balance between the mechanical wear and the corrosive damage of the abraded metallic target. It will be shown that the mean value of the RMS acoustic signal, A(t), and also the PSD of A(t), are related to the mechanical wear of the target and allow real-time measurement of the actual mechanical perturbation in terms of the mass of the ablated material.

  14. Acoustic scattering from a water-filled cylindrical shell: measurements, modeling, and interpretation.

    PubMed

    España, Aubrey L; Williams, Kevin L; Plotnick, Daniel S; Marston, Philip L

    2014-07-01

    Understanding the physics governing the interaction of sound with targets in an underwater environment is essential to improving existing target detection and classification algorithms. To illustrate techniques for identifying the key physics, an examination is made of the acoustic scattering from a water-filled cylindrical shell. Experiments were conducted that measured the acoustic scattering from a water-filled cylindrical shell in the free field, as well as proud on a sand-water interface. Two modeling techniques are employed to examine these acoustic scattering measurements. The first is a hybrid 2-D/3-D finite element (FE) model, whereby the scattering in close proximity to the target is handled via a 2-D axisymmetric FE model, and the subsequent 3-D propagation to the far field is determined via a Helmholtz integral. This model is characterized by the decomposition of the fluid pressure and its derivative in a series of azimuthal Fourier modes. The second is an analytical solution for an infinitely long cylindrical shell, coupled with a simple approximation that converts the results to an analogous finite length form function. Examining these model results on a mode-by-mode basis offers easy visualization of the mode dynamics and helps distinguish the different physics driving the target response. PMID:24993199

  15. Linear and Nonlinear Acoustic Measurements of Buried Landmines: Detection Schemes Near Resonance

    NASA Astrophysics Data System (ADS)

    Sabatier, James M.

    2003-03-01

    Measurements of the acoustic impedance of an anti-personnel and anti-tank plastic, blast-hardened landmines reveal resonances in the frequency range between 100 and 1000 Hz. The top surface resonances are due to its complicated mechanical structure vibrating in air. The lowest mode results from the blast hardened design of the landmine. Typically, a portion or cavity of the landmine is designed to absorb the shock from an explosion that is intended to detonate the landmine but still allow the landmine to trigger its explosive device when a slow steady pressure is applied. The mechanical design of the blast hardened aspects results in a high Q simple harmonic oscillator resonance of the top surface. At higher frequencies the top surface behaves like thin circular plate acoustic modes. When these landmines are buried in soils, the modes are mass loaded. Resonances from measurements of the normal component of the acoustically induced soil surface particle velocity are used for detection schemes. Since the interface between the top plate and the soil responds to pressure fluctuations nonlinearly, characteristics of landmines, the soil, and the interface are rich in nonlinear physics and allow for new methods of landmine detection not previously exploited.

  16. Evaluation of stage acoustics in Seoul Arts Center Concert Hall by measuring stage support.

    PubMed

    Jeon, Jin Yong; Barron, Michael

    2005-01-01

    Stage acoustics is an important characteristic for concert halls, both for the acoustic quality on stage and for the audience. However, relatively little research has been conducted into the question. This study was based on the investigation of an actual concert hall stage, that of the Seoul Arts Center Concert Hall in Korea. The stage acoustics was evaluated in the actual hall, and with two models: a 1:25 scale model and a computer model. The study was based on the stage support parameter ST1 proposed by Gade as a measure of support for individual performers [Acustica 65, 193-203 (1989)]. The variation of support was measured on the empty stage of the actual hall and in the two models. The effect of musicians on stage, the effect of moving the orchestra, the effect of ceiling height and of stage-wall profile were also investigated. Conclusions are drawn both relating to the Seoul Concert Hall stage and stages in general. PMID:15704416

  17. Design and Instrumentation of a Measurement and Calibration System for an Acoustic Telemetry System

    PubMed Central

    Deng, Zhiqun; Weiland, Mark; Carlson, Thomas; Eppard, M. Brad

    2010-01-01

    The Juvenile Salmon Acoustic Telemetry System (JSATS) is an active sensing technology developed by the U.S. Army Corps of Engineers, Portland District, for detecting and tracking small fish. It is used primarily for evaluating behavior and survival of juvenile salmonids migrating through the Federal Columbia River Power System to the Pacific Ocean. It provides critical data for salmon protection and development of more “fish-friendly” hydroelectric facilities. The objective of this study was to design and build a Measurement and Calibration System (MCS) for evaluating the JSATS components, because the JSATS requires comprehensive acceptance and performance testing in a controlled environment before it is deployed in the field. The MCS consists of a reference transducer, a water test tank lined with anechoic material, a motion control unit, a reference receiver, a signal conditioner and amplifier unit, a data acquisition board, MATLAB control and analysis interface, and a computer. The fully integrated MCS has been evaluated successfully at various simulated distances and using different encoded signals at frequencies within the bandwidth of the JSATS transmitter. The MCS provides accurate acoustic mapping capability in a controlled environment and automates the process that allows real-time measurements and evaluation of the piezoelectric transducers, sensors, or the acoustic fields. The MCS has been in use since 2009 for acceptance and performance testing of, and further improvements to, the JSATS. PMID:22319288

  18. Rotating rake design for unique measurement of fan-generated spinning acoustic modes

    NASA Technical Reports Server (NTRS)

    Konno, Kevin E.; Hausmann, Clifford R.

    1993-01-01

    In light of the current emphasis on noise reduction in subsonic aircraft design, NASA has been actively studying the source of and propagation of noise generated by subsonic fan engines. NASA/LeRC has developed and tested a unique method of accurately measuring these spinning acoustic modes generated by an experimental fan. This mode measuring method is based on the use of a rotating microphone rake. Testing was conducted in the 9 x 15 Low-speed Wind Tunnel. The rotating rake was tested with the Advanced Ducted Propeller (ADP) model. This memorandum discusses the design and performance of the motor/drive system for the fan-synchronized rotating acoustic rake. This novel motor/drive design approach is now being adapted for additional acoustic mode studies in new test rigs as baseline data for the future design of active noise control for subsonic fan engines. Included in this memorandum are the research requirements, motor/drive specifications, test performance results, and a description of the controls and software involved.

  19. Design and instrumentation of a measurement and calibration system for an acoustic telemetry system.

    PubMed

    Deng, Zhiqun; Weiland, Mark; Carlson, Thomas; Eppard, M Brad

    2010-01-01

    The Juvenile Salmon Acoustic Telemetry System (JSATS) is an active sensing technology developed by the U.S. Army Corps of Engineers, Portland District, for detecting and tracking small fish. It is used primarily for evaluating behavior and survival of juvenile salmonids migrating through the Federal Columbia River Power System to the Pacific Ocean. It provides critical data for salmon protection and development of more "fish-friendly" hydroelectric facilities. The objective of this study was to design and build a Measurement and Calibration System (MCS) for evaluating the JSATS components, because the JSATS requires comprehensive acceptance and performance testing in a controlled environment before it is deployed in the field. The MCS consists of a reference transducer, a water test tank lined with anechoic material, a motion control unit, a reference receiver, a signal conditioner and amplifier unit, a data acquisition board, MATLAB control and analysis interface, and a computer. The fully integrated MCS has been evaluated successfully at various simulated distances and using different encoded signals at frequencies within the bandwidth of the JSATS transmitter. The MCS provides accurate acoustic mapping capability in a controlled environment and automates the process that allows real-time measurements and evaluation of the piezoelectric transducers, sensors, or the acoustic fields. The MCS has been in use since 2009 for acceptance and performance testing of, and further improvements to, the JSATS. PMID:22319288

  20. 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.

  1. Determination of acoustic speed for improving leak detection and location in gas pipelines

    NASA Astrophysics Data System (ADS)

    Li, Shuaiyong; Wen, Yumei; Li, Ping; Yang, Jin; Yang, Lili

    2014-02-01

    The commonly used cross-correlation technique for leak location requires that the acoustic speed is known and invariable. In practice, the gas leakage-induced acoustic waves propagate along multiple paths including in-pipe gas and pipe wall, and the acoustic waves in different transmission paths exhibit different acoustic speeds and different dispersive behaviors, which bring a great challenge for leak detection and location in the gas pipelines. In this study, based on the vibration theory of cylindrical elastic thin shell, the wavenumber formulae in different transmission paths are derived to predict the acoustic speeds and the acoustical coupling between the in-pipe gas and the pipe wall is analyzed to determine the dominant transmission path. In addition, the velocity dispersions in the dominant transmission path are suppressed by selection of a characteristic frequency band of the gas leakage-induced acoustic waves. The theoretical predictions are verified in the experiment and the results show that the theoretical acoustic speed is slightly larger than the measured acoustic speed. Thus, the theoretical acoustic speed formula is modified considering the effect of the structural loss factor and consequently the location error using the modified acoustic speed is reduced by two times compared to that using the theoretical acoustic speed.

  2. Determination of acoustic speed for improving leak detection and location in gas pipelines.

    PubMed

    Li, Shuaiyong; Wen, Yumei; Li, Ping; Yang, Jin; Yang, Lili

    2014-02-01

    The commonly used cross-correlation technique for leak location requires that the acoustic speed is known and invariable. In practice, the gas leakage-induced acoustic waves propagate along multiple paths including in-pipe gas and pipe wall, and the acoustic waves in different transmission paths exhibit different acoustic speeds and different dispersive behaviors, which bring a great challenge for leak detection and location in the gas pipelines. In this study, based on the vibration theory of cylindrical elastic thin shell, the wavenumber formulae in different transmission paths are derived to predict the acoustic speeds and the acoustical coupling between the in-pipe gas and the pipe wall is analyzed to determine the dominant transmission path. In addition, the velocity dispersions in the dominant transmission path are suppressed by selection of a characteristic frequency band of the gas leakage-induced acoustic waves. The theoretical predictions are verified in the experiment and the results show that the theoretical acoustic speed is slightly larger than the measured acoustic speed. Thus, the theoretical acoustic speed formula is modified considering the effect of the structural loss factor and consequently the location error using the modified acoustic speed is reduced by two times compared to that using the theoretical acoustic speed. PMID:24593385

  3. Measurement of acoustic impedance and reflectance in the human ear canal.

    PubMed

    Voss, S E; Allen, J B

    1994-01-01

    The pressure reflectance R (omega) is the transfer function which may be defined for a linear one-port network by the ratio of the reflected complex pressure divided by the incident complex pressure. The reflectance is a function that is closely related to the impedance of the 1-port. The energy reflectance R (omega) is defined as magnitude of [R]2. It represents the ratio of reflected to incident energy. In the human ear canal the energy reflectance is important because it is a measure of the inefficiency of the middle ear and cochlea, and because of the insight provided by its simple frequency domain interpretation. One may characterize the ear canal impedance by use of the pressure reflectance and its magnitude, sidestepping the difficult problems of (a) the unknown canal length from the measurement point to the eardrum, (b) the complicated geometry of the drum, and (c) the cross-sectional area changes in the canal as a function of distance. Reported here are acoustic impedance measurements, looking into the ear canal, measured on ten young adults with normal hearing (ages 18-24). The measurement point in the canal was approximately 0.85 cm from the entrance of the canal. From these measurements, the pressure reflectance in the canal is computed and impedance and reflectance measurements from 0.1 to 15.0 kHz are compared among ears. The average reflectance and the standard deviation of the reflectance for the ten subjects have been determined. The impedance and reflectance of two common ear simulators, the Brüel & Kjaer 4157 and the Industrial Research Products DB-100 (Zwislocki) coupler are also measured and compared to the average human measurements. All measurements are made using controls that assure a uniform accuracy in the acoustic calibration across subjects. This is done by the use of two standard acoustic resistors whose impedances are known. From the experimental results, it is concluded that there is significant subject variability in the magnitude

  4. A Tool Measuring Remaining Thickness of Notched Acoustic Cavities in Primary Reaction Control Thruster NDI Standards

    NASA Technical Reports Server (NTRS)

    Sun, Yushi; Sun, Changhong; Zhu, Harry; Wincheski, Buzz

    2006-01-01

    Stress corrosion cracking in the relief radius area of a space shuttle primary reaction control thruster is an issue of concern. The current approach for monitoring of potential crack growth is nondestructive inspection (NDI) of remaining thickness (RT) to the acoustic cavities using an eddy current or remote field eddy current probe. EDM manufacturers have difficulty in providing accurate RT calibration standards. Significant error in the RT values of NDI calibration standards could lead to a mistaken judgment of cracking condition of a thruster under inspection. A tool based on eddy current principle has been developed to measure the RT at each acoustic cavity of a calibration standard in order to validate that the standard meets the sample design criteria.

  5. A pilot study of scanning acoustic microscopy as a tool for measuring arterial stiffness in aortic biopsies

    PubMed Central

    Akhtar, Riaz; Cruickshank, J. Kennedy; Zhao, Xuegen; Derby, Brian; Weber, Thomas

    2016-01-01

    This study explores the use of scanning acoustic microscopy (SAM) as a potential tool for characterisation of arterial stiffness using aortic biopsies. SAM data is presented for human tissue collected during aortic bypass graft surgery for multi-vessel coronary artery disease. Acoustic wave speed as determined by SAM was compared to clinical data for the patients namely, pulse wave velocity (PWV), blood pressure, cholesterol and glucose levels. There was no obvious trend relating acoustic wave speed to PWV values, and an inverse relationship was found between systolic and diastolic blood pressure and acoustic wave speed. However, in patients with a higher cholesterol or glucose level, the acoustic wave speed increased. A more detailed investigation is needed to relate SAM data to clinical measurements. PMID:26985242

  6. Impact of acoustic velocity structure to measurement of ocean bottom crustal deformation

    NASA Astrophysics Data System (ADS)

    Ikuta, R.; Tadokoro, K.; Okuda, T.; Sugimoto, S.; Watanabe, T.; Eto, S.; Ando, M.

    2010-12-01

    We are developing a geodetic method of monitoring crustal deformation under the ocean using kinematic GPS and acoustic ranging. The goal of our research is to achieve sub-centimeter accuracy in measuring oceanic crustal deformation by a very short-time measurement like 10 hours. In this study, we focused on lateral variation of acoustic velocity structure in seawater and introduced an inclined acoustic velocity structure model to improve accuracy of the measurement. We have a few measurement sites along Nankai trough, Japan. In each sites, we deployed a trio of transponders on ocean floor (seafloor benchmark units) within distance comparable with the depth. An ultrasonic signal is generated from a surface vessel drifting over the benchmark unit, which is received and replied by the benchmark unit. In this system, both acoustic velocity structure and the benchmark unit positions were determined simultaneously for the each measurement using a tomographic technique. This tomographic technique was adopted on an assumption that the acoustic velocity structure is horizontally layered and changes only in time, not in space. Ikuta et al., (AGU fall meeting 2009) reported an approach to improve accuracy of benchmark positioning using a new additional assumption. The additional assumption was that the configuration of the transponders trio constituting one benchmark unit does not change. They determined the time evolution of weight center for the fixed transponder triangle between different measurements using all repetitively obtained data sets at once. This is contrasting to the previous method in which each data set for different measurement was solved independently. This assumption worked well in reducing number of unknown parameters. As a result, repeatability of benchmark positioning improved from 5 cm to 3 cm. We conducted numerical experiments synthesizing acoustic travel-time data to evaluate the robustness of this new approach. When acoustic travel-time data is

  7. Measurement of Vertical Temperature Distribution Using a Single Pair of Loudspeaker and Microphone with Acoustic Reflection

    NASA Astrophysics Data System (ADS)

    Saito, Ikumi; Mizutani, Koichi; Wakatsuki, Naoto; Kawabe, Satoshi

    2009-07-01

    It is important to maintain an adequate indoor temperature for comfortable working conditions, improvement of the rate of production of farm goods grown in greenhouses, and for saving energy. Thus, it is necessary to measure the temperature distribution to realize efficient air-conditioning systems. However, we have to use many conventional instruments to measure the temperature distribution. We proposed a measurement system for vertical temperature distribution using a single pair of loudspeaker (SP) and microphone (MIC), and acoustic reflectors. This system consists of SP, MIC, and multiple acoustic reflectors, and it can be used to determine the temperature distribution from the mean temperature of the area bounded by two reflectors. In experiments, the vertical temperature distribution was measured using five sound probes in a large facility every 20 s for 24 h. From the results of this experiment, it was verified that this system can be used to measure the vertical temperature distribution from the mean temperature of each area bounded by two reflectors. This system could be used to measure the change in the temperature distribution over time. We constructed a simple system to measure the vertical temperature distribution.

  8. A calibration technique for measuring the complex permittivity of materials with planar transmission lines

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A simple two-standard calibration procedure for determining the permittivity of a material from the propagation constant measured with planar transmission lines is presented. The suitability of this procedure is demonstrated by using a coplanar waveguide transmission-line sensor to measure the permi...

  9. Twin-tube practical acoustic thermometry: theory and measurements up to 1000 °C

    NASA Astrophysics Data System (ADS)

    Sutton, G.; Edwards, G.; Veltcheva, R.; de Podesta, M.

    2015-08-01

    We present details of a Practical Acoustic Thermometer (PAT), in which temperature is inferred from measurements of the speed of sound along acoustic waveguides. We describe both the theory of operation, and measurements on three devices at temperatures up to 1000 °C. Because the relationship between the speed of sound in a simple gas and absolute temperature is well understood, the mean temperature along a tube may be estimated from measurements of the frequency-dependent propagation constant. A PAT device made from two tubes of different lengths allows the temperature measurement region to be localised, creating an instrument functionally similar to conventional contact thermometers. Three twin-tube PAT devices were constructed and tested. PAT-A, made of silica, served to validate the technique with differences between the acoustic thermometer and a reference thermocouple of less than 2 °C at temperatures in the range from 100 °C to 1000 °C. PAT-B and PAT-C were made of Inconel-600, potentially more suitable for use in harsh environments. The Inconel devices deviated from expected behaviour in a reproducible manner, which after calibration allowed measurements with errors of less than  ±1 °C in the range to 700 °C. No drift was observed up to 700 °C. The drift observed during prolonged exposure to higher temperatures is described and its likely causes discussed. In the longer term, similar technology may provide a means for the measurement of temperature in harsh environments such as those found in the nuclear industry.

  10. Room Acoustics

    NASA Astrophysics Data System (ADS)

    Kuttruff, Heinrich; Mommertz, Eckard

    The traditional task of room acoustics is to create or formulate conditions which ensure the best possible propagation of sound in a room from a sound source to a listener. Thus, objects of room acoustics are in particular assembly halls of all kinds, such as auditoria and lecture halls, conference rooms, theaters, concert halls or churches. Already at this point, it has to be pointed out that these conditions essentially depend on the question if speech or music should be transmitted; in the first case, the criterion for transmission quality is good speech intelligibility, in the other case, however, the success of room-acoustical efforts depends on other factors that cannot be quantified that easily, not least it also depends on the hearing habits of the listeners. In any case, absolutely "good acoustics" of a room do not exist.

  11. Mathematical justification of the acoustic method for measuring the impedance of the respiratory tract.

    PubMed

    Bogomolov, A V; Dragan, S P

    2015-01-01

    A new method for measuring a complex frequency-dependent acoustic impedance of the respiratory tract based on two-microphone method was developed. The measuring device consists of a waveguide connected through a mouthpiece to the patient's mouth. A sound field with a frequency range from 5 to 100 Hz is created in the waveguide. The impedance of the respiratory tract is determined at free respiration of the patient in the set frequency range; the duration of examination does not exceed 15 s. The criteria for the recognition of respiratory tract pathologies are proposed. PMID:26518558

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

    NASA Astrophysics Data System (ADS)

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

    2007-06-01

    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, 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.

  13. 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.

  14. Transmission eigenvalues

    NASA Astrophysics Data System (ADS)

    Cakoni, Fioralba; Haddar, Houssem

    2013-10-01

    iterative least square method to identify the spherically stratified index of refraction from transmission eigenvalues. On the characterization of transmission eigenvalues in terms of far-field measurements, a promising new result is obtained by Kirsch and Lechleiter [21] showing how one can identify the transmission eigenvalues using the eigenvalues of the scattering operator which are available in terms of measured scattering data. In the paper by Kleefeld [22], an accurate method for computing transmission eigenvalues based on a surface integral formulation of the interior transmission problem and numerical methods for nonlinear eigenvalue problems is proposed and numerically validated for the scalar problem in three dimensions. On the other hand, the paper by Sun and Xu [23] investigates the computation of transmission eigenvalues for Maxwell's equations using a standard iterative method associated with a variational formulation of the interior transmission problem with an emphasis on the effect of anisotropy on transmission eigenvalues. From the perspective of using transmission eigenvalues in non-destructive testing, the paper by Cakoni and Moskow [24] investigates the asymptotic behavior of transmission eigenvalues with respect to small inhomogeneities. The paper by Nakamura and Wang [25] investigates the linear sampling method for the time dependent heat equation and analyses the interior transmission problem associated with this equation. Finally, in the paper by Finch and Hickmann [26], the spectrum of the interior transmission problem is related to the unique determination of the acoustic properties of a body in thermoacoustic imaging. We hope that this collection of papers will stimulate further research in the rapidly growing area of transmission eigenvalues and inverse scattering theory.

  15. Correlation of rheological characteristics of lubricants with transmission efficiency measurements

    NASA Technical Reports Server (NTRS)

    Jacobson, B. O.; Hamrock, B. J.; Hoeglund, E.

    1985-01-01

    The power efficiency of a helicopter transmission has been analyzed for 11 lubricants by looking at the Newtonian and non-Newtonian properties of the lubricants. A non-Newtonian property of the lubricants was the limiting shear strength proportionality constant. The tests were performed on a high-pressure, short-time shear strength analyzer. A power efficiency formula that was obtained by analyzing the Newtonian and non-Newtonian properties of the lubricants is presented in detail.

  16. Measurement of impulse peak insertion loss from two acoustic test fixtures and four hearing protector conditions with an acoustic shock tube

    PubMed Central

    Murphy, William J.; Fackler, Cameron J.; Berger, Elliott H.; Shaw, Peter B.; Stergar, Mike

    2015-01-01

    Impulse peak insertion loss (IPIL) was studied with two acoustic test fixtures and four hearing protector conditions at the E-A-RCAL Laboratory. IPIL is the difference between the maximum estimated pressure for the open-ear condition and the maximum pressure measured when a hearing protector is placed on an acoustic test fixture (ATF). Two models of an ATF manufactured by the French-German Research Institute of Saint-Louis (ISL) were evaluated with high-level acoustic impulses created by an acoustic shock tube at levels of 134 decibels (dB), 150 dB, and 168 dB. The fixtures were identical except that the E-A-RCAL ISL fixture had ear canals that were 3 mm longer than the National Institute for Occupational Safety and Health (NIOSH) ISL fixture. Four hearing protection conditions were tested: Combat Arms earplug with the valve open, ETYPlugs® earplug, TacticalPro headset, and a dual-protector ETYPlugs earplug with TacticalPro earmuff. The IPILs measured for the E-A-RCAL fixture were 1.4 dB greater than the National Institute for Occupational Safety and Health (NIOSH) ISL ATF. For the E-A-RCAL ISL ATF, the left ear IPIL was 2.0 dB greater than the right ear IPIL. For the NIOSH ATF, the right ear IPIL was 0.3 dB greater than the left ear IPIL. PMID:26356380

  17. Measurement of impulse peak insertion loss from two acoustic test fixtures and four hearing protector conditions with an acoustic shock tube.

    PubMed

    Murphy, William J; Fackler, Cameron J; Berger, Elliott H; Shaw, Peter B; Stergar, Mike

    2015-01-01

    Impulse peak insertion loss (IPIL) was studied with two acoustic test fixtures and four hearing protector conditions at the E-A-RCAL Laboratory. IPIL is the difference between the maximum estimated pressure for the open-ear condition and the maximum pressure measured when a hearing protector is placed on an acoustic test fixture (ATF). Two models of an ATF manufactured by the French-German Research Institute of Saint-Louis (ISL) were evaluated with high-level acoustic impulses created by an acoustic shock tube at levels of 134 decibels (dB), 150 dB, and 168 dB. The fixtures were identical except that the E-A-RCAL ISL fixture had ear canals that were 3 mm longer than the National Institute for Occupational Safety and Health (NIOSH) ISL fixture. Four hearing protection conditions were tested: Combat Arms earplug with the valve open, ETYPlugs ® earplug, TacticalPro headset, and a dual-protector ETYPlugs earplug with TacticalPro earmuff. The IPILs measured for the E-A-RCAL fixture were 1.4 dB greater than the National Institute for Occupational Safety and Health (NIOSH) ISL ATF. For the E-A-RCAL ISL ATF, the left ear IPIL was 2.0 dB greater than the right ear IPIL. For the NIOSH ATF, the right ear IPIL was 0.3 dB greater than the left ear IPIL. PMID:26356380

  18. Ultrasonic database development for the acoustic inspection device: the velocity-attenuation measurement system (VAMS)

    NASA Astrophysics Data System (ADS)

    Diaz, Aaron A.; Burghard, Brion J.; Valencia, Juan D.; Samuel, Todd J.

    2004-07-01

    The inspection of sealed containers is a critical task for personnel charged with enforcing government policies, maintaining public safety, and ensuring national security. The Pacific Northwest National Laboratory (PNNL) has developed a portable, handheld acoustic inspection device (AID) that provides non-invasive container interrogation and material identification capabilities. The AID technology has been deployed worldwide and user"s are providing feedback and requesting additional capabilities and functionality. Recently, PNNL has developed a laboratory-based system for automated, ultrasonic characterization of fluids to support database development for the AID. Using pulse-echo ultrasound, ultrasonic pulses are launched into a container or bulk-solid commodity. The return echoes from these pulses are analyzed in terms of time-of-flight and frequency content (as a function of temperature) to extract physical property measurements (acoustic velocity and attenuation) of the material under test. These measured values are then compared to a tailored database of materials and fluids property data acquired using the Velocity-Attenuation Measurement System (VAMS). This bench-top platform acquires key ultrasonic property measurements as a function of temperature and frequency. This paper describes the technical basis for operation of the VAMS, recent enhancements to the measurement algorithms for both the VAMS and AID technologies, and new measurement data from laboratory testing and performance demonstration activities. Applications for homeland security and counterterrorism, law enforcement, drug-interdiction and fuel transportation compliance activities will be discussed.

  19. The influence of phonetic context and formant measurement location on acoustic vowel space

    NASA Astrophysics Data System (ADS)

    Turner, Greg S.; Hutchings, David T.; Sylvester, Betsy; Weismer, Gary

    2003-04-01

    One way of depicting vowel production is by describing vowels within an F1/F2 acoustic vowel space. This acoustic measure illustrates the dispersion of F1 and F2 values at a specific moment in time (e.g., the temporal midpoint of a vowel) for the vowels of a given language. This measure has recently been used to portray vowel production in individuals with communication disorders such as dysarthria and is moderately related to the severity of the speech disorder. Studies aimed at identifying influential factors effecting measurement stability of vowel space have yet to be completed. The focus of the present study is to evaluate the influence of phonetic context and spectral measurement location on vowel space in a group of neurologically normal American English speakers. For this study, vowel space was defined in terms of the dispersion of the four corner vowels produced within a CVC syllable frame, where C includes six stop consonants in all possible combinations with each vowel. Spectral measures were made at the midpoint and formant extremes of the vowels. A discussion will focus on individual and group variation in vowel space as a function of phonetic context and temporal measurement location.

  20. System and method for sonic wave measurements using an acoustic beam source

    DOEpatents

    Vu, Cung Khac; Sinha, Dipen N.; Pantea, Cristian

    2015-08-11

    A method and system for investigating structure near a borehole are described herein. The method includes generating an acoustic beam by an acoustic source; directing at one or more azimuthal angles the acoustic beam towards a selected location in a vicinity of a borehole; receiving at one or more receivers an acoustic signal, the acoustic signal originating from a reflection or a refraction of the acoustic wave by a material at the selected location; and analyzing the received acoustic signal to characterize features of the material around the borehole.