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Journal of the Acoustical Society of America

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May 2009

Volume 125, Issue 5, pp. EL177-3491

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Sound speed and density characterization of milk adulterated with melamine

Luis Elvira, Jaime Rodríguez, and Lawrence C. Lynnworth

J. Acoust. Soc. Am. Volume 125, Issue 5, pp. EL177-EL182 (2009); (6 pages) | Cited 2 times

Online Publication Date: 09 Apr 2009

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Milk contaminated with melamine resulted in an important health hazard that affected many babies in China recently. Ultrasonic characterization of adulterated milk may detect gross levels of melamine contamination. Sound speed and density measurements were made in skim milk as a function of melamine adulteration. An ultrasonic measurement technique to implement milk quality control is discussed.
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43.20.Hq Velocity and attenuation of acoustic waves
43.35.Bf Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in liquids, liquid crystals, suspensions, and emulsions
43.58.Dj Sound velocity
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Microbubble tunneling in gel phantoms

Charles F. Caskey, Shengping Qin, Paul A. Dayton, and Katherine W. Ferrara

J. Acoust. Soc. Am. Volume 125, Issue 5, pp. EL183-EL189 (2009); (7 pages) | Cited 9 times

Online Publication Date: 09 Apr 2009

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Insonified microbubbles were observed in vessels within a gel with a Young’s modulus similar to that of tissue, demonstrating shape instabilities, liquid jets, and the formation of small tunnels. In this study, tunnel formulation occurred in the direction of the propagating ultrasound wave, where radiation pressure directed the contact of the bubble and gel, facilitating the activity of the liquid jets. Combinations of ultrasonic parameters and microbubble concentrations that are relevant for diagnostic imaging and drug delivery and that lead to tunnel formation were applied and the resulting tunnel formation was quantified.
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43.80.Gx Mechanisms of action of acoustic energy on biological systems: physical processes, sites of action
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Real-time algorithm for acoustic imaging with a microphone array

Xun Huang

J. Acoust. Soc. Am. Volume 125, Issue 5, pp. EL190-EL195 (2009); (6 pages) | Cited 5 times

Online Publication Date: 09 Apr 2009

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Acoustic phased array has become an important testing tool in aeroacoustic research, where the conventional beamforming algorithm has been adopted as a classical processing technique. The computation however has to be performed off-line due to the expensive cost. An innovative algorithm with real-time capability is proposed in this work. The algorithm is similar to a classical observer in the time domain while extended for the array processing to the frequency domain. The observer-based algorithm is beneficial mainly for its capability of operating over sampling blocks recursively. The expensive experimental time can therefore be reduced extensively since any defect in a testing can be corrected instantaneously.
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43.60.Fg Acoustic array systems and processing, beam-forming
43.60.Lq Acoustic imaging, displays, pattern recognition, feature extraction
43.60.Mn Adaptive processing
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Vowel-pitch matching in Wagner’s operas: Implications for intelligibility and ease of singing

John Smith and Joe Wolfe

J. Acoust. Soc. Am. Volume 125, Issue 5, pp. EL196-EL201 (2009); (6 pages) | Cited 2 times

Online Publication Date: 13 Apr 2009

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European vowels are mainly distinguished by the two lowest resonance frequencies (R1 and R2) of the vocal tract. Once the pitch frequency f0 exceeds the value of R1 in normal speech, sopranos can deliberately “tune” R1 to match f0. This increases loudness, uniformity of tone, and ease of singing, at some cost to intelligibility. Resonance tuning would be assisted if the pitch of the note written for a vowel corresponded with its usual range of R1. Analysis of several soprano roles indicates that Wagner aided the acoustics of the soprano voice at high pitch when setting text to music.
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43.75.Rs Singing
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Time-domain simulations of sound propagation in a stratified atmosphere over an impedance ground

Benjamin Cotté and Philippe Blanc-Benon

J. Acoust. Soc. Am. Volume 125, Issue 5, pp. EL202-EL207 (2009); (6 pages) | Cited 1 time

Online Publication Date: 13 Apr 2009

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Finite-difference time-domain simulations of broadband sound propagation in a stratified atmosphere are presented. A method recently proposed to obtain an impedance time-domain boundary condition is implemented in a linearized Euler equations solver, which enables to study long range sound propagation over an impedance ground. Some features of the pressure pulse evolution with time are analyzed in both upward-and downward-refracting conditions, and the time-domain simulations are compared to parabolic equation calculations in the frequency domain to show the effectiveness of the proposed impedance boundary condition.
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43.28.Js Numerical models for outdoor propagation
43.28.En Interaction of sound with ground surfaces, ground cover and topography, acoustic impedance of outdoor surfaces
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The pitch levels of female speech in two Chinese villages

Diana Deutsch, Jinghong Le, Jing Shen, and Trevor Henthorn

J. Acoust. Soc. Am. Volume 125, Issue 5, pp. EL208-EL213 (2009); (6 pages) | Cited 2 times

Online Publication Date: 14 Apr 2009

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The pitch levels of female speech in two villages situated in a relatively remote area of China were compared. The dialects spoken in the two villages are similar to Standard Mandarin, and all subjects had learned to read and speak Standard Mandarin at school. Subjects read out a passage of roughly 3.25 min in Standard Mandarin, and pitch values were obtained at 5-ms intervals. The overall pitch levels in the two villages differed significantly, supporting the conjecture that pitch levels of speech are influenced by a mental representation acquired through long-term exposure to the speech of others.
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43.71.Bp Perception of voice and talker characteristics
43.71.Es Vowel and consonant perception; perception of words, sentences, and fluent speech
43.71.An Models and theories of speech perception
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Fluid loading effects for acoustical sensors in the atmospheres of Mars, Venus, Titan, and Jupiter

T. G. Leighton

J. Acoust. Soc. Am. Volume 125, Issue 5, pp. EL214-EL219 (2009); (6 pages) | Cited 3 times

Online Publication Date: 17 Apr 2009

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This paper shows that corrections for fluid loading must be undertaken to Earth-based calibrations for planetary probe sensors, which rely on accurate and precise predictions of mechanical vibrations. These sensors include acoustical instrumentation, and sensors for the mass change resulting from species accumulation upon oscillating plates. Some published designs are particularly susceptible (an example leading to around an octave error in the frequency calibration for Venus is shown). Because such corrections have not previously been raised, and would be almost impossible to incorporate into drop tests of probes, this paper demonstrates the surprising results of applying well-established formulations.
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43.40.Yq Instrumentation and techniques for tests and measurement relating to shock and vibration, including vibration pickups, indicators, and generators, mechanical impedance
43.28.Vd Measurement methods and instrumentation to determine or evaluate atmospheric parameters, winds, turbulence, temperatures, and pollutants in air
43.28.Tc Sound-in-air measurements, methods and instrumentation for location, navigation, altimetry, and sound ranging
43.40.Fz Acoustic scattering by elastic structures
43.30.Jx Radiation from objects vibrating under water, acoustic and mechanical impedance
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Radiation force calculation for oblique ultrasonic beams

K. Beissner

J. Acoust. Soc. Am. Volume 125, Issue 5, pp. 2827-2829 (2009); (3 pages)

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The acoustic radiation force exerted on a perfect absorber in a lossless fluid has recently been calculated for the case of a rectangular transducer emitting a static (i.e., “frozen”) ultrasonic field in the forward direction. The calculation is extended here, at least approximately, to the case of an oblique beam. This is important for measuring the ultrasonic power of scanning diagnostic devices.
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43.25.Qp Radiation pressure
43.80.Vj Acoustical medical instrumentation and measurement techniques

Sound absorption by Menger sponge fractal

Tetsuji Kawabe, Takatsuna Miyazaki, Daisuke Oka, Sin’ichiro Koyanagi, and Atsushi Hinokidani

J. Acoust. Soc. Am. Volume 125, Issue 5, pp. 2830-2833 (2009); (4 pages)

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For the purpose of investigation on acoustic properties of fractals, the sound absorption coefficients are experimentally measured by using the Menger sponge which is one of typical three-dimensional fractals. From the two-microphone measurement, the frequency range of effectively absorbing sound waves is shown to broaden with degree of fractality, which comes from the fractal property of the homothetic character. It is shown that experimental features are qualitatively explained by an electrical equivalent circuit model for the Menger sponge.
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43.55.Ev Sound absorption properties of materials: theory and measurement of sound absorption coefficients; acoustic impedance and admittance
43.20.Bi Mathematical theory of wave propagation
43.55.Rg Sound transmission through walls and through ducts: theory and measurement
43.20.Mv Waveguides, wave propagation in tubes and ducts

Quantitative evaluation of fracture healing process of long bones using guided ultrasound waves: A computational feasibility study

Xiasheng Guo, Di Yang, Dong Zhang, Weiguo Li, Yong Qiu, and Junru Wu

J. Acoust. Soc. Am. Volume 125, Issue 5, pp. 2834-2837 (2009); (4 pages)

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The feasibility of monitoring changes in guided waves’ characteristics in a fractured long bone as modeled by a hollow cylinder and a callus at different healing stages is studied. Various guided wave modes are detected and extracted from a broadband signal at several discrete locations. The energy-spectrum and vFEP (effective velocity of the first energy peak in callus region) of guided modes are found sensitive to the healing process in different aspects and stages. The healing process may be divided into several sub-courses, each of which can be evaluated by different combinations of guided wave modes. The energy-spectrum indicates that the longitudinal tube modes L(0,1) and L(0,2) are suitable for early healing; L(0,1), L(0,2), L(0,3), and L(0,5) for midway-course; and L(0,1) and L(0,3) for late consolidation, while L(0,2), L(0,5), and L(0,8) are suitable for detecting the change in callus geometrics. The vFEP results suggest that L(0,5) for monitoring early-course; L(0,3) and L(0,7) for midway process; L(0,2) for later consolidation, and L(0,7) for monitoring geometrical variation.
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43.80.Ev Acoustical measurement methods in biological systems and media
43.80.Qf Medical diagnosis with acoustics
43.80.Jz Use of acoustic energy (with or without other forms) in studies of structure and function of biological systems
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A simple method avoiding non-uniqueness in the boundary element method for acoustic scattering problem

Kunikazu Hirosawa, Takashi Ishizuka, and Kyoji Fujiwara

J. Acoust. Soc. Am. Volume 125, Issue 5, pp. 2838-2846 (2009); (9 pages) | Cited 3 times

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The boundary element method (BEM) is widely used for sound field analysis problems; however, it has a non-uniqueness problem in the exterior domain. Various methods to avoid this problem have been developed; however, these are not easily applied to the BEM. In this paper, a simple method called the “ICA-Ring (inner cavity ringing) method” is proposed for avoiding the non-uniqueness problem, and this method is applied to the BEM in both single and plural domains. The concept of the ICA-Ring method is that a scatterer in free space is hollowed as a shell and the volume is smaller; the eigenfrequencies are shifted to a higher range. Next, the mechanism of the non-uniqueness problem in plural domains and a reason of the application of the ICA-Ring method to the case of plural domains are explained. Finally, some results calculated by the BEM using the ICA-Ring method are shown. The calculational condition is that a cylinder with radius 0.125 m floats in two-dimensional free space. In this case, no calculational errors exist in 1–6000 Hz in both single and plural domains, when the thickness of the shell is 20 mm. The ICA-Ring method does not need to modify an existing computer program of conventional BEM.
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43.20.Rz Steady-state radiation from sources, impedance, radiation patterns, boundary element methods
43.20.Fn Scattering of acoustic waves
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Low-frequency geoacoustic model for the effective properties of sandy seabottoms

Ji-Xun Zhou, Xue-Zhen Zhang, and D. P. Knobles

J. Acoust. Soc. Am. Volume 125, Issue 5, pp. 2847-2866 (2009); (20 pages) | Cited 12 times

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The debate on the sound speed dispersion and the frequency dependence of sound attenuation in seabottoms has persisted for decades, mainly due to the lack of sufficient experimental data in the low-frequency (LF) to high-frequency speed/attenuation transition band. This paper analyzes and summarizes a set of LF measurements in shallow water that have resulted in the identification of nonlinear frequency dependence of sound attenuation in the effective media of sandy seabottoms. The long-range acoustic measurements were conducted at 20 locations in different coastal zones around the world. The seabed attenuations, inverted from different acoustic field measurements and characteristics, exhibit similar magnitude and nonlinear frequency dependence below 1000 Hz. The resulting effective sound attenuation can be expressed by α(dB/m) = (0.37±0.01)(f/1000)(1.80±0.02) for 50–1000 Hz. The corresponding average sound speed ratio at the bottom-water interface in the 50–600 Hz range is 1.061±0.009. Both the LF-field-derived sound speed and attenuation can be well described by the Biot–Stoll model with parameters that are consistent with either theoretical considerations or experimental measurements. A combination of the LF-field-inverted data with the SAX99, SAX04, and other high-frequency measurements offers a reference broadband data set in the 50–400 000 Hz range for sonar prediction and sediment acoustics modeling.
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43.30.Ma Acoustics of sediments; ice covers, viscoelastic media; seismic underwater acoustics
43.30.Pc Ocean parameter estimation by acoustical methods; remote sensing; imaging, inversion, acoustic tomography
43.30.Zk Experimental modeling
43.20.Jr Velocity and attenuation of elastic and poroelastic waves

Bayesian inversion of reverberation and propagation data for geoacoustic and scattering parameters

Stan E. Dosso, Peter L. Nielsen, and Christopher H. Harrison

J. Acoust. Soc. Am. Volume 125, Issue 5, pp. 2867-2880 (2009); (14 pages) | Cited 4 times

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This paper applies nonlinear Bayesian inference theory to quantify the information content of reverberation and short-range propagation data, both individually and in joint inversion, to resolve seabed geoacoustic and scattering properties. The inversion of reverberation data alone is shown to poorly resolve seabed properties because of strong multi-dimensional correlations between parameters. Inversion of propagation data alone is limited by different correlations, but better constrains the geoacoustic parameters. However, propagation data are insensitive to scattering parameters such as Lambert’s scattering coefficient. In each case the parameter correlations are inherent in the physics of the forward problem (reverberation and propagation) and cannot be overcome by processing or inversion techniques; rather, the inversion of more informative data is required. This is accomplished here by joint inversion of reverberation and propagation data, weighted according to their respective maximum-likelihood error estimates. Joint inversion of reverberation and propagation data collected on the Malta Plateau (Strait of Sicily) resolves both geoacoustic and scattering properties and achieves smaller uncertainties for all parameters than obtained by the inversion of either data set alone.
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43.30.Pc Ocean parameter estimation by acoustical methods; remote sensing; imaging, inversion, acoustic tomography
43.30.Wi Passive sonar systems and algorithms, matched field processing in underwater acoustics
43.60.Pt Signal processing techniques for acoustic inverse problems

The impact of ocean sound speed variability on the uncertainty of geoacoustic parameter estimates

Yong-Min Jiang and N. Ross Chapman

J. Acoust. Soc. Am. Volume 125, Issue 5, pp. 2881-2895 (2009); (15 pages) | Cited 6 times

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This paper investigates the influence of water column variability on the estimates of geoacoustic model parameters obtained from matched field inversions. The acoustic data were collected on the New Jersey continental shelf during shallow water experiments in August 2006. The oceanographic variability was evident when the data were recorded. To quantify the uncertainties of the geoacoustic parameter estimates in this environment, Bayesian matched field geoacoustic inversion was applied to multi-tonal continuous wave data. The spatially and temporally varying water column sound speed is parametrized in terms of empirical orthogonal functions and included in the inversion. Its impact on the geometric and geoacoustic parameter estimates is then analyzed by the inter-parameter correlations. Two different approaches were used to obtain information about the variation of the water sound speed. One used only the profiles collected along the experimental track during the experiment, and the other also included observations collected over a larger area. The geoacoustic estimates from both the large and small sample sets are consistent. However, due to the diversity of the oceanic sound speed, more empirical orthogonal functions are needed in the inversion when more sound speed profile samples are used.
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43.30.Pc Ocean parameter estimation by acoustical methods; remote sensing; imaging, inversion, acoustic tomography
43.60.Pt Signal processing techniques for acoustic inverse problems

Passive acoustic detection of schools of herring

Thomas R. Hahn and Gary Thomas

J. Acoust. Soc. Am. Volume 125, Issue 5, pp. 2896-2908 (2009); (13 pages) | Cited 1 time

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Herring (Clupea pallasii and C. harengus) have been observed to release gas from their bladders during vertical migration likely to adjust buoyancy and also when under strong predation pressure. Based on recently measured and modeled sound for individual fish, spectral levels are estimated for entire herring schools in the ocean for both scenarios, and the feasibility of passive detection is explored. For a typical school of migrating herring near-surface spectral levels of about 50 dB rel., 1 μPa/√Hz at 3–7 kHz are predicted. If wind conditions are calm where migrating herring are found, such as for Pacific herring in Prince William Sound, Alaska, passive detection is very likely. For an exemplary 10 metric ton compact school, peak spectral source levels of about 80–90 dB rel. 1 μPa/√Hz ref. 1 m are predicted, yielding a range of detection against calm wind background of about 1000 m. Field measurements of potential gas-release events agree with the predictions for the compact school scenario with regard to levels and spectral shape and indicate that passive acoustic monitoring is feasible and could be a prime tool to study predator-prey interactions.
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43.30.Sf Acoustical detection of marine life; passive and active
43.30.Nb Noise in water; generation mechanisms and characteristics of the field
43.80.Ka Sound production by animals: mechanisms, characteristics, populations, biosonar

Three-dimensional source tracking in an uncertain environment

Dag Tollefsen and Stan E. Dosso

J. Acoust. Soc. Am. Volume 125, Issue 5, pp. 2909-2917 (2009); (9 pages) | Cited 3 times

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This paper develops an approach to three-dimensional source tracking in an uncertain ocean environment using a horizontal line array (HLA). The tracking algorithm combines matched-field focalization for environmental (seabed and water column) and source-bearing model parameters with the Viterbi algorithm for range-depth estimation and includes physical constraints on source velocity. The ability to track a source despite environmental uncertainty is examined using synthetic test cases for various track geometries and with varying degrees of prior information for environmental parameters. Performance is evaluated for a range of signal-to-noise ratios in terms of the probability of estimating a track within acceptable position/depth errors. The algorithm substantially outperforms tracking with poor environmental estimates and generally obtains results close to those obtained with exact environmental knowledge. The approach is also applied to measured narrowband data recorded on a bottom-moored HLA in shallow water (the Barents Sea) and shown to successfully track both a towed submerged source and a surface ship in cases where simpler tracking algorithms failed.
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43.30.Wi Passive sonar systems and algorithms, matched field processing in underwater acoustics
43.30.Pc Ocean parameter estimation by acoustical methods; remote sensing; imaging, inversion, acoustic tomography

Absolute calibration of hydrophones immersed in sandy sediment

Gary B. N. Robb, Stephen P. Robinson, Pete D. Theobald, Gary Hayman, Victor F. Humphrey, Timothy G. Leighton, Lian Sheng Wang, Justin K. Dix, and Angus I. Best

J. Acoust. Soc. Am. Volume 125, Issue 5, pp. 2918-2927 (2009); (10 pages)

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An absolute calibration method has been developed based on the method of three-transducer spherical-wave reciprocity for the calibration of hydrophones when immersed in sandy sediment. The method enables the determination of the magnitude of the free-field voltage receive sensitivity of the hydrophone. Adoption of a co-linear configuration allows the acoustic attenuation within the sediment to be eliminated from the sensitivity calculation. Example calibrations have been performed on two hydrophones inserted into sandy sediment over the frequency range from 10 to 200 kHz. In general, a reduction in sensitivity was observed, with average reductions over the frequency range tested of 3.2 and 3.6 dB with respect to the equivalent water-based calibrations for the two hydrophones tested. Repeated measurements were undertaken to assess the robustness of the method to both the influence of the sediment disturbance associated with the hydrophone insertion and the presence of the central hydrophone. A simple finite element model, developed for one of the hydrophone designs, shows good qualitative agreement with the observed differences from water-based calibrations. The method described in this paper will be of interest to all those undertaking acoustic measurements with hydrophones immersed in sediment where the absolute sensitivity is important.
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43.30.Xm Underwater measurement and calibration instrumentation and procedures
43.30.Ma Acoustics of sediments; ice covers, viscoelastic media; seismic underwater acoustics
43.30.Yj Transducers and transducer arrays for underwater sound; transducer calibration
43.58.Vb Calibration of acoustical devices and systems
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Material properties from acoustic radiation force step response

Marko Orescanin, Kathleen S. Toohey, and Michael F. Insana

J. Acoust. Soc. Am. Volume 125, Issue 5, pp. 2928-2936 (2009); (9 pages) | Cited 5 times

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An ultrasonic technique for estimating viscoelastic properties of hydrogels, including engineered biological tissues, is being developed. An acoustic radiation force is applied to deform the gel locally while Doppler pulses track the induced movement. The system efficiently couples radiation force to the medium through an embedded scattering sphere. A single-element, spherically-focused, circular piston element transmits a continuous-wave burst to suddenly apply and remove a radiation force to the sphere. Simultaneously, a linear array and spectral Doppler technique are applied to track the position of the sphere over time. The complex shear modulus of the gel was estimated by applying a harmonic oscillator model to measurements of time-varying sphere displacement. Assuming that the stress-strain response of the surrounding gel is linear, this model yields an impulse response function for the gel system that may be used to estimate material properties for other load functions. The method is designed to explore the force-frequency landscape of cell-matrix viscoelasticity. Reported measurements of the shear modulus of gelatin gels at two concentrations are in close agreement with independent rheometer measurements of the same gels. Accurate modulus measurements require that the rate of Doppler-pulse transmission be matched to a priori estimates of gel properties.
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43.35.Mr Acoustics of viscoelastic materials
43.25.Qp Radiation pressure
43.80.Ev Acoustical measurement methods in biological systems and media

Thermoacoustic mixture separation with an axial temperature gradient

D. A. Geller and G. W. Swift

J. Acoust. Soc. Am. Volume 125, Issue 5, pp. 2937-2945 (2009); (9 pages) | Cited 1 time

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The theory of thermoacoustic mixture separation is extended to include the effect of a nonzero axial temperature gradient. The analysis yields a new term in the second-order mole flux that is proportional to the temperature gradient and to the square of the volumetric velocity and is independent of the phasing of the wave. Because of this new term, thermoacoustic separation stops at a critical temperature gradient and changes direction above that gradient. For a traveling wave, this gradient is somewhat higher than that predicted by a simple four-step model. An experiment tests the theory for temperature gradients from 0 to 416 K/m in 50–50 He–Ar mixtures.
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43.35.Ud Thermoacoustics, high temperature acoustics, photoacoustic effect
43.20.Mv Waveguides, wave propagation in tubes and ducts
43.35.Ty Other physical effects of sound

Correction for partial reflection in ultrasonic attenuation measurements using contact transducers

Martin Treiber, Jin-Yeon Kim, Laurence J. Jacobs, and Jianmin Qu

J. Acoust. Soc. Am. Volume 125, Issue 5, pp. 2946-2953 (2009); (8 pages) | Cited 3 times

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This research investigates the influence of partial reflection on the measurement of the absolute ultrasonic attenuation coefficient using contact transducers. The partial, frequency-dependent reflection arises from the thin fluid-layer interface formed between the transducer and specimen surface. It is experimentally shown that neglecting this reflection effect leads to a significant overestimation in the measured attenuation coefficient. A systematic measurement procedure is proposed that simultaneously obtains the ultrasonic signals needed to calculate both the reflection coefficient of the interface and the attenuation coefficient, without disturbing the existing coupling conditions. The true attenuation coefficient includes a correction based on the measured reflection coefficient—this is called the reflection correction. It is shown that including the reflection correction also reduces the variation (random error) in the measured attenuation coefficient. The accuracy of the proposed method is demonstrated for a material with a known attenuation coefficient. The proposed method is then used to measure the high attenuation coefficient of a cement-based material.
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43.35.Yb Ultrasonic instrumentation and measurement techniques
43.20.Ye Measurement methods and instrumentation
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Dynamic equations for fluid-loaded porous plates using approximate boundary conditions

Peter D. Folkow and Martin Johansson

J. Acoust. Soc. Am. Volume 125, Issue 5, pp. 2954-2966 (2009); (13 pages) | Cited 2 times

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Systematically derived equations for fluid-loaded thin poroelastic layers are presented for time-harmonic conditions. The layer is modeled according to Biot theory for both open and closed pores. Series expansion techniques in the thickness variable are used, resulting in separate symmetric and antisymmetric plate equations. These equations, which are believed to be asymptotically correct, are expressed in terms of approximate boundary conditions and can be truncated to arbitrary order. Analytical and numerical results are presented and compared to the exact three dimensional theory and a flexural plate theory. Numerical comparisons are made for two material configurations and two thicknesses. The results show that the presented theory predicts the plate behavior accurately.
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43.40.Dx Vibrations of membranes and plates
43.20.Gp Reflection, refraction, diffraction, interference, and scattering of elastic and poroelastic waves
43.20.Tb Interaction of vibrating structures with surrounding medium
43.40.Yq Instrumentation and techniques for tests and measurement relating to shock and vibration, including vibration pickups, indicators, and generators, mechanical impedance

Optimal simulations of ultrasonic fields produced by large thermal therapy arrays using the angular spectrum approach

Xiaozheng Zeng and Robert J. McGough

J. Acoust. Soc. Am. Volume 125, Issue 5, pp. 2967-2977 (2009); (11 pages) | Cited 5 times

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The angular spectrum approach is evaluated for the simulation of focused ultrasound fields produced by large thermal therapy arrays. For an input pressure or normal particle velocity distribution in a plane, the angular spectrum approach rapidly computes the output pressure field in a three dimensional volume. To determine the optimal combination of simulation parameters for angular spectrum calculations, the effect of the size, location, and the numerical accuracy of the input plane on the computed output pressure is evaluated. Simulation results demonstrate that angular spectrum calculations performed with an input pressure plane are more accurate than calculations with an input velocity plane. Results also indicate that when the input pressure plane is slightly larger than the array aperture and is located approximately one wavelength from the array, angular spectrum simulations have very small numerical errors for two dimensional planar arrays. Furthermore, the root mean squared error from angular spectrum simulations asymptotically approaches a nonzero lower limit as the error in the input plane decreases. Overall, the angular spectrum approach is an accurate and robust method for thermal therapy simulations of large ultrasound phased arrays when the input pressure plane is computed with the fast nearfield method and an optimal combination of input parameters.
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43.40.Yq Instrumentation and techniques for tests and measurement relating to shock and vibration, including vibration pickups, indicators, and generators, mechanical impedance
43.20.El Reflection, refraction, diffraction of acoustic waves
43.20.Rz Steady-state radiation from sources, impedance, radiation patterns, boundary element methods

Decentralized harmonic control of sound radiation and transmission by a plate using a virtual impedance approach

Nicolas Quaegebeur, Philippe Micheau, and Alain Berry

J. Acoust. Soc. Am. Volume 125, Issue 5, pp. 2978-2986 (2009); (9 pages) | Cited 2 times

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The problem under study in this article is the active control of sound transmission and radiation of a panel under a periodic excitation. The control strategy investigated uses independent control loops between an individual polyvinylidene fluoride (PVDF) sensor and an individual lead zirconate titanate (PZT) actuator. The specific approach employed here uses the concept of virtual impedance. The aim is to determine for each frequency the optimal impedance between each PVDF sensor and the corresponding PZT actuator in order to reduce the sound power radiated by the plate. Theoretical predictions are compared to measurements of the sound radiated and transmission loss of a panel mounted with eight PZT-PVDF units. Reductions of up to 20 dB of the acoustic power can be achieved around mechanical resonances of the system, while the control strategy has little effect for off-resonance excitations.
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43.40.Yq Instrumentation and techniques for tests and measurement relating to shock and vibration, including vibration pickups, indicators, and generators, mechanical impedance
43.50.Ki Active noise control
43.50.Gf Noise control at source: redesign, application of absorptive materials and reactive elements, mufflers, noise silencers, noise barriers, and attenuators, etc.
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Subjective evaluation of heavy-weight floor impact sounds in relation to spatial characteristics

Jin Yong Jeon, Pyoung Jik Lee, Jae Ho Kim, and Seung Yup Yoo

J. Acoust. Soc. Am. Volume 125, Issue 5, pp. 2987-2994 (2009); (8 pages) | Cited 3 times

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This study investigated the effect of a spatial factor, the magnitude of interaural cross-correlation (IACC) function, on subjective responses to heavy-weight floor impact sounds. Heavy-weight impact sounds were generated by a heavy/soft impact source (impact ball) in real apartments, so that impact sound pressure levels (SPLs) (LAmax) and IACC could be analyzed. Just noticeable differences (JNDs) of impact SPL and IACC were investigated through the use of impact ball sounds. JNDs were determined by the criteria of 75% correct answers by participants, and it was found that JNDs of impact SPL and IACC were around 1.5 dB and 0.12–0.13, respectively. In addition, the annoyance caused by an impact ball was evaluated by changes in these two parameters. The results show that annoyance increased with increasing impact SPL and with decreasing IACC; the contributions of the two parameters to the scale value of annoyance were 79.3% and 20.4%, respectively. This indicates that the effects of IACC should be considered for the evaluation of annoyance, and the subjective response to impact ball sounds can be improved by controlling IACC, as well as impact SPL.
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43.50.Ba Noisiness: rating methods and criteria
43.50.Jh Noise in buildings and general machinery noise
43.50.Pn Impulse noise and noise due to impact

On the level-dependent attenuation of a perforated device

Lan Chen, Jinqiu Sang, and Xiaodong Li

J. Acoust. Soc. Am. Volume 125, Issue 5, pp. 2995-3005 (2009); (11 pages)

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Show Abstract
To investigate the physical principle governing the level-dependent attenuation of a perforated earplug, a mathematical model is first established with the transfer-matrix method to calculate the noise reduction through a simplified device, one perforated panel with back cavity, mounted in an impedance tube. The model prediction is compared with the measured noise reduction through two series of large-scale devices and one device with the dimensions of the ear canal under continuous noise and sinusoidal excitations. The model helps to improve significantly the level-dependent attenuation of the large-scale device. It also illustrates that the attenuation is not solely determined by the resistance of the orifice, which has been a well accepted design concept, but resulted from an incorporated effect of the acoustic filter comprised of the acoustic impedance of the orifice and other elements in the earplug-ear-canal system. This mechanism can interpret a resonance at low incident levels on improper design and reveal approaches to eliminate it. Finally, the model’s potential contributions to the design of a perforated earplug are discussed, along with the threshold of level-dependent attenuation supported with experimental evidence.
Show PACS
43.50.Hg Noise control at the ear
43.66.Vt Hearing protection
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