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Journal of the Acoustical Society of America

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Dec 2009

Volume 126, Issue 6, pp. EL171-3387

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Exploiting forward scattering for detecting submerged proud/half-buried unexploded ordnance

J. A. Bucaro, B. H. Houston, H. Simpson, L. R. Dragonette, L. Kraus, and T. Yoder

J. Acoust. Soc. Am. Volume 126, Issue 6, pp. EL171-EL176 (2009); (6 pages) | Cited 3 times

Online Publication Date: 04 Nov 2009

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Laboratory underwater bistatic scattering measurements are reported for free, proud, and half-buried unexploded ordnances for 0° and 90° source angles. Forward echoes are larger than backscattered returns, and half burial significantly decreases the latter but not the former. Results agree with analytic predictions borrowed from radar. The forward echo and source signal are separated by measurements made with and without the target, a method not possible in a target search. For this, a method is described that uses knowledge of the source location and the hyperbolic character in time-cross range of the signals received at points along a line.
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43.20.Fn Scattering of acoustic waves
43.30.Vh Active sonar systems
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Masking with interaurally “double-delayed” stimuli: The range of internal delays in the human brain

Torsten Marquardt and David McAlpine

J. Acoust. Soc. Am. Volume 126, Issue 6, pp. EL177-EL182 (2009); (6 pages) | Cited 1 time

Online Publication Date: 04 Nov 2009

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Is binaural processing in humans different to that of other mammals? While psychophysical data suggest that the range of internal delays necessary for processing interaural time differences is at least ±3 ms, physiological data from small mammals indicate a more limited range. This study demonstrates that binaural detection is impeded by reduced interaural coherence in auditory channels remote from the signal frequency, in accordance with the wider critical bandwidths reported for binaural processing. This explains previous psychophysical data without requiring long internal delays. The current psychophysical data support the view that human binaural processing is similar to that of other mammals.
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43.66.Pn Binaural hearing
43.66.Dc Masking
43.66.Ba Models and theories of auditory processes
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Accuracy of the deterministic travel time retrieval from cross-correlations of non-diffuse ambient noise

Oleg A. Godin

J. Acoust. Soc. Am. Volume 126, Issue 6, pp. EL183-EL189 (2009); (7 pages) | Cited 9 times

Online Publication Date: 04 Nov 2009

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Measurements of long-range cross-correlations of ambient noise underlie acoustic noise interferometry, a promising technique for passive remote sensing of the environment. Previously established simple, exact relations between deterministic Green’s functions and the cross-correlation function of perfectly diffuse noise do not necessarily hold for noise fields in the ocean and atmosphere. Here, the method of a stationary phase is applied to study the information content of the cross-correlation function of non-diffuse noise and to quantify the accuracy of passive measurements of the acoustic travel times.
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43.30.Pc Ocean parameter estimation by acoustical methods; remote sensing; imaging, inversion, acoustic tomography
43.20.Bi Mathematical theory of wave propagation
43.30.Nb Noise in water; generation mechanisms and characteristics of the field
43.60.Rw Remote sensing methods, acoustic tomography
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Acoustic measurements of clay-size particles

Wayne O. Carpenter, Jr., James P. Chambers, Daniel G. Wren, Roger A. Kuhnle, and Jeffrey A. Diers

J. Acoust. Soc. Am. Volume 126, Issue 6, pp. EL190-EL195 (2009); (6 pages) | Cited 2 times

Online Publication Date: 16 Nov 2009

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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 μm) in a fluvial environment. A small laboratory tank with a pitch-catch transducer configuration measured a 35 dB change in signal level over a wide range of kaolinite and bentonite concentrations (1–14 g/l) over a range of distances (180–357 mm). The data suggest that a fixed distance of 180 mm between the transducers will be capable of measuring the entire range of concentrations.
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43.30.Ma Acoustics of sediments; ice covers, viscoelastic media; seismic underwater acoustics
43.35.Bf Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in liquids, liquid crystals, suspensions, and emulsions
43.35.Yb Ultrasonic instrumentation and measurement techniques
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The intelligibility of pointillistic speech

Gerald Kidd, Jr., Timothy M. Streeter, Antje Ihlefeld, Ross K. Maddox, and Christine R. Mason

J. Acoust. Soc. Am. Volume 126, Issue 6, pp. EL196-EL201 (2009); (6 pages)

Online Publication Date: 16 Nov 2009

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A form of processed speech is described that is highly discriminable in a closed-set identification format. The processing renders speech into a set of sinusoidal pulses played synchronously across frequency. The processing and results from several experiments are described. The number and width of frequency analysis channels and tone-pulse duration were variables. In one condition, various proportions of the tones were randomly removed. The processed speech was remarkably resilient to these manipulations. This type of speech may be useful for examining multitalker listening situations in which a high degree of stimulus control is required.
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43.66.Mk Temporal and sequential aspects of hearing; auditory grouping in relation to music
43.72.Gy Narrow, medium, and wideband speech coding
43.72.Ja Speech synthesis and synthesis techniques
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A special relation between Young’s modulus, Rayleigh-wave velocity, and Poisson’s ratio

Peter G. Malischewsky and Tran Thanh Tuan

J. Acoust. Soc. Am. Volume 126, Issue 6, pp. 2851-2853 (2009); (3 pages)

Online Publication Date: 14 Dec 2009

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Bayón et al. [(2005). J. Acoust. Soc. Am. 117, 3469–3477 ] described a method for the determination of Young’s modulus by measuring the Rayleigh-wave velocity and the ellipticity of Rayleigh waves, and found a peculiar almost linear relation between a non-dimensional quantity connecting Young’s modulus, Rayleigh-wave velocity and density, and Poisson’s ratio. The analytical reason for this special behavior remained unclear. It is demonstrated here that this behavior is a simple consequence of the mathematical form of the Rayleigh-wave velocity as a function of Poisson’s ratio. The consequences for auxetic materials (those materials for which Poisson’s ratio is negative) are discussed, as well as the determination of the shear and bulk moduli.
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43.20.Jr Velocity and attenuation of elastic and poroelastic waves
43.20.Bi Mathematical theory of wave propagation

Authors’ Response to Strasberg’s “Comment on ‘Measurement of the frequency dependence of the ultrasonic parametric threshold amplitude for a fluid-filled cavity’ ” [ J. Acoust. Soc. Am. 125, 1857 (2009) ]

A. Teklu, Michael S. McPherson, M. A. Breazeale, Roger D. Hasse, and Nico F. Declercq

J. Acoust. Soc. Am. Volume 126, Issue 6, pp. 2854-2855 (2009); (2 pages) | Cited 1 time

Online Publication Date: 14 Dec 2009

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This letter is a response to Strasberg’s recent paper, “Comment on ‘Measurement of the frequency dependence of the ultrasonic parametric threshold amplitude for a fluid-filled cavity.’” The authors dispute the conclusions of Strasberg regarding the effect observed by Teklu et al. [ J. Acoust. Soc. Am. 120, 657–660 (2006) ] published previously in JASA.
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43.25.Gf Standing waves; resonance

Broadband directive sources for acoustic discrete-time simulations

José Escolano, José J. López, and Basilio Pueo

J. Acoust. Soc. Am. Volume 126, Issue 6, pp. 2856-2859 (2009); (4 pages) | Cited 1 time

Online Publication Date: 14 Dec 2009

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This work investigates a generalized implementation of directive sources on discrete-time methods. Results based on previous work for sinusoidal sources have been extended to accomplish real life source requirements, which have a frequency-dependent pattern and show gradual transitions between the different directivities at successive frequencies. One of the main advantages of this method lies in its capacity to be applied to any discrete-time method, since it is based on a proper combination of impulse responses radiated from discrete positions, which, in turn, will produce a particular pressure distribution at far-field. Furthermore, some considerations about mesh-dispersion effects on source modeling are addressed using some examples.
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43.55.Ka Computer simulation of acoustics in enclosures, modeling
43.58.Ta Computers and computer programs in acoustics

Effects of voicing in the recognition of concurrent syllables

Martin D. Vestergaard and Roy D. Patterson

J. Acoust. Soc. Am. Volume 126, Issue 6, pp. 2860-2863 (2009); (4 pages) | Cited 6 times

Online Publication Date: 14 Dec 2009

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This letter reports a study designed to measure the benefits of voicing in the recognition of concurrent syllables. The target and distracter syllables were either voiced or whispered, producing four combinations of vocal contrast. Results show that listeners use voicing whenever it is present either to detect a target syllable or to reject a distracter. When the predictable effects of audibility were taken into account, limited evidence remained for the harmonic cancellation mechanism thought to make rejecting distracter syllables more effective than enhancing target syllables.
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43.71.Bp Perception of voice and talker characteristics
43.71.An Models and theories of speech perception
43.66.Ba Models and theories of auditory processes
43.72.Qr Auditory synthesis and recognition
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On the use of leaky modes in open waveguides for the sound propagation modeling in street canyons

Adrien Pelat, Simon Félix, and Vincent Pagneux

J. Acoust. Soc. Am. Volume 126, Issue 6, pp. 2864-2872 (2009); (9 pages) | Cited 3 times

Online Publication Date: 14 Dec 2009

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An urban, U-shaped, street canyon being considered as an open waveguide in which the sound may propagate, one is interested in a multimodal approach to describe the sound propagation within. The key point in such a multimodal formalism is the choice of the basis of local transversal modes on which the acoustic field is decomposed. For a classical waveguide, with a simple and bounded cross-section, a complete orthogonal basis can be analytically obtained. The case of an open waveguide is more difficult, since no such a basis can be exhibited. However, an open resonator, as displays, for example, the U-shaped cross-section of a street, presents resonant modes with complex eigenfrequencies, owing to radiative losses. This work first presents how to numerically obtain these modes. Results of the transverse problem are also compared with solutions obtained by the finite element method with perfectly mathed layers. Then, examples are treated to show how these leaky modes can be used as a basis for the modal decomposition of the sound field in a street canyon.
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43.20.Mv Waveguides, wave propagation in tubes and ducts
43.28.Js Numerical models for outdoor propagation
43.50.Vt Topographical and meteorological factors in noise propagation

Three dimensional finite element modeling of smart foam

Pierre Leroy, Noureddine Atalla, Alain Berry, and Philippe Herzog

J. Acoust. Soc. Am. Volume 126, Issue 6, pp. 2873-2885 (2009); (13 pages) | Cited 6 times

Online Publication Date: 14 Dec 2009

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The “smart foam” concept and design originate from the combination of the passive dissipation capability of foam in the medium and high frequency ranges and the active absorption ability of piezoelectric actuator (generally polyvinylidene fluoride) in the low frequency range. This results into a passive/active absorption control device that can efficiently operate over a broad range of frequencies. In this paper, a full three dimensional finite element model of smart foam is presented including its experimental validation. The modeling tool uses quadratic poroelastic elements, as well as elastic, fluid, and piezoelectric elements. The weak integral formulation of the different media involved is presented with the associated coupling conditions. A simplified orthotropic model of poroelastic media is presented. To validate the developed model, a prototype of a smart foam has been realized and its passive absorption and radiation measured in an impedance tube and compared to predictions. The experimental validation demonstrates the validity of the model. This modeling tool constitutes a general platform to simulate and optimize various configurations of smart foams.
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43.20.Tb Interaction of vibrating structures with surrounding medium
43.20.Jr Velocity and attenuation of elastic and poroelastic waves
43.38.Fx Piezoelectric and ferroelectric transducers
43.50.Ki Active noise control
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Short-range shock formation and coalescence in numerical simulation of broadband noise propagation

Micah R. Shepherd, Kent L. Gee, and Mark S. Wochner

J. Acoust. Soc. Am. Volume 126, Issue 6, pp. 2886-2893 (2009); (8 pages) | Cited 2 times

Online Publication Date: 14 Dec 2009

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The number of jet and rocket noise studies has increased in recent years as researchers have sought to better understand aeroacoustic source and radiation characteristics. Although jet and rocket noise is finite-amplitude in nature, little is known about the existence of shock formation and coalescence close to the source. A numerical experiment is performed to propagate finite-amplitude noise and determine the extent of the nonlinearity over short distances with spherical spreading. The noise is filtered to have a haystack shape in the frequency domain, as is typical of such sources. The effect of the nonlinearity is compared in both the temporal and frequency domains as a function of distance. Additionally, the number of zero-crossings and overall sound pressure level is compared at several distances. The results indicate that the center frequency plays a particularly important role in the amount of coalescence and spectral redistribution that occurs. The general applicability of these results to actual near-field finite-amplitude jet and rocket noise experiments is also presented.
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43.25.Cb Macrosonic propagation, finite amplitude sound; shock waves
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Geostatistical modeling of sound propagation: Principles and a field application experiment

Olivier Baume, Benoit Gauvreau, Michel Bérengier, Fabrice Junker, Hans Wackernagel, and Jean-Paul Chilès

J. Acoust. Soc. Am. Volume 126, Issue 6, pp. 2894-2904 (2009); (11 pages) | Cited 1 time

Online Publication Date: 14 Dec 2009

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The assessment of noise sources for environmental purposes requires reliable methods for mapping. Numerical models are well adapted for sophisticated simulations and sensitivity analyses; however, real-time mapping of large frequency bands must be based on fast and acceptable computations and honor in situ measurements. In this paper, a real-time mapping procedure of noise exposure is proposed. The procedure is based on geostatistical modeling of spatial variations and applied to a case study taken from an experimental campaign, where a point source was placed on a flat meadow. An analytical approximation of the acoustic field was first computed with the Embleton model. The difference between this approximation and the actual measurements (Leq15 min 1/3-octave bands samples from 19 microphones spread over the meadow) showed spatial structure, which has been modeled with a variogram. Finally, the geostatistical technique of kriging with external drift provided an optimal interpolation of the acoustic field data while encapsulating the first approximation from the Embleton model. Systematic geostatistical inference and real-time mapping with the proposed procedure can be envisaged in simple cases.
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43.28.Tc Sound-in-air measurements, methods and instrumentation for location, navigation, altimetry, and sound ranging
43.28.Lv Statistical characteristics of sound fields and propagation parameters
43.28.En Interaction of sound with ground surfaces, ground cover and topography, acoustic impedance of outdoor surfaces
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Measurements and inversion of acoustic scattering from suspensions having broad size distributions

Benjamin D. Moate and Peter D. Thorne

J. Acoust. Soc. Am. Volume 126, Issue 6, pp. 2905-2917 (2009); (13 pages) | Cited 9 times

Online Publication Date: 14 Dec 2009

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Measurements are presented from a multi-frequency acoustic backscatter study of aqueous suspensions of irregularly shaped quartz sediments having broad particle size distributions. Using the backscattered sound from a homogenous suspension, measurements of the ensemble backscatter form function and ensemble normalized total scattering cross section were obtained. Three different size distribution types are examined; namely Gaussian, log-normal, and bi-modal distributions, each covering a range of particle sizes similar to those observed in sandy marine environments near the seabed. The measurements of ensemble scattering are compared with theoretical predictions, derived by integrating the intrinsic scattering properties of the sediments over the probability density functions of the size distributions used in the present study. The results show that the ensemble scattering parameters are significant functions of both the width and type of size distribution in suspension. The impact of errors in size distribution width on inversion predictions of both mean size and suspended concentration is also examined. The validity of the theoretical predictions is discussed, along with the implication of the inversion results for using acoustic backscatter data to measure suspended concentration and particle size in sandy marine environments.
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43.30.Ft Volume scattering
43.20.Fn Scattering of acoustic waves
43.30.Gv Backscattering, echoes, and reverberation in water due to combinations of boundaries
43.30.Pc Ocean parameter estimation by acoustical methods; remote sensing; imaging, inversion, acoustic tomography

Automatic recognition of fin and blue whale calls for real-time monitoring in the St. Lawrence

Xavier Mouy, Mohammed Bahoura, and Yvan Simard

J. Acoust. Soc. Am. Volume 126, Issue 6, pp. 2918-2928 (2009); (11 pages) | Cited 3 times

Online Publication Date: 14 Dec 2009

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Monitoring blue and fin whales summering in the St. Lawrence Estuary with passive acoustics requires call recognition algorithms that can cope with the heavy shipping noise of the St. Lawrence Seaway and with multipath propagation characteristics that generate overlapping copies of the calls. In this paper, the performance of three time-frequency methods aiming at such automatic detection and classification is tested on more than 2000 calls and compared at several levels of signal-to-noise ratio using typical recordings collected in this area. For all methods, image processing techniques are used to reduce the noise in the spectrogram. The first approach consists in matching the spectrogram with binary time-frequency templates of the calls (coincidence of spectrograms). The second approach is based on the extraction of the frequency contours of the calls and their classification using dynamic time warping (DTW) and the vector quantization (VQ) algorithms. The coincidence of spectrograms was the fastest method and performed better for blue whale A and B calls. VQ detected more 20 Hz fin whale calls but with a higher false alarm rate. DTW and VQ outperformed for the more variable blue whale D calls.
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43.30.Sf Acoustical detection of marine life; passive and active
43.60.Bf Acoustic signal detection and classification, applications to control systems
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Eigenmodal resonances of polydisperse bubble systems on a rigid boundary

Suhith Illesinghe, Andrew Ooi, and Richard Manasseh

J. Acoust. Soc. Am. Volume 126, Issue 6, pp. 2929-2938 (2009); (10 pages) | Cited 4 times

Online Publication Date: 14 Dec 2009

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This paper presents theory and experimental data on the resonance frequency of systems consisting of different-sized air bubbles attached to a rigid wall. Effects of the change in resonant frequency with bubble size and distance between the bubbles were studied. It was found that the symmetric mode resonance frequency of the bubble system decreased with increasing r = R02/R01, where R01 and R02 are the equilibrium radii of bubbles in the system. Both the symmetric and antisymmetric modes of oscillation were detected in the experiments, with the resonant frequency of the symmetric mode dominant at small bubble separation and the frequency of the antisymmetric mode dominant when the bubbles were farther apart. A linear coupled-oscillator theoretical model was used to describe the oscillations of the bubble system, in which the method of images was used to approximate the effects of the wall. It was found that there was fair to good agreement between the predictions of the coupled-oscillator model with the experimental data.
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43.35.Bf Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in liquids, liquid crystals, suspensions, and emulsions
43.20.Fn Scattering of acoustic waves
43.20.Px Transient radiation and scattering
43.20.Bi Mathematical theory of wave propagation

Angular and frequency spectral analysis of the ultrasonic backward beam displacement on a periodically grooved solid

Sarah W. Herbison, Nico F. Declercq, and Mack A. Breazeale

J. Acoust. Soc. Am. Volume 126, Issue 6, pp. 2939-2948 (2009); (10 pages) | Cited 2 times

Online Publication Date: 14 Dec 2009

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The ultrasonic backward beam displacement, which has been shown to occur when a bounded beam is incident upon a periodically corrugated liquid-solid interface, is studied experimentally. This effect has been previously studied on a periodic water-brass interface at one particular frequency (6 MHz) and one corresponding angle of incidence (22.5°), but the question has remained whether it would also exist at other frequency and angle combinations. The knowledge of whether this phenomenon is a coincidence or whether it will occur for other frequency and angle combinations contributes to a better understanding of the interaction of ultrasound with periodic structures and diffraction effects, in particular. Potential applications exist in the study of phononic crystals and in the non-destructive evaluation of materials. The present work reports results from recent experiments on the same periodically grooved brass sample that was employed in the first investigations of this phenomenon. Through the examination of frequency spectra in the form of angular and classical spectrograms, the experiments reported here show the backward beam displacement to occur for multiple angles of incidence and frequencies. Furthermore, evidence is shown as to the exact cause of the backward beam displacement, namely, a backward propagating Scholte–Stoneley wave.
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43.35.Bf Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in liquids, liquid crystals, suspensions, and emulsions
43.30.Hw Rough interface scattering
43.20.El Reflection, refraction, diffraction of acoustic waves
43.35.Pt Surface waves in solids and liquids

Resonant ultrasound studies of the layered perovskite system Ca2−xSrxRuO4

Yanbing Luan, Veerle Keppens, Rongying Jin, and David Mandrus

J. Acoust. Soc. Am. Volume 126, Issue 6, pp. 2949-2953 (2009); (5 pages) | Cited 1 time

Online Publication Date: 14 Dec 2009

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The elastic response of the layered perovskite system Ca2−xSrxRuO4 (0.2 ≤ x ≤ 2) has been studied as a function of temperature and doping concentration x using resonant ultrasound spectroscopy. The elastic constants c11 and c44 have been obtained for three polycrystalline samples (x = 1.0, 0.5, and 0.3) and show a softening trend with increasing Ca-content. In addition, the temperature-dependence of the elastic response of five single-crystals (x = 2.0, 1.9, 0.5, 0.3, and 0.2) has been measured. For 2.0 ≥ x ≥ 0.5, a dramatic softening over a wide temperature range is observed upon cooling, which is attributed to the rotational instability of RuO6 octahedra (for x = 2.0 and 1.9) and the static rotation of the octahedra (for x = 0.5). For the Ca-rich samples (x = 0.3 and 0.2), the softening occurs in a very narrow temperature range, corresponding to the structural phase transition from high-temperature tetragonal to low-temperature orthorhombic symmetry.
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43.35.Cg Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in solids; elastic constants

Estimating the shell parameters of SonoVue® microbubbles using light scattering

Juan Tu, Jingfeng Guan, Yuanyuan Qiu, and Thomas J. Matula

J. Acoust. Soc. Am. Volume 126, Issue 6, pp. 2954-2962 (2009); (9 pages) | Cited 11 times

Online Publication Date: 14 Dec 2009

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Experiments were performed to measure the dynamical response of individual SonoVue® microbubbles subjected to pulsed ultrasound. Three commonly used bubble dynamic models (i.e., Hoff’s, Sarkar’s, and linearized Marmottant’s models) were compared to determine the most appropriate model for fitting to the experimental data. The models were evaluated against published optical microscopy data. The comparison suggests that it is difficult to rank these models for lipid-shelled microbubbles undergoing small-amplitude oscillations, because under these conditions the shell parameters in these models are closely related. A linearized version of the Marmottant model was used to estimate the shell parameters (i.e., shear modulus and shear viscosity) of SonoVue® microbubbles from the experimental light scattering data, as a function of ambient microbubble radius. The SonoVue® microbubble shell elasticity and dilatational viscosity increase with ambient bubble radius, in agreement with previously published data. The results suggest that light scattering, used in conjunction with one of several popular bubble dynamics models, is effective at characterizing microbubble response and evaluating shell parameters.
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43.35.Ei Acoustic cavitation in liquids
43.80.Vj Acoustical medical instrumentation and measurement techniques

The natural frequencies of microbubble oscillation in elastic vessels

Sergey Martynov, Eleanor Stride, and Nader Saffari

J. Acoust. Soc. Am. Volume 126, Issue 6, pp. 2963-2972 (2009); (10 pages) | Cited 12 times

Online Publication Date: 14 Dec 2009

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A theoretical model for the dynamics of a bubble in an elastic blood vessel is applied to study numerically the effect of confinement on the free oscillations of a bubble. The vessel wall deformations are described using a lumped-parameter membrane-type model, which is coupled to the Navier–Stokes equations for the fluid motion inside the vessel. It is shown that the bubble oscillations in a finite-length vessel are characterized by a spectrum of frequencies, with distinguishable high-frequency and low-frequency modes. The frequency of the high-frequency mode increases with the vessel elastic modulus and, for a thin-wall vessel, can be higher than the natural frequency of bubble oscillations in an unconfined liquid. In the limiting case of an infinitely stiff vessel wall, the frequency of the low-frequency mode approaches the well-known solution for a bubble confined in a rigid vessel. In order to interpret the results, a simple two-degree-of-freedom model is applied. The results suggest that in order to maximize deposition of acoustic energy, a bubble confined in a long elastic vessel has to be excited at frequencies higher than the natural frequency of the equivalent unconfined bubble.
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43.35.Pt Surface waves in solids and liquids
43.20.Ks Standing waves, resonance, normal modes
43.80.Qf Medical diagnosis with acoustics
43.80.Sh Medical use of ultrasonics for tissue modification (permanent and temporary)

Post-processing of guided wave array data for high resolution pipe inspection

Alexander Velichko and Paul D. Wilcox

J. Acoust. Soc. Am. Volume 126, Issue 6, pp. 2973-2982 (2009); (10 pages) | Cited 1 time

Online Publication Date: 14 Dec 2009

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This paper describes a method for processing data from a guided wave transducer array on a pipe. The raw data set from such an array contains the full matrix of time-domain signals from each transmitter-receiver combination. It is shown that for certain configurations of an array, the total focusing method can be applied, which allows the array to be focused at every point on a pipe in both transmission and reception. The effect of array configuration parameters on the sensitivity of the proposed method to random and coherent noise is discussed. Experimental results are presented using electromagnetic acoustic transducers for exciting and detecting the S0 Lamb wave mode in a 12-in. diameter steel pipe at 200 kHz excitation frequency. The results show that using the imaging algorithm, a 2-mm (0.08 wavelength) diameter half-thickness hole can be detected.
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43.35.Zc Use of ultrasonics in nondestructive testing, industrial processes, and industrial products
43.20.Mv Waveguides, wave propagation in tubes and ducts
43.60.Fg Acoustic array systems and processing, beam-forming
43.60.Jn Source localization and parameter estimation
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Analytical modeling of piezoelectric ceramic transducers based on coupled vibration analysis with application to rectangular thickness poled plates

Boris S. Aronov, Corey L. Bachand, and David A. Brown

J. Acoust. Soc. Am. Volume 126, Issue 6, pp. 2983-2990 (2009); (8 pages)

Online Publication Date: 14 Dec 2009

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The energy method for analyzing piezoelectric ceramic transducers [ B. S. Aronov, J. Acoust. Soc. Am. 117, 210–220 (2005) ] is applied to the treatment of transducers with mechanical systems that can be considered as two-dimensional. Analysis is made following the general outline of the theory of coupled vibration in two degrees-of-freedom systems and its extension in calculating the resonance frequencies of elastic bodies, as suggested by Giebe and Blechschmidt [ Ann. Physik, Ser. 5 18, 417–485 (1933) ]. The approach to the problem is illustrated with examples of piezoceramic rectangular thickness poled plates. The resonance frequencies and effective coupling coefficients are presented as functions of the plates’ aspect ratio.
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43.38.Ar Transducing principles, materials, and structures: general
43.38.Fx Piezoelectric and ferroelectric transducers
43.38.Pf Hydroacoustic and hydraulic transducers
43.30.Yj Transducers and transducer arrays for underwater sound; transducer calibration
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Estimation of vehicle speed using wayside sound pressure onset rate

Jeffrey A. Zapfe, Eric W. Wood, and Marc S. Newmark

J. Acoust. Soc. Am. Volume 126, Issue 6, pp. 2991-2997 (2009); (7 pages) | Cited 1 time

Online Publication Date: 14 Dec 2009

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Transportation-related environmental noise studies, particularly those associated with rail traffic, often require long term measurements near existing rights of way. In addition to the sound produced by passing vehicles, it is also useful to know their speed. Previously, speed measurements have generally required an additional piece of instrumentation, such as a second microphone, video camera, or a radar gun—resulting in added measurement cost and complexity. The present study shows how estimations of vehicle speed can be obtained using a single wayside microphone. The method is based on the rate of pressure rise as the vehicle approaches, specifically the maximum onset rate. This paper shows how the maximum onset rate depends only on the vehicle speed, the microphone distance, and the speed of sound. In order to demonstrate the feasibility of the approach field test data are presented for train passages ranging in speed from 33.5 to 55.6 m/s, as measured by a microphone located 28.65 m from the tracks. Speed estimates derived from the onset rate were generally accurate to within 8% of the independently measured speed of the train.
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43.50.Lj Transportation noise sources: air, road, rail, and marine vehicles
43.50.Yw Instrumentation and techniques for noise measurement and analysis
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Determination of elastic constants of generally anisotropic inclined lamellar structure using line-focus acoustic microscopy

Jin-Yeon Kim and Stanislav I. Rokhlin

J. Acoust. Soc. Am. Volume 126, Issue 6, pp. 2998-3007 (2009); (10 pages) | Cited 5 times

Online Publication Date: 14 Dec 2009

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A methodology for measuring elastic constants of different phases in materials with lamellar microstructure by line-focus acoustic microscopy is developed. The material microstructure investigated is modeled by generally anisotropic multilayers arbitrarily inclined to the sample surface on which acoustic microscopy measurements are performed. To calculate surface acoustic wave (SAW) propagation in such structures quasi-static effective elastic constants are determined and compared with calculated frequency-dependent constants. As a model material, practically important, Ti–6Al–2Sn–4Zr–2Mo alloy is selected. Time-resolved line-focus acoustic microscopy experiments are performed on a Ti-6242 α/β single colony (Ti–6Al–2Sn–4Zr–2Mo alloy) and on a Ti–6Al α-phase single crystal for which elastic constants of different phases are determined using inversion of measured SAW velocities. To validate the experimental methodology, SAW velocities in an X-cut quartz crystal are measured as a function of sample orientation angle and compared with predictions based on the known elastic moduli of quartz.
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43.35.Sx Acoustooptical effects, optoacoustics, acoustical visualization, acoustical microscopy, and acoustical holography

Sound propagation in and low frequency noise absorption by helium-filled porous material

Y. S. Choy, Lixi Huang, and Chunqi Wang

J. Acoust. Soc. Am. Volume 126, Issue 6, pp. 3008-3019 (2009); (12 pages) | Cited 1 time

Online Publication Date: 14 Dec 2009

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Low-frequency noise is difficult to deal with by traditional porous material due to its inherent high acoustic impedance. This study seeks to extend the effective range of sound absorption to lower frequencies by filling a low density gas, such as helium, in the porous material. Compared with conventional air-filled absorption material, the helium-filled porous material has a much reduced characteristic impedance; hence, a good impedance matching with pure air becomes more feasible at low frequencies. The acoustic properties of a series of helium-filled porous materials are investigated with a specially designed test rig. The characteristic of the sound propagation in a helium-filled porous material is established and validated experimentally. Based on the measured acoustic properties, the sound absorption performance of a helium-filled absorber (HA) of finite thickness is studied numerically as well as experimentally. For a random incidence field, the HA is found to perform much better than the air-filled absorber at low frequencies. The main advantage of HA lies in the middle range of oblique incidence angles where wave refraction in the absorber enhances sound absorption. The advantage of HA as duct lining is demonstrated both numerically and experimentally.
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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.Jr Velocity and attenuation of elastic and poroelastic waves
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