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Journal of the Acoustical Society of America

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Jun 2012

Volume 131, Issue 6, pp. EL421-4870

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Vowel enhancement effects in cochlear-implant users

Ningyuan Wang, Heather Kreft, and Andrew J. Oxenham

J. Acoust. Soc. Am. Volume 131, Issue 6, pp. EL421-EL426 (2012); (6 pages) | Cited 3 times

Online Publication Date: 04 May 2012

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Auditory enhancement of certain frequencies can occur through prior stimulation of surrounding frequency regions. The underlying neural mechanisms are unknown, but may involve stimulus-driven changes in cochlear gain via the medial olivocochlear complex (MOC) efferents. Cochlear implants (CIs) bypass the cochlea and stimulate the auditory nerve directly. If the MOC plays a critical role in enhancement then CI users should not exhibit this effect. Results using vowel stimuli, with and without preceding sounds designed to enhance formants, provided evidence of auditory enhancement in both normal-hearing listeners and CI users, suggesting that vowel enhancement is not mediated solely by cochlear effects.
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43.64.Me Effects of electrical stimulation, cochlear implant
43.66.Ba Models and theories of auditory processes
43.71.Es Vowel and consonant perception; perception of words, sentences, and fluent speech
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Categorical perception of intonation contrasts: Effects of listeners’ language background

Chang Liu and Amanda Rodriguez

J. Acoust. Soc. Am. Volume 131, Issue 6, pp. EL427-EL433 (2012); (7 pages)

Online Publication Date: 04 May 2012

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Intonation perception of English speech was examined for English- and Chinese-native listeners. F0 contour was manipulated from falling to rising patterns for the final words of three sentences. Listener’s task was to identify and discriminate the intonation of each sentence (question versus statement). English and Chinese listeners had significant differences in the identification functions such as the categorical boundary and the slope. In the discrimination functions, Chinese listeners showed greater peakedness than English peers. The cross-linguistic differences in intonation perception were similar to the previous findings in perception of lexical tones, likely due to listeners’ language background differences.
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43.71.Hw Cross-language perception of speech
43.71.Sy Spoken language processing by humans
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Sound propagation in saturated gas-vapor-droplet suspensions with droplet evaporation and nonlinear relaxation

Max Kandula

J. Acoust. Soc. Am. Volume 131, Issue 6, pp. EL434-EL440 (2012); (7 pages)

Online Publication Date: 04 May 2012

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The Sound attenuation and dispersion in saturated gas-vapor-droplet mixture in the presence of evaporation has been investigated theoretically. The theory is based on an extension of the work of Davidson [J. Atmos. Sci. 32(11), 2201–2205 (1975)] to accommodate the effects of nonlinear particle relaxation processes of mass, momentum and energy transfer on sound attenuation and dispersion. The results indicate the existence of a spectral broadening effect in the attenuation coefficient (scaled with respect to the peak value) with a decrease in droplet mass concentration. It is further shown that for large values of the droplet concentration the scaled attenuation coefficient is characterized by a universal spectrum independent of droplet mass concentration.
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43.20.Hq Velocity and attenuation of acoustic waves
43.25.Ed Effect of nonlinearity on velocity and attenuation
43.50.Nm Aerodynamic and jet noise
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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Field transformational approach to three-dimensional scattering from two-dimensional rough surfaces

Kevin B. Smith

J. Acoust. Soc. Am. Volume 131, Issue 6, pp. EL441-EL447 (2012); (7 pages) | Cited 1 time

Online Publication Date: 04 May 2012

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In 1985, Tappert and Nghiem-Phu introduced a field-transformation technique for computing rough surface scattering from a parabolic equation model utilizing a split-step Fourier marching algorithm. The approach was based on a two-dimensional parabolic equation with a standard operator approximation that was capable of computing scattering from a one-dimensional rough surface. Although this approach has been used extensively and effectively, extensions of this approach to higher order approximations or three-dimensional propagation have only recently been investigated. In this work, the expressions that incorporate higher-order approximations and three-dimensional scattering from two-dimensional rough surfaces are presented. The implications of some computationally necessary approximations are also provided.
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43.30.Hw Rough interface scattering
43.20.Fn Scattering of acoustic waves
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Echolocation behavior of franciscana dolphins (Pontoporia blainvillei) in the wild

Mariana L. Melcón, , Mauricio Failla, , and Miguel A. Iñíguez

J. Acoust. Soc. Am. Volume 131, Issue 6, pp. EL448-EL453 (2012); (6 pages)

Online Publication Date: 08 May 2012

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Franciscana dolphins are small odontocetes hard to study in the field. In particular, little is known on their echolocation behavior in the wild. In this study we recorded 357 min and analyzed 1019 echolocation signals in the Rio Negro Estuary, Argentina. The clicks had a peak frequency at 139 kHz, and a bandwidth of 19 kHz, ranging from 130 to 149 kHz. This is the first study describing echolocation signals of franciscana dolphins in the wild, showing the presence of narrow-band high frequency signals in these dolphins. Whether they use other vocalizations to communicate or not remains uncertain.
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43.80.Ka Sound production by animals: mechanisms, characteristics, populations, biosonar
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About the transition frequency in Biot’s theory

Patrick S. Kurzeja and Holger Steeb

J. Acoust. Soc. Am. Volume 131, Issue 6, pp. EL454-EL460 (2012); (7 pages) | Cited 1 time

Online Publication Date: 09 May 2012

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Biot’s theory of wave propagation in porous media includes a characteristic frequency which is used to distinguish the low-frequency from the high-frequency range. Its determination is based on an investigation of fluid flow through different pore geometries on a smaller scale and a subsequent upscaling process. This idea is limited due to the assumptions made on the smaller scale. It can be enhanced for a general two-phase system by three properties: Inertia of the solid, elasticity of the solid, and frequency dependent corrections of the momentum exchange. They become important for highly porous media with liquids.
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43.20.Bi Mathematical theory of wave propagation
43.20.Jr Velocity and attenuation of elastic and poroelastic waves
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“Ladder” structure in tonal noise generated by laminar flow around an airfoil

Tze Pei Chong and Phillip Joseph

J. Acoust. Soc. Am. Volume 131, Issue 6, pp. EL461-EL467 (2012); (7 pages)

Online Publication Date: 14 May 2012

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The presence of a “ladder” structure in the airfoil tonal noise was discovered in the 1970s, but its mechanism hitherto remains a subject of continual investigation in the research community. Based on the measured noise results and some numerical analysis presented in this letter, the variations of four types of airfoil tonal noise frequencies with the flow velocity were analyzed individually. The ladder structure is proposed to be caused by the acoustic/hydrodynamic frequency lag between the scattering of the boundary layer instability noise and the discrete noise produced by an aeroacoustic feedback loop.
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43.28.Ra Generation of sound by fluid flow, aerodynamic sound and turbulence
43.28.Bj Mechanisms affecting sound propagation in air, sound speed in the air
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Discriminating resonant targets from clutter using Lanczos iterated single-channel time reversal

Zachary J. Waters and Paul E. Barbone

J. Acoust. Soc. Am. Volume 131, Issue 6, pp. EL468-EL474 (2012); (7 pages)

Online Publication Date: 16 May 2012

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Power iterated single-channel time-reversal is extended to employ Lanczos iterations. The properties of these algorithms are studied in the presence of varying levels of noise and broadband clutter. It is shown the Lanczos iterated method possesses superior convergence properties in comparison to the standard power iterated technique. Results demonstrate that such algorithms provide an efficient means through which to isolate and extract the properties of resonant scatterers in the presence of noise and coherent interference.
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43.60.Tj Wave front reconstruction, acoustic time-reversal, and phase conjugation
43.30.Zk Experimental modeling
43.20.Fn Scattering of acoustic waves
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Exploiting pattern transformation to tune phononic band gaps in a two-dimensional granular crystal

F. Göncü, S. Luding, and K. Bertoldi

J. Acoust. Soc. Am. Volume 131, Issue 6, pp. EL475-EL480 (2012); (6 pages)

Online Publication Date: 17 May 2012

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The band structure of a two-dimensional granular crystal composed of silicone rubber and polytetrafluoroethylene (PTFE) cylinders is investigated numerically. This system was previously shown to undergo a pattern transformation with uniaxial compression by Göncü et al. [Soft Matter 7, 2321 (2011)]. The dispersion relations of the crystal are computed at different levels of deformation to demonstrate the tunability of the band structure, which is strongly affected by the pattern transformation that induces new band gaps. Replacement of PTFE particles with rubber ones reveals that the change of the band structure is essentially governed by pattern transformation rather than particles’ mechanical properties.
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43.20.El Reflection, refraction, diffraction of acoustic waves
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A parametric study of error in the parabolic approximation of focused axisymmetric ultrasound beams

Joshua E. Soneson

J. Acoust. Soc. Am. Volume 131, Issue 6, pp. EL481-EL486 (2012); (6 pages)

Online Publication Date: 24 May 2012

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The parabolic approximation results in a tractible model for studying ultrasound beams, but the limits of validity of the approximation are often presented only qualitatively. In this work the most common model for axisymmetric ultrasound beam propagation, the Kuznetsov–Zabolotskaya–Khokhlov equation, is directly compared with the more general Westervelt equation with regard to diffractive and absorptive effects in continuous wave beams. The parametric study compares the solutions of the two models as a function of source frequency and focusing geometry using peak focal pressure, the axial location at which that peak occurs, and the loss due to absorption as metrics.
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43.80.Sh Medical use of ultrasonics for tissue modification (permanent and temporary)
43.35.Bf Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in liquids, liquid crystals, suspensions, and emulsions
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Modified locus equations categorize stop place in a perceptually realistic time frame

Ariane E. Rhone and Allard Jongman

J. Acoust. Soc. Am. Volume 131, Issue 6, pp. EL487-EL491 (2012); (5 pages)

Online Publication Date: 25 May 2012

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Slope and y-intercepts of locus equations have previously been shown to successfully classify place of articulation for English voiced stop consonants when derived from measurements at vowel onset and vowel midpoint. However, listeners are capable of identifying English voiced stops when less than 30 ms of vowel is presented. The present results show that modified locus equation measurements made within the first several pitch periods of a vowel following an English voiced stop were also successful at classifying place of articulation, consistent with the amount of vocalic information necessary for perceptual identification of English voiced stops /b d g/.
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43.70.Fq Acoustical correlates of phonetic segments and suprasegmental properties: stress, timing, and intonation
43.70.Mn Relations between speech production and perception
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Piecewise coherent mode processing of acoustic data recorded on two horizontally separated vertical line arrays

Ilya A. Udovydchenkov, Michael G. Brown, and Timothy F. Duda

J. Acoust. Soc. Am. Volume 131, Issue 6, pp. EL492-EL498 (2012); (7 pages)

Online Publication Date: 25 May 2012

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Abstract: Motivated by measurements made in the 2004 Long-Range Ocean Acoustic Propagation Experiment (LOAPEX), the problem of mode processing transient acoustic signals collected on two nearby vertical line arrays is considered. The first three moments (centroid, variance, and skewness) of broadband distributions of acoustic energy with fixed mode number (referred to as modal group arrivals) are estimated. It is shown that despite the absence of signal coherence between the two arrays and poor high mode number energy resolution, the centroid and variance of these distributions can be estimated with tolerable errors using piecewise coherent mode processing as described in this paper.
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43.30.Bp Normal mode propagation of sound in water
43.60.Ac Theory of acoustic signal processing
43.60.Fg Acoustic array systems and processing, beam-forming
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Temporal offset judgments for concurrent vowels by young, middle-aged, and older adults

Daniel Fogerty, Diane Kewley-Port, and Larry E. Humes

J. Acoust. Soc. Am. Volume 131, Issue 6, pp. EL499-EL505 (2012); (7 pages)

Online Publication Date: 25 May 2012

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Temporal processing declines with age may reduce the processing of concurrent vowels. For this study, listeners categorized vowel pairs varying in temporal asynchrony as one sound, two overlapping sounds, or two sounds separated by a gap. Two boundaries separating the three response categories, multiplicity and gap-identification, were measured. Compared to young and middle-aged listeners, older listeners required longer temporal offsets for multiplicity. Middle-aged and older listeners also required longer offsets for gap-identification. For older listeners, correlations with various temporal processing tasks indicated that vowel temporal-order thresholds were related to multiplicity, while age and non-speech gap-detection thresholds were related to gap-identification.
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43.71.Rt Sensory mechanisms in speech perception
43.71.Es Vowel and consonant perception; perception of words, sentences, and fluent speech
43.66.Sr Deafness, audiometry, aging effects
43.71.An Models and theories of speech perception
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Resonance frequencies of a spherical aluminum shell subject to static internal pressure

Andrew A. Piacsek, Sami Abdul-Wahid, and Robert Taylor

J. Acoust. Soc. Am. Volume 131, Issue 6, pp. EL506-EL512 (2012); (7 pages)

Online Publication Date: 29 May 2012

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Measurements of the vibrational response of a spherical aluminum shell subject to changes in the interior pressure clearly demonstrate that resonance frequencies shift higher as the pressure is increased. The frequency shift appears to be smaller for longitudinal modes than for bending wave modes. The magnitude of frequency shift is comparable to analytical predictions made for thin cylindrical shells. Changes in the amplitudes of resonance peaks are also observed. A possible application of this result is a method for noninvasively monitoring pressure changes inside sealed containers, including intracranial pressure in humans.
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43.40.Ey Vibrations of shells
43.25.Gf Standing waves; resonance
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Acoustic scattering from a finite plate: Generation of guided Lamb waves S0, A0 and A

N. Cité, F. Chati, D. Décultot, F. Léon, and G. Maze

J. Acoust. Soc. Am. Volume 131, Issue 6, pp. 4233-4242 (2012); (10 pages)

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In the domain of renewable energies, marine current turbines constitute one of the possibilities of producing electrical energy. Naked-eye inspection, or with the aid of video monitoring systems of these machines to ensure their perfect working order, can be difficult in a turbid environment. Acoustic methods are conceivable. The study focuses on the blades of these machines, by considering rectangular plates. The propagation of Lamb waves in a plate is studied by analyzing experimental time signals obtained from acoustic scattering. These signals are analyzed employing the ray theory. In vacuum, the flexural wave is the A0 Lamb wave, whilst in water this wave splits in a bifurcation: the A wave with a phase velocity always smaller than the sound speed in water, and the A0 wave with a phase velocity always higher than the sound speed in water. In the central bandpass of the transducers used in the experiments, mainly the A and S0 waves exist. However, signals observed in the third harmonic bandpass of the transducers are also analyzed. In order to complement these results, resonance frequencies of the plate studied are calculated taking into account the boundary conditions and compared with the resonance frequencies of the experimental spectra.
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43.20.El Reflection, refraction, diffraction of acoustic waves
43.20.Fn Scattering of acoustic waves
43.20.Ks Standing waves, resonance, normal modes
43.40.Fz Acoustic scattering by elastic structures

Scattering measurements from a dissolving bubble

George Kapodistrias and Peter H. Dahl

J. Acoust. Soc. Am. Volume 131, Issue 6, pp. 4243-4251 (2012); (9 pages)

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A laboratory-scale study on acoustic scattering from a single bubble undergoing dissolution in undersaturated fresh water is presented. Several experiments are performed with the acoustic source driven with five-cycle tone bursts, center frequency of 120 kHz, to insonify a single bubble located on axis of the combined beam of the set of transducers. The bubble is placed on a fine nylon thread located in the far field of the transducer set, arranged in bistatic configuration, in a tank filled with undersaturated water. Backscattered waveforms from the bubble target are acquired every few seconds for several hours until the bubble has completely dissolved, and detailed dissolution curves are produced from the acoustic data. The rate of bubble dissolution is calculated using the solution developed by Epstein and Plesset [J. Chem. Phys. 18, 1505–1509 (1950)]. The results of the experiments performed are in agreement with the calculations.
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43.20.Fn Scattering of acoustic waves
43.20.Ye Measurement methods and instrumentation
43.35.Ei Acoustic cavitation in liquids

Acoustic fields in binary gas mixtures: Mutual diffusion effects throughout and beyond the boundary layers

Cécile Guianvarc’h and Michel Bruneau

J. Acoust. Soc. Am. Volume 131, Issue 6, pp. 4252-4262 (2012); (11 pages)

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The acoustic behavior in thermo-viscous gas mixtures, both in proximity of walls and far from them (outside the boundary layers), involves deviations from the adiabatic and laminar movements in pure gases, which result from the influence of several diffusive fields, namely, shear, entropic, and concentration variation fields (their energy being provided by the acoustic field itself). Owing to the boundary conditions, that are slip condition, isothermal condition and concentration flux vanishing on the walls, a strong coupling between these fields occurs inside the boundary layers while their effects appear to be simple additive processes in the bulk of the medium. Although recent literature on this subject leads to interesting results, opening the way to several new issues [R. Raspet et al., J. Acoust. Soc. Am. 105, 65–73 (1999); R. Raspet et al., J. Acoust. Soc. Am. 112, 1414–1422 (2002); G. W. Swift and P. S. Spoor, J. Acoust. Soc. Am. 106, 1794–1800 (1999); D. A. Geller and G. W. Swift, J. Acoust. Soc. Am. 111, 1675–1684 (2002)], the results available still have limitations because they do not provide complete solutions for the propagative and diffusive fields throughout and beyond the boundary layers. The present work aims at providing these solutions in the whole domains considered. The results allow interpreting analytically the behavior of the fields above mentioned in closed cavities and ducts, and particularly in spherical cavities which are best suited to develop metrological applications.
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43.20.Hq Velocity and attenuation of acoustic waves
43.20.Bi Mathematical theory of wave propagation
43.20.Ks Standing waves, resonance, normal modes
43.20.Mv Waveguides, wave propagation in tubes and ducts

Dispersion properties of helical waves in radially inhomogeneous elastic media

D. E. Syresin, T. V. Zharnikov, and V. V. Tyutekin

J. Acoust. Soc. Am. Volume 131, Issue 6, pp. 4263-4271 (2012); (9 pages)

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In this paper, a method describing dispersion curve calculation for waves propagating in radially layered, inhomogeneous isotropic elastic waveguides is developed. Particular emphasis is placed on the helical waves with noninteger azimuthal wavenumbers, which can be potentially applied in such fields as nondestructive evaluation, acoustic tomography, etc., stipulating their practical importance. To solve the problem under consideration, the matrix Riccati equation is formulated for an impedance matrix. The use of the latter yields a simple form of the dispersion equation. Numerical computation of dispersion curves can encounter difficulties, which are due to potential singularities of the impedance matrix and the necessity to separate roots of the dispersion equation. These difficulties are overcome by employing the Cayley transform and invoking the parametric continuation method. The method developed by the authors is demonstrated by calculating dispersion diagrams in support of helical waves for several models of practical interest. Such computations for an inhomogeneous layer and its approximation by a set of homogeneous layers using a transfer matrix and Riccati equation methods revealed higher computational accuracy of the latter. Dispersion curves calculated for layers with different types of inhomogeneity demonstrated significant discrepancies at low frequencies.
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43.20.Mv Waveguides, wave propagation in tubes and ducts
43.20.Jr Velocity and attenuation of elastic and poroelastic waves
43.35.Cg Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in solids; elastic constants

Asymptotic expansions for the coupled wavenumbers in an infinite orthotropic flexible fluid-filled cylindrical shell

M. V. Kunte, Abhijit Sarkar, and Venkata R. Sonti

J. Acoust. Soc. Am. Volume 131, Issue 6, pp. 4272-4282 (2012); (11 pages) | Cited 1 time

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Analytical expressions are found for the coupled wavenumbers in flexible, fluid-filled, circular cylindrical orthotropic shells using the asymptotic methods. These expressions are valid for arbitrary circumferential orders. The Donnell–Mushtari shell theory is used to model the shell and the effect of the fluid is introduced through the fluid-loading parameter μ. The orthotropic problem is posed as a perturbation on the corresponding isotropic problem by defining a suitable orthotropy parameter ε, which is a measure of the degree of orthotropy. For the first study, an isotropic shell is considered (by setting ε = 0) and expansions are found for the coupled wavenumbers using a regular perturbation approach. In the second study, asymptotic expansions are found for the coupled wavenumbers in the limit of small orthotropy (ε≪1). For each study, isotropy and orthotropy, expansions are found for small and large values of the fluid-loading parameter μ. All the asymptotic solutions are compared with numerical solutions to the coupled dispersion relation and the match is seen to be good. The differences between the isotropic and orthotropic solutions are discussed. The main contribution of this work lies in extending the existing literature beyond in vacuo studies to the case of fluid-filled shells (isotropic and orthotropic).
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43.20.Mv Waveguides, wave propagation in tubes and ducts
43.40.Ey Vibrations of shells
43.20.Tb Interaction of vibrating structures with surrounding medium

Quantitative estimation of ultrasound beam intensities using infrared thermography—Experimental validation

Dushyanth Giridhar, Ronald A. Robinson, Yunbo Liu, Jack Sliwa, Vesna Zderic, and Matthew R. Myers

J. Acoust. Soc. Am. Volume 131, Issue 6, pp. 4283-4291 (2012); (9 pages)

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Infrared (IR) thermography is a technique that has the potential to rapidly and noninvasively determine the intensity fields of ultrasound transducers. In the work described here, IR temperature measurements were made in a tissue phantom sonicated with a high-intensity focused ultrasound (HIFU) transducer, and the intensity fields were determined using a previously published mathematical formulation relating intensity to temperature rise at a tissue/air interface. Intensity fields determined from the IR technique were compared with those derived from hydrophone measurements. Focal intensities and beam widths determined via the IR approach agreed with values derived from hydrophone measurements to within a relative difference of less than 10%, for a transducer with a gain of 30, and about 13% for a transducer with a gain of 60. At axial locations roughly 1 cm in front (pre-focal) and behind (post-focal) the focus, the agreement with hydrophones for the lower-gain transducer remained comparable to that in the focal plane. For the higher-gain transducer, the agreement with hydrophones at the pre-focal and post-focal locations was around 40%.
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43.20.Ye Measurement methods and instrumentation
43.80.Vj Acoustical medical instrumentation and measurement techniques
43.80.Ev Acoustical measurement methods in biological systems and media
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Linear and nonlinear Biot waves in a noncohesive granular medium slab: Transfer function, self-action, second harmonic generation

J-B. Legland, V. Tournat, O. Dazel, A. Novak, and V. Gusev

J. Acoust. Soc. Am. Volume 131, Issue 6, pp. 4292-4303 (2012); (12 pages)

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Experimental results are reported on second harmonic generation and self-action in a noncohesive granular medium supporting wave energy propagation both in the solid frame and in the saturating fluid. The acoustic transfer function of the probed granular slab can be separated into two main frequency regions: a low frequency region where the wave propagation is controlled by the solid skeleton elastic properties, and a higher frequency region where the behavior is dominantly due to the air saturating the beads. Experimental results agree well with a recently developed nonlinear Biot wave model applied to granular media. The linear transfer function, second harmonic generation, and self-action effect are studied as a function of bead diameter, compaction step, excitation amplitude, and frequency. This parametric study allows one to isolate different propagation regimes involving a range of described and interpreted linear and nonlinear processes that are encountered in granular media experiments. In particular, a theoretical interpretation is proposed for the observed strong self-action effect.
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43.25.Dc Nonlinear acoustics of solids
43.20.Gp Reflection, refraction, diffraction, interference, and scattering of elastic and poroelastic waves
43.25.Ed Effect of nonlinearity on velocity and attenuation
43.25.Zx Measurement methods and instrumentation for nonlinear acoustics

Nonequilibrium phenomena in damaged media and their effects on the elastic properties

M. Scalerandi, A. S. Gliozzi, C. L. E. Bruno, and P. Antonaci

J. Acoust. Soc. Am. Volume 131, Issue 6, pp. 4304-4315 (2012); (12 pages) | Cited 1 time

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Concrete, particularly if damaged, exhibits a peculiar nonlinear elastic behavior, which is mainly due to the coupling between nonequilibrium and nonlinear features, the two of which are intrinsically connected. More specifically, the formulation of a constitutive equation able to properly predict the dynamic behavior of damaged concrete is made difficult by the concomitant presence of two mechanisms: The modification of the microstructure of the medium and the transition to a new elastic state caused by a finite amplitude excitation (conditioning). Memory of that new state is kept when the excitation is removed, before relaxation back to the original elastic state takes place. Indeed, besides accounting for linear and nonlinear parameters, a realistic constitutive equation to be used in reliable prediction models should take into account nonequilibrium effects. Specific parameters, sensitive to finite amplitude excitations, should be introduced to provide information about conditioning effects. In this paper, experimental results indicating that nonlinearity of damaged concrete is memory-dependent will be presented and the implications of such findings in the development of physical models, with relevant outcomes for the characterization of hysteretical features, will be discussed.
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43.25.Ed Effect of nonlinearity on velocity and attenuation
43.25.Dc Nonlinear acoustics of solids
43.25.Zx Measurement methods and instrumentation for nonlinear acoustics
43.35.Yb Ultrasonic instrumentation and measurement techniques

Nonlinear elastic imaging using reciprocal time reversal and third order symmetry analysis

Francesco Ciampa and Michele Meo

J. Acoust. Soc. Am. Volume 131, Issue 6, pp. 4316-4323 (2012); (8 pages) | Cited 1 time

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This paper presents a nonlinear imaging method for the detection of the nonlinear signature due to impact damage in complex anisotropic solids with diffuse field conditions. The proposed technique, based on a combination of an inverse filtering approach with phase symmetry analysis and frequency modulated excitation signals, is applied to a number of waveforms containing the nonlinear impulse responses of the medium. Phase symmetry analysis was used to characterize the third order nonlinearity of the structure by exploiting its invariant properties with the phase angle of the input waveforms. Then, a “virtual” reciprocal time reversal imaging process, using only one broadcasting transducer and one receiving transducer, was used to insonify the defect taking advantage of multiple linear scattering as mode conversion and boundary reflections. The robustness of this technique was experimentally demonstrated on a damaged sandwich panel, and the nonlinear source, induced by low-velocity impact loading, was retrieved with a high level of accuracy. Its minimal processing requirements make this method a valid alternative to the traditional nonlinear elastic wave spectroscopy techniques for materials showing either classical or non-classical nonlinear behavior.
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43.25.Ed Effect of nonlinearity on velocity and attenuation
43.40.Fz Acoustic scattering by elastic structures
43.40.Le Techniques for nondestructive evaluation and monitoring, acoustic emission

Modeling nonlinear ultrasound propagation in heterogeneous media with power law absorption using a k-space pseudospectral method

Bradley E. Treeby, Jiri Jaros, Alistair P. Rendell, and B. T. Cox

J. Acoust. Soc. Am. Volume 131, Issue 6, pp. 4324-4336 (2012); (13 pages) | Cited 3 times

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The simulation of nonlinear ultrasound propagation through tissue realistic media has a wide range of practical applications. However, this is a computationally difficult problem due to the large size of the computational domain compared to the acoustic wavelength. Here, the k-space pseudospectral method is used to reduce the number of grid points required per wavelength for accurate simulations. The model is based on coupled first-order acoustic equations valid for nonlinear wave propagation in heterogeneous media with power law absorption. These are derived from the equations of fluid mechanics and include a pressure-density relation that incorporates the effects of nonlinearity, power law absorption, and medium heterogeneities. The additional terms accounting for convective nonlinearity and power law absorption are expressed as spatial gradients making them efficient to numerically encode. The governing equations are then discretized using a k-space pseudospectral technique in which the spatial gradients are computed using the Fourier-collocation method. This increases the accuracy of the gradient calculation and thus relaxes the requirement for dense computational grids compared to conventional finite difference methods. The accuracy and utility of the developed model is demonstrated via several numerical experiments, including the 3D simulation of the beam pattern from a clinical ultrasound probe.
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43.25.Jh Reflection, refraction, interference, scattering, and diffraction of intense sound waves
43.20.Bi Mathematical theory of wave propagation
43.35.Bf Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in liquids, liquid crystals, suspensions, and emulsions
43.25.Cb Macrosonic propagation, finite amplitude sound; shock waves

Acoustic radiation force of a Bessel beam on a porous sphere

Mahdi Azarpeyvand

J. Acoust. Soc. Am. Volume 131, Issue 6, pp. 4337-4348 (2012); (12 pages) | Cited 1 time

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The possibility of using acoustic Bessel beams to produce an axial pulling force on porous particles is examined in an exact manner. The mathematical model utilizes the appropriate partial-wave expansion method in spherical coordinates, while Biot’s model is used to describe the wave motion within the poroelastic medium. Of particular interest here is to examine the feasibility of using Bessel beams for (a) acoustic manipulation of fine porous particles and (b) suppression of particle resonances. To verify the viability of the technique, the radiation force and scattering form-function are calculated for aluminum and silica foams at various porosities. Inspection of the results has shown that acoustic manipulation of low porosity (<0.3) spheres is similar to that of solid elastic spheres, but this behavior significantly changes at higher porosities. Results have also shown a strong correlation between the backscattered form-function and the regions of negative radiation force. It has also been observed that the high-order resonances of the particle can be effectively suppressed by choosing the beam conical angle such that the acoustic contribution from that particular mode vanishes. This investigation may be helpful in the development of acoustic tweezers for manipulation of micro-porous drug delivery carrier and contrast agents.
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43.25.Qp Radiation pressure
43.20.Gp Reflection, refraction, diffraction, interference, and scattering of elastic and poroelastic waves
43.40.Fz Acoustic scattering by elastic structures
43.25.Uv Acoustic levitation
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