Volume 132, Issue 1, July 2012
- jasa express letters
- letters to the editor
- general linear acoustics 
- nonlinear acoustics 
- underwater sound 
- ultrasonics, quantum acoustics, and physical effects of sound 
- structural acoustics and vibration 
- noise: its effects and control 
- architectural acoustics 
- acoustical measurements and instrumentation 
- acoustic signal processing 
- psychological acoustics 
- speech production 
- speech processing and communication systems 
- music and musical instruments 
- bioacoustics 
- acoustical news
- acoustical standards news
- book reviews
- reviews of acoustical patents
Index of content:
- JASA EXPRESS LETTERS
132(2012); http://dx.doi.org/10.1121/1.4721646View Description Hide Description
Axisymmetric monopole resonances of an oblate spheroidal cavity in a soft elastic medium are computed using both separation of variables and finite-element approaches. The resonances are obtained for compression wavelengths much longer than the cavity size and thus have a low-frequency character. Resonant frequencies for high-aspect-ratio oblate spheroids (either air-filled or evacuated) are found to be significantly lower than their spherical counterparts with equivalent volume. This finding contrasts with the case of an air bubble in water which features weak shape dependence. The results are relevant to the design of locally-resonant acoustic media using soft-lithography techniques with elastomers.
How the cross-sectional discontinuity between ear canal and probe affects the ear canal length estimationa)132(2012); http://dx.doi.org/10.1121/1.4723565View Description Hide Description
Many ear canal probes both deliver and measure sound via narrow tubes. This study investigates the effect of the cross-sectional discontinuity at the interface between ear canal models and the connecting tubes of a commercially available otoacoustic emission probe on the “acoustically” estimated cavity lengths. Rigid cavities having the same length but different diameters were produced, and modeled by the finite element method. Cavities with a diameter larger than 8 mm had acoustic lengths that considerably overestimated the real geometry. A length correction was derived, which, in most applications, compensates for the measurement errors emerging from the discontinuity effects.
132(2012); http://dx.doi.org/10.1121/1.4726195View Description Hide Description
As a complement to experimental efforts in seismics and acoustics to infer geo-acoustic properties of the propagation environment from the second order statistics of ambient noise measurements, a set of exact, explicit, closed form expressions for the cross-spectral density and spatialcoherence of diffuse random wave fields is presented. Taken together, the expressions are well suited for modeling broadband, diffuse wavecoherence in realistic scenarios involving directive, ambient noise from local (i.e., volume) and distant (i.e., plane wave) source features in an open, dispersive, attenuating medium.
132(2012); http://dx.doi.org/10.1121/1.4728193View Description Hide Description
Two experimentsmeasured human sensitivity to temporal jitter in 25-click trains with inter-click intervals (ICIs) between 5 and 100 ms. In a naturalistic experiment using wideband clicks, jitter thresholds were a nonmonotonic function of ICI, peaking for ICIs near 40–60 ms. In a subsequent experiment, clicks were high-passed and presented against a low-frequency noise masker. Jitter threshold vs ICI functions lost the positive slope over short ICIs but retained the negative slope at long ICIs. The same behavior was seen in click rate discrimination tasks. Different processes mediate regularity analysis for click trains with ICIs above and below 40–60 ms.
132(2012); http://dx.doi.org/10.1121/1.4722171View Description Hide Description
This letter presents a single-channel speech dereverberation approach using a non-causal minimum variance distortionless response (MVDR) filter. The non-causal filter is adopted to utilize the additional information of the desired signal that lies in subsequent frames. Note that the desired signal output has minimal distortion due to the introduction of the MVDR criterion. The proposed system further suppresses the late reverberation by employing a statistical reverberant model. Experimental results demonstrate the superiority of the proposed algorithm to conventional approaches.
Vibro-acoustic response of an infinite, rib-stiffened, thick-plate assembly using finite-element analysis132(2012); http://dx.doi.org/10.1121/1.4730029View Description Hide Description
The vibration of and sound radiation from an infinite, fluid-loaded, thick-plate assembly stiffened periodically with ribs are investigated numerically using finite-element analysis. First, numerical simulations are compared to the analytical solutions presented recently for this particular problem [Hull and Welch, J. Sound Vib. 329, 4192–4211 (2010)]. It is shown that the solutions reported in this reference are partially incorrect because the number of modes was not chosen correctly. Subsequently, the numerical model is used to study the effect of repeated and equally spaced void inclusions on the vibro-acoustic response of the system.
Stress-dependent changes in the diffuse ultrasonic backscatter coefficient in steel: Experimental results132(2012); http://dx.doi.org/10.1121/1.4729600View Description Hide Description
In this article, the effects of uniaxial compressive loading on the ultrasonic scattering from polycrystalline grains are shown for 10 MHz ultrasound in annealed, 1018 steel. The results show a decreasing value of the stress-dependent backscatter coefficient for normal incident ultrasound when the compression loading is perpendicular to the scattering direction. The change due to scattering is about 2 orders of magnitude greater than changes observed by others using ultrasonic wavespeed measurements. It is anticipated that this research can serve as the basis for many methods associated with nondestructive determination of stress in structural materials.
132(2012); http://dx.doi.org/10.1121/1.4730038View Description Hide Description
In December 2011 a long-range acoustic communication experiment was conducted in deep water, west of Izu-Ogasawara Islands, Japan. The experiment involved a stationary source (450–550 Hz) and an 18-element vertical array (102-m aperture), both deployed at around the sound channel axis. Initial analysis of data demonstrates that a data rate of 400 bits/s can be achieved over ∼600-km range in deep water using 16 quadrature amplitude modulation and passive time reversal equalization.
Comparative investigation of elastic properties in a trabecula using micro-Brillouin scattering and scanning acoustic microscopy132(2012); http://dx.doi.org/10.1121/1.4730329View Description Hide Description
Micro-Brillouin scattering (μ-BR) and a 200 MHz scanning acoustic microscope (SAM) with similar spatial resolutions were applied to evaluate tissue elastic properties in two directions in a trabecula. Acoustic impedancemeasured by SAM was in the range of 5–9 Mrayl. Wavevelocities determined by μ-BR were in the range of (4.75–5.11) × 103 m/s. Both exhibited a similar trend of variation across the trabecula and were significantly correlated (R 2 = 0.63–0.67, p < 0.01). μ-BR is useful for the evaluation of tissue stiffness within a trabecula. Combined with SAM or nanoindentation, it can provide additional information to assess elastic anisotropy at the micro-scale.
- LETTERS TO THE EDITOR
Detection of simultaneous modulation of interaural time and level differences: Effects of modulation rate and relative phase (L)a)132(2012); http://dx.doi.org/10.1121/1.4728199View Description Hide Description
The binaural system is known to be sluggish, i.e., unable to track modulations in interaural parameters even at a relatively slow rate. The present study evaluated the binaural system’s sensitivity to modulation phase rather than to modulation magnitude. The detectability of simultaneous modulations in interaural time and level differences with various relative phases were measured. It was found that for modulation rates up to 10–20 Hz, the detectability varied with the relative phase. This indicates that information about higher rates is lost at or below the level of cue integration.
132(2012); http://dx.doi.org/10.1121/1.4726029View Description Hide Description
An asynchronous multiuser system is proposed to support multiple-access underwater communications without the use of code-division multiple-access or a feedback channel. The rich multipath channels experienced by spatially separated users will be sufficient to ensure separation of collided packets at the base station. The iterative receiver will employ a combination of adaptive time-reversal processing, matching pursuit, and successive interference cancellation in a block-wise fashion to achieve multiuser separability. Data collected during the KAM11 experiment are used to illustrate the system’s capability in a dynamic, time-varying environment.
- GENERAL LINEAR ACOUSTICS 
132(2012); http://dx.doi.org/10.1121/1.4726052View Description Hide Description
Animals live in cluttered auditory environments, where sounds arrive at the two ears through several paths. Reflections make sound localization difficult, and it is thought that the auditory system deals with this issue by isolating the first wavefront and suppressing later signals. However, in many situations, reflections arrive too early to be suppressed, for example, reflections from the ground in small animals. This paper examines the implications of these early reflections on binaural cues to sound localization, using realistic models of reflecting surfaces and a spherical model of diffraction by the head. The fusion of direct and reflected signals at each ear results in interference patterns in binaural cues as a function of frequency. These cues are maximally modified at frequencies related to the delay between direct and reflected signals, and therefore to the spatial location of the sound source. Thus, natural binaural cues differ from anechoic cues. In particular, the range of interaural time differences is substantially larger than in anechoic environments. Reflections may potentially contribute binaural cues to distance and polar angle when the properties of the reflecting surface are known and stable, for example, for reflections on the ground.
- NONLINEAR ACOUSTICS 
Amplitude-dependent internal friction, hysteretic nonlinearity, and nonlinear oscillations in a magnesite resonator132(2012); http://dx.doi.org/10.1121/1.4728167View Description Hide Description
The results of experimental and theoretical studies of low-frequency nonlinear acoustics phenomena (amplitude-dependent loss, resonance frequency shifts, and a generation of second and third harmonics) in a magnesite rod resonator are presented. Acceleration and velocity oscillograms of vibrations of the free boundary of the resonator caused by harmonic excitations were measured and analyzed. A theoretical description of the observed amplitude dependences was carried out within the framework of the phenomenological state equations that contain either of the two types of hysteretic nonlinearity (elastic and inelastic). The type of hysteresis and parameters of acoustic nonlinearity of magnesite were established from comparing the experimental measurements with the theoretical dependences. The values of the parameters were anomalously high even when compared to those of other strongly nonlinear polycrystalline materials such as granite, marble, limestone, sandstone, etc.
132(2012); http://dx.doi.org/10.1121/1.4726009View Description Hide Description
The transport of bubbles to a neighboring surface is very important in surface chemistry, bioengineering, and ultrasonic cleaning, etc. This paper proposes a multi-bubble transport method by using an acoustic standing wave field and establishes a model that explains the multi-bubble translation by expressing the balance between Bjerknes forces and hydrodynamic forces on a bubble in a liquid medium. Results indicated that the influence of primary Bjerknes force, secondary Bjerknes force, and buoyancy force on the bubble translation depends on the position of the target bubble in the acoustic field. Moreover, it was found that increasing the size of a bubble or pressure amplitude can accelerate the bubble motion and enhance the bubble-bubble interaction. The secondary Bjerknes force between two bubbles can switch from an attractive one when they oscillate in phase to a repulsive one when the bubble oscillations are out of phase. These findings provide an insight into the multi-bubble translation near a surface and can be applied to future bubble motion control studies, especially in drug delivery, sonoporation, and ultrasonic cleaning.
- UNDERWATER SOUND 
132(2012); http://dx.doi.org/10.1121/1.4726075View Description Hide Description
Weston’s ray invariant or “characteristic time” in a range-dependent environment is exactly equivalent to the Wentzel–Kramers–Brillouin phase integral for ducted normal modes. By considering a ray element it is shown that the ray invariant can also be written in terms of ray cycle distance and cycle time. This leads to a useful formula for group velocity in terms of cycle distance and mode number. Drawing a distinction between the ray and wave interpretation, the Airy phase (i.e., the existence of a group velocity minimum) can be included in this approach. Favorable comparisons are made with group velocities derived from a normal modemodel. The relationship is valid for variable sound speed and variable bathymetry, and this is demonstrated numerically. The formula is applicable to active sonar, multipath pulse shape, target signatures, reverberation, tomography, and underwater communications.
132(2012); http://dx.doi.org/10.1121/1.4728227View Description Hide Description
The change-of-variables theorem of probability theory is applied to compute acoustic field and array beam power probability density functions (pdfs) in uncertain ocean environments represented by stratified, attenuating ocean waveguide models. Computational studies for one and two-layer waveguides investigate the functional properties of the acoustic field and array beam power pdfs. For the studies, the acoustic parameter uncertainties are represented by parametric pdfs. The field and beam response pdfs are computed directly from the parameter pdfs using the normal-mode representation and the change-of-variables theorem. For two-dimensional acoustic parameter uncertainties of sound speed and attenuation, the field and beam power pdfs exhibit irregular functional behavior and singularities associated with stationary points of the mapping, defined by acoustic propagation, from the parameter space to the field or beam power space. Implications for the assessment of orthogonal polynomial expansion and other methods for computing acoustic field pdfs are discussed.
132(2012); http://dx.doi.org/10.1121/1.4728198View Description Hide Description
Rubber layers with air-filled cavities or local resonance scatters can be used as anechoic coatings. A lot of researches have focused on the absorption mechanism of the anechoic coatings. As the anechoic coatings are bonded to the hull of submarine, the vibration of the hull should not be neglected when the analysis of the absorption characters is carried out. Therefore, it is more reasonable to treat the anechoic coating and the backing as a whole when the acoustic performance is analyzed. Considering the effects of the steel plate backing, the sound absorption performances on different models of anechoic coatings are investigated in this paper. The Finite Element Method is used to illustrate the vibrational behaviors of the anechoic coatings under the steel backings by which the displacement contours is obtained for analysis. The theoretical results show that an absorption peak is induced by the resonance of the steel slab and rubber layer. At the frequency of this absorption peak, the steel plate and the coating vibrates longitudinally like a mass-spring system in which the steel slab serves for mass and the coating layer is the spring. To illuminate the effects of the steel slab backing on the acoustic absorption, the thicknesses of the steel slab and the anechoic layer are discussed. Finally, an experiment is performed and the results show a good agreement with the theoretical analysis.
Shipping noise in whale habitat: Characteristics, sources, budget, and impact on belugas in Saguenay–St. Lawrence Marine Park hub132(2012); http://dx.doi.org/10.1121/1.4728190View Description Hide Description
A continuous car ferry line crossing the Saguenay Fjord mouth and traffic from the local whale-watching fleet introduce high levels of shipping noise in the heart of the Saguenay–St. Lawrence Marine Park. To characterize this noise and examine its potential impact on belugas, a 4-hydrophone array was deployed in the area and continuously recorded for five weeks in May–June 2009. The source levels of the different vessel types showed little dependence on vessel size or speed increase. Their spectral range covered 33 dB. Lowest noise levels occurred at night, when ferry crossing pace was reduced, and daytime noise peaked during whale-watching tour departures and arrivals. Natural ambient noise prevailed 9.4% of the time. Ferry traffic added 30–35 dB to ambient levels above 1 kHz during crossings, which contributed 8 to 14 dB to hourly averages. The whale-watching fleet added up to 5.6 dB during peak hours. Assuming no behavioral or auditory compensation, half of the time, beluga potential communication range was reduced to less than ∼30% of its expected value under natural noise conditions, and to less than ∼15% for one quarter of the time, with little dependence on call frequency. The echolocation band for this population of belugas was also affected by the shipping noise.
132(2012); http://dx.doi.org/10.1121/1.4728224View Description Hide Description
Source localization by matched-field processing (MFP) generally involves solving a number of computationally intensive partial differential equations. This paper introduces a technique that mitigates this computational workload by “compressing” these computations. Drawing on key concepts from the recently developed field of compressed sensing, it shows how a low-dimensional proxy for the Green’s function can be constructed by backpropagating a small set of random receiver vectors. Then the source can be located by performing a number of “short” correlations between this proxy and the projection of the recorded acoustic data in the compressed space. Numerical experiments in a Pekeris ocean waveguide are presented that demonstrate that this compressed version of MFP is as effective as traditional MFP even when the compression is significant. The results are particularly promising in the broadband regime where using as few as two random backpropagations per frequency performs almost as well as the traditional broadband MFP but with the added benefit of generic applicability. That is, the computationally intensive backpropagations may be computed offline independently from the received signals, and may be reused to locate any source within the search grid area.
132(2012); http://dx.doi.org/10.1121/1.4725764View Description Hide Description
The interaction between fluid loaded fiber-optic cantilevers and a low frequency acoustic wave is investigated as the basis for an acoustic vector sensor. The displacements of the prototype cantilevers are measured with an integrated fiber laser strain sensor. A theoretical model predicting the frequency dependent shape of acoustically driven planar and cylindrical fiber-optic cantilevers incorporating effects of fluid viscosity is presented. The model demonstrates good agreement with the measured response of two prototype cantilevers, characterized with a vibrating water column, in the regime of Re ≥ 1. The performance of each cantilever geometry is also analyzed. Factors affecting the sensor performance such as fluid viscosity,laser mode profile, and support motion are considered. The planar cantilever is shown to experience the largest acoustically induced force and hence the highest acoustic responsivity. However, the cylindrical cantilever exhibits the smoothest response in water, due to the influence of viscous fluid damping, and is capable of two axis particle velocity measurement. These cantilevers are shown to be capable of achieving acoustic resolutions approaching the lowest sea-state ocean noise.