Volume 128, Issue 4, October 2010
- jasa express letters
- letters to the editor
- general linear acoustics 
- nonlinear acoustics 
- aeroacoustics, atmospheric sound 
- underwater sound 
- transduction 
- noise: its effects and control 
- architectural acoustics 
- acoustic signal processing 
- physiological acoustics 
- psychological acoustics 
- speech production 
- speech perception 
- speech processing and communication systems 
- music and musical instruments 
- bioacoustics 
- acoustical news
- book reviews
- reviews of acoustical patents
- second pan-american/iberian meeting on acoustics
- award encomiums
- second pan-american/iberian meeting on acoustics
Index of content:
- JASA EXPRESS LETTERS
Radiated signal characteristics of marine vessels in the cepstral domain for shallow underwater channel128(2010); http://dx.doi.org/10.1121/1.3484230View Description Hide Description
This work examines the distribution of cepstral energy of the radiated signal of a marine vessel and the underwater channel modeled as a block-adaptive linear system. Detailed simulation analysis of the signal at the receiver of a passive sonar has led to the observation that, in the cepstral domain the radiated signal of a marine vessel largely occupies the lower cepstral indices while the underwater channel occupies the higher indices, such that for several range and depth conditions, the two can be separated out. This finding can facilitate the design of filters in the cepstral domain for reducing distortions due to the underwater channel. The work presents analytical justification and simulation studies in this regard.
128(2010); http://dx.doi.org/10.1121/1.3484232View Description Hide Description
Unwanted sounds from a commercially available audiometer were evaluated in terms of their effects on extended high-frequency (EHF) audiometry. Although the manufacturer reported that the audiometer conformed to relevant International Electrotechnical Commission (IEC) standards, the audiograms obtained using the audiometer were erroneous because the subjects had responded falsely to noisegenerated with the test tone presentation before detecting the test tone. Analyses of acoustic and electric output signals revealed that the audiometergenerated most of the unwanted sounds, not the earphones that were used. Based on the measurement results, clinical implications of the measurement results are discussed for conducting more reliable EHF audiometry.
128(2010); http://dx.doi.org/10.1121/1.3484233View Description Hide Description
Three experiments on loudness of sounds with linearly increasing levels were performed: global loudness was measured using direct ratings, loudness change was measured using direct and indirect estimations. Results revealed differences between direct and indirect estimations of loudness change, indicating that the underlying perceptual phenomena are not the same. The effect of ramp size is small for the former and important for the latter. A similar trend was revealed between global loudness and direct estimations of loudness change according to the end level, suggesting they may have been confounded. Measures provided by direct estimations of loudness change are more participant-dependent.
Phonemic restoration in sensorineural hearing loss does not depend on baseline speech perception scores128(2010); http://dx.doi.org/10.1121/1.3475794View Description Hide Description
The brain can restore missing speech segments using linguistic knowledge and context. The phonemic restoration effect is commonly quantified by the increase in intelligibility of interrupted speech when the silent gaps are filled with noise bursts. In normal hearing, the restoration effect is negatively correlated with the baseline scores with interrupted speech; listeners with poorer baseline show more benefit from restoration. Reanalyzing data from Başkent et al. [(Year: 2010). Hear. Res.260, 54–62], correlations with mild and moderate hearing impairment were observed to differ than with normal hearing. This analysis further shows that hearing impairment may affect top-down restoration of speech.
128(2010); http://dx.doi.org/10.1121/1.3467491View Description Hide Description
Current acoustic techniques for studying cavitationdynamics are only readily applicable to single-bubble activity, while optical methods can only be used in transparent media. However, multi-bubble cavitation often occurs in opaque media such as biological tissue. Here, the signals received passively by each of the 64 channels of a diagnostic ultrasound array are used to localize and separate emissions from several bubble clusters cavitating in agar gel, thereby providing a method of observing cavitationdynamics. The method has a high spatiotemporal resolution and is applicable to cavitation in opaque media.
128(2010); http://dx.doi.org/10.1121/1.3479686View Description Hide Description
In 2008 the Louis S. St-Laurent (LSSL) surveyed deep Arctic waters using a three-airgun seismic source. Signals from the seismic survey were detected between 400 km and 1300 km range on a directional autonomous acoustic recorder deployed in water 53 m deep off the Alaskan North Slope. Observations of received signal levels between 10–450 Hz versus LSSL range roughly fit a cylindrical transmission loss model plus 0.01 dB/km attenuation in deep ice-free waters, and fit previous empirical models in ice-covered waters. The transition between ice-free and ice-covered propagation conditions shifted 200 km closer to the recorder during the survey.
128(2010); http://dx.doi.org/10.1121/1.3486198View Description Hide Description
Quasi-periodic bursts of acoustic oscillations were observed during the start-up process in a looped-tube thermoacoustic engine. The acoustic oscillations have a constant frequency of 111 Hz, while the bursts have “quasi-periods” in the order of 14–25 s. The quasi-periodic bursts show a new mode of amplitude growth in this thermoacoustic engine. The envelope of the acoustic oscillations has a fishbone-like shape. The nature of the observed fishbone-like instabilities suggests a strong interaction between the acoustic and temperature field.
128(2010); http://dx.doi.org/10.1121/1.3479976View Description Hide Description
A method of manipulating microparticles in a liquid using ultrasound is proposed and demonstrated. An ultrasonic standing wave with nodal planes whose positions are controllable by varying the relative phase of two applied sinusoidal signals is generated using a pair of acoustically matched piezoelectric transducers. The resulting acoustic radiation force is used to trap micron scale particles at a series of arbitrary positions (determined by the relative phase) and then move them in a controlled manner. This method is demonstrated experimentally and polystyrene particles are trapped and moved in one dimension through .
128(2010); http://dx.doi.org/10.1121/1.3486199View Description Hide Description
This study examined the effects of age and hearing loss on short-term adaptation to accented speech. Data from younger and older listeners in a prior investigation [Gordon-Salant et al. (2010). J. Acoust. Soc. Am.128, 444–455] were re-analyzed to examine changes in recognition over four administrations of equivalent lists of English stimuli recorded by native speakers of Spanish and English. Results showed improvement in recognition scores over four list administrations for the accented stimuli but not for the native English stimuli. Group effects emerged but were not involved in any interactions, suggesting that short-term adaptation to accented speech is preserved with aging and with hearing loss.
- LETTERS TO THE EDITOR
Constraining the minute amount of audible energy radiated from binary collisions of light plastic spheres in conditions of incomplete angular coverage of the measured pressure128(2010); http://dx.doi.org/10.1121/1.3479536View Description Hide Description
Usually, the energy released as air-coupled sound following a collision is dismissed as negligible. The goal of this Letter is to quantify the value of this small but measurable quantity, since it can be useful to impact studies. Measurements of sound radiation from binary collisions of polypropylene balls were performed in order to constrain the fraction of incident energy radiated as sound in air. In the experiments, one ball is released from rest, directly above a stationary target ball. The transient acoustic waveforms are detected by a microphone rotated about the impact point at a radius of 10 cm. The sound pressure was measured as a function of the polar angle (the azimuthal symmetry of the problem was verified by rotating the microphone in the horizontal plane). The angular pattern has two main lobes that are asymmetric with respect to the impact plane. This asymmetry is ascribable to interference and/or scattering effects. Gaps in the acoustic measurements at the “poles” (i.e., around 0° and 180°) pose a challenge similar to that of extrapolating the cosmic microwave background in the galactic “cut.” The data was continued in the gaps by polynomial interpolation rather than least-squares fitting, a choice dictated by the accuracy of the reconstructed pattern. The acoustic energy radiated during the impact, estimated by multiplying the collision time by the sound intensity integrated over a spherical surface centered at the impact point, is calculated as four orders of magnitude smaller than the incident energy ( versus 1.6 mJ).
128(2010); http://dx.doi.org/10.1121/1.3474897View Description Hide Description
To better understand the processing of complex high-frequency sounds, modulation-detection thresholds were measured for sinusoidal frequency modulation (SFM), quasi-frequency modulation (QFM), sinusoidal amplitude modulation (SAM), and random-phase FM (RPFM). At the lowest modulation frequency (5 Hz) modulation thresholds expressed as AM depth were similar for RPFM, SAM and QFM suggesting the predominance of envelope cues. At the higher modulation frequencies (20 and 40 Hz) thresholds expressed as total frequency excursions were similar for SFM and QFM suggesting a common mechanism, one perhaps based on single-channel FM-to-AM conversion or on a multi-channel place mechanism. The fact that the nominal envelopes of SFM and QFM are different (SFM has a flat envelope), seems to preclude processing based on the envelope of the external stimulus. Also, given the 4-kHz carrier and the similarity to previously published results obtained with a 1-kHz carrier, processing based on temporally-coded fine structure for all four types of modulation appears unlikely.
Radiofrequency electrode vibration-induced shear wave imaging for tissue modulus estimation: A simulation study128(2010); http://dx.doi.org/10.1121/1.3466880View Description Hide Description
Quasi-static electrode displacement elastography, used for in-vivoimaging of radiofrequency ablation-induced lesions in abdominal organs such as the liver and kidney, is extended in this paper to dynamic vibrational perturbations of the ablationelectrode. Propagation of the resulting shear waves into adjoining regions of tissue can be tracked and the shear wavevelocity used to quantify the shear (and thereby Young’s) modulus of tissue. The algorithm used utilizes the time-to-peak displacement data (obtained from finite element analyses) to calculate the speed of shear wave propagation in the material. The simulation results presented illustrate the feasibility of estimating the Young’s modulus of tissue and is promising for characterizing the stiffness of radiofrequency-ablated thermal lesions and surrounding normal tissue.
On the limitation of a diffusion equation model for acoustic predictions of rooms with homogeneous dimensions128(2010); http://dx.doi.org/10.1121/1.3479756View Description Hide Description
In recent years a model for predicting sound fields in enclosures has been proposed, based on the mathematical theory of diffusion. This model is held to be valid for predicting the late reverberation component of the impulse response, on the basis that sufficient reflection events must occur [Valeau et al., J. Acoust. Soc. Am.119, 1504–1513 (2006)]. The present work determines numerically the extent of reflections necessary for the solution of the diffusionequationmodel to be accurate in quasi-cubic rooms. Some preliminary numerical experiments have been carried out to determine after how many mean-free times of the impulse response, which is obtained by a geometrical-acoustic approach, gives a similar result to the solution obtained from a diffusionequationmodel.
- GENERAL LINEAR ACOUSTICS 
128(2010); http://dx.doi.org/10.1121/1.3479545View Description Hide Description
For the problem of edge diffraction from an edge of finite length a frequency-domain solution, obtained from an analytical time-domain solution, has been presented by Svensson et al. [Acta. Acust. Acust.95, 568–572]. This formulation takes the form of a Fourier-type integral whose evaluation is expensive in the high frequency range. This paper demonstrates that by using tailored highly oscillatory quadrature methods based on asymptotic properties of the integral, accurate approximations in the high frequency case can be obtained with little computational effort.
128(2010); http://dx.doi.org/10.1121/1.3483722View Description Hide Description
The Green’s function for wave propagation can be extracted by cross-correlating field fluctuations excited on a closed surface that surrounds the employed receivers. This study treats an acoustic multiple scattering medium with discrete scatterers and shows that for a given source the cross-correlation of waves propagating along most combinations of scattering paths gives unphysical arrivals. Because theory predicts that the true Green’s function is retrieved, such unphysical arrivals must cancel after integration over all sources. This cancellation occurs because the scattering amplitude of each scatterer satisfies the generalized optical theorem. The cross-correlation of scatteredwaves with themselves does not lead to the correct retrieval of scatteredwaves, because the cross-terms between the direct and scatteredwaves is essential.
128(2010); http://dx.doi.org/10.1121/1.3479022View Description Hide Description
Significant reduction in target strength and radiation signature can be achieved by surrounding an object with multiple concentric layers comprised of three acoustic fluids. The idea is to make a finely layered shell with the thickness of each layer defined by a unique transformation rule. The shell has the effect of steering incident acoustic energy around the structure, and conversely, reducing the radiation strength. The overall effectiveness and the precise form of the layering depends upon the densities and compressibilities of the three fluids. Nearly optimal results are obtained if one fluid has density equal to the background fluid, while the other two densities are much greater and much less than the background values. Optimal choices for the compressibilities are also found. Simulations in 2D and 3D illustrate effectiveness of the three fluid shell. The limited range of acoustic metafluids that are possible using only two fluid constituents is also discussed.
- NONLINEAR ACOUSTICS 
128(2010); http://dx.doi.org/10.1121/1.3474896View Description Hide Description
The computational details related to calculating the acoustic radiation force on an object using a 2-D grid finite-difference time-domain method (FDTD) are presented. The method is based on propagating the stress and velocity fields through the grid and determining the energy flow with and without the object. The axial and radial acoustic radiation forces predicted by FDTD method are in excellent agreement with the results obtained by analytical evaluation of the scattering method. In particular, the results indicate that it is possible to trap the steel cylinder in the radial direction by optimizing the width of Gaussian source and the operation frequency. As the sizes of the relating objects are smaller than or comparable to wavelength, the algorithm presented here can be easily extended to 3-D and include torque computation algorithms, thus providing a highly flexible and universally usable computation engine.
128(2010); http://dx.doi.org/10.1121/1.3478787View Description Hide Description
The parametrically driven, damped, inverted pendulum can be dynamically stabilized in particular regions of the parameter space. The impact of damping on dynamic stabilization can be stabilizing or destabilizing depending on the location in parameter space (i.e., drive frequency and amplitude). Floquet analysis and numerical simulations were used to determine the stable regions. An experiment was conducted that verifies the model. Physical explanations and simple bounding approximations are provided to summarize findings. The utility of the highly damped pendulum results are illustrated by drawing the analogy to dynamic stabilization of the Rayleigh-Taylor instability: it permits ready demonstration that dynamic stabilization is impossible in that system absent surface tension.
- AEROACOUSTICS, ATMOSPHERIC SOUND 
128(2010); http://dx.doi.org/10.1121/1.3474234View Description Hide Description
An extended Fourier pseudospectral time-domain (PSTD) method is presented to model atmospheric sound propagation by solving the linearized Euler equations. In this method, evaluation of spatial derivatives is based on an eigenfunction expansion. Evaluation on a spatial grid requires only two spatial points per wavelength. Time iteration is done using a low-storage optimized six-stage Runge-Kutta method. This method is applied to two-dimensional non-moving media models, one with screens and one for an urban canyon, with generally high accuracy in both amplitude and phase. For a moving atmosphere, accurate results have been obtained in models with both a uniform and a logarithmic wind velocity profile over a rigid ground surface and in the presence of a screen. The method has also been validated for three-dimensional sound propagation over a screen. For that application, the developed method is in the order of 100 times faster than the second-order-accurate FDTD solution to the linearized Euler equations. The method is found to be well suited for atmospheric sound propagation simulations where effects of complex meteorology and straight rigid boundary surfaces are to be investigated.
Measured wavenumber: Frequency spectrum associated with acoustic and aerodynamic wall pressure fluctuations128(2010); http://dx.doi.org/10.1121/1.3478780View Description Hide Description
Direct measurements of the wavenumber-frequency spectrum of wall pressurefluctuations beneath a turbulent plane channel flow have been performed in an anechoic wind tunnel. A rotative array has been designed that allows the measurement of a complete map, measuring points, of cross-power spectral densities over a large area. An original post-processing has been developed to separate the acoustic and the aerodynamic exciting loadings by transforming space-frequency data into wavenumber-frequency spectra. The acoustic part has also been estimated from a simple Corcos-like model including the contribution of a diffuse sound field. The measured acoustic contribution to the surface pressurefluctuations is 5% of the measuredaerodynamic surface pressurefluctuations for a velocity and boundary layer thickness relevant for automotive interior noise applications. This shows that for aerodynamically induced car interior noise, both contributions to the surface pressurefluctuations on car windows have to be taken into account.