Volume 134, Issue 4, October 2013
- jasa express letters
- letters to the editor
- general linear acoustics 
- aeroacoustics, atmospheric sound 
- underwater sound 
- structural acoustics and vibration 
- 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
- part 2 special issue on deep-water ocean acoustics
Index of content:
- JASA EXPRESS LETTERS
134(2013); http://dx.doi.org/10.1121/1.4818937View Description Hide Description
Clutter is related to false alarms for active sonar. It is demonstrated that, in shallow water, target-like clutter in reverberation signals can be caused by nonlinear internal waves. A nonlinear internal wave is modeled using measured stratification on the New Jersey shelf. Reverberation in the presence of the internal wave is modeled numerically. Calculations show that acoustic energy propagating near a sound speed minimum is deflected as a high intensity, higher angle beam into the bottom, where it is backscattered along the reciprocal path. The interaction of sound with the internal wave is isolated in space, hence resulting in a target-like clutter, which is found to be greater than 10 dB above the mean reverberation level.
134(2013); http://dx.doi.org/10.1121/1.4819183View Description Hide Description
A psychophysical matching paradigm has been used to better quantify voice quality under laboratory conditions. The goals of this study were to establish which of two candidate comparison stimuli would best ensure that the range of perceived vocal roughness could be adequately bracketed using a matching task and to provide a general solution to the problem of estimating vocal roughness. Psychometric functions for roughness matching indicated that a speech-like sawtooth-plus-noise complex (20 dB signal-to-noise ratio) amplitude modulated by a sinusoidal function raised to the 4th power yielded a comparison stimulus with a perceptual dynamic range well suited for roughness matching.
134(2013); http://dx.doi.org/10.1121/1.4818939View Description Hide Description
Most of acoustical experiments face multipath propagation issues. The times of arrival of different ray paths on a sensor can be very close. To estimate them, high resolution algorithms have been developed. The main drawback of these methods is their need of a full rank spectral matrix of the signals. The frequential smoothing technique overcomes this issue by dividing the received signal spectrum into several overlapping sub-bands. This division yields a transfer matrix that may suffer rank deficiency. In this paper, a new criterion to optimally choose the sub-band frequencies is proposed. Encouraging results were obtained on real-world data.
134(2013); http://dx.doi.org/10.1121/1.4818940View Description Hide Description
The work described herein discusses the application of a frequency-wavenumber signal processing technique to signals from rectangular infrasound arrays for detection and estimation of the direction of travel of infrasound. Arrays of 100 sensors were arranged in square configurations with sensor spacing of 2 m. Wind noise data were collected at one site. Synthetic infrasound signals were superposed on top of the wind noise to determine the accuracy and sensitivity of the technique with respect to signal-to-noise ratio. The technique was then applied to an impulsive event recorded at a different site. Preliminary results demonstrated the feasibility of this approach.
134(2013); http://dx.doi.org/10.1121/1.4819182View Description Hide Description
Interleaved masking in cochlear implants is analogous to acoustic simultaneous masking and is relevant to speech processing strategies that interleave pulses on concurrently activated electrodes. In this study, spatial decay of masking as the distance between masker and probe increases was compared between forward and interleaved masking in the same group of cochlear implant users. Spatial masking patterns and the measures of place specificity were similar between forward and interleaved masking. Unlike acoustic hearing where broader tuning curves are obtained in simultaneous masking, the type of masking experiment did not influence the measure of place specificity in cochlear implants.
134(2013); http://dx.doi.org/10.1121/1.4819184View Description Hide Description
Using molecular psychophysics, temporal loudness weights were measured for 2-s, 1-kHz tones with flat, increasing and decreasing time-intensity profiles. While primacy and recency effects were observed for flat profile stimuli, the so-called “level dominance” effect was observed for both increasing and decreasing profile stimuli, fully determining their temporal weights. The weighs obtained for these profiles were basically zero for all but the most intense parts of these sounds. This supports the view that the “level dominance” effect is prominent with intensity-varying sounds and that it persists over time since temporal weights are not affected by the direction of intensity change.
134(2013); http://dx.doi.org/10.1121/1.4819185View Description Hide Description
This letter investigates the use of multiple line arrays (LAs) in a Time-Reversal Mirror for localizing and characterizing multipole aeroacoustic sources in a uniform subsonic mean flow using a numerical Time-Reversal (TR) method. Regardless of the original source characteristics, accuracy of predicting the source location can be significantly improved using at least two LAs. Furthermore, it is impossible to determine the source characteristics using a single LA, rather a minimum of two are required to establish either the monopole or dipole source nature, while four LAs (fully surrounding the source) are required for characterizing a lateral quadrupole source.
134(2013); http://dx.doi.org/10.1121/1.4820466View Description Hide Description
Level differences at equal loudness were measured for bandpass noises centered at 1.5 kHz with bandwidths from 5 to 405 Hz and a 1.5-kHz pure tone. Irrespective of the reference (tone or 135-Hz wide noise), the data indicate a decrease in loudness with increasing bandwidth. This is at odds with the assumption of stationary loudness models that loudness for sounds with a subcritical bandwidth is determined by the intensity and center frequency only. It is also not in agreement with dynamic loudness models, which predict higher levels for a tone than for equally loud noises, i.e., the opposite effect.
134(2013); http://dx.doi.org/10.1121/1.4820459View Description Hide Description
A method to estimate source range in environments that exhibit three-dimensional propagation effects is presented. A hybrid modeling technique using vertical modes and horizontal rays is employed. Results are obtained in a computationally efficient manner and require limited knowledge of the environment. The method is applied to data recorded on a horizontal line array located 12 km east of the southern coast of Florida. The results show an average error of 3.7% in estimating the range of an acoustic source located 20 to 63 km away from the array.
134(2013); http://dx.doi.org/10.1121/1.4820807View Description Hide Description
Acoustic attenuation performance through a constricted duct is greatly improved by an annular resonator. A method based on the Green's function for a semi-infinite circular duct is proposed to calculate the transmission loss, where the velocity distributions are assumed to be uniform at the constriction inlet/outlets and at the inlet to the annular resonator. From an analogous acoustical circuit, the effect of higher order evanescent modes on the quarter-wave resonance is described by an extra length. The improved acoustic attenuation performance is also confirmed by an experiment.
134(2013); http://dx.doi.org/10.1121/1.4820808View Description Hide Description
Perceived listening effort was assessed for a monaural irregular-rhythm detection task while competing signals were presented to the contralateral ear. When speech was the competing signal, listeners reported greater listening effort compared to either contralateral steady-state noise or no competing signal. Behavioral thresholds for irregular-rhythm detection were unaffected by competing speech, indicating that listeners compensated for this competing signal with effortful listening. These results suggest that perceived listening effort may be associated with suppression of task-irrelevant information, even for conditions where informational masking and competition for linguistic processing resources would not be expected.
134(2013); http://dx.doi.org/10.1121/1.4818938View Description Hide Description
Guyana dolphins show remarkable intraspecific whistle variation. This variation has been largely explained in terms of distance among populations; however, other factors such as behavior may also be important. A broadband recording system recorded the whistles of Guyana dolphins under three behavioral states. A discriminant analysis found that during social and travel events, dolphins emit whistles with high delta and minimum frequency, respectively. Whistle duration was also important in discriminating behaviors. This study indicates that behavior is an important factor contributing to whistle variation of Guyana dolphins. Understanding how dolphin whistles vary with behavioral context will advance our understanding of dolphin communication and enable appropriate comparative studies.
134(2013); http://dx.doi.org/10.1121/1.4818936View Description Hide Description
Ambient noise measurements at three sites along the Indian continental shelf, with different water column and seabed, are analyzed to derive vertical directionality and further estimation of seabed characteristics. Directionality pattern is interpreted using features in the sound speed profiles, in terms of noise notch, surface duct, surface bottom reflections, direct arrivals, and high bottom loss arrivals. Reflection loss estimated from the field directionality is seen to be the same for a particular site and gives an estimate of the sea bottom. Seabed characteristics such as critical angle and reflection coefficient from field directionality correlate well with theoretical estimation using ground truths.
134(2013); http://dx.doi.org/10.1121/1.4820468View Description Hide Description
For shallow-water waveguides and mid-frequency broadband acoustic signals, ocean acoustic tomography (OAT) is based on the multi-path aspect of wave propagation. Using arrays in emission and reception and advanced array processing, every acoustic arrival can be isolated and matched to an eigenray that is defined not only by its travel time but also by its launch and reception angles. Classically, OAT uses travel-time variations to retrieve sound-speed perturbations; this assumes very accurate source-to-receiver clock synchronization. This letter uses numerical simulations to demonstrate that launch-and-reception-angle tomography gives similar results to travel-time tomography without the same requirement for high-precision synchronization.
- LETTERS TO THE EDITOR
134(2013); http://dx.doi.org/10.1121/1.4818774View Description Hide Description
Isentropic wave propagation in a viscous fluid with a uniform mean flow confined by a rigid-walled circular pipeline is considered. A method based on the Fourier−Bessel theory, which is complete and orthogonal in Lebesgue space, is introduced to solve the convected acoustic equations. After validating the method's convergence, the cut-off frequency of wave modes is addressed. Furthermore, the effect of flow profile on wave attenuation is analyzed. Meanwhile, measurement performance of an ultrasonic flow meter based on wave propagation is numerically accounted.
134(2013); http://dx.doi.org/10.1121/1.4819115View Description Hide Description
Broadband underwater acoustic communication signals undergo either a compression or dilation in the presence of relative motion between a source and a receiver. Consequently, underwater acoustic communications with a mobile source/receiver require Doppler compensation through resampling. However, resampling may not be necessary when a channel-estimate-based time reversal approach is applied with frequent channel updates. Using experimental data (20–30 kHz), it is demonstrated that the performance of time reversal communication without resampling is similar to the case with resampling, along with the benefit of a modest computational saving.
134(2013); http://dx.doi.org/10.1121/1.4820885View Description Hide Description
Source localization using the steered response power (SRP) usually requires a costly grid-search procedure. To address this issue, a modified SRP algorithm was recently introduced, providing improved robustness when using coarser spatial grids. In this letter, an iterative method based on the modified SRP is presented. A coarse spatial grid is initially evaluated with the modified SRP, selecting the point with the highest accumulated value. Then, its corresponding volume is iteratively decomposed by using a finer spatial grid. Experiments have shown that this method provides almost the same accuracy as the fine-grid search with a substantial reduction of functional evaluations.
134(2013); http://dx.doi.org/10.1121/1.4820897View Description Hide Description
A subjective listening task was used to measure the salience of enhanced components using typical intensity-enhancement stimuli, time-reversed versions of those stimuli, and stimuli which contained a frequency shift of the target component. Twenty-five listeners judged whether or not a pitch “stood out” within an inharmonic complex. For comparison, judgments also were made for stimuli with a single segment that consisted of a simultaneously masked target. The results indicate that the perceived salience of enhanced components is greater than might be predicted by the effective magnitude of those components, and that informational masking is likely involved.
Differences in short-term training for interaural phase difference discrimination between two different forced-choice paradigms134(2013); http://dx.doi.org/10.1121/1.4819116View Description Hide Description
Improvement in interaural phase difference (IPD) discrimination over 2 to 3 h was compared for two two-alternative forced-choice paradigms: A three-interval paradigm, in which the IPD was in interval two or three, and a paradigm with two intervals of four stimuli in which the IPD was in the second and fourth stimuli of one interval (AAAA vs ABAB). The difference in performance between the beginning and end of the testing period was smaller for the two-interval paradigm, supporting the use of this paradigm for fast measurement of discrimination thresholds without the need for a long period of training.
- GENERAL LINEAR ACOUSTICS 
Transformation of body force localized near the surface of a half-space into equivalent surface stresses134(2013); http://dx.doi.org/10.1121/1.4816489View Description Hide Description
An electromagnetic acoustic transducer (EMAT) or a laser used to generate elastic waves in a component is often described as a source of body force confined in a layer close to the surface. On the other hand, models for elastic wave radiation more efficiently handle sources described as distributions of surface stresses. Equivalent surface stresses can be obtained by integrating the body force with respect to depth. They are assumed to generate the same field as the one that would be generated by the body force. Such an integration scheme can be applied to Lorentz force for conventional EMAT configuration. When applied to magnetostrictive force generated by an EMAT in a ferromagnetic material, the same scheme fails, predicting a null stress. Transforming body force into equivalent surface stresses therefore, requires taking into account higher order terms of the force moments, the zeroth order being the simple force integration over the depth. In this paper, such a transformation is derived up to the second order, assuming that body forces are localized at depths shorter than the ultrasonic wavelength. Two formulations are obtained, each having some advantages depending on the application sought. They apply regardless of the nature of the force considered.