Volume 128, Issue 5, November 2010
- jasa express letters
- letters to the editor
- general linear acoustics 
- aeroacoustics, atmospheric sound 
- underwater sound 
- ultrasonics, quantum acoustics, and physical effects of sound 
- transduction 
- structural acoustics and vibration 
- noise: its effects and control 
- architectural acoustics 
- acoustic signal processing 
- physiological acoustics 
- psychological acoustics 
- speech production 
- speech perception 
- music and musical instruments 
- bioacoustics 
- acoustical news
- acoustical standards news
- book reviews
- reviews of acoustical patents
Index of content:
- JASA EXPRESS LETTERS
128(2010); http://dx.doi.org/10.1121/1.3462235View Description Hide Description
This study reports that killer whales, the largest dolphin, produce whistles with the highest fundamental frequencies ever reported in a delphinid. Using wide-band acoustic sampling from both animal-attached (Dtag) and remotely deployed hydrophone arrays, ultrasonicwhistles were detected in three Northeast Atlantic populations but not in two Northeast Pacific populations. These results are inconsistent with analyses suggesting a correlation of maximum frequency of whistles with body size in delphinids, indicate substantial intraspecific variation in whistle production in killer whales, and highlight the importance of appropriate acoustic sampling techniques when conducting comparative analyses of sound repertoires.
128(2010); http://dx.doi.org/10.1121/1.3484492View Description Hide Description
Bicoherence analysis has been used to characterize nonlinear effects in the propagation of noise from a model-scale, Mach-2.0, unheated jet. Nonlinear propagation effects are predominantly limited to regions near the peak directivity angle for this jet source and propagation range. The analysis also examines the practice of identifying nonlinear propagation by comparing spectra measured at two different distances and assuming far-field, linear propagation between them. This spectral comparison method can lead to erroneous conclusions regarding the role of nonlinearity when the observations are made in the geometric near field of an extended, directional radiator, such as a jet.
128(2010); http://dx.doi.org/10.1121/1.3497358View Description Hide Description
Inspired by recent evidence that a binary pattern may provide sufficient information for human speech recognition, this letter proposes a fundamentally different approach to robust automatic speech recognition. Specifically, recognition is performed by classifying binary masks corresponding to a word utterance. The proposed method is evaluated using a subset of the TIDigits corpus to perform isolated digit recognition. Despite dramatic reduction of speech information encoded in a binary mask, the proposed system performs surprisingly well. The system is compared with a traditional HMM based approach and is shown to perform well under low SNR conditions.
128(2010); http://dx.doi.org/10.1121/1.3486197View Description Hide Description
Natural languages contain numerous non-adjacent relationships between words or morphemes in a sentence, often straddling phonological phrase boundaries (e.g., [these sheep] [have …]). Since phonological phrases are considered the main processing unit for infants, this may cause the acquisition of cross-phrase dependencies to be challenging. This study, however, shows that by 17 months of age, French-learning infants have nonetheless gained sensitivity to remote determiner-auxiliary co-occurrences that are interceded by phonological phrase boundaries. Infants thus possess a robust mechanism for tracking non-adjacent dependencies. This ability is essential for early grammatical development.
128(2010); http://dx.doi.org/10.1121/1.3499699View Description Hide Description
Normal and malignant mammary epithelial cells were studied using laboratory measurements, wavelet analysis, and numerical simulations of monolayercell cultures to determine whether microscopic breast cancer can be detected in vitro with high-frequency ultrasound. Pulse-echo waveforms were acquired by immersing a broadband, unfocused 50-MHz transducer in the growth media of cell culture well plates and collecting the first reflection from the well bottoms. The simulations included a multilayer pulse-reflection model and a model of two-dimensional arrays of spherical cells and nuclei. The results show that normal and malignant cells produce time-domain signals and spectral features that are significantly different.
128(2010); http://dx.doi.org/10.1121/1.3499701View Description Hide Description
The authors previously reported that same/different judgments on pitchsequences were more accurate for tones with resolved (low-rank) harmonics compared to unresolved (high-rank) harmonics, even when discriminability between tones was equated [Cousineau et al. (2009). J. Acoust. Soc. Am.126, 3179–3187]. Here, peripheral resolvability, defined by the number of harmonics per cochlear filter, was contrasted with harmonic number. Tones were presented either diotically or dichotically. In the latter case, even and odd harmonics were presented to different ears, thus halving the number of harmonics per cochlear filter. Performance was better for dichotic than for diotic presentations. This indicates that peripheral resolvability is necessary and sufficient for efficient pitch-sequence processing.
128(2010); http://dx.doi.org/10.1121/1.3488589View Description Hide Description
Ambient noise measurements were carried out in shallow brackish water within a frequency range extending up to 70 kHz. The high-frequency spectral slopes become steeper above 10 kHz at intermediate and high wind speeds. This is because the start of the wind speed dependence shifts rapidly to higher wind speeds at frequencies above 13 kHz. A physical explanation for this observation may be the low proportion of bubbles in brackish water that are small enough to radiate sound above 10 kHz. Such bubbles apparently do not begin to develop in brackish water until high wind speeds are attained.
Applications of Fresnel-Kirchhoff diffraction theory in the analysis of human-motion Doppler sonar grams128(2010); http://dx.doi.org/10.1121/1.3499702View Description Hide Description
Observed human-gait features in Dopplersonar grams are explained by using the Boulic-Thalmann (BT) model to predict joint angle time histories and the temporal displacements of the body center of mass. Body segments are represented as ellipsoids. Temporally dependent velocities at the proximal and distal end of key body segments are determined from BT. Dopplersonar grams are computed by mapping velocity-time dependent spectral acoustic-cross sections for the body segments onto time-velocity space, mimicking the Short Time Fourier Transform used in the Dopplersonar processing. Comparisons to measured data indicate that dominant returns come from trunk, thigh and lower leg.
128(2010); http://dx.doi.org/10.1121/1.3488794View Description Hide Description
L2 studies demonstrate that learners differ in their speech perception patterns. Recent explanations attribute this variation to the different initial stages with which learners start their L2 development. Spanish listeners’ categorization of Standard Southern British English and American English vowels is compared. The results show that, on the basis of steady-state F1 and F2 values, listeners classify the vowels of these two English varieties differently. This finding suggests that the dialect to which learners are exposed determines their initial stage for L2 perception and the tasks they need to perform to successfully acquire a new sound system.
128(2010); http://dx.doi.org/10.1121/1.3501110View Description Hide Description
This paper reports a new effect whereby a physiological-level direct-current electrical field (at 1.4 V/cm) can induce time-varying mechanical strain in various types of biological tissues and gel phantoms. This effect cannot be explained by the piezoelectric effect, tissue contraction, temperature changes, and electrorestriction. The induced strain in tissues was analyzed by processing ultrasound echo signals. The sample expanded perpendicularly to the applied electric field. The expansion rate depended on the history of the applied electric field. The speed of sound changed little compared with the expansion. The new effect might be related to electrokineticeffects.
128(2010); http://dx.doi.org/10.1121/1.3492794View Description Hide Description
Low frequency (61 Hz) shear wave speeds have been measured in viscoelastic wormlike micellar (WM) fluids for a concentration range of 20/12–160/96 mM CTAB/NaSAL. The strain induced birefringence of the WM fluids was exploited to optically track the shear pulse using crossed polarizing filters and high speed video. It was found that shear speed increases roughly linearly with concentration at a rate of 3.5 mm s−1 mM−1 CTAB. Further, comparison with elastic and loss moduli obtained from rheology data show that shear wave propagation is dominated by the elastic modulus for this frequency range.
128(2010); http://dx.doi.org/10.1121/1.3501112View Description Hide Description
In this work, a numerical method for modeling the scatteredacoustic pressure from fluid occlusions is described. The method is based on the asymptotic series expansion of the pressure expressed in terms of sound speed contrast between the host medium and entrained fluid occlusions. Padé approximants are used to extend the applicability of the result for larger values of sound speed contrast. For scattering from a circular cylinder, an improvement in convergence between the exact and numerical solutions is demonstrated. In the case of scattering from an inhomogeneous medium, a numerical solution with reduced order of Padé approximants is presented.
128(2010); http://dx.doi.org/10.1121/1.3492798View Description Hide Description
This study compares the phonatory behavior of an asymmetric vocal foldmodel to that of each individual vocal foldmodel in a hemi-configuration. Although phonation frequencies of the two folds in hemi-configurations had a ratio close to 1:3, a subharmonic synchronization between the two folds was not observed in the asymmetric model. Instead, the vibratory behavior was dominated by the dynamics of one fold only, and the other fold was enslaved to vibrate at the same frequency. Increasing subglottal pressure induced a shift in relative dominance between the two folds, leading to abrupt changes in both vibratory pattern and frequency.
128(2010); http://dx.doi.org/10.1121/1.3501116View Description Hide Description
A method is reported for determining ground impedance in long-range propagation experiments by using the definition of impedance directly. The method is envisioned as way of measuring the impedence at multiple locations along the propagation path, using the signals broadcast during the experiment itself. In a short-range (10 m) test, the direct method was in good agreement with a more conventional model-based least-squares method. The utility of the direct method was demonstrated in a 400 m propagation experiment in a agricultural field. The resulting impedance was consistent with the impedance measured previously in the same field.
128(2010); http://dx.doi.org/10.1121/1.3501962View Description Hide Description
This study measured the role of spectral details and temporal envelope (E) and fine structure (TFS) cues in reconstructing sentences from speech fragments. Four sets of sentences were processed using a 32-band vocoder. Twenty one bands were either processed or removed, leading to sentences differing in their amount of spectral details, E and TFS information. These sentences remained perfectly intelligible, but intelligibility significantly fell after the introduction of periodic silent gaps of 120-ms. While the role of E was unclear, the results unambiguously showed that TFS cues and spectral details influence the ability to reconstruct interrupted sentences.
Auditory sensitivity may require dynamically unstable spike generators: Evidence from a model of electrical stimulation128(2010); http://dx.doi.org/10.1121/1.3469765View Description Hide Description
The response of the auditory nerve to electrical stimulation is highly sensitive to small modulations . This report demonstrates that dynamical instability (i.e., a positive Lyapunov exponent) can account for this sensitivity in a modified FitzHugh-Nagumo model of spike generation, so long as the input noise is not too large. This finding suggests both that spike generator instability is necessary to account for auditory nerve sensitivity and that the amplitude of physiological noise, such as that produced by the random behavior of voltage-gated sodium channels, is small. Based on these results with direct electrical stimulation, it is hypothesized that spike generator instability may be the mechanism that reconciles high sensitivity with the cross-fiber independence observed under acoustic stimulation.
128(2010); http://dx.doi.org/10.1121/1.3474220View Description Hide Description
For oscillations of gas bubbles in liquids, the polytropic exponent and thermal damping constant for the high frequency region have been re-evaluated based on the framework by Prosperetti [J. Acoust. Soc. Am.61, 17–27 (2007)]. It is seen that the approximation of in Prosperetti (1977) should be dropped for . The ratios of bubble radii to wavelengths are the paramount parameters categorizing the behavior into three different regions.
128(2010); http://dx.doi.org/10.1121/1.3496388View Description Hide Description
Poor drug penetration through tumor tissue has emerged as a fundamental obstacle to cancer therapy. The aim of this study was to examine the ability of cavitation instigated by high-intensity focused ultrasound (HIFU) to increase convective transport of a model therapeutic in an in vitrotumor model. Cavitation activity was quantified by analyzing passively recorded acoustic emissions, and mass transfer was quantified using post-treatment image analysis of the distribution of a dye-labeled macromolecule. The strong correlation between cavitation activity and drug delivery suggests the potential for non-invasive treatment and monitoring.
128(2010); http://dx.doi.org/10.1121/1.3501115View Description Hide Description
The focus of this paper is to experimentally extract the Doppler signatures of a walking human’s individual body segments using an ultrasonicDoppler system (UDS) operating at 40 kHz. In a human’s walk, the major contribution to Dopplervelocities and acoustic scattering is from the foot, lower leg, thigh (upper leg) and torso. The Doppler signature of these human body segments are extracted experimentally. The measurements were made by illuminating one of these body segments at a time and blocking the remaining body segments using acoustic screens. The results obtained in our experiment were verified with the results published by Bradley using a physics-based model for Dopplersonar spectrograms.
128(2010); http://dx.doi.org/10.1121/1.3505760View Description Hide Description
The axial resolution of conventional acoustic micro imaging is limited by the wavelength of acoustic waves. Acoustic time-frequency domain imaging was recently proposed to overcome the wavelength limit [Zhang et al., J. Acoust. Soc. Am.118, 3706–3720 (2005)]. A continuous wavelet transform based acoustic time-frequency domain imaging technique is investigated in this paper. Experiments are performed on real 3D data collected from microelectronic packages. Results demonstrate the proposed technique reveals more image details and enhances the image contrast in comparison with conventional time domain imaging.