Volume 127, Issue 4, April 2010
- jasa express letters
- letters to the editor
- general linear acoustics 
- nonlinear 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 
- acoustical measurements and instrumentation 
- acoustic signal processing 
- physiological acoustics 
- psychological acoustics 
- speech production 
- speech perception 
- bioacoustics 
- acoustical news
- reviews of acoustical patents
Index of content:
- JASA EXPRESS LETTERS
127(2010); http://dx.doi.org/10.1121/1.3310248View Description Hide Description
This article addresses the problem of the unsupervised separation of speech signals in realistic scenarios. An initialization procedure is proposed for independent component analysis (ICA) algorithms that work in the time-frequency domain and require the prewhitening of the observations. It is shown that the proposed method drastically reduces the permuted solutions in that domain and helps to reduce the execution time of the algorithms. Simulations confirm these advantages for several ICA instantaneous algorithms and the effectiveness of the proposed technique in emulated reverberant environments.
127(2010); http://dx.doi.org/10.1121/1.3310274View Description Hide Description
Previous investigations using in vivomodels to study the role of intrinsic laryngealmuscles in phonation have used neuromuscular stimulation to study voice parameters. However, these studies used coarse stimulation techniques using limited levels of neuromuscular stimulation. In the current investigation, a technique for fine control of laryngeal posturing was developed using graded stimulation of the laryngeal nerves. Vocal fold strain history to graded stimulation and a methodology for establishing symmetric laryngeal activation is presented. This methodology has immediate applications for the study of laryngeal paralysis and paresis, as well as general questions of neuromuscular control of the larynx.
127(2010); http://dx.doi.org/10.1121/1.3327238View Description Hide Description
This paper describes two methods for vibration damping in a broad band frequency range using a piezoelectric patch. The first method, applied to an adaptive device, uses a bias (static voltage control), which applies stresses or releases stresses in a piezoelectric component to modify its mechanical characteristics and thereby its resonance frequency. The second method is based on a semipassive approach [synchronized switch damping (SSD)], developed to control structural vibration damping using a piezoelectric component. Attenuations of 10 and 4.8 dB in vibration velocity have been obtained using the adaptive frequency and SSD methods.
127(2010); http://dx.doi.org/10.1121/1.3327245View Description Hide Description
In acoustical and seismic fields, wavefield extraction has always been a crucial issue to solve inverse problem. Depending on the experimental configuration, conventional methods of wavefield decomposition might no longer likely to hold. In this paper, an original approach is proposed based on a multichannel decomposition of the signal into a weighted sum of elementary functions known as chirplets. Each chirplet is described by physical parameters and the collection of chirplets makes up a large adaptable dictionary, so that a chirplet corresponds unambiguously to one wave component.
127(2010); http://dx.doi.org/10.1121/1.3313921View Description Hide Description
The purpose of this study was to conduct an identification experiment with synthetic vowels based on the same sets of speaker-dependent area functions as in Bunton and Story [(2009) J. Acoust. Soc. Am.125, 19–22], but with additional time-varying characteristics that are more representative of natural speech. The results indicated that vowels synthesized using an area function model that allows for time variation of the vocal tract shape and includes natural vowel durations were more accurately identified for 7 of 11 English vowels than those based on static area functions.
127(2010); http://dx.doi.org/10.1121/1.3336398View Description Hide Description
The difference-frequency band of the Kongsberg TOPAS PS18 parametric sub-bottom profiling sonar, nominally 1–6 kHz, is being used to observe Atlantic herring. Representative TOPAS echograms of herring layers and schools observed in situ in December 2008 and November 2009 are presented. These agree well with echograms of volume backscattering strength derived simultaneously with the narrowband Simrad EK60/18- and 38-kHz scientific echo sounder, also giving insight into herring avoidance behavior in relation to survey vessel passage. Progress in rendering the TOPAS echograms quantitative is described.
127(2010); http://dx.doi.org/10.1121/1.3338987View Description Hide Description
8-kHz bottom backscatteringmeasurements at low grazing angles (6°–31°) are presented. The experiment was performed at a very shallow water site with a silty bottom on the south coast of Korea. Backscattering strengths between −42 and −30 dB were obtained and were compared to a theoreticalbackscatteringmodel and Lambert’s law. The fit of the theoreticalmodel to the measurements suggests that sediment volume scattering is dominant over scattering from bottom interface roughness. Combining these results with previous measurements found in the published literature implies that backscattering strengths from silty sediment increase slightly as the frequency increases.
127(2010); http://dx.doi.org/10.1121/1.3359815View Description Hide Description
The ability to make intensity judgments for sequential stimuli was examined with an intensity-discrimination task involving three 50-ms noise bursts with non-overlapping frequency ranges. Targets (single bursts) presented in three-burst sequences were required to be as much as 5 dB more intense than targets presented as single bursts in isolation, especially for the later targets. Randomizing target position in the sequence did not reliably reduce performance, nor were thresholds for younger and older listeners reliably different. These increases in increment detection threshold are indications of a specific intensity-processing deficit for stimuli occurring later in a sequence.
127(2010); http://dx.doi.org/10.1121/1.3361042View Description Hide Description
Determining the absolute onset time of reflections in an acoustic impulse response (IR) has applications for both subjective and physical acoustics problems. Although computationally simple, a first-order energetic analysis of the IR can lead to false-positive identification of reflections. This letter reports on a method to determine reflection onset timings using a modified running local kurtosis analysis to identify regions in the IR where the distribution is non-normal. IRs from both real and virtual rooms are used to validate the method and to find optimum analysis window sizes.
- LETTERS TO THE EDITOR
Comments on “On pore fluid viscosity and the wave properties of saturated granular materials including marine sediments” [J. Acoust. Soc. Am.122, 1486–1501 (2007)]127(2010); http://dx.doi.org/10.1121/1.3337240View Description Hide Description
The ability of the grain shearing (GS) and viscous grain shearing (VGS) models to relate geophysical and acoustic properties is tested by a method based on the claimed tight coupling between compressional and shear wave speeds and attenuations, which allows the test result to be quantified in a single parameter. The VGS model is claimed to provide a better fit to the measured sound speed and attenuation in sandy sediments below 10 kHz. In situmeasurements of wave speeds and attenuations from the Sediment Acoustics Experiment 1999 (SAX99) and published laboratory measurements by Prasad and Meissner [Geophysics57, 710–719 (1992)] on a number of sand samples were used to test the models. By this metric, the SAX99 data show that the VGS model is no better than the original GS model because the improved agreement of compressional wave speeds at low frequencies is achieved at the expense of gross overestimation of the shear wave attenuation. When applied to the measurements by Prasad and Meissner, it is shown that the GS models are not applicable at any significant confining pressures, and at zero pressure they may only be applicable to a small subset of the sand samples.
Response to “Comments on ‘Pore fluid viscosity and the wave properties of saturated granular materials including marine sediments [J. Acoust. Soc. Am.127, 2095–2098 (2010)]’ ”127(2010); http://dx.doi.org/10.1121/1.3337241View Description Hide Description
Chotiros and Isakson [J. Acoust. Soc. Am.127, 2095–2098 (2010)] raised three main issues concerning the grain-shearing and viscous-grain-shearing (VGS) theories of wave propagation in saturated marine sediments. (1) They introduced the -ratio as a test of the two theories, (2) they then used the -ratio to compare the theories with published measurements of compressional and shear wave properties of laboratory sediments under high confinement pressures, and (3) they pointed out that the VGS theory overestimates the shear attenuationmeasured during the Sediment Acoustics Experiment 1999 (SAX99) by about an order of magnitude. With regard to the -ratio, it provides an incomplete test of the theories and, moreover, it returns ambiguous results. As for the tests against measurements made under high confinement pressures, they are invalid because the theories are not applicable under such conditions. The third point is correct, but a minor modification to the VGS theory resolves the difficulty.
127(2010); http://dx.doi.org/10.1121/1.3337232View Description Hide Description
In the theory of weakly nonlinear elasticity,Hamilton et al. [J. Acoust. Soc. Am.116, 41–44 (2004)] identified as the fourth-order expansion of the strain-energy density for incompressible isotropic solids. Subsequently, much effort focused on theoretical and experimental developments linked to this expression in order to inform the modeling of gels and soft biological tissues. However, while many soft tissues can be treated as incompressible, they are not in general isotropic, and their anisotropy is associated with the presence of oriented collagen fiber bundles. Here the expansion of is carried up to fourth order in the case where there exists one family of parallel fibers in the tissue. The results are then applied to acoustoelasticity, with a view to determining the second- and third-order nonlinear constants by employing small-amplitude transverse waves propagating in a deformed soft tissue.
127(2010); http://dx.doi.org/10.1121/1.3337228View Description Hide Description
The majority of acoustic impact studies developed over the last 50 years have used a similar acoustic parameter (, ) but the noise mapping methodology has been very uneven. The selection of the measurement points, the measurement periods, or the evaluation indices have not followed a unique criterion. Therefore, it is not possible to compare the sound pollution levels between different cities from those studies, at least in a rigorous sense. Even more, different studies carried out in the same city by different researchers during different years and using different methodologies are not conclusive whether the acoustic pollution increases or decreases. The present paper shows results, with statistical significance, about the evolution of the acoustic pollution obtained for two Spanish cities, Pamplona and Madrid. In both cases, it can be concluded that noise pollution decreases over time .
127(2010); http://dx.doi.org/10.1121/1.3353116View Description Hide Description
The current study investigated the robustness of priming from a masked speech priming method introduced by Kouider and Dupoux [(2005). Psychol. Sci.16, 617–625]. In this procedure, a compressed spoken prime is embedded in auditory masking stimuli and presented immediately prior to an uncompressed auditory target. The degree to which spoken stimuli could be compressed without significant data loss was first determined. Using this compression level, repetition and form priming were measured for the target words with a high versus low number of phonological neighbors. The results indicated that robust masked speech priming occurred only for word targets that had few neighbors.
Accuracy of formant measurement for synthesized vowels using the reassigned spectrogram and comparison with linear prediction127(2010); http://dx.doi.org/10.1121/1.3308476View Description Hide Description
This brief report describes a small study which was undertaken with nine synthetic vowel tokens, in an effort to demonstrate the validity of the reassigned spectrogram as a formant measurement tool. The reassigned spectrogram’s performance is also compared with that of a typical pitch-asynchronous linear predictive analysis and is found to be superior. In this study, reassigned spectrograms were further processed to highlight the formants and then were used to measure these synthetic vowelformants generally to within 0.5% of their known true values, far surpassing the accuracy of a typical linear predictive analysis procedure which was inaccurate by as much as 17%. The overall accuracy of reassigned spectrographic formant measurement is thus demonstrated in these cases.
- GENERAL LINEAR ACOUSTICS 
The direct field boundary impedance of two-dimensional periodic structures with application to high frequency vibration prediction127(2010); http://dx.doi.org/10.1121/1.3314254View Description Hide Description
Large sections of many types of engineering construction can be considered to constitute a two-dimensional periodic structure, with examples ranging from an orthogonally stiffened shell to a honeycomb sandwich panel. In this paper, a method is presented for computing the boundary (or edge) impedance of a semi-infinite two-dimensional periodic structure, a quantity which is referred to as the direct field boundary impedance matrix. This terminology arises from the fact that none of the waves generated at the boundary (the direct field) are reflected back to the boundary in a semi-infinite system. The direct field impedance matrix can be used to calculate elastic wave transmission coefficients, and also to calculate the coupling loss factors (CLFs), which are required by the statistical energy analysis (SEA) approach to predicting high frequency vibration levels in built-up systems. The calculation of the relevant CLFs enables a two-dimensional periodic region of a structure to be modeled very efficiently as a single subsystem within SEA, and also within related methods, such as a recently developed hybrid approach, which couples the finite element method with SEA. The analysis is illustrated by various numerical examples involving stiffened plate structures.
- NONLINEAR ACOUSTICS 
127(2010); http://dx.doi.org/10.1121/1.3298432View Description Hide Description
A penumbra caustic is an interrupted fold caustic. It looks like a fold caustic but with a finite size. This kind of caustic results from the focusing of a semi-infinite concave wavefront. The pressure around the extremity of the penumbra caustic can be expressed analytically in terms of incomplete Airy function for linear monochromatic waves. Using asymptotic expansions in the vicinity of the extremity, that classical result is rederived. It can be matched with the classical Fresnel diffraction before the extremity and with the classical diffraction catastrophe theory after the extremity. Nevertheless the linear modeling is not valid for incoming shock waves. A theoretical description of the phenomenon of focusing of shock waves at a penumbra caustic is given. It relies on the Zabolotskaya–Khokhlov equation. Numerical simulations are used to compute the behavior of this phenomenon. In particular, the numerical simulations show the presence of a triple point inside the pressure field. Finally, the theory and the numerical simulations are applied to explain the apparent paradox of non-causality around fold caustic.
127(2010); http://dx.doi.org/10.1121/1.3294714View Description Hide Description
This paper investigates the characteristics of the second harmonic generation of Lamb waves in a plate with quadratic nonlinearity. Analytical asymptotic solutions to Lamb waves are first obtained through the use of a perturbation method. Then, based on a careful analysis of these asymptotic solutions, it is shown that the cross-modal generation of a symmetric second harmonic mode by an antisymmetric primary mode is possible. These solutions also demonstrate that modes showing internal resonance—nonzero power flux to the second harmonic mode, plus phase velocity matching—are most useful for measurements. In addition, when using finite wave packets, which is the case in most experimental measurements, group velocity matching is required for a cumulative increase in the second harmonic amplitude with propagation distance. Finally, five mode types (which are independent of material properties) that satisfy all three requirements for this cumulative increase in second harmonic amplitude—nonzero power flux, plus phase and group velocity matching—are identified. These results are important for the development of an experimental procedure to measurematerial nonlinearity with Lamb waves.
127(2010); http://dx.doi.org/10.1121/1.3311883View Description Hide Description
Particles suspended in a fluid that is exposed to an acoustic standing wave experience a time-averaged force that drives them to either the pressure nodes or anti-nodes of the wave. Several filter designs have been successfully implemented using this force to filter small particles in liquids with low flow rates and small cross-sectional areas. It has been suggested that the filtration of small solid particles out of a gas, such as carbon in air (smoke), would be a possible application of acoustic standing wave based particle separation. This study shows the limiting factors, in both power requirements and design factors, of an acoustic filter designed for filtering smoke particles across large cross-sectional areas. It is shown that while filtration is possible, the power needed is impractical. It is also shown that operating the filter within certain settling time parameters optimizes the energy usage of the filter.
- AEROACOUSTICS, ATMOSPHERIC SOUND 
127(2010); http://dx.doi.org/10.1121/1.3327814View Description Hide Description
Multimode sound radiation from an unflanged, semi-infinite, rigid-walled circular duct with uniform subsonic mean flow everywhere is investigated theoretically. The multimode directivity depends on the amplitude and directivity function of each individual cut-on mode. The amplitude of each mode is expressed as a function of cut-on ratio for a uniform distribution of incoherent monopoles, a uniform distribution of incoherent axial dipoles, and for equal power per mode. The directivity function of each mode is obtained by applying a Lorentz transformation to the zero-flow directivity function, which is given by a Wiener–Hopf solution. This exact numerical result is compared to an analytic solution, valid in the high-frequency limit, for multimode directivity with uniform flow. The high-frequency asymptotic solution is derived assuming total transmission of power at the open end of the duct, and gives the multimode directivity function with flow in the forward arc for a general family of mode amplitude distribution functions. At high frequencies the agreement between the exact and asymptotic solutions is shown to be excellent.