Free interfacial vibrations in cylindrical shells

The 2D equations in the Kirchhoff-Love theory are subjected to asymptotic analysis in the case of free interfacial vibrations of a longitudinally inhomogeneous infinite cylindrical shell. Three types of interfacial vibrations, associated with bending, super low-frequency semi-membrane, and extensional motions, are investigated. It is remarkable that for extensional modes natural frequencies have asymptotically small imaginary parts caused by a weak coupling with propagating bending waves. Bending and extensional vibrations correspond to Stonely-type plate waves, while semi-membrane ones are strongly dependent on shell curvature and do not allow flat plate interpretation. The paper represents generalization of the recent authors' publication [Kaplunov et al., J. Acoust. Soc. Am. 107, 1383-1393 (2000)] dealing with edge vibrations of a semi-infinite cylindrical shell.     

Focus, prosodic context, and phonological feature specification: patterns of variation in fricative production

Because they consist, in large part, of random turbulent noise, fricatives present a challenge to attempts to specify the phonetic correlates of phonological features. Previous research has focused on temporal properties, acoustic power, and a variety of spectral properties of fricatives in a number of contexts [Jongman et al., J. Acoust. Soc. Am. 108, 1252-1263 (2000); Jesus and Shadle, J. Phonet. 30, 437-467 (2002); Crystal and House, J. Acoust. Soc. Am. 83, 1553-1573 (1988a)]. However, no systematic investigation of the effects of focus and prosodic context on fricative production has been carried out. Manipulation of explicit focus can serve to selectively exaggerate linguistically relevant properties of speech in much the same manner as stress [de Jong, J. Acoust. Soc. Am. 97, 491-504 (1995); de Jong, J. Phonet. 32, 493-516 (2004); de Jong and Zawaydeh, J. Phonet. 30, 53-75 (2002)]. This experimental technique was exploited to investigate acoustic power along with temporal and spectral characteristics of American English fricatives in two prosodic contexts, to probe whether native speakers selectively attend to subsegmental features, and to consider variability in fricative production across speakers. While focus in general increased noise power and duration, speakers did not selectively enhance spectral features of the target fricatives.     

Acoustic fields in binary gas mixtures: mutual diffusion effects throughout and beyond the boundary layers

The acoustic behavior in thermo-viscous gas mixtures, both in proximity of walls and far from them (outside the boundary layers), involves deviations from the adiabatic and laminar movements in pure gases, which result from the influence of several diffusive fields, namely, shear, entropic, and concentration variation fields (their energy being provided by the acoustic field itself). Owing to the boundary conditions, that are slip condition, isothermal condition and concentration flux vanishing on the walls, a strong coupling between these fields occurs inside the boundary layers while their effects appear to be simple additive processes in the bulk of the medium. Although recent literature on this subject leads to interesting results, opening the way to several new issues [R. Raspet et al., J. Acoust. Soc. Am. 105, 65-73 (1999); R. Raspet et al., J. Acoust. Soc. Am. 112, 1414-1422 (2002); G. W. Swift and P. S. Spoor, J. Acoust. Soc. Am. 106, 1794-1800 (1999); D. A. Geller and G. W. Swift, J. Acoust. Soc. Am. 111, 1675-1684 (2002)], the results available still have limitations because they do not provide complete solutions for the propagative and diffusive fields throughout and beyond the boundary layers. The present work aims at providing these solutions in the whole domains considered. The results allow interpreting analytically the behavior of the fields above mentioned in closed cavities and ducts, and particularly in spherical cavities which are best suited to develop metrological applications.     

Effects of perilymph viscosity on low-frequency intracochlear pressures and the cochlear input impedance of the cat

Cochlear model calculations are shown to be in reasonable agreement with recent low-frequency measurements of intracochlear pressures and the cochlear input impedance of the cat [V. Nedzelnitsky, J. Acoust. Soc. Am. 68, 1676-1689 (1980); T. J. Lynch, III, V. Nedzelnitsky, and W. T. Peake, J. Acoust. Soc. Am. 72, 108-130 (1982)]. Included in the cochlear model are perilymph viscosity, the measured variation of the area of the scala vestibuli with distance from the stapes [P. Dallos, J. Acoust. Soc. Am. 48, 489-499 (1970)], and finite impedance of the round window membrane. The WKB approximation and its extension to the low-frequency region is used in order to exhibit explicitly the dependence of the model results on the cochlear parameters.     

Spectral weighting strategies for sentences measured by a correlational method

Listeners' ability to understand speech in adverse listening conditions is partially due to the redundant nature of speech. Natural redundancies are often lost or altered when speech is filtered, such as done in AI/SII experiments. It is important to study how listeners recognize speech when the speech signal is unfiltered and the entire broadband spectrum is present. A correlational method [R. A. Lutfi, J. Acoust. Soc. Am. 97, 1333-1334 (1995); V. M. Richards and S. Zhu, J. Acoust. Soc. Am. 95, 423-424 (1994)] has been used to determine how listeners use spectral cues to perceive nonsense syllables when the full speech spectrum is present [K. A. Doherty and C. W. Turner, J. Acoust. Soc. Am. 100, 3769-3773 (1996); C. W. Turner et al., J. Acoust. Soc. Am. 104, 1580-1585 (1998)]. The experiments in this study measured spectral-weighting strategies for more naturally occurring speech stimuli, specifically sentences, using a correlational method for normal-hearing listeners. Results indicate that listeners placed the greatest weight on spectral information within bands 2 and 5 (562-1113 and 2807-11,000 Hz), respectively. Spectral-weighting strategies for sentences were also compared to weighting strategies for nonsense syllables measured in a previous study (C. W. Turner et al., 1998). Spectral-weighting strategies for sentences were different from those reported for nonsense syllables.     

Measurements of mutual radiation impedance between baffled cylindrical shell transducers

The mutual radiation impedances between two baffled cylindrical shell transducers, made of PZT-4 piezoelectric rings with one half of the cylindrical surface covered by a compliant baffle, were determined in experiments as a function of separation distance using an experimental technique recently described [B. Aronov, J. Acoust. Soc. Am. 119, 3822-3830 (2006)]. Two baffled cylindrical shell transducers were connected electrically in parallel and the input electrical admittance was measured at different separations when the two transducers were operated in phase and then 180 degrees out-of-phase in both the coaxial and horizontal (side-by-side) alignments. The mutual radiation impedances were then computed using an electrical equivalent circuit to determine the significance of interaction for cylindrical elements in these array geometries.     

On the interpretability of speech/nonspeech comparisons: a reply to Fowler

Fowler [J. Acoust. Soc. Am. 88, 1236-1249 (1990)] makes a set of claims on the basis of which she denies the general interpretability of experiments that compare the perception of speech sounds to the perception of acoustically analogous nonspeech sound. She also challenges a specific auditory hypothesis offered by Diehl and Walsh [J. Acoust. Soc. Am. 85, 2154-2164 (1989)] to explain the stimulus-length effect in the perception of stops and glides. It will be argued that her conclusions are unwarranted.     

A comparison of broadband models for sand sediments

Chotiros and Isakson [J. Acoust. Soc. Am. 116(4), 2011-2022 (2004)] recently proposed an extension of the Biot-Stoll model for poroelastic sediments that makes predictions for compressional wave speed and attenuation, which are in much better accord with the experimental measurements of these quantities extant in the literature than either those of the conventional Biot-Stoll model or the rival model of Buckingham [J. Acoust. Soc. Am. 108(6), 2796-2815 (2000)]. Using a local minimizer, the Nelder-Mead simplex method, it is shown that there are generally at least two choices of the Chotiros-Isakson parameters which produce good agreement with experimental measurements. Since one postulate of the Chotiros-Isakson model is that, due to the presence of air bubbles in the pore space, the pore fluid compressibility is greater than that of water, an alternative model based on a conjecture by Biot [J. Acoust. Soc. Am. 34(5), 1254-1264 (1962)], air bubble resonance, is considered. While this model does as well or better than the Chotiros-Isakson model in predicting measured values of wave speed and attenuation, the Rayleigh-Plesset theory of bubble oscillation casts doubt on its plausibility as a general explanation of large dispersion of velocity with respect to frequency.     

Unification and extension of monolithic state space and iterative cochlear models

Time domain cochlear models have primarily followed a method introduced by Allen and Sondhi [J. Acoust. Soc. Am. 66, 123-132 (1979)]. Recently the "state space formalism" proposed by Elliott et al. [J. Acoust. Soc. Am. 122, 2759-2771 (2007)] has been used to simulate a wide range of nonlinear cochlear models. It used a one-dimensional approach that is extended to two dimensions in this paper, using the finite element method. The recently developed "state space formalism" in fact shares a close relationship to the earlier approach. Working from Diependaal et al. [J. Acoust. Soc. Am. 82, 1655-1666 (1987)] the two approaches are compared and the relationship formalized. Understanding this relationship allows models to be converted from one to the other in order to utilize each of their strengths. A second method to derive the state space matrices required for the "state space formalism" is also presented. This method offers improved numerical properties because it uses the information available about the model more effectively. Numerical results support the claims regarding fluid dimension and the underlying similarity of the two approaches. Finally, the recent advances in the state space formalism [Bertaccini and Sisto, J. Comp. Phys. 230, 2575-2587 (2011)] are discussed in terms of this relationship.     

Illusory spectrotemporal ripples created with binaurally correlated noise

Binaural disparities are the primary acoustic cues employed in sound localization tasks. However, the degree of binaural correlation in a sound serves as a complementary cue for detecting competing sound sources [J. F. Culling, H. S. Colburn, and M. Spurchise, "Interaural correlation sensitivity," J. Acoust. Soc. Am. 110(2), 1020-1029 (2001) and L. R. Bernstein and C. Trahiotis, "On the use of the normalized correlation as an index of interaural envelope correlation," J. Acoust. Soc. Am. 100, 1754-1763 (1996)]. Here a random chord stereogram (RCS) sound is developed that produces a salient pop-out illusion of a slowly varying ripple sound [T. Chi et al., "Spectro-temporal modulation transfer functions and speech intelligibility," J. Acoust. Soc. Am. 106(5), 2719-2732 (1999)], even though the left and right ear sounds alone consist of noise-like random modulations. The quality and resolution of this percept is systematically controlled by adjusting the spectrotemporal correlation pattern between the left and right sounds. The prominence and limited time-frequency resolution for resolving the RCS suggests that envelope correlations are a dominant binaural cue for grouping acoustic objects.     

Pitch and rhythm paradoxes: comments on "Auditory paradox based on fractal waveform"

Schroeder [J. Acoust. Soc. Am. 79, 186-189 (1986)] describes the paradox of acoustic waveforms that sound lower when reproduced at higher speeds. The author has also demonstrated this paradox [J.C. Risset, J. Acoust. Soc. Am. 46, 88 (A) (1969); see also Seventh ICA, Budapest, S10, 613-616 (1971)]; in addition he has recently synthesized a rhythmic analog of the paradox, namely rhythmical sequences that can sound slower when reproduced at higher speeds.     

Some remarks on Pastore (1988)

Pastore [J. Acoust. Soc. Am. 84, 2262-2266 (1988)] has written a lengthy response to Kewley-Port, Watson, and Foyle [J. Acoust. Soc. Am. 83, 1133-1145 (1988)]. In this reply to Pastore's letter, several of his arguments are addressed, and new data are reported which support the conclusion of the original article. That conclusion is, basically, that the temporal acuity of the auditory system does not appear to be the origin of categorical perception of speech or nonspeech sounds differing in temporal onsets.     

A pseudo-inverse algorithm for simultaneous measurements using multiple acoustical sources

Simultaneous multiple acoustical sources measurement (SMASM) has been proposed for more effective and reliable identification of acoustical systems under critical conditions [N. Xiang and M. R. Schroeder, J. Acoust. Soc. Am. 113, 2754-2761 (2003); N. Xiang, J. N. Daigle, and M. Kleiner, J. Acoust. Soc. Am. 117, 1889-1894 (2005)]. This paper presents a pseudo-inverse algorithm for the SMASM correlation technique as an alternative way of extracting impulse responses of acoustical channels. Simulations and room acoustics experiments are carried out and the results prove the feasibility of the proposed algorithm.     

Compilation of empirical ultrasonic properties of mammalian tissues. II

The compilation of the literature on ultrasonic propagation properties of mammalian tissues [J. Acoust. Soc. Am. 64, 423 (1978)] is continued with the addition of 45 papers yielding over 700 lines of parametric data.     

Comodulation masking release: effects of training and experimental design on use of within- and across-channel cues

The effects of training and experimental design on comodulation masking release (CMR) were assessed. The study of Dau et al. [(2009), J. Acoust. Soc. Am. 125, 2182-2188], which used auditory-grouping manipulations to distinguish the use of within- and across-channel cues to CMR, was replicated in Experiment One but using naive subjects and an experimental design that minimized familiarization with the cues. Subjects made effective use of within- but not across-channel cues. Experiment Two examined training effects over more testing sessions, across four experimental designs (to minimize or maximize repeated exposure to the cues) and using an auditory grouping manipulation ("postcursors") to distinguish the use of within- and across-channel cues. Naive subjects were tested with either two or four flanking bands (FBs), to determine if training effects varied with the amount of FB information. Within-channel cues could be used from the outset, but effective use of across-channel cues required training when they were less salient. Increased repeated exposure enhanced the effects of training. Experiment Three tested naive subjects using two FBs, but with noise presented continuously and a different auditory grouping manipulation, after Grose et al. [(2009), J. Acoust. Soc. Am. 125, 282-293]. CMR was large from the outset.     

Modeling of nonlinear ultrasound propagation in tissue from array transducers

A computationally efficient model capable of simulating finite-amplitude ultrasound beam propagation in water and in tissue from phased linear arrays and other transducers of arbitrary quasiplanar geometry is described. It is based on a second-order operator splitting approach [Tavakkoli et al., J. Acoust. Soc. Am. 104, 2061-2072 (1998)], with a fractional step-marching scheme, whereby the effects of diffraction, attenuation, and nonlinearity can be computed independently over incremental steps. This approach is an extension to that of Christopher and Parker [J. Acoust. Soc. Am. 90, 507-521; 90, 488-499 (1991)], wherein linear and nonlinear effects are propagated separately over incremental steps, and the computation of the diffractive substeps are based on an angular spectrum technique with a modified sampling scheme for accurate and efficient implementation of diffractive propagation from nonradially symmetric sources. Results of the model are compared with published data. Predicted field profiles for nonlinear propagation in tissue from realistic array transducers using the pulse inversion method are presented.     

Analysis of unidirectional broadband piezoelectric spherical shell transducers for underwater acoustics

This paper presents an analytical investigation and experimental verification of the properties of unidirectional broadband piezoelectric acoustic transducers utilizing axisymmetric vibrations of both complete and incomplete spherical piezoelectric shells and is a continuation of a previous paper that presented the electromechanical modal analysis part of the problem [J. Acoust. Soc. Am. 130(2), 753-763 (2011)]. The analysis covers the treatment of the acoustic radiation and reception problem by including analysis of the acoustic impedances and diffraction coefficients as a function of geometry and modal excitation as well as providing specific design examples including multimode spherical acoustic transducers with conformal baffles, and transducers made of incomplete shells (e.g., hemispheres and caps) with free circumferential boundary conditions. The energy method is used to obtain equivalent parameters for a multi-contour electromechanical circuit representation of the transducer and to calculate the transducer performance characteristic as sound projectors and as receivers. Experimental results are obtained on representative piezoceramic transducer prototypes and are in good agreement with the analytical results.     

Intensity perception. XIII. Perceptual anchor model of context-coding

In our preliminary theory of intensity resolution [e.g., see N. I. Durlach and L. D. Braida, J. Acoust. Soc. Am. 46, 372-383 (1969)], two modes of memory operation are postulated: the trace mode and the context-coding mode. In this paper, we present a revised model of the context-coding mode which describes explicitly a process by which sensations are coded relative to the context and which predicts a resolution edge effect [L. D. Braida and N. I. Durlach, J. Acoust. Soc. Am. 51, 483-502 (1972); J. E. Berliner, L. D. Braida, and N. I. Durlach, J. Acoust. Soc. Am. 61, 1256-1267 (1977)]. The sensation arising from a given stimulus presentation is coded by determining its distance from internal references or perceptual anchors. The noise in this process, combined with the sensation noise, constitutes the limitation on resolution in the model. In the revised model the probability density functions of the decision variable are not precisely Gaussian (and cannot be expressed analytically in closed form). This paper outlines the predictions of the model for one-interval paradigms and for fixed-level two-interval paradigms and derives estimates of the values of model parameters.     

Acoustic radiation torque and the conservation of angular momentum (L)

This note concerns the evaluation of the static acoustic radiation torque exerted by an acoustic field on a scatterer immersed in a nonviscous fluid based on far-field scattering. The radiation torque is expressed as the integral of the time-averaged flux of angular momentum over a spherical surface far removed from the scattering object with its center at the centroid of the object. That result was given previously [G. Maidanik, J. Acoust. Soc. Am. 30, 620-623 (1956)]. Another expression given recently [Z. W. Fan et al., J. Acoust. Soc. Am. 124, 2727-2732 (2008)] is simplified to this formula. Comments are made on obtaining it directly from the general theorem of angular momentum conservation in the integral form.