bluuebunny/crossref_metadata_2025 huggingface dataset:
Thresholds for primary auditory fibers using statistically defined criteria
Authors: Geisler C. Daniel , Deng Li , Greenberg Steven R.
Published: October 2005

The discharge behavior of auditory-nerve fibers near ‘‘threshold’’ was investigated in anesthetized cats using low-intensity sinusoidal stimuli presented at the respective characteristic frequencies. Particular attention was paid to fibers with ‘‘low’’ and ‘‘medium’’ rates. Estimates of threshold derived from statistically significant increases in discharge rate indicate that the average threshold values for low-spontaneous fibers are only slightly higher (ca. 5 dB) than the averages for the corresponding high-spontaneous fibers, with the medium-spontaneous fibers having intermediate averages. The difference between these average values is considerably less than the more than 20-dB difference obtained using threshold criteria based on an absolute increment in discharge rate [e.g., M. C. Liberman, J. Acoust. Soc. Am. 63, 442–455 (1978)]. The main reason for the difference between the results of the two techniques is the fact that the slopes of the rate-intensity functions for the high-spontaneous fibers are considerably steeper near ‘‘threshold’’ than those for fibers of the other two classes. The results are taken as supportive of a recent model of primary-fiber discharge [C. D. Geisler, Brain Res. 212, 198–201 (1981)].
Ultrasonic attenuation and velocity properties in rat liver as a function of fat concentration: A study at 100 MHz using a scanning laser acoustic microscope
Authors: Tervola K. M. U. , Gummer M. A. , Erdman J. W. , O’Brien W. D.
Published: October 2005

This study examines the extent to which ultrasonic attenuation coefficients and velocity properties change between normal and fatty rat liver. The view of this problem is toward the application in clinical medicine in the future. Fatty livers were produced in rats by feeding them alcohol diets in liquid form. The animals were sacrificed and the fat concentration of the liver specimens determined. The fat concentration varied from 2.5% to 16.8% wet weight. The ultrasonic attenuation coefficient and velocity properties in 28 specimens were measured at 100 MHz with the scanning laser acoustic microscope (SLAM). Regression analysis was applied to the liver’s ultrasonic propagation properties as a function of fat concentration. The results show that the attenuation coefficient increases at a rate of 1.08 dB/mm/% fat and the velocity decreases at a rate of 2.3 m/s/% fat as the fat concentration increases.
Thresholds for discrimination between pure and tempered intervals: The relevance of nearly coinciding harmonics
Authors: Vos Joos , van Vianen Ben G.
Published: October 2005

Thresholds for discrimination between pure and tempered musical intervals consisting of simultaneous complex tones (fundamental frequencies f1 and f2) were investigated. For these tones the main clue for the discrimination of pure intervals ( f1:f2=p:q; p and q small integers) from moderately tempered intervals ( f1:f2∼p:q) is absence versus presence of beats. The strength of the beats (level difference between envelope maximum and minimum or level-variation depth D) was manipulated by introduction of differences in level (ΔL) between the two tones. In each of three experiments the discrimination thresholds (DTs) were determined for 13 intervals with different values for p and/or q. Experiment 1 showed that there is a simple relation between frequency-ratio complexity and discriminability: DTs gradually increased (smaller values of ΔL) with increasing p+q. Experiment 2, in which tones with harmonics of equal amplitude were used, indicated that level of the interfering harmonics was not responsible for the relation between DT and p+q. Yet, Experiment 3, in which the spectral content of the tones was varied, clearly showed that for all intervals DT had been determined by the interference between nearly coinciding harmonics. Detailed analysis of the results revealed that the relation between DT and ratio complexity might have been the result of masking.
Penalty for impulse noise, derived from annoyance ratings for impulse and road-traffic sounds
Authors: Vos Joos , Smoorenburg Guido F.
Published: October 2005

In the laboratory, four groups of 16 subjects rated the annoyance caused by three types of impulse sounds (regular and irregular gunfire noise and metal-construction noise) and by road-traffic sounds, all presented in background noise. The subjects were presented with the sounds for 5-min periods. The annoyance ratings were related to the A-weighted equivalent level (Leq) of the sounds. From these annoyance ratings a correction term or penalty was derived, which, added to the Leq of the impulse sounds, gives the level of equally annoying traffic noise. The correction was determined for conditions in which (1) only the annoyance caused by specific sources, or (2) the annoyance caused by the total sound (specific source plus background) had to be rated. In addition, the indoor Leq of the constantly present background noise was 35 or 55 dB(A) by and large, the results showed that for lower levels of the sounds an impulse-noise correction of at least 10 dB was required, whereas for higher levels the derived correction was about equal to the ISO/R 1996 penalty of 5 dB. This conclusion, based on the relation between Leq and annoyance ratings, is consistent with the correction based on Leq and the percentage of subjects who reported to be ‘‘very much annoyed.’’ For equivalent levels of the impulse sounds at which 33% of the subjects claimed to be very much annoyed, the correction was 10 dB for the conditions in which the indoor Leq of the background noise was 35 dB(A), and 5 dB when this Leq was 55 dB(A). With this criterion of 33%, source-specific and total annoyance yielded the same penalty for impulse noise.
Touch as a communicative sense: Introduction
Authors: Sherrick Carl E.
Published: October 2005

A brief survey is made of some of the threads of research and theory that have converged upon the problems of application of the touch sense to the task of substituting for the hearing process.
Tactile pattern perception and its perturbations
Authors: Craig James C.
Published: October 2005

One of the problems encountered in conveying information to the skin by means of vibratory patterns is that presenting patterns, such as letters of the alphabet, in close spatial and temporal proximity, may result in considerable masking. Generally, there is more interference when the masking stimulus follows the target (backward masking) than when it precedes it (forward masking). Masking has also been demonstrated with vibrotactile patterns derived from speech signals. Masking may be reduced by increasing the temporal and spatial separation between patterns; however, other problems may arise when such separations are made. Because stimulus onset asynchrony appears to be the critical temporal dimension for masking, it may prove difficult to reduce masking by increasing the temporal separation between patterns without also reducing the rate at which the patterns are presented. Increasing the spatial separation between patterns may lead to problems in combining the patterns from spatially distinct sites on the skin. This latter difficulty may be due to problems in attending to several sites of stimulation simultaneously.
Speech recognition and the Articulation Index for normal and hearing- impaired listeners
Authors: Kamm Candace A. , Dirks Donald D. , Bell Theodore S.
Published: October 2005

The purpose of this experiment was to determine the applicability of the Articulation Index (AI) model for characterizing the speech recognition performance of listeners with mild-to-moderate hearing loss. Performance–intensity functions were obtained from five normal-hearing listeners and 11 hearing-impaired listeners using a closed-set nonsense syllable test for two frequency responses (uniform and high-frequency emphasis). For each listener, the fitting constant Q of the nonlinear transfer function relating AI and speech recognition was estimated. Results indicated that the function mapping AI onto performance was approximately the same for normal and hearing-impaired listeners with mild-to-moderate hearing loss and high speech recognition scores. For a hearing-impaired listener with poor speech recognition ability, the AI procedure was a poor predictor of performance. The AI procedure as presently used is inadequate for predicting performance of individuals with reduced speech recognition ability and should be used conservatively in applications predicting optimal or acceptable frequency response characteristics for hearing-aid amplification systems.
Wavelength-dependent bulk parameters for coherent sound in correlated distributions of small-spaced scatterers
Authors: Twersky Victor
Published: October 2005

Earlier results for coherent propagation of sound in correlated random distributions of two-parameter particles of radius a (with minimum separation b≥2a small compared to wavelength λ=2π/k) are generalized to obtain the refractive and absorptive terms and the corresponding bulk parameters to order (ka)2. The present development includes higher order terms of the earlier multiple scattering by monopoles and dipoles, as well as scattering and multipole-coupling effects through quadrupole terms. The correlation aspects are determined by the statistical mechanics radial distribution function f(R) for impenetrable particles of diameter b. The new terms for slab scatterers and spheres involve the integral of f R (first moment), or of R f ln R for cylinders. The new packing factor is evaluated exactly for slabs as a simple algebraic function of the volume fraction w, and it is shown that the bulk index of refraction reduces to that of one particle in the limit w=1. Similar results are obtained for spheres in terms of the Percus–Yevick approximation and the unrealizable limit w=1.
Evidence for ultrasonic finite-amplitude distortion in muscle using medical equipment
Authors: Starritt H. C. , Perkins M. A. , Duck F. A. , Humphrey V. F.
Published: October 2005

Finite-amplitude distortion of ultrasonic waves from medical equipment has been observed to occur following transmission through calf muscle in human volunteers. Measurements were made using both dynamic pulse-echo imaging equipment and physiotherapy equipment. In both cases irradiation was carried out under operating conditions commonly used clinically. Pressure waveforms were measured at the skin surface using a broadband polyvinylidene difluoride membrane hydrophone. Using a pulsed, weakly focused 2.5-MHz beam with input peak pressure of 0.8 MPa and a pressure gain of 5.3 at the focus, the mean second harmonic peak magnitude (16 measurements) was 17 dB below the fundamental peak. A 1.1-MHz continuous wave therapy set with input peak pressure of 0.5 MPa showed mean second harmonic magnitude 23 dB below the fundamental.
The range dependence of normal incidence acoustic backscatter from a rough surface
Authors: Pace Nicholas G. , Al-Hamdani Zyad K. S. , Thorne Peter D.
Published: October 2005

A theoretical expression for the normal incidence, high-frequency, backscattering coefficient as a function of range from an isotropic rough surface which has both a Gaussian height distribution and a Gaussian autocorrelation function is presented and its correctness substantiated with a series of experimental measurements. Ideally the backscattering coefficient of a rough surface should be dependent only on properties of the surface. For the usual definition of backscattering coefficient this is shown to be true in the farfield of the surface scattering patch. In the nearfield of the surface, the backscattering coefficient is shown to be independent of all statistical properties of the surface and dependent only on its reflection coefficient. In a range interval between the nearfield and farfield, the backscattering coefficient is shown to depend on both the surface statistics and the measurement geometry.
On the resolution of planar ultrasonic tomography
Authors: Lin Zse-Cherng , Wade Glen
Published: October 2005

A theoretical study of depth and lateral resolution of image reconstruction in planar ultrasonic tomography is presented. An ambiguity function of this system is derived based on the back-and-forth propagation with plane-wave insonification. We show that both the depth and lateral resolution are dependent on the wavelength of the insonification and the range of values of the incident angles employed. The analysis yields a theoretical resolution limit for this type of planar ultrasonic tomography. We conclude that the depth resolution in particular can be significantly improved by increasing the extent of the angular view.
Active incoherent ultrasonic imaging through an inhomogeneous layer
Authors: Yokota Takayoshi , Sato Takuso , Hirama Makoto
Published: October 2005

In this paper, a method of active incoherent ultrasonic imaging which has been proposed in previous work [Sato et al., Acoustical Imaging (Plenum, New York, 1982), Vol. 11, pp. 289–308; Yokota and Sato, Acoustical Imaging (Plenum, New York, 1983), Vol. 12, pp. 621–634] is extended to the case where an inhomogeneous layer exists between the objects and aperture. Data acquisition is carried out by repeating transmission of burst ultrasonic waves from each transducer on the aperture and reception of the reflected waves on the same aperture. The compensation for the effect of the inhomogeneous layer is then carried out by using the space invariant property of the spatial frequency components of the object. The coherence function of the revised wave field is derived from these data, and the image is reconstructed by means of the nonlinear 2-D power spectral estimation. An algorithm of image reconstruction which includes cases where the inhomogeneous layer is located some distance from the aperture is demonstrated by several computer simulations and experiments.
Influence of direct current on dc receptor potentials from cochlear inner hair cells in the guinea pig
Authors: Nuttall Alfred L.
Published: October 2005

Inner hair cell responses to sound were monitored while direct current was applied across the membranous labyrinth in the first turn of the guinea pig cochlea. The current injection electrodes were positioned in the scala vestibuli and on the round window membrane. Positive and negative current (<100 μA) caused changes in the sound-evoked dc receptor potentials which were dependent on the sound frequency and intensity. The frequencies most affected by this extracellular current were those comprising the ‘‘tip’’ portion of the inner hair cell frequency tuning characteristic (FTC). The influence of current increased with increasing frequency. Positive current increased the amount of dc receptor potential for the affected frequencies while negative current decreased the potential. Current-induced changes (on a percentage basis) were greater for low intensity sounds and the negative current direction. These frequency specific changes are evidenced as a loss in sensitivity for the tip area of the FTC and a downward shift of the inner hair cell characteristic frequency. Larger current levels (>160 μA) cause more complex changes including unrecoverable loss of cell performance. In separate experiments positive and negative currents (<1.1 μA) were injected into the inner hair cell from the recording electrode during simultaneous measurement of the sound-evoked dc receptor potential. This condition caused a shift in IHC sensitivity that was independent of sound frequency and intensity. Positive current decreased the sensitivity of the level of the cell while negative current increased the responses. The effect of current level on sound-evoked dc receptor potential was nonlinear, as comparatively greater increases in cell response were observed for negative than decreases for positive current. The intracellular current injection results are accounted for by the mechano-resistive model of hair cell transduction, where nonlinear responses with current level may reflect outward rectification. Response changes induced by extracellular current are evidence of current effects on both inner and outer hair cells. The frequency and intensity dependences are hypothesized to represent voltage mediated control of inner hair cell response by the outer hair cells.
Intermodal timing relations and audio-visual speech recognition by normal-hearing adults
Authors: McGrath Matthew , Summerfield Quentin
Published: October 2005

Audio-visual identification of sentences was measured as a function of audio delay in untrained observers with normal hearing; the soundtrack was replaced by rectangular pulses originally synchronized to the closing of the talker’s vocal folds and then subjected to delay. When the soundtrack was delayed by 160 ms, identification scores were no better than when no acoustical information at all was provided. Delays of up to 80 ms had little effect on group-mean performance, but a separate analysis of a subgroup of better lipreaders showed a significant trend of reduced scores with increased delay in the range from 0–80 ms. A second experiment tested the interpretation that, although the main disruptive effect of the delay occurred on a syllabic time scale, better lipreaders might be attempting to use intermodal timing cues at a phonemic level. Normal-hearing observers determined whether a 120-Hz complex tone started before or after the opening of a pair of liplike Lissajou figures. Group-mean difference limens (70.7% correct DLs) were −79 ms (sound leading) and +138 ms (sound lagging), with no significant correlation between DLs and sentence lipreading scores. It was concluded that most observers, whether good lipreaders or not, possess insufficient sensitivity to intermodal timing cues in audio-visual speech for them to be used analogously to voice onset time in auditory speech perception. The results of both experiments imply that delays of up to about 40 ms introduced by signal-processing algorithms in aids to lipreading should not materially affect audio-visual speech understanding.
An approach to normalization of coarticulation effects for vowels in connected speech
Authors: Kuwabara Hisao
Published: October 2005

A method is proposed to reduce the ambiguity of vowels in connected speech by normalizing the coarticulation effects. The method is applied to vowels in phonetic environments where great ambiguity would be likely to occur, taking as their features the first and second formant trajectories. The separability between vowel clusters is found to be greatly improved for the vowel samples. In addition, distribution of the vowels on a feature plane characterized by this method seems to reflect their perceptual nature when presented to listeners without isolation from their phonetic environments. The results suggest that the method proposed here is useful for automatic speech recognition and help infer some possible mechanisms underlying dynamic aspects of human speech recognition.
Experimental modal analysis technique for three-dimensional acoustic cavities
Authors: Kung Chaw-Hua , Singh Rajendra
Published: October 2005

This paper substantially advances Nieter and Singh’s acoustic modal analysis technique [J. Acoust. Soc. Am. 72, 319–326 (1983)] which used the coincident-quadrature response method to extract acoustic global properties of one-dimensional systems. Here a technique to identify modal parameters including damping of a three-dimensional cavity is proposed. The cavity is excited by a convertible acoustic driver whose volume velocity is monitored. Acoustic transfer impedance database is obtained for a number of cavity boundary locations which are chosen such that all modes of interest can be adequately described. The vector diagram method is used to fit the measured database in the neighborhood of each resonance frequency with a circle. The experimental technique proposed here has been verified by applying it first to a cylindrical cavity whose exact eigensolutions are known. Then for an annularlike cavity, experimentally extracted natural frequencies and pressure mode shapes are found to agree well with the results of a finite element model. The significance of this paper lies in the successful demonstration of an experimental technique which can be used for diagnosing the acoustics of irregular shaped cavities. The proposed technique also offers an alternative to the finite element method for acoustic modal analysis of three-dimensional ducts and resonators of irregular shapes and/or with complicated boundary conditions.
The use of acoustic pressure measurements to determine the particle motions associated with the low order acoustic modes in enclosures
Authors: Byrne Kerry P.
Published: October 2005

This paper describes a procedure for experimentally deriving, in terms of the particle motions, the shapes of the low order acoustic modes in enclosures. The procedure is based on finding differentiable functions which approximate the shape functions of the low order acoustic modes when the modes are defined in terms of the acoustic pressure. The differentiable approximating functions are formed from polynomials which are fitted by a least-squares procedure to experimentally determined values which define the shapes of the low order acoustic modes in terms of the acoustic pressure. The experimentally determined values are found by a conventional technique in which the transfer functions, which relate the acoustic pressures at an array of points in the enclosure to the volume velocity of a fixed point source, are measured. The gradient of the function which approximates the shape of a particular mode in terms of the acoustic pressure is evaluated to give the mode shape in terms of the particle motion. The procedure was tested by using it to experimentally determine, in terms of the particle motions, the shapes of the low order acoustic modes in a small rectangular enclosure. Details of the experimental technique used and some of the results obtained are given.
Optimization of the transmitting characteristics of a Tonpilz-type transducer by proper choice of impedance matching layers
Authors: Van Crombrugge Michel , Thompson William
Published: October 2005

Many attempts have been made to design broad bandwidth transducers. Most of these have been concentrated on simple configurations such as a single piezoceramic disk with a small number of impedance matching layers on its front and/or back faces. For the complex-structured Tonpilz transducer, some methods described in the literature are not appropriate and simple trial-and-error attempts to choose matching layers are time consuming. Consequently, a systematic procedure based on the Mason equivalent circuit representation of the transducer and a nonlinear goal programming algorithm has been implemented. This procedure allows one to design both broadband and high-power transducers. The mathematical implementation of this procedure produces excellent results. Moreover, it could easily be adapted for other design objectives such as minimization of weight, cost, size, etc.
Lateral-position-based models of interaural discrimination
Authors: Stern Richard M. , Colburn H. Steven
Published: October 2005

This letter investigates the hypothesis that lateral position is the only cue available for interaural discrimination experiments using 500-Hz stimuli. The discussion of this hypothesis is in the context of comparisons of the experimental data to predictions of the ‘‘position-variable’’ model of binaural interaction. The model predicts the mean and variance of the subjective lateral position of stimuli used in the discrimination experiments, assuming that discrimination performance is based on optimal processing of this subjective position. To the extent that the laterality predictions of the model are accurate, data that are inconsistent with its predictions would also be problematical for any model based on the subjective laterality of a single binaural image. The predictions (at least qualitatively) describe much of the observed experimental data, including a number of results that have not been addressed by any previous theory. Nevertheless, the observed performance is significantly better than the corresponding predictions for three types of experiments in which the utility of the position cue has been eliminated by experimental design. We believe that our results indicate that changes in lateral position are the primary cue in most interaural discrimination experiments, but that secondary attributes of the perceptual images can be useful when performance based on position alone would be poor.
Acoustoelastic waves in orthotropic media
Authors: Pao Yih-Hsing , Gamer Udo
Published: October 2005

The equations of acoustoelasticity are formulated in both natural and initial frames of reference and applied to investigate the propagation of ultrasonic waves in orthotropic elastic solids with initial stresses. The foundation of the equations is re-examined for the purpose of applying them to the measurement of residual stresses.
Interlaboratory variability in the determination of sound power
Authors: Halliwell R. E.
Published: October 2005

Sound power measurements of a reference sound source were made at a number of laboratories in Canada and the United States. The same reference source and the same measurement equipment were used in all cases. The variability of the results reflects differences in the laboratories.
Reply to ‘‘Re-analysis of data presented in ‘Community response to blasting’ ’’ [J. Acoust. Soc. Am. 7
8, 799–800 (1985)]
Authors: Fidell Sanford , Horonjeff Richard
Published: October 2005

The conclusions of Bullen and Job [J. Acoust. Soc. Am. 78, 799–800 (1985)], differ little from those of Fidell et al. [J. Acoust. Soc. Am. 74, 888–893 (1983)].
On the existence of quasi-S waves in a prestressed elastic solid
Authors: Sidhu R. S. , Singh Sarva Jit
Published: October 2005

The condition on the incremental elastic coefficients for the existence of real values of the phase velocity of quasi-S plane waves in a prestressed elastic solid is obtained. It is shown that if this condition is violated then quasi-S waves do not exist for a certain range of the angle of propagation.
Auditory brain stem responses from human infants: Pure-tone masking profiles for clicks and filtered clicks
Authors: Folsom Richard C.
Published: October 2005

The effects of simultaneous pure-tone maskers on ABR wave V latency and amplitude were examined in three-month-old infants as a means of delineating the frequency specificity of these responses in the immature auditory system. Masking profiles at two intensities (60 and 40 dBn HL) were obtained for click, as well as 4000- and 1000-Hz filtered-click stimuli. Infant profiles, obtained by measuring both latency and amplitude shifts as a result of the discrete-frequency maskers, were compared to adult data obtained under an identical masking paradigm. Both latency and amplitude analyses showed masking profiles for infants which reveal greater low-frequency contribution to responses than found in adult profiles. Additionally, the infant profiles reveal clear differences in the degree of high-frequency spread of masking when comparisons are made to the adult data.
Matched beam theory for unambiguous broadband direction finding
Authors: Henderson T. L.
Published: October 2005

Acoustic direction finding via paired beams is treated in detail for an implementation that is based upon the use of even-symmetric and odd-symmetric beam patterns. Included are beam matching, a new approach to analysis and elimination of angle ambiguities, simplified formulas for frequency sensitivity, steerable broadband nulls without the use of time delays, and the synthesis of interferometric outputs whose relative phase delay (not time delay) is independent of frequency and gives an unambiguous indication of direction.
On the use of focused horizontal arrays as mode separation and source location devices in ocean acoustics. Part II: Theoretical and numerical modeling results
Authors: Lynch James F. , Schwartz Daniel K. , Sivaprasad Kondagunta
Published: October 2005

This paper extends and completes the description of the properties of focused horizontal arrays in normal mode fields presented in the earlier paper [J. Acoust. Soc. Am. 74, 1406–1417 (1983)]. The topics treated in this paper are: mode resolution criteria, an intercomparison of the resolution powers of cw array based mode resolution techniques, ray-mode picture transitions, the direct measurement of ocean waveguide range variability, and modal ‘‘Doppler amplification’’ by nonlinear curved array refocusing. Both theoretical and numerical results are presented.
Sound intensity in diffuse sound fields
Authors: van Zyl B. G. , Anderson F. , Erasmus P. J.
Published: October 2005

The net sound intensity field in a room containing a random noise source is the vector sum of the direct field and the reverberant intensity field. If the room is diffuse, the net reverberant intensity will be zero and only the direct field will constitute a net intensity flow. The net sound intensity field in the vicinity of a source placed in a diffuse room will therefore be identical to that in a free field, decreasing by 6 dB per doubling of the radial distance from a simple source. In any other environment the reverberant field will also yield a flow and the resulting distortion of the free-field radiation pattern will reflect a lack of directional diffusion. A simple descriptive model of the intensity field in various types of acoustic environment is presented.
Effect of directivity on the sound field produced by a source above a reflecting plane
Authors: Moreland J. B.
Published: October 2005

In this paper, the effect of source directivity on the sound field produced by a source near a reflecting plane by using a collinear array of point sources operating in phase, located above a reflecting plane, but in an otherwise reflection-free environment is analytically and experimentally investigated. It was found that the presence of the reflecting plane and the source directivity can have a considerable effect on the sound pressure levels (SPL). When radiating a third-octave band of noise centered at 500 Hz, for example, the variations in SPL with source orientation were as much as 12 dB. Furthermore, the maximum correction factor occurred when the mainlobe of the source directivity pattern pointed toward the reflecting plane rather than, as might be expected, toward the receiver. Finally, reasonably good agreement is found between the measured and corrected SPL, with the rms error being less than 2.6 for the 500-Hz octave and third-octave bands.
Ray theory modeling applied to low-frequency acoustic interaction with horizontally stratified ocean bottoms
Authors: Lawrence Martin W.
Published: October 2005

Ray theory is applied to the interaction of acoustic waves with a horizontally stratified ocean bottom. The model applies to a fluid bottom, with absorption. Local ray calculations are used throughout. At discontinuous interfaces, rays are allowed to split and each resulting ray is then followed. Corrections that are found to be essential for good agreement with full-wave treatments are caustic boundary corrections and beam displacement corrections. The nature of the π/2 phase shift associated with caustics is examined, leading to a+π/2 phase shift for beam displacement caustics, in contrast to the −π/2 phase shift for refraction caustics. Good agreement is observed between pressure fields calculated with this theory in comparison with fields calculated by normal modes, even when many caustic boundary regions overlap in the ray theory model, and even for layers of thickness comparable to a wavelength.
Harmonic response of cylindrical and toroidal shells to an internal acoustic field. Part I: Theory
Authors: El-Raheb Michael , Wagner Paul
Published: October 2005

The coupled elastic and acoustic response of a system of cylindrical and toroidal shells enclosing an acoustic medium is presented in two parts. The first part develops the theory to model the elastodynamics of cylindrical and toroidal segments of shell. The elastic simulation is based on transfer matrices while the acoustic simulation adapts a Green’s function and curved surface elements. Equilibrium of the acoustic pressure and internal elastic reactions of the shell and compatibility between the acoustic and elastic accelerations at the shell–fluid interface determine the coupled response. The second part discusses numerical results based on the theory for both shell configurations with a plane of symmetry as well as asymmetric ones.
The nearfield response of a line-driven fluid-loaded plate
Authors: Feit D. , Liu Y. N.
Published: October 2005

A line-driven fluid-loaded elastic plate is considered. The plate response and radiated pressure field are obtained by a numerical evaluation of the Fourier integral representations of the solution for frequencies below and above coincidence. Below coincidence the plate response is dominated by a fluid-modified flexural wave that propagates to infinity undiminished in amplitude. The pressure field in the vicinity of the plate reveals distinctive pressure nulls due to an interference between a cylindrically spreading acoustic wave emanating at the drive line and the evanescent wave associated with the flexural wave. Above coincidence, the plate response decays exponentially, while the pressure field displays a directive lobe in the coincidence direction.
Spherical acoustic resonator: Effects of shell motion
Authors: Mehl James B.
Published: October 2005

The exact theory of classical elasticity is used to calculate the response of an isotropic spherical shell to an acoustic mode of the fluid enclosed by the shell. The results are used to calculate the shifts of the acoustic resonance frequencies from the values which correspond to perfectly rigid shell walls. Acoustic modes with pressure proportional to Ynm (θ, φ) excite shell vibrations with the radial displacement also proportional to Ynm. The shell response depends upon the mode index n, the ratio of the shell diameters, Poisson’s ratio for the shell material, and a dimensionless frequency parameter. Numerical results for a useful range of acoustic frequencies are presented for radial (n=0) modes and for nonradial modes with mode indices n between 1 and 3. Numerical calculations of the shell resonance frequencies are presented for a wide range of shell thicknesses.
Central factors in the discrimination and identification of complex sounds
Authors: Watson Charles S. , Foyle David C.
Published: October 2005

The paper by Jesteadt and Norton [J. Acoust. Soc. Am. 78, XXX–XXX (1985)] described certain similarities between psychophysical and physiological measures of frequency selectivity. Although the hearing of naturally occurring sounds is dependent upon these peripherally based relationships, recent research has shown that other, more central, processes are also strongly involved in the perception of complex acoustic events. The present paper describes research on the discrimination of complex sounds other than those of speech or music. In contrast to the more peripherally determined limits on the listener’s sensitivity for single tones and other simple stimuli, the processing of complex sounds requires the interaction of peripheral and central mechanisms. These issues are discussed in relation to recent studies of the responses of the cochlea to speech stimuli. It is suggested that the peripheral processor may be relatively transparent to the essential spectral–temporal properties of speech, whereas more central processing severely limits the rates and amount of information that can be extracted from complex sounds.
A model for the synthesis of natural sounding vowels
Authors: Allen Donald R. , Strong William J.
Published: October 2005

A model has been developed which is designed to preserve some of the naturalness that is usually lost in speech synthesis. A parametrized function is used to produce an approximation to the cross-sectional area through the glottis. A circuit model of the subglottal and glottal system is used with the supraglottal pressure to generate the glottal volume velocity. The tract used to obtain the supraglottal pressure is represented by its input-impedance inpulse response, which can be calculated from the area function of the tract. A convolution of the input-impedance impulse response with the volume velocity determines the supraglottal pressure. The two coupled equations for the volume velocity are solved simultaneously. The output of the model is generated by convolving the resulting glottal volume velocity with the transfer-function impulse response of the tract. This technique preserves the interaction between the glottal flow and the vocal tract, which is usually lost. Comparisons are made between ‘‘complete tract loading’’ and ‘‘inductive tract loading.’’ Magnitude spectra of the various pressures and the glottal volume velocity are examined in detail. Effects of varying the glottal parameters are examined for one vowel. Listening tests showed that vowels systhesized with the interaction were preferred as more natural sounding than those without the interactions.
Ultrasonic absorption of bovine serum albumin solutions in the frequency range 200 kHz–1 MHz
Authors: Barnes C. , Evans J. A. , Lewis T. J.
Published: October 2005

The ultrasonic absorption of solutions of two electrolytes, magnesium and manganous sulfates, and also of the globular protein bovine serum albumin, has been measured using small volume spherical resonators at frequencies in the range 200 kHz–1.2 MHz. The principles of the technique are discussed and absorption values obtained for the electrolyte solutions at 20 °C are compared with existing values using other methods. For BSA, measurements were made at 8 °C over a range of pH values. Under both acid and alkaline conditions, excess losses at megahertz frequencies were found to persist down to at least 200 kHz. A new loss peak at approximately 400 kHz has been found at pH 3.2.
A scale for rate of tactual vibration
Authors: Sherrick Carl E.
Published: October 2005

Observers were asked to make estimates of the rate of mechanical vibrations presented to the finger as pulses ranging from 2 to about 300 pps. From the functions generated by this study, a set of ten values of mechanical vibration rate was selected. In a second experiment additional observers were asked to learn to identify these values of rate. Information analysis of the data showed that, when rate alone is varied, observers can identify between three and five items correctly; when rate and intensity are covaried redundantly, between five and eight items can be identified correctly. These results are viewed as supporting those from studies of the DL for rate, and as evidence for a limited but useful role of rate discrimination in tactile displays of acoustic signals.
On the extraction of the signal-excitation function from a non-Poisson cochlear neural spike train
Authors: Jones Kenneth , Tubis Arnold , Burns Edward M.
Published: October 2005

In two recent papers in this Journal, Johnson and Swami [J. Acoust. Soc. Am. 74, 493–501 (1983)] and Gaumond et al. [J. Acoust. Soc. Am. 74, 1392–1398 (1983)] have given procedures for estimating the signal-excitation function s(t) conveyed by a non-Poisson cochlear neural spike train with a known neural recovery function r(t−t′). For a delayed step form of r(t−t′), we show how s(t) may be directly (noniteratively) determined from the post-stimulus-time (PST) histogram response. We also show that for more general recovery functions, s(t) may be determined from the PST histogram response by using a simple iterative method.
Use of acoustic filtering to control the beamwidth of steered microphone arrays
Authors: Flanagan J. L.
Published: October 2005

Computer-steered microphone arrays provide an attractive sound-transducing means for interactive communication by sizable groups of talkers. But the spatial acuity of arrays typically varies with frequency, exhibiting diminishing beamwidth as frequency increases. Frequency-weighting the receiving elements is one means to mitigate the variation and to achieve more uniform beamwidth over the useful frequency range. Acoustic low-pass filtering, accomplished in the physical housing of the receivers, provides effective and economical modification of beamwidth.
Possible mechanisms for the agitation-induced enhancement of acoustic cavitation i
n v
i
t
r
o
Authors: Saad A. H. , Williams A. R.
Published: October 2005

The amount of cavitational activity occurring within an aqueous sample exposed in vitro to therapeutic intensities of MHz ultrasound is increased if the sample chamber is rotated or its contents are stirred or injected under pressure. This enhancement of cavitation apparently results either from the generation of new nuclei because of contact of the magnetic bar with the microscopically uneven surface of the sample holder or from relocation of existing nuclei so as to make them more active within the same acoustic field. Further, this enhancement of cavitational activity was affected by the applied acoustic pressure, the rate of agitation, the volume of the sonication chamber,the position of the stirrer within the beam, and the type of surface upon which stirring was performed.
Evidence for the independent function of intonation contour type, voice quality, and F0 range in signaling speaker affect
Authors: Ladd D. Robert , Silverman Kim E. A. , Tolkmitt Frank , Bergmann Günther , Scherer Klaus R.
Published: October 2005

In three related experiments, listeners judged the affect conveyed by short recorded utterances in which the voice quality, intonation contour type, and fundamental frequency range had been systematically and independently manipulated. (Contour and range were manipulated using digital resynthesis of naturally spoken utterances.) Analyses of variance of the results showed that range and contour, and less clearly range and voice quality, had independent effects on the way the utterances were judged. The results also strongly suggest that these differences are independent of effects due to interspeaker differences and to differences of verbal content. Finally, analysis of the results suggests that differences of F0 range, as is commonly assumed, have continuous rather than categorical effects on affective judgments.
Pulsation threshold test: Evidence for the existence of two biases and discussion of their implications
Authors: Escudier Pierre , Schwartz Jean-Luc
Published: October 2005

The pulsation threshold (PT) technique developed by Houtgast [J. Acoust. Soc. Am. 51, 1885–1894 (1972)] is very often used in psychoacoustic studies, but the basic phenomenon remains incompletely explained. Moreover, in the literature there exist many variants of procedure, and a rather important degree of dispersion in experimental results. Here we report an experimental set of PT data, demonstrate the existence of two biases that explain the dispersion, and give a quantitative description of their characteristics. One of these biases can be interpreted as coming from auditory fatigue phenomena. It appears finally that the ‘‘classical’’ interpretation of PT results cannot adequately fit our observations.
Lateralization of sinusoidally amplitude-modulated tones: Effects of spectral locus and temporal variation
Authors: Bernstein Leslie R. , Trahiotis Constantine
Published: October 2005

It has long been recognized that listeners are sensitive to interaural temporal disparities (ITDs) of low-frequency (i.e., below 1600 Hz) stimuli. Within the last three decades, it has often been demonstrated that listeners are also sensitive to ITDs within the envelope of high-frequency, complex stimuli. Because these studies, for the most part, employed discrimination tasks, few data exist concerning the extent of laterality produced by ITDs as a function of the spectral locus of the stimulus. To this end, we employed an acoustic ‘‘pointing’’ task in which listeners varied the interaural intensity difference of a 500-Hz narrow-band noise (the pointer) so that it matched the intracranial position of a second, experimenter-controlled stimulus (the target). Targets were sinusoidally amplitude-modulated tones centered on 500 Hz, 1, 2, 3, or 4 kHz and modulated at rates ranging from 50 to 800 Hz. Targets were presented with either the entire waveform delayed or with only the envelope delayed. Our results suggest that: (1) for low-frequency targets, lateralization is influenced by ITDs in the envelope but is dominated by ITDs in the fine structure; (2) for high-frequency targets, envelope-based delays produce displacements of the acoustic images which are affected greatly by the rate of modulation; rather large extents of laterality could be produced with high rates of modulation; these data are consistent with those obtained previously in discrimination experiments; (3) for low rates of modulation (e.g., 100 Hz), delays of the entire waveform (both envelope and fine structure) produce much greater displacements of the acoustic image for low-frequency than for high-frequency targets (where fine-structure-based cues are not utilizable); (4) there appear to be no consistent relations among extent of laterality, rate of modulation, and the frequency of the carrier within and across listeners.
Introduction: Workshop on basic research in hearing
Authors: Watson Charles S. , Dolan Terrence R. , Hind Joseph E. , Hirsh Ira J. , McFadden Dennis , Yost William A.
Published: October 2005

In the past few years exciting research techniques and methodologies have emerged in neurophysiology of hearing and in psychoacoustics. A CHABA symposium was held in the fall of 1983 for the purpose of discussing the merits of these techniques and methodologies. A rationale is presented for the selection of symposium topics. An evaluation of the methodologies and techniques is offered.
The use of intracellular techniques in the study of the cochlear nucleus
Authors: Rhode William S.
Published: October 2005

This paper describes part of the anatomy and physiology of the cochlear nucleus and some of the recent techniques developed to study the structure and function of the cochlear nucleus. The cochlear nucleus is the first region in the brain stem that receives information from the auditory nerve. The use of intercellular markers has made possible a new detail of description that should increase significantly our understanding of how the cochlear nucleus organizes the neural information transmitted to it from the auditory nerve.
Passive harmonic source ranging in waveguides by using mode filter
Authors: Shang E. C. , Clay C. S. , Wang Y. Y.
Published: October 2005

The conventional beam-forming technique cannot be used for source location in a waveguide because of the modal interference structure of the field. In this paper a new method of passive source ranging in a layered waveguide is proposed. The mode filtering processor was used to process the field data of a vertical array to obtain individual modes. The source range information can be extracted by measurement of three individual mode phases. The source range was expressed in terms of the ‘‘mode interference distance’’ as follows: r=Li j*Di j+Δri j; Δri j=Di j ×(δφi j/2π), where Li j is a certain integer, δφi j is the phase difference of the ith and jth modes, Di j is the ‘‘mode interference distance’’ defined by Di j=2π/(ki−k j), and ki is the wavenumber of the ith mode given by a numerical mode code. The information of Li j can be estimated by means of comparison with the phase of the jth mode with another mode, say the mth mode, and then Li j would be estimated by solving the following equation: (δφ jm/2π) =fractional part {(Di j/D jm) *[Li j+(δφi j/2π)]}.