bluuebunny/crossref_metadata_2025 huggingface dataset:
Propagation of noise above ground having an impedance discontinuity
Authors: Daigle G. A. , Nicolas J. , Berry J.-L.
Published: October 2005

Controlled measurements above ground with an impedance discontinuity are described. The measurements were made outdoors with a source above asphalt and a receiver above grass, and indoors above surfaces of known impedance in the absence of atmospheric turbulence. The results were obtained for several sources and receiver heights and for various percentages of hard–soft ground to propagation distances of 2.4 m indoors and 10 m outdoors. The measurements are also extended to include the case of a source above ground of finite impedance but which is still harder than the ground on the receiver side. The measurements are compared with recent theory which includes semiempirical solutions and solutions obtained numerically from Green’s theorem. Good agreement between the measured results and all the theories is obtained in most cases. However, in more extreme situations, including the ‘‘soft–softer’’ ground case, the semiempirical solutions are in difficulty. Earlier work [Nicolas et al., J. Acoust. Soc. Am. 73, 44–54 (1983)] is also extended by calculating the insertion loss of a barrier on ground with an impedance discontinuity. The previously measured insertion loss is recompared with the predicted insertion loss and good agreement is now obtained.
Morphometric analysis of hair cells in the chinchilla cochlea
Authors: Bohne Barbara A. , Carr Charles D.
Published: October 2005

Ten chinchilla cochleas which ranged in length from 16.00 to 19.71 mm were used for this study. The cross-sectional area and perimeter of the inner and outer hair cells and their nuclei were determined at two locations per cochlear turn and at the junction between each of the turns (11 locations from apex to base). Some interanimal variation in hair cell dimensions was noted. However, none of these size variations could be attributed to any known differences among the animals. It was concluded that the data reported here represent the natural variation in hair cell size in chinchillas. The data establish a baseline to which the dimensions of cells from abnormal cochleas can be compared, regardless of the length of the cochlea or the base-to-apex location of the cells.
Frequency characteristics of the middle ear
Authors: Kringlebotn M. , Gundersen T.
Published: October 2005

For 68 temporal bones, frequency curves for the round window volume displacement have been measured for a constant sound pressure at the eardrum. Phase curves were measured for 33 of the specimens. The level averaged amplitude curve is approximately flat below 1 kHz, where the round window volume displacement per unit sound pressure at the eardrum is 6.8×10−5 mm3/Pa, and falls off by about 15 dB/oct at higher frequencies. For the 20 ears having the largest sound transmission magnitude at low frequencies, the corresponding amplitude curve is displaced about 5 dB towards higher levels. The phase of the round window volume displacement lags the eardrum sound pressure phase. In average for 33 temporal bones, the phase lag increases from zero at the lowest frequencies to π near 2 kHz and to about 1.5 π at 10 kHz.
Sound scattering by a group of oscillatory cylinders
Authors: Lin Wen H. , Raptis A. C.
Published: October 2005

This paper is mainly concerned with an analytical study of multiple scattering of a plane sound wave by a group of circular, rigid cylinders oscillating in an ideal fluid. The objectives of the study are to investigate the phenomenon of multiple scattering due to the presence and the movement of many scatterers in the passage of sound waves and to determine the effects of multiple scattering and scatterers’ oscillations on the associated scattering functions. The fluid medium is assumed inviscid and compressible and the solid cylinders are assumed to move freely under the action of the sound waves. The acoustical radiation field caused by the translatory oscillations of the cylinders was taken into account for the correction to the main scattering caused by the mere presence of the rigid cylinders.
Demonstration of adaptation in beluga whale echolocation signals
Authors: Au Whitlow W. L. , Carder Donald A. , Penner Ralph H. , Scronce Billy L.
Published: October 2005

The echolocation signals of the same beluga whale (Delphinapterus leucas) were measured first in San Diego Bay, and later in Kaneohe Bay, Oahu, Hawaii. The ambient noise level in Kaneohe Bay is typically 12 – 17 dB greater than in San Diego Bay. The whale demonstrated the adaptiveness of its biosonar by shifting to higher frequencies and intensities after it was moved to Kaneohe. In San Diego, the animal emitted echolocation signals with peak frequencies between 40 and 60 kHz, and bandwidths between 15 and 25 kHz. In Kaneohe, the whale shifted its signals approximately an octave higher in frequencies with peak frequencies between 100 and 120 kHz, and bandwidths between 20 and 40 kHz. Signal intensities measured in Kaneohe were up to 18 dB higher than in San Diego. The data collected represent the first quantitative evidence of the adaptive capability of a cetacean biosonar system.
Use of a resonating cavity to measure body volume
Authors: Deskins W. Gregory , Winter Dean C. , Sheng Hwai-ping , Garza Cutberto
Published: October 2005

A technique to estimate the body volume of newborns has been developed using the principle of the Helmholtz resonator. The change in the resonance frequency of a small cavity after an infant is placed inside can be used to determine the body volume of the infant. A prototype system, termed an acoustic plethysmograph, was built and used to measure the volume of newborn miniature pigs. Results of the animal body volume measurements compare favorably (within an average of 1.1%) with body volumes measured by hydrostatic weighing.
A self-calibrating diver’s rangefinder
Authors: Woodward B.
Published: October 2005

An underwater rangefinder with a self-calibrating facility has been developed for use by divers as an accurate surveying instrument. It can measure range to a passive target or transponder to ±0.1 m and local acoustic velocity to ±0.2 ms−1 with a built-in velocimeter which updates the displayed range automatically. Its design, operation, and applications are presented.
On limitations of minimum mean-square error deconvolution in deriving impulse responses of rooms
Authors: Walsh John P.
Published: October 2005

Least-squares deconvolution filtering has been utilized extensively in both seismic processing and image restoration. Recently, Berkhout et al. [J. Acoust. Soc. Am. 68, 179–183 (1980)] have proposed the application of a particular seismic processing technique to room acoustics measurements, with the goal of computing the impulse response from the room’s response to a finite-length wavelet. We demonstrate mathematically and experimentally that the assumptions made in defining the method may preclude its usefulness in deriving the true impulse response of a room, showing that in most cases it will whiten the trace. In the common situations where the reflection factors are not constant as a function of frequency, the assumption of a ‘‘white’’ reflection series is not valid; we show how to remove this constraint. However, we also call into question the assumption of a stationary impulse response, and this is less susceptible to easy remedy. The use of a pseudoinverse filter based upon the premises of singular value decomposition is suggested as one way of avoiding these problems and its performance for synthetic and real data is briefly described.
Spatial variation of phase in ducts and the measurement of acoustic energy reflection coefficients
Authors: Stinson Michael R.
Published: October 2005

The sound pressure in a one-dimensional duct contains amplitude and phase components, both of which vary with position. The spatial variation of phase is examined in this paper and is shown to be closely related to the relative flow of incident and reflected acoustic energy. A technique that determines the acoustic reflection coefficient of the duct termination by measuring the maximum rate change of phase with position is discussed. For the measurements of phase variation a single moveable probe microphone is used with a phasemeter. Good agreement has been obtained between this method and the more usual impedance tube method, which considers the amplitude component of sound pressure. The phase measurements, though, can be applied equally well to ducts of conical, rather than uniform, cross section, and require a relatively small length of duct in which to translate the probe (as little as 1/20 wavelength, for moderate reflectivities). Some preliminary measurements have been made in human ear canals. The eardrum reflection coefficients obtained in the 10- to 15-kHz range are between 0.6 and 0.85, somewhat higher than those obtained by other methods.
Generalized thermoelastic waves in transversely isotropic media
Authors: Singh Harinder , Sharma Jagan Nath
Published: October 2005

In this paper the propagation of generalized thermoelastic waves in transversely isotropic media has been investigated. The basic equations have been solved by a general method after decoupling the SH wave, which is not affected by thermal variations and is independent of the rest of the motion. The discussion of the frequency equation reveals that in general there are three distinct waves in transversely isotropic media. The particle paths during the motion are found to be elliptic. The inclinations of the major axes with wave normal and the eccentricities of elliptical paths have been determined. The results have been verified numerically and are represented graphically for a single crystal of zinc in the case of waves of assigned frequency.
Re-analysis of data presented in ‘‘Community response to blasting’’ by Fidell e
t a
l. [J. Acoust. Soc. Am. 7
4, 888–893 (1983)]
Authors: Bullen R. B. , Job R. F. S.
Published: October 2005

Fidell et al. [J. Acoust. Soc. Am. 74, 888–893 (1983)] have presented a study of community reaction to blast noise from three mining sites. Fidell et al. observed a stronger relationship between high centiles of ground vibration levels and annoyance than between average vibration levels and annoyance. They judged from the correlations that ‘‘a centile-related threshold model of blast-induced annoyance yields a more adequate account of the data than the ... equal energy model’’ (p. 891). In this letter it is suggested that this conclusion is not warranted from the data presented by Fidell et al.
Comments on ‘‘Comparison of the T-matrix and Helmholtz integral equation methods for wave scattering calculations’’ [J. Acoust. Soc. Am. 7
7, 369–374 (1985)]
Authors: Waterman P. C.
Published: October 2005

Some remarks are presented as appropriate regarding the T-matrix method as employed in the paper by Tobocman [J. Acoust. Soc. Am. 77, 369–374 (1985)].
Postnatal development of physiological responses in auditory nerve fibers
Authors: Dolan D. F. , Teas D. C. , Walton J. P.
Published: October 2005

The discharges of auditory nerve fibers in kittens 4–37 days of age were recorded from micropipette electrodes. Tuning curves, thresholds, and the degree of tuning (Q10) are compared over this age range. The tuning curves for fibers during the first postnatal week are relatively flat, with thresholds above 100 dB SPL. The response areas of VIII-nerve fibers during this period are restricted to low-to-middle frequencies. With increasing age there is a reduction in threshold and an increase in the sharpness of tuning which is dependent on fiber CF. Response characteristics similar to adult VIII-nerve fibers were observed first for fibers with CFs near 5 kHz. For the response measures used here, VIII-nerve fibers in kittens are adultlike by the third to fourth postnatal week. The results are discussed in relation to the morphological development of the cochlea reported by other investigators.
Random vibration of a prestressed, orthotropic, thick rectangular plate on a generalized flexible foundation
Authors: Chonan S.
Published: October 2005

This paper is concerned with the random vibration of a simply supported, prestressed, orthotropic rectangular plate resting on a generalized elastic foundation. The plate is subjected to random forces that are correlated in time, while uncorrelated in space. The foundation produces both normal and tangential restoring forces against the deformation of the plate. The problem is studied on the basis of a thick plate theory which takes into account the effect of the second-order increments of the normal stresses in plate, as well as the effect of the rotatory inertia and shear deformations. The mean-square displacement and moment of the plate are calculated for various values of the parameters included. The results are also compared with those from the classical thin plate theory.
Acoustic and physical property relationships in marine sediment
Authors: Bachman Richard T.
Published: October 2005

I n situ sediment acoustic impedance measured from a ship underway is being used to infer the physical properties of the sea bed. These inferences rely on published regression relationships developed to estimate impedance from sediment density or porosity. Thus the equations must be rearranged to yield the desired parameter when impedance is known. Rearranging or inverting regression equations is not a valid technique. It is justified only when properly derived equations are unavailable. Herein are regressions of sediment density, porosity, and mean grain size on impedance to complement relationships already in the literature. Presented also are data and methods to place confidence limits on the predictions.
Low-frequency acoustic response of shallow water ducts
Authors: Eller Anthony I. , Gershfeld David A.
Published: October 2005

The ocean bottom can exert a dominating influence on the propagation of sound in shallow water. Not only does the bottom act to confine the acoustic field as in a duct or waveguide, but in addition the bottom provides the major source of acoustic loss at low frequency. This paper examines the effects on shallow water propagation of two canonical models of bottom structure—an isovelocity fast sediment whose sound speed is substantially greater than that of water, and a slow sediment whose sound speed at the interface equals that of water and which has a positive, upward refracting gradient. Each of these models gives rise to an optimal frequency, in the sense of a least attenuation rate. The second model predicts, also, a very low-frequency region, below about 25 Hz, where attenuation rates decrease with decreasing frequency.
Parabolic equation modeling of the effects of ocean currents on sound transmission and reciprocity in the time domain
Authors: Nghiem-Phu Lan , Tappert Frederick
Published: October 2005

Transmission loss in the time domain is examined in the presence of ocean currents using the Parabolic Equation (PE) method. The transmission loss functions in the time domain are computed from solutions of the Parabolic Equation obtained by using the Split-Step Fourier (SSF) algorithm. Within the context of the parabolic approximation, a nonreciprocal relationship when ocean currents are included is derived theoretically. Current effects on one-way and reciprocal pulse responses are illustrated by means of a numerical example. Approximations are presented together with an efficient technique for assessing the influence of ocean currents on reciprocal transmission between various positions of sources and receivers.
A wide-angle three-dimensional parabolic wave equation
Authors: Siegmann William L. , Kriegsmann Gregory A. , Lee Ding
Published: October 2005

A third-order partial differential equation with wide-angle capability is formulated to predict three-dimensional underwater sound propagation. The development is based on physical acoustic characteristics and mathematical theory. Both operator and asymptotic analyses are given to thoroughly discuss the validity of the formulation. Physical conditions are indicated when a three-dimensional approach is needed.
Measurement of the waveform parameters of shallow explosive charges
Authors: Chapman N. Ross
Published: October 2005

Measurements of the properties of shallow underwater explosions have been obtained in recent experiments with 0.82-kg SUS (signal underwater sound) charges at depths from 23.5 to 194.5 m. The data were recorded in the farfield with a high-resolution digital recording system to ensure good reproduction of both the high- and low-frequency components of the waveform. The measurements provide new results for the pressures, impulses, durations, and time constants of the shock wave and the first bubble pulse, and in addition, extend the available information to include the properties of the subsequent bubble pulses and the negative phases. Comparison of the data with previously published semiempirical relationships based on experiments with deeper charges indicates that those expressions generally do not provide adequate descriptions of the shallow charge data. In particular, there is significant disagreement with the measurements of the shock wave decay constant, and with the measurements of all of the bubble phase properties. The effect of vertical migration is appreciable for shallow charges and was observed in the measurements of bubble pulse periods, pressures, and impulses. Semiempirical relationships were derived from the data for the properties of both the shock wave and the bubble pulse series. These expressions account for the depth dependence due to migration observed in the bubble phase properties and consequently provide parameter values appropriate for modeling the pressure waveform of shallow charges.
Scattering of low-frequency acoustic waves by baffled membranes and plates
Authors: Ahluwalia Daljit S. , Kriegsmann Gregory A. , Reiss Edward L.
Published: October 2005

The method of matched asymptotic expansions is used to study the scattering of plane, monochromatic, acoustic waves from baffled flexible surfaces in the limit as L/λ→0. Here, λ is the wavelength of the incident acoustic wave and L is a characteristic size of the flexible surface, such as its maximum diameter. The baffled surface is either a membrane or a thin plate. Uniform asymptotic expansions of the scattered fields are obtained for both surfaces as L/λ→0. Thus, for example, it is valid in the nearfields and farfields of the flexible surface. The method is applied to obtain the fields scattered by rectangular membranes and plates. It is found that plates are more efficient scatterers than ‘‘similar’’ membranes if the plates are sufficiently thin.
Rather-high-frequency sound scattering by swimbladdered fish
Authors: Foote Kenneth G.
Published: October 2005

A new model describes acoustic scattering by swimbladdered fish of lengths from at least 8 to 36 wavelengths. It represents a fish by an ideal pressure-release surface having the exact size and shape as the swimbladder. The backscattering cross section, or target strength, is computed by means of the Kirchhoff approximation. To test the model, predictions of target strengths based on swimbladder morphometries of 15 gadoids of lengths from 31.5 to 44.5 cm are compared with conventional target strength measurements on the same, surface-adapted fish, anesthetized before acoustic measurement, and shock-frozen immediately afterwards. Details are given of the swimbladder morphometry. In essence, this consists of slicing the frozen fish with a microtome, photographing the exposed swimbladder cross sections, digitizing the contours, and triangulating the surface between pairs of contours on adjacent, parallel planes. Theory and experiment are compared through the dorsal and ventral aspect target strength functions, their averages, and simulated probability density functions.
Echo fluctuations from the rough seafloor: Predictions based on acoustically measured microrelief properties
Authors: Stanton T. K.
Published: October 2005

Description of echo fluctuations due to a rough seafloor requires knowledge of the product σ2IC, where σ is the rms roughness and IC is the integral of the two-dimensional correlation function C(ξ,η) of the floor [IC≡∫∫C(ξ,η)dξ dη; ξ and η are the x and y correlation parameters]. Under small roughness conditions (4k2σ2≪1, where k is the acoustic wavenumber) we recently derived a simple formula relating the PDF of the echo amplitude to the product σ2IC [T. K. Stanton, J. Acoust. Soc. Am. 75, 809–818 (1984)]. The calculations involved normal incidence sonar pings. In this paper, we do similar calculations by performing both inverse and forward calculations involving the echo PDF. We first do the inverse problem by extracting σ2IC from coherence function data published by Dunsiger et al. [A. D. Dunsiger, N. A. Cochrane, and W. J. Vetter, IEEE J. Ocean. Eng. OE-6 (3), 94–106 (1981)]. Their data were from a downward-looking towed boomer source. We then use that information as input into our theory to predict the echo amplitude PDF from several downward looking sonars for a range of frequencies and beamwidths. Dunsiger et al.’s data were specific to their boomer source. However, once we carefully extract σ2IC from their data, the product may be used for any sonar as shown in our examples.
Harmonic response of cylindrical and toroidal shells to an internal acoustic field. Part II: Results
Authors: El-Raheb Michael , Wagner Paul
Published: October 2005

General systems of cylindrical and toroidal shells enclosing an acoustic medium are studied by their response to acoustic excitation by a plane wave with harmonic time dependence. Noteworthy features are: (i) at frequencies low compared to the fundamental the torus’ cross section deforms as an ogive due to meridional curvature, (ii) coupled elastic resonances lag resonances of the empty system, (iii) additional circumferential harmonics appear besides 0 and 1 when the exciting frequency is closest to resonances of the shell’s cross section, (iv) longitudinal acoustic resonances lag resonances of the system with rigid walls, and (v) nonresonant response peaks occur at coincidence. The present analysis demonstrates the inadequacy of beam theory to model the response of short and thin shell configurations at frequencies above the fundamental elastic resonance.
Speech perception: Some new directions in research and theory
Authors: Pisoni David B.
Published: October 2005

The perception of speech is one of the most fascinating attributes of human behavior; both the auditory periphery and higher centers help define the parameters of sound perception. In this paper some of the fundamental perceptual problems facing speech sciences are described. The paper focuses on several of the new directions speech perception research is taking to solve these problems. Recent developments suggest that major breakthroughs in research and theory will soon be possible. The current study of segmentation, invariance, and normalization are described. The paper summarizes some of the new techniques used to understand auditory perception of speech signals and their linguistic significance to the human listener.
Differential sensitivity to tonal frequency and to the rate of amplitude modulation of broadband noise by normally hearing listeners
Authors: Formby C.
Published: October 2005

Differential sensitivities for tones which varied in frequency (containing cues for place and periodicity) and for broadband noise which varied in the rate of sinusoidal amplitude modulation (presumably containing only a periodicity cue) were measured at common frequencies and modulation rates of the stimulus for four normally hearing listeners. A forced-choice adaptive psychophysical procedure was used in all measurements. Through 60 Hz, tonal-frequency and rate discrimination were similar (on average, 2.5–3.0 Hz) across listeners. From 80–400 Hz, differential sensitivity for tones was between 1.0 and 2.0 Hz, whereas values for rate discrimination increased almost linearly from about 3.6 to 122.0 Hz. Apparently, differential sensitivities for both tonal frequency and modulation rate are mediated similarly, presumably by the same (periodicity) mechanism, through 60 Hz. Above 60 Hz, the listener is more sensitive to differences in tonal frequency than modulation rate. Detection thresholds for sinusoidal amplitude modulation of noise also were measured for these listeners. An average modulation threshold function was obtained and a half-power frequency was estimated for the function at 60 Hz; from this value a time constant of 2.65 ms may be derived, which is consistent with time constants measured by other psychophysical methods. These data further point to some change in perceptual quality above about 60 Hz, that frequency above which we found tonal-frequency and rate discrimination functions to separate.
Underwater transducer wetting agents
Authors: Ivey Larry E. , Thompson Corley M.
Published: October 2005

Air bubbles on the surface of a sonar transducer cause disturbances in the calibration response. Several materials have been used at various facilities to cause the air bubbles to release more easily from the transducer surface. This report explains the mechanism of these surface active materials and compares them in terms of surface tension in solution, persistence on a rubber surface, and compatibility with other materials. Also reported are the results of field tests of each of the surface active materials on ten soiled transducers. The best materials proved to be Aerosol OT-100R,a combination of OT-100 and JoyR detergent, and JoyR detergent alone.
Free vibrations of a pyroelectric layer of hexagonal (6 mm) class
Authors: Paul H. S. , Renganathan K.
Published: October 2005

The exact frequency equation for the free vibrations of a pyroelectric (thermo-piezoelectric) layer of (6 mm) class is obtained. The surfaces of the layer are kept traction free, completely coated with electrodes which are shorted and thermally insulated. The symmetric and the antisymmetric modes of vibration are discussed numerically. The dispersion curves have been presented graphically for a barium titanate (BaTiO3) layer.
Optimal design of a foil electret earphone for use in telephony
Authors: Busch-Vishniac Ilene J.
Published: October 2005

This paper describes the optimal design of a foil electret earphone for use in telephony. The sensitivity (ratio of the sound pressure generated to the signal supplied) was maximized while meeting material, geometric, and performance constraints. First, a generalized reduced gradient optimization scheme based on the leading order approximations to the diaphragm motions was used. Second, the region of the approximate optimum was examined and an exhaustive search conducted for the optimal design based on exact numerical solution for the diaphragm motion. The results indicate that it is theoretically possible to design a foil electret earphone suitable for telephony which produces a sound pressure level of just over 90 dB in response to a 1-V rms signal. The optimum earphone has a center circular portion surrounded by an annulus and uses thin, highly tensioned Mylar as a diaphragm. The electret material is mounted on the back electrode.
Cue enhancement by stimulus repetition: Natural and synthetic speech comparisons
Authors: Clark John E. , Dermody P. , Palethorpe Sallyanne
Published: October 2005

This study investigates perceptual differences between natural and synthesized speech as measured by the effects of stimulus repetition on test item identification accuracy. The results show that identification accuracy is enhanced by repetition for natural speech but not for synthesis, suggesting that there are appreciable differences in their perceptual properties, at least inder the conditions of this experiment.
Additivity of simultaneous masking, revisited
Authors: Moore Brian C. J.
Published: October 2005

Lutfi [J. Acoust. Soc. Am. 73, 262–267 (1983)] compared simultaneous masking functions (signal threshold versus masker level) for individual sinusoidal and narrow-band noise maskers, and for those maskers presented in pairs. Lutfi found that the pairs of maskers produced 10–17 dB ‘‘excess’’ masking over that predicted from the linear sum of their individual masking and explained the results in terms of a model in which the effects of the maskers are summed after undergoing independent compressive transformations. This paper describes experiments similar to those of Lutfi, and presents evidence suggesting that Lutfi’s results may have been influenced by two factors: (1) combination-product detection, and (2) the use of different detection cues for single maskers and for pairs of maskers. Experiment I showed that when the stimulus conditions were chosen so as to minimize the likelihood of combination-product detection, ‘‘excess’’ masking was only 3–5 dB. Experiment II supported the idea that for a single narrow-band noise masker, subjects make use of the relatively slow envelope fluctuations to enhance performance. When two independent narrow-band noise maskers are added, the effectiveness of this cue is reduced, and between 3 and 9 dB of ‘‘excess’’ masking occurs. When the two noises are derived from the same source, and have correlated envelope fluctuations, no ‘‘excess’’ masking occurs. The results indicate that Lufti’s compressive-nonlinearity model clearly fails in some situations.
Localization of sound in rooms, II: The effects of a single reflecting surface
Authors: Rakerd Brad , Hartmann W. M.
Published: October 2005

Auditory localization was studied in a room bounded by a single acoustically reflective surface. The position of that surface was varied so as to simulate a floor, a ceiling, and a left or right side walls. The surface was eliminated in one condition so that we could examine localization in free field for purposes of comparison. Using a source identification method we assessed the influences of these various room configurations on the localization of both slow-onset and impulsive sine tones of low frequency (500 Hz). We also measured the steady-state interaural-time-difference (ITD) and interaural-intensity-difference (IID) cues available to subjects in the different room configurations and compared these data with the perceptual judgments. Our results indicate the following: (1) A sound must include transients if the precedence effect is to operate as an aid to its localization in rooms. (2) Even if transients are present the precedence effect does not eliminate all influences of room reflections. (3) Due to the interference of reflections large interaural intensity differences may occur in a room and these have a considerable influence on localization; this is true even at low frequencies for which IID cues do not exist in a free field. (4) Listeners appear to have certain expectations about the reliability and plausibility of various directional cues and perceptually weight the cues accordingly; we suggest that this may explain, in part, the large variation in time-intensity trading ratios reported in the literature and also the differing reports regarding the importance of onsets for localization. (5) In this study we find that onset cues are of some importance to localization even in free field.
Vibrotactile forward masking: Psychophysical evidence for a triplex theory of cutaneous mechanoreception
Authors: Gescheider George A. , Sklar Bradley F. , Van Doren Clayton L. , Verrillo Ronald T.
Published: October 2005

Threshold shifts for the detection of vibrotactile test stimuli were determined as a function of the intensity of a masker. A 50-ms sinusoidal test stimulus was applied to the thenar eminence of the hand 25 ms after the termination of a 700-ms sinusoidal masker applied to the same site. The frequency of the test stimulus and the frequency of the masker were varied. To eliminate the influence of the Pacinian receptor system, stimuli were delivered through a 0.01-cm2 contactor. The results support the hypothesis that the detection of vibration delivered through a small contactor is determined by two separate populations of non-Pacinian receptors. The study constitutes a psychophysical demonstration of the existence of three receptor systems responsible for the detection of vibration.
The structure and function of actin in hair cells
Authors: Saunders James C. , Schneider Mark E. , Dear Steven P.
Published: October 2005

Within the last 7 years, the protein actin has been identified in the stereocilia and cuticular plate region of the hair cell. An intensive effort has been mounted to describe the structural organization of this protein, to identify actin-associated proteins in these regions, and to identify the functional role of these proteins. The paracrystalline array of actin and its cross bridges imparts rigidity and stiffness to the stereocilia, which are important in determining their response properties. It also appears that these properties can be changed if the paracrystalline array is damaged by noise exposure. The functional implications of stereocilia rigidity and stiffness, as well as potential contractile mechanisms in the hair cell, are discussed. Finally, it is suggested that changes in the cross-sectional shape of the stereocilia caused by shearing of actin filaments during stereocilia deflections can be related to the mechano-electrical events in the plasma membrane of the cell. This may be the link between the transmission of vibrational energy through the sensory accessory structures of the peripheral ear, and the initiation of electrochemical events associated with transduction.
Applications of neuronal labeling techniques to the study of the peripheral auditory system
Authors: Liberman M. Charles , Simmons Dwayne D.
Published: October 2005

Horseradish peroxidase (HRP) techniques have recently been applied to the study of the peripheral auditory system. These techniques make it possible to trace single, auditory-nerve fibers from their peripheral terminals on sensory cells to their central terminations within the cochlear nucleus. For the large, myelinated axons of type-I neurons contacting inner hair cells, HRP can be injected intracellularly through the same electrode used to record neural activity, allowing correlations to be made between structure and function on a single-cell basis. From these data, a cochlear frequency map has been constructed, and morphological correlates of differences in spontaneous discharge have been identified. For the small, unmyelinated axons of type-II neurons contacting outer hair cells, single-unit recordings have not yet been made; however, these neurons have been labeled by gross extracellular injections of HRP. Extracellular injections have also been used to study the peripheral terminations of single efferent neurons projecting to the outer hair cell region. The afferent fibers to the outer hair cell (OHC) region contact primarily OHCs from the third row, while efferent fibers primarily contact cells from the first row. Single efferent fibers innervate OHCs over a significantly larger cochlear length than single afferent fibers of either type. Possible functional interpretations of these morphological differences are discussed.
Use of brain slices in the study of the auditory system: Spatial and temporal summation of synaptic inputs in cells in the anteroventral cochlear nucleus of the mouse
Authors: Oertel Donata
Published: October 2005

One of the more dramatic technological developments in recent years in neurobiology is the ability to extract a slice of brain tissue and to maintain its viability over extended periods of time. The development of brain slice preparations of the mammalian central nervous system provides a powerful tool for studying the physiology and pharmacology of neurons. In vitro preparations allow stable intracellular recordings to be made from cells. The characteristics of synaptic potentials and the intrinsic electrical properties can be measured while the extracellular environment is controlled and manipulated. Intracellular physiological studies in the anteroventral cochlear nucleus reveal that different morphological classes of cells have characteristic intrinsic electrical properties. Bushy cells are particularly well suited to preserve and convey the temporal firing pattern of inputs from the auditory nerve. Stellate cells can transform inputs from the auditory nerve by summing in time and space.
Acoustic emissions from the ear: A summary of results from humans and animals
Authors: Zurek P. M.
Published: October 2005

As mentioned in Saunders et al. [J. Acoust. Soc. Am. 78, xxx–xxx (1985)] an understanding of the transduction of sound into the auditory neural code is a major goal of the hearing scientist. A variety of tools has been and is being used to achieve that goal. The recent discovery of physical acoustic emissions from the ear provides both new insight into possible transduction mechanisms and a useful new tool for research. The existence of narrow-band spontaneous acoustic emissions from the ear suggests the possibility of active cochlear processes that were not seriously considered a decade ago. Acoustic emissions, both spontaneous and evoked, also provide a simple and noninvasive means of monitoring a by-product of cochlear-mechanical activity. In the present paper, results of studies of acoustic emissions from human ears are briefly summarized and compared to results obtained with animals. Differences between human and animal emissions are noted and the implications of these differences and hypotheses to explain them are discussed.
Patterns of organization in auditory cortex
Authors: Brugge John F.
Published: October 2005

Previous work has described recently developed techniques that are contributing to advances in the study of the auditory system; some of these techniques have been used to make significant progress in this field. This paper includes a discussion of the tonotopic and binaural organizations of the auditory cortex (especially area AI), the neuronal connections between auditory cortical fields, the relationships between the functional maps and the connectivity patterns, the nature of binaural processing within AI, and the techniques used to assess the structural and functional properties of this portion of the central auditory pathway.
Three-dimensional eigenrays through ocean mesoscale structure
Authors: Mercer J. A. , Felton W. J. , Booker J. R.
Published: October 2005

The numerical performance of an ocean sound-speed model incorporated into a three-dimensional ray-tracing computer program is partially verified by comparison with a program whose input sound-speed structure varies in only two dimensions. A further comparison is made after including in the model a three-dimensional symmetric Gaussian eddy on the line of sight between the source and receiver. The center of the eddy is then displaced laterally 60 km off the line of sight, and source rays that were previously eigenrays are traced with the three-dimensional code to their divergent locations. The final eigenrays are found by an inexpensive technique that reduces calculations by an order of magnitude or more compared to conventional methods. The results illustrate the importance and practicality of tracing rays in three dimensions.
Modeling of reciprocity in the time domain using the parabolic equation method
Authors: Nghiem-Phu Lan , Tappert Frederick
Published: October 2005

Transmission loss in the time domain is carefully defined, and it is shown to be reciprocal on the basis of the reduced wave equation in fully range-dependent and lossy oceanic environments when currents and other reciprocity-breaking effects are absent. Under the same conditions, it is shown theoretically that time-domain transmission loss as computed by the two-dimensional parabolic equation (PE) method is reciprocal. In a range-dependent bottom-limited ocean, we have numerically computed the time-domain transmission loss and have independently computed its reciprocal using the parabolic equation method and split-step Fourier algorithm. The numerical results confirm that the PE model is accurately reciprocal.
Diffraction of magnetoelastic shear waves by a rigid strip
Authors: Chattopadhyay A. , Maugin G. A.
Published: October 2005

This paper discusses the two-dimensional problem of the diffraction of magnetoelastic shear waves by a rigid strip in an infinite elastic perfect conductor. This problem is reduced to a system of dual integral equations of which the solution provides the diffracted field. The method of steepest descent has been used in the determination of the diffracted fields at a large distance from the strip. Diffraction patterns for displacement and stress fields have been computed and the effect of the magnetic field is distinctly marked.
Relation between creeping-wave acoustic transients and the complex-frequency poles of the singularity expansion method
Authors: Gaunaurd Guillermo , Überall Herbert
Published: October 2005

The Singularity Expansion Method (SEM), as developed for radar scattering, is applied to the problem of acoustic transients of short duration. The scattering amplitude of an impenetrable (rigid or soft) sphere is separated, via the Watson transformation, into a specularly reflected wave and into a remainder which represents creeping waves, but which is transformed here into the usual SEM series of poles in the complex-frequency plane, and their residues. While in the time domain, these give rise to a series of damped sinusoidal signals, a summation of the series using the method of stationary phase, which is being carried out here, determines the shapes of creeping-wave pulses for the case of an incident δ-function pulse.
A reply to comments by Moore [J. Acoust. Soc. Am. 7
8, 253–255 (1985)]
Authors: Lutfi Robert A.
Published: October 2005

Lutfi’s [J. Acoust. Soc. Am. 76, 1045–1050 (1984)] model predicts the results of studies cited by Moore [J. Acoust. Soc. Am. 78, xxx-xxx (1985)]. Differences between simultaneous and forward masked measures of frequency selectivity can be accounted for without involving additional tuning mechanisms.
Release from masking caused by envelope fluctuations
Authors: Buus So/ren
Published: October 2005

This paper examines how short-term energy fluctuations in a masker affect the thresholds for tones at frequencies above those of the masker. Two equally intense tones at 1060 and 1075 Hz produce up to 25 dB less masking than does a 1075-Hz tone set to the overall level of the two-tone complex. At wider frequency separations, two-tone complexes also produce less masking than the pure tone. These results indicate that envelope fluctuations in a masker, whose spectrum is confined to a single critical band, may result in release from masking. The release from masking probably is related to the comodulation masking release reported by Hall et al. [J. Acoust. Soc. Am. 76, 50–56 (1984b)] for modulated-noise maskers with bandwidths greater than one critical band. Further measurements with maskers, whose intensity level in the critical band around 1 kHz was 90 dB SPL, show similar masking by a pure tone and a 625- to 1075-Hz bandpass noise, but less masking by narrow-band noises. These results are inconsistent with a simple frequency selective energy-detector model and indicate that the auditory system can use periods of low masker energy as brief as a few ms to enhance detection of a tone. The results also imply that the upward spread of excitation is best represented by masking patterns for noises with bandwidths of several critical bands.
Frequency and intensity discrimination in humans and monkeys
Authors: Sinnott Joan M. , Petersen Michael R. , Hopp Steven L.
Published: October 2005

Frequency and intensity DLs were compared in humans and monkeys using a repeating standard ‘‘yes–no’’ procedure in which subjects reported frequency increments, frequency decrements, intensity increments, or intensity decrements in an ongoing train of 1.0-kHz tone bursts. There was only one experimental condition (intensity increments) in which monkey DLs (1.5–2.0 dB) overlapped those of humans (1.0 –1.8 dB). For discrimination of both increments and decrements in frequency, monkey DLs (16–33 Hz) were approximately seven times larger than those of humans (2.4–4.8 Hz), and for discrimination of intensity decrements, monkey DLs (4.4–7.0 dB) were very unstable and larger than those of humans (1.0 –1.8 dB). For intensity increment discrimination, humans and monkeys also exhibited similar DLs as SL was varied. However, for frequency increment discrimination, best DLs for humans occurred at a high (50 dB) SL, whereas best DLs for monkeys occurred at a moderate (30 dB) SL. Results are discussed in terms of various neural mechanisms that might be differentially engaged by humans and monkeys in performing these tasks; for example, different amounts of temporal versus rate coding in frequency discrimination, and different mechanisms for monitoring rate decreases in intensity discrimination. The implications of these data for using monkeys as models of human speech sound discrimination are also discussed.
Frequency and intensity discrimination in human infants and adults
Authors: Sinnott Joan M. , Aslin Richard N.
Published: October 2005

Frequency and intensity DLs were measured in 26 human infants (ages 7–9 months) and six young adults using a repeating standard ‘‘yes–no’’ operant headturning technique and an adaptive staircase (tracking) psychophysical procedure. Subjects were visually reinforced for responding to frequency increments, frequency decrements, intensity increments, or intensity decrements in an ongoing train of 1.0-kHz tone bursts, and stimulus control was monitored using randomly interleaved probe and catch trials. Infants were easily conditioned to respond to both increments and decrements in frequency, and DLs ranged from 11–29 Hz, while adult DLs ranged from 3–5 Hz. Infants also easily discriminated intensity increments, and DLs ranged from 3–12 dB, while adult DLs ranged from 1–2 dB. No infants successfully discriminated intensity decrements, although adults experienced no difficulty with this task and produced DLs similar to those for increments. The apparent inability of infants to discriminate intensity decrements suggests that the infant CNS may not be well adapted to monitor rate decreases in populations of peripheral auditory neurons.
Pitch discrimination of harmonic complex signals: Residue pitch or multiple component discriminations?
Authors: Faulkner Andrew
Published: October 2005

Two models for pitch discrimination of harmonic complex sounds are discussed, a multiple-band probability summation model using comparisons among component frequencies, and a model in which residue pitches are compared. The second model is based on Goldstein’s optimum-processor pitch theory [J. Acoust. Soc. Am. 54, 1496–1516 (1973)], and is distinguished from the multiple-band model by an internal noise process. Pitch difference limens from 2I2AFC tasks show that when the test signals comprise corresponding harmonics, relative pitch difference limens are less than the smaller relative difference limens for the component frequencies, which is consistent with the multiple-band model. The absence of corresponding harmonics significantly reduces relative pitch discriminability; this effect supports the model on Goldstein’s theory. It appears that residue pitch comparisons are not used for pitch discrimination between sounds with corresponding components; rather, comparisons based on residue pitch are only employed where there are no common resolved components in the signals to be discriminated.
Prediction of the effectiveness of noise control treatments in urban rail elevated structures
Authors: Remington Paul J. , Wittig Larry E.
Published: October 2005

An analytical model is presented for the generation of noise from an open tie deck elevated structure during the passage of a train. Predictions are compared with measurements before and after installation of resilient fasteners. The model is found to be reasonably accurate, predicting an A-weighted sound level reduction of approximately 2 dB less than actually occurs. The analytical model is then used to estimate the noise reduction achievable through a variety of noise reduction techniques. Resilient rail fasteners seem to be the most promising technique, offering an A-weighted sound level reduction of nearly 10 dB.