bluuebunny/crossref_metadata_2025 huggingface dataset:
Nearfield discrimination capabilities of a line array
Authors: Rockmore Anthony J. , Bershad Neil J.
Published: October 2005

This paper studies the ability of a line array to discriminate between two nearfield acoustic point sources from the viewpoint of statistical hypothesis testing. The optimum binary detectors are presented for noise alone and noise plus point source interference environments. Under a small signal-to-noise power ratio assumption, general expressions are presented for the performance of these detectors. For a uniformly spaced line array with a large aperture (compared to the source range) in a spatially white noise environment, the detector performance is shown to be linearly proportional to signal-to-noise ratio, inversely proportional to hydrophone spacing and proportional to a factor involving the ratio of the separation of the two sources to the acoustic wavelength. When operating in a noise plus interference environment, the performance of this detector is severely degraded. The optimum detector for noise plus interference is shown to perform significantly better.

Subject Classification: 60.20, 60.30.
Experimental observations of a mechanical cochlear model
Authors: Chadwick R. S. , Adler D.
Published: October 2005

A two-chamber cochlear model was built with the basilar membrane modeled by a thin elastic beam. For various input frequencies the steady-state envelopes of the beam oscillations were measured using several combinations of elastic beams and viscous fluids. The frequency dependence of the thickness of the periodic boundary layer adjacent to the beam was also determined. The experimental results are in general agreement with theoretical predictions, and the ability of viscous damping to alter the shape of the envelopes is confirmed. An optical lever suitable for measuring relatively small displacements is also described.

Subject Classification: 65.26, 65.35.
Underwater localization of pulsed pure tones by the California sea lion (Z
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Authors: Moore Patrick W. B. , Au Whitlow W. L.
Published: October 2005

The results of a study to determine the pulsed pure-tone sound-localization capability of a California sea lion, Zalophus californianus, in the horizontal plane are presented. The minimum audible angle (MAA) was determined as a function of frequency from 0.5 to 16 kHz in 1-octave steps. The results suggested that the animal utilized time-difference cues for the lower frequencies (0.5 to 1.0 kHz) and intensity-difference cues for the higher frequencies (4.0 to 16.0 kHz). The MAAs for the lower frequencies were smaller than for the higher frequencies, and for the transitional frequencies (2.0 to 4.0 kHz) the animal experienced extreme difficulties in localizing the sound. To further investigate the effects of sound intensity difference in the localization process, an experiment using a sea lion skull with hydrophones attached close to each bulla was conducted. Intensity differences were measured with the skull directed at different azimuths in relatioship to a sound source. The results of the measurements using the skull considered together with the behavioral data support the contention that the sea lion used both time and intensity cues for underwater localization.

Subject Classification: 65.62; 80.50.
Low-frequency phase distortion of speech recordings
Authors: Holmes J. N.
Published: October 2005

Low-frequency phase distortion introduced by good quality audio tape recorders causes large errors in the reproduced waveform. It is advocated that a low-frequency rectangular wave should always precede the speech on recordings intended for wide distribution, so that the correct phase relationships of spectrum components can be identified. Examples of phase correction by backwards filtering with a sampled-data filter are given. In the absence of a calibration signal, one example used knowledge of typical glottal pulse shapes as a guide for phase correction.

Subject Classification: XX.XX.
Extensional vibration of thin plates of various shapes
Authors: Chen Stanley S. H. , Liu Ta Ming
Published: October 2005

The problem of free extensional (in plane) vibration of thin plates of Hookean material of various shapes was studied. Solutions for dilatational and rotational vibrations were obtained separately. The boundary conditions were satisfied in a least-square sense. Numerical computations were performed for circular, elliptical, triangular, square, and hexagonal plates. The nodal pattern corresponding to each natural frequency for different modes was obtained. The frequency parameters computed for the circular plate are found to be within 0.05% of published results. For plates where known results were not available, the accuracy was checked by taking additional terms in the series solution and by dividing the boundary perimeter into finer intervals. It was found that the circular plate had the lowest fundamental frequency (k1) at 2.049. The value increases as the shape is changed from a circle, with the triangular plate having the highest value at 6.733 in dilatational vibration while the frequencies in rotational vibration (h1) were found to be 3.737 and 16.364, respectively.

Subject Classification: 40.24.
Transmissibility across simply supported thin plates. I. Rectangular and square plates with and without damping layers
Authors: Ochs J. B. , Snowdon J. C.
Published: October 2005

The transmissibility across thin, simply supported, rectangular, and square aluminum plates has been determined experimentally and found to agree closely with theoretical prediction through the frequency range of measurement, which extended from 25 to 3025 Hz. Both the rectangular and the square plates considered were uniquely supported by spring-steel flanges, which were designed to provide, for the first time, true simple supports that simulated almost identically the idealized supports assumed as boundary conditions in theoretical analyses for more than a century. For example, the first 20 resonant frequencies of the rectangular plate with these novel supports differed, with only one exception, by less than 0.55% from their predicted values. One important result obtained for the damped plates considered—which comprised aluminum plates plus applied tiles of high-damping compound to yield composite plates having damping factors of essentially 0.3—was that the measured transmissibility across the plates could be duplicated closely by an expression for transmissibility developed for an internally damped homogeneous plate having damping factors equal to those of the composite plates.

Subject Classification: 40.24, 40.60, 40.20.
Vibrating modes for simply supported polar-orthotropic sector plates
Authors: Rubin C.
Published: October 2005

A method is shown which will provide natural frequencies and mode shapes for the free vibrations of a simply supported polar orthotropic sectorial plate. The special case of a wedge-shaped plate is also treated. The solution applies to any sectorial plate with radial edges simply supported and arbitrary boundary conditions along the circular edges. A series solution which converges rapidly for many natural frequencies is obtained for radial, circular, and mixed modes. An evaluation of the affect of plate orthotropy on the modes is presented. The solution is easily reduced to the isotropic case.

Subject Classification: 40.24.
Intelligibility of speech under nonexponential decay conditions
Authors: Yegnanarayana B. , Ramakrishna B. S.
Published: October 2005

In this paper, subjective studies made on nonexponentially decaying sounds are described. The various decay conditions are realized by changing the position of the pickup microphone in a reverberation room with a highly absorbing sample on the floor. It is shown, by means of articulation tests, that intelligibility of speech is more close to a highly absorbing sample than away from it. It is also shown that the perception of decay is mainly due to the initial portion of a nonexponential decay. The significance of these studies is determining the acoustics of halls is explained.

Subject Classification: 55.20; 70.35; 55.30.
Cochlear nerve fiber responses: Distribution along the cochlear partition
Authors: Pfeiffer Russell R. , Kim Duck O.
Published: October 2005

Fourier analysis of discharge patterns in response to sinusoidal acoustic stimulation provides a consistent and repeatable measure of response phase and amplitude. The distribution of the fundamental components of response for large populations of fibers as a function of their characteristic frequency provides a link between the spatiotemporal characteristics of basilar membrane vibration and single fiber response.

Subject Classification: 65.42, 65.40.
Convenient system for precise ultrasonic measurements using the time-interval-averaging method
Authors: Kondo Ken-ichi , Itoh Kiyoshi , Sawaoka Akira , Saito Shinroku
Published: October 2005

A convenient system for ultrasonic measurements has been developed by using the time interval averaging (TIA) method. Since a standard type of universal counter with TIA circuit can be used, the system consists of simple and low-priced equipment. The sensitivity for relative changes in travel time of ultrasonic waves is better than 0.4 nsec. The travel time is automatically shown on the counter withount any manual adjustment.

Subject Classification: 85.22; 35.24, 35.80.
Scattering of obliquely incident plane acoustic waves by an elastic disk
Authors: Knittel Max R. , Nichols Charles S. , Barach Don
Published: October 2005

In a previous paper, the authors developed a formulation for mathematically modeling the scattering of plane acoustic waves by an elastic body, and results were presented for the scattering of normally incident plane waves from a disk. In this paper, results are presented for scattering of obliquely incident plane waves from the same disk. Total scattering cross sections are calculated as functions of frequency and incident angle. For an incident wave angle of 60°, the calculated displacement distributions on the disk are decomposed into the disk’s free vibrational eigenmodes at selected frequencies. The scattering patterns of total pressure and of scattered pressure and contour plots of the nearfield pressure distributions are also presented for frequencies of interest.

Subject Classification: 30.35, 30.40, 30.30.
Determination of the wave velocity in an inhomogeneous medium from the reflection coefficient
Authors: Razavy M.
Published: October 2005

In this paper, we study the problem of obtaining the velocity of the wave propagation in an inhomogeneous medium from the reflection coefficient (given for all frequencies) for a one-dimensional wave equation. Following the work of Kay and Moses, we reduce the problem to that of determining a ’’potential’’ for a Schrödinger-type equation. However, in our work this ’’potential’’ depends quadratically on the wavenumber, and this dependence changes the structure of the spectral function and integral equations of the inverse problem. In the first part of the paper, we assume that the wave velocity c (x) has the same value at x=+∞ and at x=−∞. Then we relax this condition on c (x) and consider the cases where c (+∞) is different from c (−∞), but both quantities have well-defined values. For certain types of velocities, we obtain the reflection coefficient analytically. We then use these reflection coefficients to get approximate solutions to the inverse problem. Finally, we present an example of a heterogeneous medium which is transparent for all frequencies of the incident wave.

Subject Classification: 20.30, 20.35, 20.15.
Laser-excited broadside array generated from a spherically spreading laser beam
Authors: Larson Richard S.
Published: October 2005

The problem of the generation of sound from an intensity-modulated laser is generalized to include the effect of spherical spreading of the propagating laser beam. It is shown that divergence of the laser beam reduces the sound generated perpendicular to the axis of the laser beam and increases the beam width of the sound wave.

Subject Classification: 35.65.
Incoherent ultrasonic imaging system
Authors: Sato Takuso , Wadaka Shusou
Published: October 2005

Fundamental construction and some experimental results of incoherent ultrasonic imaging systems are presented. A means for the generation of incoherent ultrasonic fields, a proper scanning method of receivers for the detection of coherence functions, and methods of signal processing for the reconstruction of images from the detected coherence functions are proposed and their properties are discussed theoretically. A concrete system based on these discussions is constructed. The experimental results show the usefulness of the proposed system, though the experiments are carried out only for one-dimensional objects. Moreover, as an example for showing the special feature of the system, it is applied to imaging in a turbulent medium. The effectiveness of the method is illustrated by comparing the result with that of a holographic imaging system.

Subject Classification: 35.65; 60.30.
Bearing estimation using a large towed array
Authors: Hinich Melvin J. , Rule William
Published: October 2005

When a towed array of hydrophones is significantly nonlinear due to bending, ordinary linear array beamforming gives a biased estimate of the true source bearing. By processing the array as a sequence of smaller aperture subarrays and then computing the mean of the subarray bearings, the variation due to bending is reduced and a reasonably precise estimate is obtained if the average bending angle with respect to the nominal axis is small. The median and mean subarray bearings are analyzed for a theoretical statistical model and are tested using artificial data for various sinusoidal array geometries.

Subject Classification: 60.20; 30.82.
Synthetic whole-nerve action potentials for the cat
Authors: de Boer E.
Published: October 2005

In response to a tone burst, a pattern of activity is set up in the set of auditory nerve fibers. A simplified model is described in this paper that can represent this pattern both with respect to the number of nerve fibers involved and the detailed time course of the firings. The parameters of the model concerning frequency selectivity and latency are adapted from measurements with the so-called reverse correlation technique. Further properties incorporated in the model are saturation for excitation over 40 dB above threshold and high sensitivity. When specific assumptions are made regarding the contribution of the firing of each nerve fiber to the whole-nerve potential, the waveform of the action potential (AP) can be synthesized from the model. The theory gives a quantitative account of the dependence of the AP latency upon stimulus intensity. Two main contributing factors are frequency selectivity and latency distribution of nerve fibers. Experimental AP amplitudes show a more complex course as a function of stimulus intensity than the theory predicts. Several possible improvements of the method are discussed. Since AP recordings are often used for diagnostic purposes, a separate section of the paper is dedicated to the connection between the properties of auditory nerve fibers and of the whole-nerve AP in abnormal ears.

Subject Classification: 65.42, 65.35.
Nonmonotonic behavior of distortion product 2f1−f2: Psychophysical observations
Authors: Hall J. L.
Published: October 2005

A detailed study was made of the amplitude and phase characteristics of auditory distortion product 2f1−f2 in the neighborhood of an amplitude minimum. For f2=1.0, 1.2, and 1.4 kHz, f1 was varied from 0.68⋅f2 to 0.88⋅f2, and the (equal) intensity of the two primary tones was varied from 50 to 70 dB SPL. For the one subject investigated, the ampltiude of the 2f1−f2 distortion product exhibited a single minimum in the portion of the f1/f2 versus intensity plane explored. The value of f1/f2 at the minimum was 0.8 and was roughly constant for various frequencies of f2. The primary-tone amplitude at the minimum decreased with increasing f2 from 60 dB SPL at 1 kHz to less than 50 dB SPL at 1.4 kHz. The 2f1−f2 phase in the neighborhood of the null was complicated. It changed abruptly at the minimum, it changed more rapidly with f1/f2 at primary-tone intensities below the null than above, and it changed slowly with primary-tone intensity at f1/f2 ratios both below and above the null. Therefore, a complete circuit around the null in the f1/f2 versus intensity plane resulted in a change of 2f1−f2 phase of 360°.

Subject Classification: 65.56.
Sound source inside and outside of a lined segment of rectangular duct
Authors: Mariano S.
Published: October 2005

The effect of changes in source position on the attenuation by a lined duct segment has been analyzed. The results show that variations in source position produce significant changes in the attenuation. This is the direct consequence of modifications in the model content of the exciting pressure field.

Subject Classification: 20.45, 20.35.
Narrow-bandwidth pulses in elastic bars
Authors: Fraser W. B.
Published: October 2005

A ’’two-timing’’ perturbation method is used in conjunction with Mindlin and Herrmann’s approximate one-dimensional elastic bar theory to investigate the propagation of a high-frequency, narrow-bandwidth pulse in an elastic bar.

Subject Classification: 40.22; 20.15.
Comments on ’’Radial vibrations of axially polarized piezoelectric ceramic cylinders’’ [N. T. Adelman, Y. Stavsky, and E. Segal, J. Acoust. Soc. Am. 57, 356–360 (1975)]
Authors: Onoe Morio
Published: October 2005

Attention is called to a previous work done by the author in 1963. An explicit formula for electrical admittance and the piezoelectric excitation of even-numbered overtone modes of vibration are quoted.

Subject Classification: 40.26; 85.52.
Reply to ’’Comments on ’Radial vibrations of axially polarized piezoelectric ceramic cylinders’ ’’ [M. Onoe, J. Acoust. Soc. Am. 58, 1099(L) (1975)]
Authors: Adelman N. T. , Stavsky Y. , Segal E.
Published: October 2005

The authors reply to comments by M. Onoe.

Subject Classification: 40.26; 85.52.
Static acoustic impedance of the chinchilla middle ear: Awake and sedated
Authors: Woodford Charles M. , Henderson Donald , Hamernik Roger P. , Feldman Alan S.
Published: October 2005

The static acoustic impedance of the chinchilla ear was measured in 50 animals, using the Grason–Stadler model 1720 Otoadmittance meter. The mean acoustic impedance in the awake animal was found to be 747 acoustic ohms. The standard deviation was 171 acoustic ohms. Acoustic impedance measures were obtained under the influence of various doses of Diabutal. The results indicate that there in an increase in negative pressure in the middle ear and concommitant decrease in acoustic impedance following administration of this anesthetic. The magnitude of the change in acoustic impedance was dependent upon the dosage administered. In addition, various aspects of the chinchilla tympanogram are discussed.

Subject Classification: 65.24, 65.22.
Automation of impedance tube measurements
Authors: Dunlop J. I.
Published: October 2005

An apparatus is described that enables the automatic determination of impedance tube data, namely, the positions of the first two minima and the standing-wave ratios along the tube.

Subject Classification: 85.20.
History and present status of liquid surface acoustical holography
Authors: Brenden Byron B.
Published: October 2005

Use of the liquid surface as a detector of ultrasonic energy dates back to 1935. Its use as a detector in acoustical holography began early in 1964. The dynamic response of the liquid surface permits real-time viewing of the image at frame rates of more than 100 per second. Color translation has been demonstrated but is not currently being used in practical systems. Images of soft tissue structures in the hand, arm, and in excised organs show much interesting and useful detail including tendons, muscles, tendon attachments to the skeletal structure, veins, and arteries.

Subject Classification: 10.60; 35.65.
Comments on ’’Measured jet noise compared to California noise codes and health limits’’ [S. R. Lane, J. Acoust. Soc. Am. 56, 1805–1810 (1974)]
Authors: Hildebrand B. G.
Published: October 2005

In this paper on jet noise measurements the author claims that noise measurements he made under aircraft approach paths to Los Angeles International Airport, and noise measured by Hydrospace Research Corporation and the City of Inglewood, California, show that airplane noise consistently exceeds SENEL limits of the California Noise Rule. The author’s SENEL values were estimated by adding ’’appropriate factors’’ to dBA meter readings. He drew an erroneous conclusion from the Hydrospace and the Inglewood data as a result of extrapolating noise levels specified by the California Noise Rule to large distances. Contrary to his belief, the Hydrospace and Inglewood data show that airplanes do not consistently violate the California Noise Rule. Lane’s reported results do not agree with results reported in similar tests conducted by The Boeing Company, Hydrospace Research Corporation, or the City of Inglewood.

Subject Classification: 50.50, 50.75, 50.55.
Finite-amplitude standing waves within real cavities
Authors: Coppens Alan B. , Sanders James V.
Published: October 2005

A three-dimensional mathematical model for acoustical standing waves in lossy fluid-filled cavities has been obtained which requires empirical values for the resonance frequencies fn and quality factors Qn (all measured in the linear acoustic régime) of the pertinent standing waves which the cavity can support. The nonlinear distortion of the observed pressure waveform depends strongly on the f’s and Q’s of those standing waves excited by harmonics of the driving frequency. The model is applicable to nonideal cavities if the deviations from idealized geometry and boundary conditions are small. It is restricted to small values of M (1+1/2 B/A) Q1 where M is the peak Mach number and Q1 the quality factor of the fundamental component of the driven standing wave, and B/A is the parameter of nonlinearity of the fluid. Comparisons between the model and experiment are made for a rectangular cavity driven in one- and two-dimensional modes. Agreement is excellent except when there are degeneracies involving the predicted nonlinearly excited standing waves and other standing waves of the cavity. Small discrepancies appear to result from the coupling of energy from the nonlinearly excited standing wave into its degenerate neighbor.

Subject Classification: 25.25; 55.20.
Measurement of freeway noise and community response
Authors: Jenkins M. A. , Pahl Juergen
Published: October 2005

Personal interviews were conducted with 562 freeway-proximal residents and 134 residents in control neighborhoods. Five factor-analyzed scales were used to measure community response to freeway noise in terms of (1) subjective reactions and (2) behavioral interruptions due to noise. The social survey allowed for spontaneously mentioned and directly elicited responses. Noise exposure was measured by an Environmental Noise Classifier; one representative noise sample was taken for every residence, and L10, L50, L90, NPL, and TNI were computed. These noise measures correlated highly with each other, except TNI, and none of the measures demonstrated superiority over the others as a predictor of community response. Community response was analyzed as a function of noise level, and all response scales increased with increasing noise levels; for example, freeway noise was reported by 50% as the main cause of dissatisfaction, by 13% as main cause for complaints, by 25% as the reason for wanting to move, and by 43% as the reason for awakening at night. Noise levels correlated 0.99 with mean annoyance ratings for groups of residents within specified noise strata, and 0.31 for ratings based on individual annoyance scores.

Subject Classification: 50.70, 50.50, 50.20, 50.75.
Identification of random auditory waveforms
Authors: Pollack Irwin
Published: October 2005

Listeners quickly learn to identify, apparently on an absolute basis, the ordering of a pair of sounds, where one sound is a specific random selection which is constant over successive observations, and where the other sound varies over successive observations. The accuracy of identification is not directly related to the uncertainty of the pool of possible waveforms. A wide range of sample durations and spectra characterize the identifiable pools. Increasing the predictability of the sequences does not improve identification accuracy. Listeners also can identify one of two selections from the same pool and can identify departures from a prototype which they have never heard. Since all random selections from the same pool have nearly identical long-term average spectra, it is concluded that the listener must perform a short-term, or running, spectrum analysis upon the signals.

Subject Classification: 65.22, 65.75, 65.68.
Perception of complex sounds: ’’Hidden auditory figures’’
Authors: Pollack Irwin
Published: October 2005

Hidden auditory figures were generated by ORing the output of a bank of counters, driven by a high-frequency periodic pulse train. The absolute detection, the relative discrimination, and the identification of hidden auditory figures of up to ten prime counts was examined. The crucial factor in detection and discrimination is the context in which the to-be-examined component is embedded. A given count may be nearly perfectly detectable if it is the smallest of the series of prime counts; that same count may be nearly undetectable if it is the largest of the series of prime counts. Within hidden auditory figures, the spread of interference is opposite in direction to most masking situations: High frequencies (represented by small counts) are more effective than low frequencies (represented by large counts). Many of the crucial details are to be found in the spectrum of these signals.

Subject Classification: 65.22, 65.56, 65.75.
Auditory intensity discrimination in the parakeet (M
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Authors: Dooling Robert J. , Saunders James C.
Published: October 2005

Three parakeets were trained by a method of avoidance conditioning to respond to intensity differences in successsively occurring tone bursts. Intensity difference limens were obtained at six sensation levels of a 2.86 kHz tone. The relative intensity difference limens (ΔI) for the parakeet were larger than similarly reported measures for man and other mammals at all sensation levels tested. Calculations of the Weber fractions at each sensation level tested showed that Weber’s law holds for the parakeet at sensation levels above 50 dB.

Subject Classification: 80.50; 65.75, 65.50.
Comments on ’’Propagation of normal mode in the parabolic approximation’’ [Suzanne T. McDaniel, J. Acoust. Soc. Am. 57, 307–311 (1975)]
Authors: Williams A. O.
Published: October 2005

Three comments are offered to complement McDaniel’s recent analysis of errors due to the parabolic approximation. First, it is shown that both the parabolic method and the somewhat similar WKB method yield good approximations for the amplitude of the acoustic field, in underwater sound propagation, but the WKB phase result is much superior. Second, another test of phase errors is proposed, that of zone or channel convergence; it turns out the parabolic method should handle such cases quite adequately. Third, the demonstrated greater success of the parabolic method for the lower normal modes of a many-mode set is explained as stemming from the algorithm used in numerical solutions.

Subject Classifications: 30.20; 20.40, 20.15.
Historical review of horns used for audience-type sound reproduction
Authors: Hilliard John K.
Published: October 2005

This paper reviews the history of horns used in loudspeaker systems for audience-type sound reproduction. It reviews the early pioneering work started around 1910 which used telephone-type transmitters before vacuum tube amplifiers were available. With the availability of amplifiers more powerful driver type loudspeakers were developed to operate with exponential straight and folded horns. Sound motion pictures created a demand for higher quality, and higher-powered loudspeaker systems for both voice and music. The many stages of development of two-way loudspeaker systems are reviewed. The limitations of each stage of development before proceeding to the next improvement is discussed. Photographs of many early horns are included as well as the more recent types.

Subject Classification: [43]10.60; [43]85.60.
Wake-related sound generation from isolated airfoils
Authors: Clark Larry T. , Chalupnik James D. , Hodder Brent
Published: October 2005

A model for the prediction of wake-related sound generation by a single airfoil is presented which assumes that the net force fluctuation on an airfoil can be expressed in terms of the net momentum fluctuation in the near wake of the airfoil. The model predicts a forcing function for sound generation which is related to the spectra of the two-point velocity correlations in the turbulent region near the airfoil trailing edge. Cross spectra were obtained from correlations of the longitudinal and transverse components of turbulence in the wake of a 36-in. chord NACA series 63-009 airfoil in the 7×10 ft tunnel at the NASA Ames Research Center using x-probe hot-wire sensors. Additional data were obtained from a 10-in. chord airfoil in a free-jet facility at the University of Washington. Based on results from these tests, a scaling model was developed using the turbulent boundary-layer thickness as the primary length measure. The model was used to predict the sound radiated from a 2-in. chord airfoil for which acoustical data is available with good agreement both in level and spectral shape. The single airfoil result is extended to a rotor geometry and comparisons studied for various aerodynamic parameters.

Subject Classification:[43]28.65; [43]50.55.
Acoustic reflection from a structured sea bottom
Authors: Williams A. O.
Published: October 2005

Acoustic reflection coefficients for reflection from ocean bottoms are sometimes calculated for postulated models of the bottom structure. A published example, using a model based on geophysical data, is examined with attention to possible simplification and to the physical links between model and computer output. It is shown that calculated results at small grazing angles have a physical cause and can be well approximated by a simpler model. It appears, however, that at larger angles the results are not physically reasonable. The cause is that a commonly used ’’pseudolinear’’ gradient of sound speed is unphysical in a half space, because at a certain finite depth the sound speed becomes infinite, and imaginary at greater depths. A physically reasonable profile of sound speed is proposed as a substitute and expressions for the reflection coefficient are derived in the approximation of vanishing absorption. At that stage, the expressions are considerably simpler than those of the published example. An extension incorporating absorption is planned.

Subject Classification: [43]30.20, [43]30.30.
Sonar for generalized target description and its similarity to animal echolocation systems
Authors: Altes Richard A.
Published: October 2005

Range-distributed targets are often characterized as arrays of point scatterers. This conceptualization corresponds to a target impulse response that is a sequence of impulses. A physically meaningful generalization of this description is obtained by modeling an impulse response in terms of pulse doublets, impulses, step functions, ramp functions, etc., i.e., as a superposition of delayed impulses and differentiated or integrated impulses. A sonar system for generalized target characterization is derived in this paper. Signals and receivers are specified for (1) optimum estimation of reflector parameters and (2) detection of a known target in clutter. The derived signals correspond closely with some of the waveforms that are used by dolphins and bats for echolocation. The corresponding echo analyzers are similar to psychoacoustic models of the mammalian hearing system.

Subject Classification: [43]60.20, [43]60.50; [43]30.82; [43]80.50.
Effective quiet and moderate TTS: Implications for noise exposure standards
Authors: Ward W. Dixon , Cushing E. Marion , Burns Edward M.
Published: October 2005

’’Effective quiet,’’ the highest SPL of a noise that will neither produce a significant temporary threshold shift (TTS) nor retard recovery from a TTS produced by a prior exposure to a higher level, is shown to be about 76 dB for octave bands of noise centered at 250 and 500 Hz, and around 68 dB for those centered at 1000, 2000, or 4000 Hz. On the other hand, a mean TTS2 (TTS 2 min after exposure) of no greater than 10 dB at all frequencies from 500 to 5600 Hz is produced by a broad-band noise whose octave-band spectrum falls off at −5 dB per octave (’’magenta’’ noise) and which has an A-weighted level of 90 dBA. When the group mean TTS2 is 10 dB, less than 10% of normal ears will show a TTS2 of 20 dB. Therefore if a 20-dB TTS2 is tolerable day after day with no adverse effects, the present industrial noise exposure limit of 8 h at 90 dBA would adequately protect more than 90% of exposed workers in noises with similarly falling spectra. Correction factors for unusual spectra should, however, be developed.

Subject Classification: [43]65.66, [43]65.64; [43]50.70.
Middle ear pressure: Effects on the auditory periphery
Authors: McPherson D. L. , Miller J. M. , Axelsson A.
Published: October 2005

The effects of direct variation in static middle ear pressure were studied in the acute guinea pig. Pressure differences of from −500 to +500 mm of H2O were examined. Pure tones were delivered to the test ear in a closed system and the sound pressure levels monitored with a condenser microphone and probe tube situated 2 mm from the tympanic membrane. The cochlear microphonic was recorded from a round window electrode. Both the relative impedance change and cochlear microphonic were noted at various middle ear pressure levels. The animals were perfused with Prussian blue and cochleas stained with osmic acid and prepared for histopathological study. It was found that negative pressure causes greater changes on impedance and transmission than positive pressure. Increase in positive pressure was found to cause a monotonic increase in input impedance and decrease in transmission. For negative pressures, the effect was nonmonotonic. Observed changes in transmission with both positive and negative pressures could be accounted for only in part by changes in input impedance of the middle ear. Morphological findings showed some discrete dilation of the vessels on the malleus and the tympanic membrane.

Subject Classification: [43]65.24, [43]65.40.
Experiments on ultrasonic cavitation in liquid helium in the presence of second sound
Authors: Dhingra H. C. , Finch R. D.
Published: October 2005

Cavitation in liquid helium was induced using an ultrasonic cylindrical transducer resonant at approximately 57 kHz. Interaction of the sound field with superfluid helium during cavitation runs was studied using a low-power second-sound signal. This signal was observed to decay when a voltage whose amplitude increased linearly with time was applied to the ultrasonic transducer. This is interpreted as being due to the growth of turbulence in the liquid. It is contended that for the sound field to induce cavitation, the liquid has to be in a state of turbulence. It is possible that there is a threshold for additional attenuation of the second-sound signal near the onset of cavitation. Some cavitation runs were also made in the presence of a high-power second-sound current. Under these circumstances turbulence was generated, either by the second-sound field or by the associated steady heat current. This turbulence lowered the cavitation threshold.

Subject Classification:[43]25.60; [43]35.32, [43]35.47.
Monaural loudness adaptation at low sensation levels in normal and impaired ears
Authors: Margolis Robert H. , Wiley Terry L.
Published: October 2005

Monaural loudness adaptation was measured in subjects with normal hearing and in subjects with noise-induced sensori-neural hearing loss using a dichotic delayed balance procedure. Adapting stimuli were presented at two sensation levels (15 and 25 dB SL), two frequencies (500 and 4000 Hz), three durations (1, 30, and 60 sec) and two inter-stimulus intervals (10 and 400 msec) and the loudness of the terminal portion of the adapting stimuli was measured with a method of constant stimuli. No loudness adaptation occurred under any conditions for the normal subjects. Hearing-impaired subjects demonstrated small amounts of loudness adaptation, but the occurrence of adaptation did not always coincide with the frequency region of the hearing loss. There was no effect of interstimulus interval for either subject group.

Subject Classification: [43]65.50, [43]65.64, [43]65.66.
Loudness adaptation in listeners with noise-induced hearing loss
Authors: Wiley Terry L. , Lilly David J. , Small Arnold M.
Published: October 2005

Loudness-adaptation measurements were made using a monaural procedure at 10-, 20-, and 40-dB SL for 500 and 4000 Hz in six subjects with noise-induced hearing loss. The results indicated loudness adaptation only for 10-dB SL at 4000 Hz (where hearing loss was present) and for only three of the subjects. The findings support similar data obtained using dichotic (heterophonic) loudness-balance and threshold tone-decay techniques.

Subject Classification: [43]65.50, [43]65.64; [43]50.70.
Effects of learning English as a second language on the acquisition of a new phonemic contrast
Authors: Streeter L. A. , Landauer T. K.
Published: October 2005

Very sharp discrimination functions for the timing of voice onset relative to stop release characterize perceptual boundaries between certain pairs of stop consonants for adult speakers of many languages. To explore how these discriminations depend on experience, we studied their development among Kikuyu children, whose native language contains no stops in which voicing is substantially delayed relative to stop release (e.g., /p/). Kikuyu distinguishes stops in which voice onset substantially precedes release (prevoiced) from those in which voice onset is nearly simultaneous with release (voiced) for apical and velar places of articulation. However, the language has only a single prevoiced labial stop. Prior to exposure to English, children discriminated prevoiced from voiced labials and voiced from voiceless labials, although these distinctions are not phonemic in Kijuyu. Moreover, the voiced/voiceless discrimination for labials ([ba] versus [pa]) improved markedly with schooling in English, rapidly surpassing the prevoiced/voiced distinction. Apparently, certain voice onset time differences are naturally discriminable, but it is also apparent that the very fine voiced/voiceless discrimination among adults for whom it is phonemic is largely attributable to experience.

Subject Classification: [43]70.30, [43]70.70.
Intensity–range relations for shallow-water sound propagation
Authors: Murphy Edward , Olesen Ole V.
Published: October 2005

Convincing experimental evidence is presented to show that various ’’decay laws’’ for the decrease of sound intensity with increasing range can give high-quality representation for shallow water data. However, while a sequence of decay laws may fit data well and are simple, the transition ranges for changeover from one law to another can show a complicated dependence on frequency and environmental parameters. Transition ranges are probably no easier to predict or model than is the transmission loss itself.

Subject Classification: [43]30.20, [43]30.25.
Cross correlation of short-time spectral histories
Authors: Flaska M. D.
Published: October 2005

Two-dimensional cross correlation of short-time power spectral histories (energy distribution functions) is a hybrid signal-processing technique that uses both coherent and incoherent processing. Background is developed which relates the energy density function to the energy distribution function and the wide-band ambiguity function. The cross correlation of a signal’s energy distribution function is shown to be a convolution of its squared magnitude ambiguity function with the squared magnitude ambiguity function of the impulse response of the filter used to obtain the energy distribution functions. The output signal-to-noise ratio is derived for a single Doppler channel, assuming sampled, single-valued, energy distribution functions. The signal-to-noise ratio is also obtained, assuming amplitude spectral analysis, for the linear frequency modulated slide waveform.

Subject Classification: [43]60.20; [43]30.20; [43]28.20.
Cochlear nonlinearity and second filter: Possible mechanism and implications
Authors: Duifhuis H.
Published: October 2005

We indicate that the directional sensitivity of the hair cell together with a directional distribution of frequency over the hair cells comprise a possible physiological basis for the second filter. Tuning disparity of the first and second filter denotes the difference in tuning frequency; at a given position x the tuning frequency of the first filter is αCF, of the second CF, with α≳1. This accounts for the asymmetry in location of two-tone suppression areas. The compressive nonlinearity is described by a νth law device with ν<1. We analyze implications of this model for two-tone suppression, sharpening, pure-tone masking, and combination tone generation. Basic features of these phenomena are described adequately. For combination tones the propagation problem needs further study. On the basis of a comparison of literature data and theoretical predictions we estimate α=1.2 and ν=0.6. Regarding accurate shape of the first and second filter, the discussed data provide means for a qualitative evaluation only. Possibilities for a quantitative analysis are indicated.

Subject Classification: [43]65.20, [43]65.35, [43]65.42, [43]65.26.
Cavitation in liquid helium using a vibrating piston
Authors: Vroulis T. , Neppiras E. A. , Finch R. D.
Published: October 2005

Experiments have been performed in which a piston is vibrated inside a glass tube containing liquid helium. The piston was driven by an electromagnetic shaker in the frequency range 20–80 Hz at an intensity capable of generating cavitation effects. At critical particle velocity amplitudes of a few centimeters per second noise is generated. This threshold velocity appears to be independent of frequency. A much higher velocity, about an order of magnitude greater, is required to produce visible bubbles in superfluid Helium II, but the two thresholds are the same in Helium I. The results are believed to indicate that fluid dynamic effects are important in cavitation nucleation.

Subject Classification: [43]25.60; [43]35.32, [43]35.47.
Dynamic effects of mechanical angular scanning of a parametric array
Authors: Widener M. W. , Rolleigh R. L.
Published: October 2005

The effect of mechanical angular scanning of a parametric array is examined theoretically and experimentally. The results indicate that difference frequency pressure level and directivity are not affected if the frequency of rotation is small compared to the difference frequency.

Subject Classification: [43]25.35; [43]30.75.
Outdoor sound propagation over ground of finite impedance
Authors: Embleton T. F. W. , Piercy J. E. , Olson N.
Published: October 2005

There is an extensive body of theory, and some laboratory measurements, of sound propagation over a surface of finite impedance. There are also reliable measurements of outdoor sound propagation in near-horizontal directions over the ground. In an attempt to relate these more closely, we have made carefully controlled measurements at ranges from 1 to 1000 ft, in most cases over grass-covered flat surfaces, to demonstrate the several phenomena that are involved. These phenomena depend on, and conversely provide a means of estimating, the values of ground impedance for waves at near-grazing angles of incidence. Such values obtained for grass-covered surfaces are in reasonable agreement with each other and with values obtained by conventional means at other angles of incidence. It is suggested that simple but accurate predictions of noise levels can be made by assuming that an excess attenuation due to finite ground impedance would always exist in a certain shadow region near the ground. This shadow region is however penetrated at low frequencies by a ground wave, to an extent that depends principally on distance and ground impedance, and at higher frequencies by interference between direct and ground-reflected waves to an extent that depends also on source and receiver heights. These phenomena, well established at ranges up to about 1000 ft and in some aspects to over 3000 ft, have been extrapolated theoretically to the order of 10 000 ft so that simple effects of topography and meteorology can be added to show how reflection or refraction acts in conjunction with ground impedance to result in penetration of the shadow region.

Subject Classification: [43]28.40; [43]20.55.
Effect of signal phase on the detectability of a tone masked by two tones
Authors: Phipps Alan R. , Henning G. Bruce
Published: October 2005

The masking effect of two pure tones of equal intensity, started in phase, on a third pure tone placed midway in frequency between them was studied as a function of the frequency separation of the maskers for two different starting phases of the signal. At large separations (50 Hz or more), the signal phase had no effect on its detectability, but when the separation was smaller, the maskers were less effective at masking a signal which began in 90° phase with respect to the maskers than one which began in the same phase. These results are considered in terms of the energy-detector model frequently used to describe auditory processing; those at small separations are found to be inconsistent with such a device. It is suggested instead that deviations in the instantaneous frequency of the out-of-phase signal plus maskers complex are responsible for the improved performance with such signals when the bandwidth is small.

Subject Classification: [43]65.58, [43]65.60, [43]65.75.
Acoustic resonance in composite cavities
Authors: Hughes R. C. , Haering R. R.
Published: October 2005

A treatment of the acoustic resonance of a composite cavity consisting of two intimately bonded one-dimensional acoustic cavities is given. We present an expression which can be numerically iterated to obtain the acoustic velocity from acoustic resonance measurements on a double cavity. A technique of evaluating the reflection coefficient of the bond interface of composite cavities is developed and it is shown that the particular metallic bond used in our experiments is nearly ’’perfect’’ acoustically. For a composite cavity consisting in part of a piezoelectric insulator, the electrical impedance and conductance are derived. Agreement between experiment and theory is good.

Subject Classification: [43]85.32; [43]20.40; [43]85.20.
Magnetomechanical characteristics of a terbium–holmium–iron alloy
Authors: Timme R. W.
Published: October 2005

The magnetostrain, permeability, magnetostrictive constant, and elastic compliance constant of the alloy Tb0.145Ho0.855Fe2 have been measured as a function of magnetic bias. The magnetomechanical coupling constant and maximum power output calculated as a function of bias field are significantly higher than published values for nickel. The dynamic strain under power drive is as large as that of a commonly used ceramic at maximum drive. These findings support the conclusion that this ternary rare earth-iron alloy can compete with nickel or ceramics as a sound projector material.

Subject Classification: [43]85.46; [43]30.85.
Pronounced binaural pitch phenomenon
Authors: Bilsen Frans A.
Published: October 2005

Using a special multiple-phase-shift filter with a flat amplitude response, a rather strong sensation of pitch was evoked by dichotic presentation of white Gaussian noise. The existence of this pitch, which resembles a periodicity pitch, can be understood on the basis of the ’’central spectrum’’ model of pitch perception [Bilsen and Goldstein, J. Acoust. Soc. Am. 55, 292–296 (1974)].

Subject Classification: [43]65.54, [43]65.62.