bluuebunny/crossref_metadata_2025 huggingface dataset:
A mapping of selective adaptation
Authors: Harris L. B. , Pastore R. E.
Published: October 2005

A series of experiments were conducted in which variations of the selective adaptation procedure were employed with a synthetic /bi/-/di/ continuum for three female observers in an effort to obtain a systematic mapping of the selective adaptation phenomenon. The first experiment consisted of a series of adaptation sequences each followed by a labeling task in which members of the continuum were randomly presented for identification. Trials were either massed (two minutes between trials) or distributed (20 minutes between trials) in presentation. The degree of adaptation in the two conditions was not significantly different. The second experiment examined adaptation onset and involved varying the number of adaptors presented prior to either a labeling or a random ABX discrimination procedure. Results indicate that labeling and discrimination do not exhibit the same course of adaptation. In the third study, the interval between the last adaptor and the first test stimulus was manipulated to observe the adaptation decay functions for both labeling and discrimination. The results again point to a dissociation between labeling and discrimination with a differential rate of decay for each measure. Findings are discussed in terms of the current hypotheses proposed to account for selective adaptation. [Supported by a grant from NSF.]
Phonetic categorization shifts for four continua embedded in fluent semantic contexts
Authors: Spencer N. J. , Halwes Terry
Published: October 2005

Initial studies on nonacoustic factors influencing categorical perception of naturally produced speech (Spencer and Halwes, APA, 1978) demonstrated that a labeling crossover between hearing “d” or “t” in a crossed spliced VOT continuum remained approximately the same for different acoustic contexts. But when the continuum steps were inserted into contrasting biasing meaningful sentence carriers, 35 of 42 listeners exhibited crossover shifts. To examine the generalizability of semantic influences on perceived phonetic content, three more series, another “tense-dense” continuum with changed sentence carriers and two “slit-split” continuua with similar sentence carriers, were prepared with the same computer editing procedures and presented in listening conditions as before. Only six of 18 listeners exhibited crossover shifts appropriate for semantic contexts in the “tense-dense” series. The results of one “slit-split” series were consistent with a semantic effect interpretation but the results of the other were not. Variability across continuua and listeners' responses suggest procedural limitations for revealing influences on phonetic categorization from listeners' attention, acoustic support, and semantic factors. [Research supported by NICHD.]
Evidence for the role of acoustic boundaries in the perception of speech sounds
Authors: Stevens Kenneth N.
Published: October 2005

Evidence from several different experiments in the past has supported the notion that cues for the perception of some of the phonetic features for consonants reside in regions of the speech signal in which there are rapid changes in the spectrum. This paper presents additional data that support this view for two features: The/s-š/ distinction and the nasal-stop distinction. In both experiments, continua of synthetic sounds were generated in which certain acoustic properties of the steady-state portion of the consonant (spectrum of fricative noise or amplitude of nasal murmur) were manipulated and acoustic events in the brief time interval immediately adjacent to the consonantal release were manipulated independently. Listener responses to these stimuli showed that the perception of the relevant phonetic dimension /s-š/ or nasal stop was influenced strongly by the acoustic properties adjacent to the consonantal release. The acoustic attributes during most of the consonantal closure interval could be manipulated over a wide range without changing the identification of the segment, as long as the attributes in the 50-odd ms in the region of the boundary were appropriate. [Work supported in part by a grant from NINCDS.]
Effects of hearing loss on the detection of amplitude modulated noise
Authors: Henderson D. , Salvi R. , Hamernik R. P. , Pavek G.
Published: October 2005

Hearing loss is known to influence auditory temporal processing; there is a decrease in the time constant of temporal integration for tone bursts however, the same hearing loss increases the time constant for gap detection and forward masking. The detection of amplitude modulated signals, another aspect of temporal processing, was studied in three monaural chinchillas using conditioned avoidance procedures. Pre-exposure pure tone thresholds were measured from 0.25 to 16 kHz and modulation thresholds (0.002 to 4.096 kHz) were obtained using sinusoidally amplitude modulated broad band noise having an SPL of 53 dB. Chinchillas were initially exposed for 7 days to an octave band of noise centered at 8 kHz. The animals developed a high frequency loss of 50–70 dB and the amplitude modulation function showed a decline in sensitivity. Then the noise exposure band was widened over the next 3 weeks. The hearing loss progressively increased toward the low frequencies; however, the amplitude modulation function remained constant until the lowest frequencies of the audiogram were shifted, then AM function was greatly reduced. The results will be discussed in terms of the influence of the sensation level of the AM noise stimulus. [Work supported by NIH, NIOSH.]
Incomplete auditory induction of tones alternated with noise: Effects occurring below the pulsation threshold
Authors: Wrightson John M. , Warren Richard M.
Published: October 2005

Alternation of two sounds can give rise to illusory continuity of the fainter when the sounds have appropriate spectral and intensity relations [Warren, Obusek, and Ackroff, Science 176, 1149–1151 (1972); Houtgast, J. Acoust. Soc. Am. 51, 1885-1894 (1972)]. We have found effects occurring below the continuity threshold when listeners estimate onset and offset times of a sinusoid (1000 ms duration; 12 frequencies, 180–8000 Hz) alternated with a narrow band noise (500 ms, 1000 Hz center frequency). For tonal frequencies corresponding to those within the noiseband, apparent offset was late and apparent onset early; effects opposite in direction to those corresponding to forward and backward masking by noise. At tonal frequencies outside those of the noiseband, onset/offset estimates were accurate. Frequency dependent effects found for illusory lengthening appear similar to those reported for continuity in auditory induction/pulsation threshold experiments, and in a direction which compensates for effects of masking. Illusory continuity appears to be the limiting case of the apparent temporal expansion found for conditions below the continuity threshold. [Research supported by NSF.]
Acoustical standards calibration at the Physics Division of the National Research Council of Canada
Authors: Wong G. S. K. , Embleton T. F. W.
Published: October 2005

This paper describes some recent research and development in acoustical standards calibration at NRC. Topics included are instrumentation and apparatus for precise reciprocity, and comparison methods of calibration of condenser microphones. Also, a two-microphone cavity technique for the overall calibration of sound level meters is discussed together with various methods of verification of acoustical calibrators.
Effects of various microphones on the calibration of artificial mouths
Authors: Whitesell Stephen R.
Published: October 2005

Artificial mouths used in telephonometric measurements are calibrated to produce a frequency-independent sound pressure of a known level at a given calibration point. Common practice in the telephone industry has been to measure this sound pressure with a Type L Laboratory Standard Microphone, using its free-field response curve. For a fixed artificial mouth calibration, the sound pressure indicated by various Type L microphones has been determined over the 100–10000-Hz frequency range. The results show an expected difference at high frequencies between “free-field” microphones and “pressure” microphones with a free-field correction applied. They also show an overall shift in level that depends on the microphone geometry. This latter result can be attributed to differences in the effective acoustic centers of the microphones. Using a Type M microphone and moving the calibration point farther from the lip ring of the artificial mouth substantially reduces the difference between the indicated and true free-field sound pressures. IEEE Standard 269–1971, “Method for Measuring Transmission Performance of Telephone Sets,” is being revised to implement these changes.
Portable programmable calculator programs for HVAC noise applications
Authors: Conant David A.
Published: October 2005

Seven RPN programs suitable for HP-97 and 41-C calculator use are briefly described in terms of their applications, accuracy, savings, and ease of use. Also presented are guidelines for approaching tabulated reference data and general calculator programming in a way that expedites clarification of the noise problem apart from tedious data reference and solution of algorithms.
Sound localization and the superior olivary complex in horses and cattle
Authors: Heffner Rickye S.
Published: October 2005

Variation in the morphology of the superior olivary complex in mammals has been linked with variation in the ability of different species to use the two primary binaural cues for sound localization: Time (Δt) and intensity (ΔI) differences. In particular, it has been shown that the hedgehog which lacks a medial superior olive is unable to localize low-frequency tones and thus appears unable to use the Δt cue [Masterton et al., J. Comp. Physiol. Psychol. 89, 379–386 (1975)]. Recently, we have found that cattle and horses are unable to localize tones above 500 Hz and 1 kHz (respectively) when a slow rise-decay time is used to avoid onset and offset artifacts. In contrast, they are able to localize low-frequency tones and high-frequency noise bursts, stimuli for which time cues (in the form of phase and envelope) are available. This finding suggests that horses and cattle are unable to use the ΔI cue for sound localization. Corresponding to these behavioral results is an atypical superior olivary complex in both horses and cattle. In these animals, the medial superior olive appears large but presents an atypical cell arrangement while the lateral superior olive is poorly developed and loosely organized. [Work supported by NSF and NIH.]
Introductory abstract
Authors: Cohen Annabel J.
Published: October 2005

The understanding of music perception and cognition is advancing on many frontiers. Technological, methodological, theoretical, and artistic developments have stimulated new areas for investigation and have placed longstanding issues in a new context. This session explores recent progress from a variety of perspectives: music theory, perceptual-cognitive and developmental psychology, brain research, and engineering psychoacoustics. Together the papers suggest the scope and potential of this multidisciplinary venture, and highlight foundational knowledge, fundamental questions, and future goals.
The SAE A-21 Committee's new method for prediction of lateral attenuation of aircraft noise
Authors: Marsh Alan H.
Published: October 2005

Lateral attenuation is the difference between an airplane's noise level at a point on the flight track and at a point to the side of the flight track such that the minimum distance to the flight path, for the location on the flight track, equals the minimum slant range, for the location to the side of the flight track. In 1979, the SAE A-21 Committee on Aircraft Noise undertook to develop a new version for an empirically based model of lateral attenuation. The model, which gives results in terms of sound exposure level or effective perceived noise level, accounts for ground effects, meteorological effects, and, for an airplane that is airborne, airplane and engine installation effects. When an airplane is airborne, lateral attenuation, Λ(β), in decibels, is a function of elevation angle β, in degrees, and is given by Λ(β) = 3.96 − 0.066β + 9.90 exp(−0.13β) for 0° ⩽ β ⩽ 60° and by Λ(β)≡ 0 for 60° < β ⩽90°. When an airplane is on a runway, lateral attenuation, G(l), in decibels, is a function of the perpendicular lateral distance l, in meters, and is given by G(l) = 15.09 [1 − exp(−2.74 10−3)] for 0 ⩽ l ⩽ 914 m and by G(l)= 13.86 for l > 914 m. When the airplane is airborne but close to the ground, there is a transition region where lateral attenuation is found from Λ(βl) = [G(l)][Λ(β)]/13.86 where 13.86 is the limit for Λ(β) at β = 0° and the limit for G(l) for l> 914 m.
Detection and assessment of secondary sonic booms in New England
Authors: Rickley Edward J. , Pierce Allan D.
Published: October 2005

Measurements in summer 1979 and subsequent analysis demonstrate that secondary sonic booms frequently reported by New England residents are caused by inbound Concord flights to New York. Ray trace computations, based on meteorological data and FAA radar tracking of Concord flights, predict signal arrival times within 20 s and predict wave front azimuthal angles with 4°. Present paper focuses on analysis and is based on comprehensive report (FAA-AEE-80-22) with same title. Sound paths leaving aircraft trajectory normal to Mach cone that reach New England classify as (1) ground wave (plane to ground, then diffracted creeping wave), (2) type I secondary sonic boom (plane to mesophere to ground), and (3) type II secondary sonic boom (plane to ground to mesophere to ground). Refraction in the mesosphere back to the ground is possible only when mesospheric winds cause effective sound speed at some altitude above aircraft to exceed that at ground. The ground wave, which has very low amplitude but is discernible in infrasonic pressure records, arrives first and is explained by Ingard-Pridmore-Brown theory of penetration into a shadow zone. Geometrical acoustics predicts type I and II secondary sonic boom arrivals only at and beyond focus lines (where ray-tube areas vanish), but a diffraction model based on theory of wave phenomena near caustics yields arrivals on near side of focus lines. [Work supported by Federal Aviation Administration.]
Progress in acoustic remote sensing of temperatures
Authors: Brown Edmund H. , Keeler R. Jeffrey
Published: October 2005

A major modification in the method of remote sensing of temperatures in the atmosphere (or oceans) by means of acoustic waves provides measurements at discrete altitudes (or depths) rather than path-averaged values. Application of the method to obtaining vertical profiles of temperature has now become merely a problem in engineering development. In this talk we describe the physical basis for the method, and show a number of experimental time series displaying excellent agreement with tower-mounted thermometers. [Work supported by the Army Research Office.]
Sparse planar microphone array for estimating bearing to near-ground sources: system considerations
Authors: Miller G. Kirby , Babian Fred E.
Published: October 2005

The maximum likelihood bearing estimator has been simulated on a computer and has been used to examine the effects on performance of both environmentally imposed conditions and system parameters. The imposed conditions include source spectra, ambient noise spatial character, wind, temperature, and array tilt due to terrain. The system parameters include microphone position error, channel amplitude match, channel phase match, operating frequency band, number of microphones, size of array, number of azimuth bins, and number of delay line taps. The results of this study indicate that a passive acoustic bearing estimation system for ground sources should be able to achieve an accuracy of a few degrees under most conditions.
Attenuation of noise by diffraction at a barrier edge
Authors: Daigle G. A. , Embleton T. F. W. , Piercy J. E.
Published: October 2005

Traffic noise attenuated by a barrier alongside a highway was measured with microphones positioned above an asphalt surface 15 and 30 m behind the barrier. The sound levels were analyzed to obtain the average sound pressure levels per ⅓-octave band. An idealized experiment was also performed using a barrier 2.5 m high and 17 m long erected on a flat asphalt surface. Sound pressure levels from a point source were measured for various source and receiver positions. Certain features of these measurements were presented at the last meeting in Los Angeles where the effects of atmospheric turbulence were discussed. The same measurements will now be compared with two versions of classical Kirchhoff-Fresnel diffraction theory which is currently used to predict the attenuation of noise by barriers. This comparison shows that the sound levels behind the barrier are higher than widely used diffraction theories by 1 to 3 dB at all frequencies—and, surprisingly, by 2 to 10 dB when compared with a theory that should be more precise. The largest discrepancies occur at the shorter source to receiver distances. An alternative diffraction theory as well as an empirical correction to Kirchhoff-Fresnel theory are offered which show good agreement with all the results. [Work supported by NSERC grant to Carleton University.]
Musical rules and pitch judgment
Authors: Cuddy Lola L.
Published: October 2005

Observed psychoacoustic events are often incompatible with musical knowledge. The point has been made particularly in the realm of pitch theory. This paper will contend that it is not the case that musical knowledge does not apply to psychophysical tasks or the musical knowledge fails to correspond with musical practice. Rather, the judgment of pitch is the result of a complex decision involving both the identification of pitch pattern and the operation of a rule-based structural system assigning the functional values of pitches. Different tasks or task demands may assign different relative weights to the system's operators. Whatever the aesthetic merits of Western-European tonality, the experimental study of it uncovers a powerful system of pitch organization and reveals the delicate interplay between perception and cognition. Examples will be drawn from our work on interval and melody recognition. [Work supported by Natural Science and Engineering Research Council of Canada and Queen's University Advisory Research Committee.]
The role of the right and left hemispheres in music perception
Authors: Gordon Harold W.
Published: October 2005

Early views on cerebral dominance put the functions of music in the left hemisphere. Subsequent empirical investigations reversed the dominance to the right hemisphere, while current research implicates both hemispheres, with most, but not all functions in the right. However, the opposite is true for musicians where most functions are processed in the left hemisphere. The apparent contradiction can be resolved, however, by recognizing that cognitive functions of the right hemisphere are organized for global or wholistic stimuli, conducive to most musical listening. Temporal stimuli or critical analyses (as performed by musicians) reduces or reverses the right hemisphere preference. What emerges is that hemispheric dominance for music, language, or other functions may depend on which hemisphere the subject chooses or learns to activate. For most music, it is the right; but for some musicians and some stimuli it may be the left. Furthermore, recent results imply that hemispheric preference in musicians may differ from subject to subject raising a more interesting question of whether it is the subjects' cognitive profiles that influence the music rather than the other way around.
Cognitive development in music: The understanding of transformations
Authors: Serafine Mary Louise
Published: October 2005

This paper puts forth a set of theoretical assertions that bear on (1) a general theory of musical cognition and (2) a conception of cognitive development in music from childhood to adulthood. The role of developmental research in addressing more general problems in musical cognition is examined. An experiment is described in which the awareness of thematic transformations was investigated in adults and children. Three degrees of transformation were investigated: (1) relative repetition (e.g., no change, change of mode or tempo), (2) ornamentation (change by addition), and (3) substantive transformation (e.g., inversion). Results are reported for child and adult subjects. The implications for a general conception of musical cognition are discussed.
A reexamination of the low frequency (50–1000 Hz) normal threshold of hearing in both free and diffuse sound fields
Authors: Berger E. H.
Published: October 2005

During the calibration of the E-A-R Corporation Acoustics Laboratory hearing protector attenuation facility, hearing threshold levels were observed that were from 2.6 to 7.1 dB less sensitive in the 125–1000 Hz frequency range, than those specified in ISO R226-1961, the International Standard which specifies the normal threshold of hearing for free field listening conditions. A complete review of the experimental design, as well as replication of the experiment, and a comprehensive literature review, indicated that ISO R226 was probably in error at frequencies below 1000 Hz. Data were collected from ten additional threshold experiments conducted since 1933. Variables that could effect the data, such as free versus diffuse sound fields, pure tones versus ⅓-octave noise band stimuli, psychophysical method, pulsed versus continuous stimuli, binaural versus monaural listening, age, sex, race, and otological rejection criteria, were analyzed. For frequencies from 50–1000 Hz and ages up to 35, the only corrections found to be necessary were for sound field and monaural listening. A second-order polynomial regression line was fitted to the corrected data. The resultant thresholds were 5–8 dB less sensitive than ISO R226 between 50 and 250 Hz, with the divergence dropping to +2.4 and −0.8 dB at 500 and 1000 Hz, respectively.
Comment on ’’Kramers–Kronig relationship between ultrasonic attenuation and phase velocity’’ [J. Acoust. Soc. Am. 69, 696–701 (1981)]
Authors: Horton C. W.
Published: October 2005

An error has been discovered that effects the results in the paper by C. W. Horton, Sr. [J. Acoust. Soc. Am. 55, 547–549 (1974)]. [AIP]
On the reflection coefficient which exceeds unity
Authors: Atalar Abdullah
Published: October 2005

The acoustic reflection coefficient at a lossy liquid–lossless solid interface is shown to be greater than unity near Rayleigh critical angle. This result does not violate the principle of energy conservation. A ray model is presented to explain the underlying physical phenomenon. The peak value of the reflection coefficient is predicted by an approximate expression.
Effects of frequency-shifted feedback on the pitch of vocal productions
Authors: Elman Jeffrey L.
Published: October 2005

Previous investigations into the effects of distorted auditory feedback on vocalizations have been limited to manipulations of intensity, background noise, temporal delay, or to selective filtering of frequency. The current study reports the results of real-time shifts of the frequency components of auditory feedback. Subjectively, such shifts are perceived primarily as an alteration in the fundamental frequency (F0) of the speech. Subjects performed a variety of tasks under conditions where they received either normal auditory feedback or frequency-shifted feedback. Under normal feedback conditions, subjects maintained approximately constant F0 as instructed. With frequency-shifted feedback, subjects attempted to compensate for the shift by adjusting their F0 up or down such that the resulting feedback appeared to be ’’normal.’’
Binaural edge pitch
Authors: Klein M. A. , Hartmann W. M.
Published: October 2005

The Huggins pitch effect is created by dichotic broadband noise with interaural phase varying from 0 to 2π over a narrow frequency region. The sensation of pitch, corresponding to the frequency of the phase shift region, is usually understood as the result of a binaural differencing operation. We report here a pitch effect created by dichotic broadband noise with interaural phase varying from 0 to π over a narrow boundary region, creating an edge in a difference channel. We call this effect Binaural Edge Pitch. For experienced listeners the effect is similar in nature and strength to the Huggins pitch. It is strongest for boundary frequencies in the 350–800 Hz range. Pitch matching experiments in this range find that the spread of matches is 1%–2% of the boundary frequency and that the pitch is 4% higher or lower than the boundary frequency. This shift is identical to the shifts which we find for the pitch of high-pass and low-pass noise bands. The correspondence argues strongly for an explanation of the Binaural Edge Pitch in terms of the Equalization–Cancellation Model of binaural processing, and pitch derived from a central spectrum.
Effects of a periodically moving boundary on mean square sound pressure distribution
Authors: Hwang Y. F. , Tichy Jiri
Published: October 2005

Previous experimental findings on the effects of a moving sound diffuser indicate that a diffuser generates frequency and amplitude modulations and also reduces the spatial fluctuation of the mean square sound pressure in a reverberant sound field. These findings are substantiated with a simplified theoretical model presented in this paper. This theoretical model also demonstrates that the reduction of the spatial mean square sound pressure fluctuation is an inherent characteristic of the modulated sound field.
New approach to the solution of eigenvalue problems in circular flow ducts (a Taylor series method)
Authors: Ko Sung-Hwan
Published: October 2005

Sound attenuation was investigated in acoustically lined circular ducts with fluid flow by using a Taylor series method for the solution of the eigenvalue problem. The governing differential equation was numerically integrated across the duct cross section from the origin to the duct wall. The singularity of the differential equation at the origin was treated by analytically solving the differential equation valid only at the origin. By using values of the radial function and its derivatives at the origin, successive approximation of the eigenvalue were performed until the boundary condition at the duct wall was satisfied. Eigenvalues obtained by this method are presented. The sound attenuation was obtained by using the calculated eigenvalues.
Audibility of harmonics in a periodic complex
Authors: Martens Jean-Pierre
Published: October 2005

An extensive study of the ability to hear out partials under isolated presentation of a periodic complex is described. It is demonstrated that, without selective attention to the partials involved, low harmonics are hard to distinguish. For the perception of high harmonics, the effect of selective attention seems negligible. Finally it appears that a simple model provides a good fit to the data.
Response to note on the Fourier Series Method
Authors: Wilson James H.
Published: October 2005

Cooper’s [J. Acoust. Soc. Am. 68, 989 (1980)] recent comments concerning the Fourier Series Method (FSM) demonstrate his total lack of physical understanding of signal processing for line array systems. For example, in his comments, Cooper stated that FSM was not correct because it could not estimate the nonomnidirectional component of the acoustic field using a one-element array or omnidirectional hydrophone. Large aperture, multielement line array systems have been developed because it is fundamentally impossible to measure the directionality of the acoustic field widh a single omnidirectional hydrophone. Cooper’s other comments show a similar low level of physical understanding of very basic signal processing concepts. Two examples are presented to show that the FSM estimates are very accurate indeed.
Reply to ’’Comments on ’Correlation of the phase and amplitude fluctuations between direct and ground-reflected sound’ ’’ [J. Acoust. Soc. Am. 70, 240 (1981)]
Authors: Daigle G. A.
Published: October 2005

An attempt has been made to incorporate the suggestions of S.F. Clifford and S. M. Wandzura.
Review of transient field theory for a baffled planar piston
Authors: Harris Gerald R.
Published: October 2005

The theoretical approaches which have been used to study the velocity potential and pressure fields radiated by a planar piston source vibrating in an infinite rigid baffle are broadly reviewed and discussed with emphasis on the basic mathematical methods employed. Attention is focused on those aspects of piston theory directly related to the point or spatially averaged transient field of a pulsed piston radiator. Studies of the nonuniformly vibrating piston are also reviewed. Much of this material has not been previously compared, so where possible common origins and general relationships are stressed.
Sources of acoustic backscattering at 87.5 kHz
Authors: Greenblatt Paul
Published: October 2005

Sources of acoustic backscattered energy at 87.5 kHz were identified using three independent approaches. The first approach combined the Johnson fluid sphere scattering model [R. K. Johnson, J. Acoust. Soc. Am. 61, 375–377 (1977)] with a hypothesized distribution of scatters. From these models the percentage of total scattering due to organisms of a particular size range was determined. The second approach inferred scatterer abundance from probability distributions of acoustic scattering strength for insonified volumes of different sizes. The third approach consisted of comparing levels and patterns of scattering strength observed with a sonar to biological samples taken in the same area at the same time. All three approaches indicated that the sources of backscattered acoustic energy came from large zooplankton and small nekton. However, the first approach underestimated the importance of large scatterers at night. Day scattering was dominated by large copepods and small euphausiids. When small fish were present, they dominated the scattering. Night samples were dominated by mesopelagic fish, squid, and euphausiids. The fish and squid usually dominated the scattering early in the evening while euphausiids tended to dominate the scattering later at night.
Reflection of acoustic waves at a water–sediment interface
Authors: Stoll Robert D. , Kan T. -K.
Published: October 2005

Reflection and refraction of plane acoustic waves are studied for the case where the sediment is modeled as a porous viscoelastic medium. The model is based on the classical work of Biot which predicts that three different kinds of attenuating body wave may propagate in the sediment. As a consequence when homogeneous plane waves in water are incident to a water–sediment interface, three nonhomogeneous waves are generated in the sediment. In these waves the direction of phase propagation and the direction of maximum attenuation are not the same and particle motion follows an elliptic path. Moreover the velocity and attenuation of the refracted waves become dependent on the angle of incidence and no ’’critical’’ angle occurs. Numerical examples show that in some cases the reflectivity of a porous viscoelastic model differs significantly from the case where the sediment is modeled as a viscoelastic solid with constant complex modulus. Finally because of the frequency dependence of reflectivity in the porous model, it is found to act as a filter with respect to broadband energy.
Stability of acoustic nonlinear dispersive eigenmodes
Authors: Banerjee P. P. , Korpel A.
Published: October 2005

In an earlier investigation, spectral evolution equations were derived for nonlinear dispersive propagation. For the special case of two harmonics, two eigenmodes were shown to exist, of which one is parametric in nature. In this paper we develop a general method of stability analysis and show that in the case of two eigenmodes their limit cycle behavior is in agreement with earlier results obtained by different, less general, methods. We will also discuss the relation of the nonlinear eignmodes to cnoidal waves and acoustic solitons.
Ambient noise vertical directionality in the northwest Atlantic
Authors: Wales Stephen C. , Diachok Orest I.
Published: October 2005

The vertical directionality of the ambient noise field was measured at a site between Cape Hatteras and Bermuda over the frequency range 45–100 Hz. The noise level was observed to decrease rapidly at angles beyond ±20 ° from the horizontal by as much as 20 dB. Slight peaks were observed near ±15 ° and at the horizontal. These peaks are hypothesized to be due to deep ocean shipping and slope enhanced signals from shipping located on the continental shelf edge, respectively. Theoretical calculations based on a parabolic equation propagation model and measured environmental information support these hypotheses.
Refracted ray characteristics from the geometrical spreading equation for depth-dependent media
Authors: Watson J. G. , Siegmann W. L. , Jacobson M. J.
Published: October 2005

Geometrical spreading of sound is investigated for propagation along purely refracted rays in motionless media with smooth, depth-dependent, sound-speed profiles. Fundamental characteristics of rays and spreading are derived which are valid for very general types of sound-speed distributions of importance in ocean acoustics. Ray turning and caustic-contact points are shown to either interlace or coincide. For periodic rays, the separations between adjacent turning or caustic-contact points are shown to either remain constant or approach zero with range, depending on a basic property of the ray period. Bounds are obtained for the separation distance, along with an asymptotic formula for the distance between nearest-neighbor turning and contact points. These results are extensions and a correction to those in a recent paper [W. A. Kinney and A. D. Pierce, J. Acoust. Soc. Am. 67, 1145–1148 (1980)]. Quantitative predictions from our formulas are compared with other calculations and serve to illustrate their usefulness. Several advantages of applying our formulation and results in the numerical computation of geometrical spreading are discussed.
An analysis of effective shear modulus for flexural and extensional waves and its application to reflection of sound by a plate
Authors: Dubbelday Pieter S. , Rudgers Anthony J.
Published: October 2005

An analytical expression is presented for the correction factor that relates the effective shear modulus in Timoshenko–Mindlin plate theory to the actual shear modulus, for an unloaded plate. This expression is obtained by comparison of the approximate theory with exact elasticity theory. A thick-plate theory is developed for extensional waves, which also introduces an effective shear modulus, with a corresponding correction factor. It is shown analytically that both correction factors produce the proper high-frequency value for the phase speed, namely, the Rayleigh wave speed. Reflection of sound by a plate is described when both flexural and extensional waves are excited. Both types of waves are described by the expressions derived in thick-plate theory. A structural response function of the plate for reflection is given for each of the two wave types separately. The structural response function pertaining to the case where both wave types occur simultaneously is expressed in terms of the two individual response functions in the same way that the total impedance of a pair of impedances in parallel is expressed in terms of the values of the individual impedances. The distribution of kinetic energy over the two types of waves as a function of the angle of incidence is shown.
An instrument to calibrate community noise analyzers
Authors: Weiss Franz
Published: October 2005

An instrument which will quickly and accurately calibrate community noise analyzers is described. The calibrator has a 0.1-dB resolution with a dynamic range of 79.9 dB.
Some notes on ’’The thermal-noise limit in detection of underwater acoustic signals’’ [J. Acoust. Soc. Am. 24, 478–480 (1952)]
Authors: Sullivan Edmund J. , Kemp Kenneth A.
Published: October 2005

Mellen’s paper [’’The thermal-noise limit in detection of underwater acoustic signals,’’ J. Acoust. Soc. Am. 24 478–480 (1952)] on the thermal-noise limit of a hydrophone is reviewed to document some minor corrections and to clarify a point concerning the free field voltage sensitivity of a transducer. Some elaboration of details in portions of the derivation is also made.
Heat generation by ultrasound in a relaxing medium
Authors: Nyborg Wesley L.
Published: October 2005

It is shown that at any point P in a continuous sound field the time-averaged rate of heat generation by relaxational absorption per unit volume is given by αp02/ρc. Here p0 is the pressure amplitude at P while α is the absorption coefficient arising from relaxation when the coefficient of shear viscosity η is zero; ρ and c are, respectively, the density and velocity of sound in the medium. The result, a familiar one for plane traveling waves, is shown here to apply generally when η = 0.
Narrow-band acoustic signals emitted by chinchilla ears after noise exposure
Authors: Zurek P. M. , Clark W. W.
Published: October 2005

Acoustic search in 21 ears of 17 chinchillas exposed to a variety of high-intensity sounds revealed two instances of a spontaneous and continuous narrow-band acoustic signal emanating from the ear. These signals, found in the 4–7 kHz region after exposure to an octave band of noise centered at 0.5 kHz, could be suppressed by external tones. The frequency selectivity and time course of the suppression effect suggest that these otoacoustic emissions originate from a vibratory source in the cochlea.
Theoretical and experimental investigations of structureborne sound transmission through a ’’T’’ joint in a finite system
Authors: Rosenhouse G. , Ertel H. , Mechel F. P.
Published: October 2005

The wave theory approach was used here for analysis of sound transmission through a ’’T’’ joint in a finite system consisting of rectangular beams. The analytical results were confirmed by experiments. A comparison of the sound transmission through a ’’T’’ joint in finite and infinite systems revealed completely different behavior. Various kinds of joints including a welded ’’T,’’ a ’’T’’ connected by screws, and a ’’T’’ incorporating a rubber layer were examined. Comparisons between the analytical and experimental results of structureborne sound transmission through the various joints showed that the analytical treatment developed is applicable for all types of ’’T’’ junctions described above.
Radiating head flexure and its effect on transducer performance
Authors: Butler John L. , Cipolla John R. , Brown Willie D.
Published: October 2005

The design of low Q underwater sound transducers often results in thin radiating head structures leading to flexural resonances that are close enough to the fundamental resonance to cause noticeable effects on it. An analysis of this flexure is presented along with a simple model that can be incorporated into transducer element and array interaction design programs. Results are presented for a particular case to illustrate the physical effects and the advantages (such as a reduction in the fundamental resonant frequency) and disadvantages (such as reduced performance above resonance) that are a consequence of flexural head motion.
Born series sums for wave propagation in anisotropic, random media
Authors: Meecham W. C. , Tavis M. T. , Yura H. T.
Published: October 2005

We use the Born series for a field propagating in a Gaussian medium with a Gaussian-form correlation function. These specializations lead to integrals for the moments with integrands which are themselves mainly of Gaussian form. The integration can be done algebraically using multivariate Gaussian distribution formulas. Specifically for moments the, say, fourth-order Born term involves a 12-fold integration of which eight can be done algebraically using the formulas. We are able, for a two-scale anisotropic medium, to sum the Born series for the average (the first moment) of the radiation field. The results reduce to familiar ones when we specialize to isotropic media. A novel characteristic is that for physically interesting parameter ranges diffraction effects can substantially reduce the phase variance, thus reducing the randomizing effect of the medium on the propagated field. Anisotropy also leads to an intensity dependence on angle. The fourth-order moment (the intensity variance) is considered through fourth-order Born terms; it is not possible to sum the Born series for this moment in terms of simple functions even for isotropic media. Previous results are in large part confirmed: when diffraction effects are slight, sound field fluctuation effects are confined to the phase, leading at sufficient range to a log-normal field distribution. When diffraction effects become appreciable, the sound amplitude fluctuates and the distribution becomes Gaussian. But the latter conversion—saturation—occurs an order of magnitude sooner (than previously supposed from order of magnitude arguments) at ΛΦ∠0.1. There is also an expected region of appreciable overshoot in the intensity variance, that variance exceeding its Gaussian value for intermediate ranges at lower frequencies.
Acoustic trauma: Single neuron basis for the ’’half-octave shift’’
Authors: Cody A. R. , Johnstone B. M.
Published: October 2005

Exposure to an intense pure tone can induce a loss of hearing sensitivity. If this loss recovers, then the desensitization is regarded as a temporary threshold shift (TTS). At the single auditory neuron level this TTS was monitored as a loss of sensitivity at the neuron’s most sensitive or characteristic frequency (CF). When pure-tone exposures were presented at frequency intervals measured from the neuron CF, then a frequency half an octave below the CF was the most effective for inducing a CF TTS. All exposure frequencies higher than half an octave below the CF produce a marked reduction in TTS growth with intensity, when compared to lower exposure frequencies. This behavior is such that, with increasing exposure frequency higher than the −1/2-octave point, the intensity needed to produce a given TTS grew faster than the neuron sensitivity. However, below the −1/2-octave point all exposure frequencies were similarly behaved. Strong similarities exist between the frequency-specific requirements for TTS and the mechanical and neural nonlinearities found in other studies. This suggests that the half-octave shift may well be a direct result of basilar membrane nonlinearities.
Computing auditory fatigue of the whole nerve action potential
Authors: Gans Donald P.
Published: October 2005

Fatigue at the level of the VIII nerve is often calculated through the measurement of the whole nerve action potential (AP). The losses have been quantified by calculating the dB shift required to record a criterion AP voltage or by determining the ratio of the pre- and post-exposure AP voltages at a constant probe intensity. The issue raised here is whether the two methods produce similar AP losses. Fifteen rats were exposed to a 6000-Hz pure tone at either 100, 105, or 110 dB SPL for five minutes. Input–output functions were determined at five probe frequencies prior to and following exposure. When the probe intensity (i.e., AP voltage) was low, AP losses appeared greater when the AP fatigue was computed at a constant intensity. This trend was reversed at higher probe levels. These results are explained on the basis of the growth behavior of the AP.
Dispersion of elastic waves in bars with polygonal cross section
Authors: Nagaya Kosuke
Published: October 2005

This paper studies harmonic wave propagation in an infinite elastic bar of polygonal cross section with stress-free surface. The frequency equations for longitudinal, torsional, and flexural waves have been obtained by making use of the Fourier expansion collocation method which has been developed by the author on the vibration and dynamic response problems of membranes and plates.
Acoustic radiation from fluid-loaded elastic plates I. Antisymmetric modes
Authors: Woolley Barry Lee
Published: October 2005

The Timoshenko–Mindlin plate equation of motion is modified in order to simultaneously specify the precise cutoff and asymptotic behavior of both antisymmetric modes of plate vibration described by it. A mathematical method for extending equations of motion to include higher order antisymmetric modes is presented. This method is illustrated by the development of an equation of motion for the first four antisymmetric modes of plate vibration.
Normal-mode propagation in deep-ocean sediment channels
Authors: Williams A. O.
Published: October 2005

E. L. Hamilton [J. Acoust. Soc. Am. 48, 1296–1298 (1970)] has discussed the likelihood of ducted acoustic transmission in deep-ocean sediment channels just below the water-bottom interface. A normal-mode solution, presented here, yields eigenfunctions, the associated eigenvalue equation, and the minimum or cutoff acoustic frequency that allows trapping of any specified mode. This cutoff frequency increases nearly linearly with mode number. Much of the acoustic energy propagated by any trapped mode travels through lossy bottom sediment. Accordingly, equations are derived for the attenuation coefficient of the nth mode. It is shown that sediment channels discriminate against long-range transmission by higher modes than the first, as well as at high acoustic freqencies and frequencies too near the cutoff value. Thus the channel acts as an acoustic filter transmitting best a rather narrow band of fairly low frequencies. There is some experimental evidence for this property. Numerical examples are given for an ’’average’’ channel, at a frequency of 100 Hz.
Fluctuations of resolved acoustic multipaths at short range in the ocean
Authors: Worcester Peter F. , Williams Gordon O. , Flatté Stanley M.
Published: October 2005

The fluctuations in acoustic transmission between a broadband source and an autonomous receiver moored somewhat below the sound channel axis at 23-km range have been examined. The transmitted signal was centered at 2273 Hz. A variety of measures of the observed fluctuations (pulse and cw) for three well-resolved paths computed from 72 h of data are compared with theoretical predictions based on sound-speed perturbations due to internal wave vertical displacements. Measurement and theory are found to be consistent for some statistics and inconsistent for others. The theoretical predictions depend sensitively on the mean sound-speed profile.
Under ice reflectivities at frequencies below 1 kHz
Authors: Yang T. C. , Votaw Charles W.
Published: October 2005

An experiment measuring sonic reflectivities below 1 kHz was done beneath large smooth ice floes in the Arctic Ocean north of Ellesmere Island. Reflectivity data are presented here for grazing angles between 14 ° and 26 °. The reflectivity is found strongly dependent on frequency as well as grazing angles. Theoretical discussions are given to interpret the data. The most significant finding of this report is that a smooth ice plate cannot be treated as totally reflective for frequencies between 200 Hz and 1 kHz, an assumption which has so far been taken for granted in the literature. In fact, the reflection loss at smooth, flat ice could account for a substantial part of the transmission loss in Arctic oceans for this frequency range.
Lateralization of jittered tones
Authors: Blauert Jens
Published: October 2005

Lateralization thresholds based on differences in interaural arrival time have been measured for jittered 4-kHz tones. The results are in good agreement with those of other authors obtained with bandpass noise as well as with AM and FM signals. However, thresholds are about two orders of magnitude higher than those of Nordmark [J. Acoust. Soc. Am. 60, 870–880 (1976)] obtained with jittered tones. These results suggest an explanation of the lateralization of jittered tones and other FM signals on the basis of an hypothesized FM-to-AM conversion which may take place peripherally.