bluuebunny/crossref_metadata_2025 huggingface dataset:
A neural-counting model incorporating refractoriness and spread of excitation: Extension of the model to include receptor saturation and spontaneous neural activity
Authors: Lachs Gerard , Saia Rosalie A. , Teich Malvin Carl
Published: October 2005

An energy-based, neural-counting model, incorporating refractoriness and spread of excitation, has recently been applied to intensity discrimination and loudness estimation for a variety of acoustic stimuli [M. C. Teich and G. Lachs, J. Acoust. Soc. Am. 66, 1738–1749 (1979); 69, 774–782 (1981); Suppl. 1 69, S104 (1981)]. Most of the comparisons with psychophysical data described in these papers utilized double-tuned filters to model the frequency dependence of individual neural channels. Such a model requires 12 dB/octave rolloffs in the tails of the tuning curves, which appears to be inconsistent with the far steeper rolloffs reported in the literature. We demonstrate, however, that psychophysical tuning curves observed by a number of researchers [D. Johnson-Davies and R. D. Patterson, J. Acoust. Soc. Am. 65, 765–770 (1979); D. M. Green et el., J. Acoust. Soc. Am. 69, 1758–1762 (1981)] may be fit by a double-tuned filter characteristic, with a judicious choice of the filter parameters. Receptor saturation and spontaneous neural activity have been incorporated into the model. The resulting theoretical firing rate-versus-frequency curves (with sound pressure level as a parameter) are in good accord with neurophysiological data ([J. E. Rose et al., J. Neurophysiol. 34, 685–699 (1971)], for sensible values of the model parameters. [Work supported by NSF.]
Population study of non-monotonic response-intensity curves in auditory nerve fibers
Authors: McGee J. , Walsh E. J. , Gorga M. P. , Farley G. R. , Javel E.
Published: October 2005

For pure-tone signals, responses of many auditory nerve fibers in cats are nonmonotonic functions of intensity. In the experiments described here, we examined responses across the fiber population to tones at 200 Hz, 500 Hz, and 1000 Hz. Below 70–90 dB SPL, responses to 200 and 500 Hz generated unimodal period histograms. Above 70–90 dB SPL, period histograms were bimodal. This was not the result of an externally generated harmonic distortion product. At yet higher intensities, period histograms became unimodal, but the average discharge phase angle changed. Typically, the second peak which emerged in the period histograms at high levels dominated the temporal response and the original peak disappeared. Only unimodal period histograms were seen at 1000 Hz; however, discharge phase shifts still occurred at high intensities. The intensity corresponding to the decline of response amplitude was independent of fiber CF and fiber sensitivity at the stimulus frequency. These findings indicate that the mechanism producing the nonmonotonic input-output functions is not confined to a restricted cochlear region. Further, cochlear mechanics is likely to be the source of the nonmonotonicities, perhaps producing standing waves in the cochlea.
Coding of tonal stimuli by neurons in anterior auditory field of cat cerebral cortex
Authors: Phillips Dennis P. , Irvine Dexter R. F.
Published: October 2005

In the cortex of barbiturate-anesthetized cats, the anterior auditory field (AAF) was defined by microelectrode maps of its frequency organization, and the responses of single neurons in that field to monaural and binaural tone-burst stimuli were examined quantitatively. AAF neurons generally had narrow, V-shaped threshold frequency tuning curves centered on a clearly defined best frequency (BF). Intensity functions at BF were commonly monotonic in shape with dynamic ranges of 15 to 40 dB. Cells with nonmonotonic intensity functions had optimal sound pressure levels in the range 15 to 70 dB. Minimum response latencies at BF were in the range 10 to 15 ms. Binaural interactions were diverse, and a number of neurons demonstrated sensitivity to interaural intensity disparities. These properties are similar to those of cells in the primary auditory cortex, A1 [D. P. Phillips and D. R. F. Irvine, J. Neurophysiol. 45, 48–58 (1981)], and the data are consistent with the view that AAF and A1 function in some sense as parallel processors. It remains, however, to determine whether their thalamic afferents are independent, collateral, or overlapping, and to establish their specific functional roles in acoustic behavior.
Sentence perception in noise
Authors: Elliott Lois L.
Published: October 2005

Previous research has shown that normal children and older people have greater difficulty understanding sentences presented in a multitalker babble than do listeners in the 17–50 year age range. Recent work demonstrates that normally hearing children with speech-production disorders and normally hearing learning-disabled adults may demonstrate poorer speech perception than normal age mates. Since everyday listening situations often involve signal-to-noise levels comparable to the experimental levels, these data should be considered in design of school classrooms and home environments. [Supported, in part, by NSF, NIH, and BEH.]
Panel discussion
Authors: Hirsh Ira J.
Published: October 2005

Future uses for automatic speech intelligibility assessment of indoor spaces such as offices, factories, restaurants, and theaters will be discussed. Panelists will include some of the invited speakers and, also, distinguished guests.
Timing in the speech of children and adults
Authors: Flege James Emil
Published: October 2005

The duration of phonetic intervals are sometimes longer in the speech of young children than adults, although it is not clear at what age timing can be said to have become “adult-like.” This study examined speech timing as a function of speaker age. Adults and three groups of children (mean ages: 5;0, 8;0, 10;8) produced utterances like “Bob Bob Bob” with a tube in the corner of the mouth. The duration of “vowels” (/a/, /I/, /i/) and singleton and abutting stops (/b/,/b♯b/,/b♯p/) was defined by means of variation in supraglottal pressure. There were few between-group differences in the absolute duration of vowels, and none for bilabial closure intervals. All groups showed the same relative effects of phonetic factors. For vowels, the effect of position-in-utterance, number of syllables per word, vowel height, and stop voicing were comparable across groups. Position-in-utterance, vocalic environment, gemination (i.e., /b/ versus /b♯b/), and position with regard to stress also showed similar effects on consonant duration for each group.
REVSIM—A numerical model for simulating quasistationary, coherent, multibeam reverberation time series
Authors: Chamberlain Stanley G. , Galli John C.
Published: October 2005

The REVSIM model produces quasistationary, coherent, multiplebeam reverberation time series which are functions of the sonar system (actual transmit/receive, horizontal/vertical beampatterns, pulse type, shape, length and power and sampling rate), platform (speed, depth, and direction) and environment (wind speed and direction, backscatterer strengths, and propagation loss). Volume, surface, and/or bottom reverberation as seen by a sonar on a moving platform are generated. The model first computes reverberation spectra for each beam based on a general formulation of Ol'shevskii. Optimal, all-pole approximations of the spectra are generated to an arbitrary degree of accuracy using modern linear spectral prediction techniques. The all-pole approximations are used to generate a set of linear, time-varying, digital filters with infinite impulse responses (IIR). The filters, when driven by stationary, white, Gaussian noise produce the quasistationary, coherent, multiple-beam reverberation time series. The principles underlying the model are given and an example is presented to illustrate the utility of the model in simulating system performance.
The influence of signal processing devices on the timbre perception of electric guitars
Authors: Cohen Elizabeth , Weir Robert H. , Hasselberger Jeff
Published: October 2005

Spectral analysis at several stages of the output of Ibanez Custom Built Fender Telecaster, and Fender Stratocaster guitars have been completed. The signals were examined in a multiplicity of pickup configurations, including both single and double coil. We examined the direct output from pickups and studied the coloration due to the addition of the following devices: reverberation units, parametric equalizers, compressor/limiters, analog delay, flanging, and phase controllers. They were studied both with the entire relay system in the circuit and with the not so common, but preferable, hardwire bypass, enabling all switching effects to be eliminated from a system. Tones were produced by plucking strings with plectrums of different materials, and allowing the strings to vibrate over the magnet-coil systems. Steel slides and bottle slides were also used to initiate tone production. Tone control settings were varied. These experiments have shown that visualization of the signal and correlation of the signal, with subjective impressions, will enable the musician to have far greater control over the signal path, and hence, musical tone production.
Nonlinear interaction of two sound waves in a waveguide
Authors: TenCate James A. , Estes James M. , Blackstock David T.
Published: October 2005

For collinear interaction of two sound waves (or of a single sound wave with itself) in a gas, the coefficient of nonlinearity is equal to one-half (γ + 1), where γ is the ratio of specific heats. For interaction at an angle θ it has been proposed that β = cos θ + one-half (γ − 1). A waveguide experiment to test this hypothesis has been designed. An intense wave of low frequency f1 travels down a rectangular waveguide (cross section a × b) in the plane wave (0,0) mode. Interacting with it is a weak wave of high frequency f2 that bounces along the guide in the (1,0) mode (angle θ = sin−1 c0/2af2). The experiment is thus a generalization of one done by Schaffer [J. Acoust. Soc. Am. Suppl. 1 57, S73 (1975)] to demonstrate the suppression of sound by sound. In our case, however, suppression is more complicated because the two waves travel at different speeds down the guide. A prediction of the null point for the high-frequency wave has been derived. Preliminary experimental results tentatively confirm the proposed β(θ) relation. [Work supported by ONR.]
Nonlinear scattering of acoustic waves by vibrating obstacles
Authors: Piquette Jean C. , Van Buren A. L.
Published: October 2005

The problem of scattering of an acoustic wave (at angular frequency ω) by an obstacle whose surface vibrates harmonically (at angular frequency Ω) was studied both theoretically and experimentally. The theoretical approach involved solving the nonlinear wave equation, subject to appropriate boundary conditions, by use of a perturbation expansion of the fields and a Green's function method. This problem was previously studied theoretically by D. Censor [(J. Sound Vib. 25, 101–110 (1972)], who used the linear wave equation together with nonlinear boundary conditions to obtain his solution. In addition to ordinary rigid-body scattering, Censor predicted nongrowing waves at the sum and difference frequencies ω± = ω ± Ω. The solution to the nonlinear wave equation also yields scattered waves at frequencies ω±. However, the amplitudes of these waves tend to grow with increasing distance from the scatterer's surface and after a very small distance dominate those predicted by Censor. Preliminary experimental results are in qualitative agreement with the theoretical results based on the nonlinear wave equation. [This work is in partial fulfillment of the requirements for the first author's Ph.D. degree from Stevens Institute of Technology, Hoboken, NJ].
Ultransonically induced contraction of an elastically relaxing solid
Authors: Winfree William P. , Cantrell John H. , Li Peter
Published: October 2005

We previously reported the experimental verification of a static displacement induced in single crystal germanium by a propagating finite-amplitude ultrasonic wave [J. H. Cantrell, Jr., and W. P. Winfree, Appl. Phys. Lett. 37, 785 (1980)]. The sign of the static displacement is predicted theoretically to be dependent on the sign of the ultrasonic nonlinearity parameter of the solid. The nonlinearity parameters of aluminum and fused silica have opposite signs and the equations predict an ultrasonically induced dilatation for aluminum (elastically stiffening solid) and a contraction for fused silica (elastically relaxing solid). We report experimental confirmation of these predictions.
Evidence for speech muscle functional compartmentalization: Theoretical and methodological implications
Authors: Abbs James H. , Gracco Vincent L.
Published: October 2005

An assumption underlying most studies using speech electromyography is that classifically defined muscles, as anatomical entities, are functionally singular in their actions. Contrary to this assumption are recent findings in humans and animals suggesting consistent functional subdivisions of anatomically distinct limb muscles with movement-related specialization of the subdivisions and differential activation from supraspinal sites and/or peripheral afferents. To evaluate this organization in the speech muscles, 3–5 electrodes with restricted pickup fields (i.e., two wires/needle) were placed in the Orbicularis Oris Inferior and muscle activity was observed for actions involving labial occlusion, elevation, and protrusion, all of which have been observed previously to involve some OOI activity. Speech tasks also were manipulated to create variations in the velocity of elevation and protrusion movement. Consistent temporal and spatial variations were observed from the multiple electrode sites suggesting functional subdivisions similar to those observed in the limb muscles. Results will be discussed in relation to organization of complex speech motor gestures and methodological implications, particularly EMG recording with restricted field electrodes. [Research supported by NINCDS Grant.]
Application of signal processing utilities to speech physiology data
Authors: Henke W. L. , Perkell J. S.
Published: October 2005

A coherent family of command level signal processing utilities is being used to process time-continuous signals from experiments on the physiology of speech production. The utilities' wide range of functionality includes the following: simultaneous sampling of up to 16 analog channels at different rates, demultiplexing and separation of channels into groups of signals at different bandwidths with time registration across bandwidth groups, highly flexible signal processing to aid in data analysis, and interactive audition, viewing, marking and labeling to record timing of events and magnitudes of signals for subsequent analysis. Signal stream processing algorithms are specified by the user as graphical block diagrams which can support all the customary forms of signal processing. Useful examples include running average of EMG signals, differentiation of movement signals to obtain velocity and aceleration, integration to provide a measure of muscular “effort,” and filtering. Fourier analysis types of processing include computation of spectra (speech and movement signals) and cross-correlation functions to examine phase relationships between EMG signals and moment parameters. More specialized processing includes ensemble averaging and algorithmic event labeling. Examples will be presented. [Work supported inpart by N.I.H. Grant No. NS04332.]
Premotion silence in rapid voluntary movements for speech: Implications for suprabulbar control mechanisms
Authors: Cole Kelly J. , Barlow Steven M.
Published: October 2005

In unprocessed speech EMG we have often observed a short-duration silent period immediately preceding phasic activity for rapid voluntary movement [e.g., K. J. Cole and J. H. Abbs, J. Acoust. Soc. Am. Suppl. 1 66, S11 (1979)]. In the limbs, similar observations have been interpreted to indicate supraspinal control mechanisms for rapid voluntary and/or highly skilled movements. For example, premotion silence has been suggested to reflect differential control of tonic and phasic motoneurons, or preemption of peripheral reflex circuits, to facilitate initial movement acceleration [R. E. Burke, Prog. Clin. Neurophysiol. 9, 59–84 (1981); K. Yabe, J. Appl. Physiol. 41, 470–473 (1976)]. Such mechanisms offer alternative explanations for paradoxical changes in firing rates of neighboring single motor units for labial closure gestures, and for apparent reductions of perioral reflex excitability prior to labial closure [e.g., R. Netsell and J. H. Abbs, J. Acoust. Soc. Am. Suppl. I 58, S41 (1975)]. A series of experiments were initiated to determine the conditions under which premotion silent periods are observed for speech and nonspeech movements, particularly for various movement parameters. Potential underlying mechanisms and the implications of premotion silence for speech motor control are discussed. [This research was supported by NIH grant 13274.]
Analytical models of sound diffraction by barriers: A review
Authors: Pierce Allan D.
Published: October 2005

During the past few years, considerable success has been achieved in the further development and numerical implementation of analytic solutions for barrier diffraction. The older Fresnel-Kirchhoff theory of diffraction has proven to be inadequate for many cases of practical application, but is an unnecessary oversimplification because simple formulas (including the Fresnel number approximation) result in the uniform asymptotic expansion limit for the exact solution of diffraction by a rigid wedge. Although the MacDonald solution in its original form is cumbersome to apply to general source-listener configurations, numerical calculations become simple when contour deformation techniques are employed. Also significant is Medwin's application of FFT algorithms to the transient solution of Biot and Tolstoy, which we now know is equivalent to MacDonald's solution. Williams' and Maliuzhinetz's solution for impedance wedges has led to approximate models for nonrigid barriers. Three-sided barriers can be handled using Keller's geometrical theory of diffraction (GTD), which also allows the theory for plane wave diffraction to be used when the source is localized and when the barrier rests on the ground. Hayek and others have used creeping wave expansions for curved barriers; Fock's theory allows a smooth transition into the shadow zone.
Cost-effective barrier design along roadways
Authors: Anderson Grant S.
Published: October 2005

The Federal Highway Administration (FHWA) method for prediction of highway traffic noise and of noise-barrier performance is incorporated in their computer program STAMINA. For the FHWA, we have recently developed and documented an adjunct computer program OPTIMA, which combines the acoustical output of STAMINA with information on barrier costs and receiver noise criteria, to guide the user towards a balanced barrier design. A balanced design is one that provides the best barrier performance for a given cost, or equivalently, one that costs the least for a given performance. The measure of barrier costs is dollars, with unit costs supplied by the user. The measure of barrier performance is the reduction in acoustic energy density, summed over all receivers, after normalization to each receiver's noise criterion. This paper introduces the mathematical concepts within OPTIMA. The use of OPTIMA, together with STAMINA, is now being taught by the FHWA to state and regional highway engineers. [Work supported by FHWA.]
Outdoor noise propagation above a porous half-space
Authors: Quartararo Louis R. , Hayek Sabih I.
Published: October 2005

Assuming an extended reaction in the lower half-space, Attenborough et al. [J. Acoust. Soc. Am. 68, 1493–1501 (1980)] have obtained an exact solution for the propagation of noise due to a point source above a homogeneous and isotropic porous ground. The acoustic pressure calculated by this extended reaction model depends upon the complex values of the density, ρ, and the sound speed, c, of the ground. In contrast, the local reaction models of Thomasson et al. and Lawhead and Rudnick depend upon the complex normal impedance of the ground, given by the product ρc. For independently varied ρ and c, noise levels are predicted using the extended reaction model, and these levels are compared to the levels predicted by the local reaction models. Measurements of noise propagating over grass, by Embleton and Piercy, and by The Applied Research Laboratory, are compared to both models. Values of ρ and c for the measured cases were obtained from the measured complex impedance of the grass, and its frequency dependent flow resistance. [Work supported by FHWA.]
Automobile interior noise: psychoacoustic difference thresholds in octave-band sound pressure levels
Authors: Gibian Gary L. , Bavonese Joseph
Published: October 2005

The present study investigates human response to spectral changes in automobile interior noise, which characteristically has strong low-frequency content and much less high-frequency content. Specifically, we determined the smallest increases and decreases in sound pressure level in each octave band of automobile interior noise that can be detected by typical vehicle occupants. Increments and decrements in 1-dB steps in each octave band with center frequencies from 63 Hz to 4 kHz were presented to a group of automobile users, using a two-alternative forced-choice procedure. Results indicate that smaller changes (2–3 dB) can be detected in the higher-frequency octave bands (2 and 4 kHz), while larger changes (5–7 dB) are required for detection in the lower-frequency octave bands (63 and 125 Hz). The difference thresholds do not appear to depend on overall sound pressure level in the range 60 to 75 dB A.
Learning to hear a single complex sound
Authors: Leek M. R. , Watson C. S. , Foyle D. C.
Published: October 2005

Many phonemic distinctions require subtle auditory discrimination. Recent studies in our laboratory and elsewhere have shown that some elements of complex nonspeech sounds can be discriminated with similar accuracy after extensive training. We extended this work in a demonstration that listeners can also learn to resolve all of the components of a single complex sound. Seven listeners were tested with 3000 to 12 000 presentations of a single ten-tone pattern (40-ms components, ranging from 300–3000 Hz). On each trial, in a modified 2AFC procedure, nine components were at 75 dB SPL, the tenth was presented at a level determined by a threshold tracking procedure. Trials to asymptotic performance ranged from 40 to more than 1200 for various components and listeners, but generally the order in which the components were learned was similar across listeners. Learning styles are listener-specific, with some learning curves showing graded improvement over several hundred trials, while others were characterized by abrupt shifts in thresholds of up to 50 dB. [Work supported by NIH/NINCDS.]
Musical modulation and the perceptual structure of tone sequences
Authors: Lyons H. I. , Cuddy Lola L.
Published: October 2005

Tone sequences vary in the degree to which they cohere as melodic patterns. Many of the factors that determine coherence may be described by musical constructs. One such construct, key centeredness, involves the organization of tones about a central tone called the tonic. Key centeredness was manipulated by composing sequences with either a single tonic within a single diatonic mode (major or minor) or with a modulation from one mode to its relative major or minor. Musically trained and untrained listeners were asked to provide a two ratings for each sequence: one a judgment of perceived structure, the other a judgement of the most probable mode of the sequence. Modulating sequences were perceived as less structured than nonmodulating sequences by both trained and untrained listeners. Judgment of most probable mode was reliable for trained musicians only. The results are consistent with the hypothesis that musical modulation elicits a set of alternative tonal organizations. The organizations are amenable to musical description and may be reliably analyzed by trained musicians. However, the degradation of good form that accompanies the increase in alternative solutions is evident across a wide range of musical experience. [Work supported by Natural Science and Engineering Research Council of Canada.]
Acoustical design of the dance hall of the Castle Restaurant
Authors: Owusu-Ansah K. A.
Published: October 2005

Castle Restaurant is situated in a quiet residential area of Kano City in Nigeria. A street separates it from the City Library now under construction. The management of the Restaurant has proposed to build a hall within the building which would be used for dancing, music, and a conference hall. This paper describes (a) the acoustic design of the hall which will meet the requirements of the multipurpose hall and (b) the steps taken to reduce the noise that would emanate from the hall so that neither the residents nor the users of the library would be disturbed.
Computer evaluation of reverberant Sound Pressure Level in interconnected spaces
Authors: Testen Joseph C.
Published: October 2005

One of the requirements of builders of U.S. Navy ships is that Sound Pressure Levels (SPL's) within compartments do not exceed specified octave-band levels. In order to anticipate future problems, a computer program (NOISE) was written in FORTRAN to compute the SPL's within as many as 30 interconnected compartments and to compare predicted values to specified values. The acoustic energy input can be either equipment Sound Power Levels (PWL's) within compartments or predetermined adjacent compartment SPL's. The program is used in conjunction with a data set containing information on Transmission Losses, Absorption Coefficients, and Airborne Noise Specified Values. A user-created file inputs data on compartment connectivity and geometry. The output contains tabular listings of SPL in each octave band with deficiencies noted for each compartment.
Multiple sources in statistical room acoustics
Authors: Keefe Douglas H.
Published: October 2005

The problem of the radiation due to pure tone excitation from two simple sources in a reverberant room is considered. The sources are separated by a fixed distance d. The room-averaged power and the spatial cross correlation have been computed for frequencies above the Schroeder frequency of the room using a modal expansion. The sources are located at (r0 + 12d) and (r0 − 12d). The room average is taken over all source locations by averaging over all r0 and over all angular orientations of d. It is assumed that d is much smaller than a typical room dimension L, so that terms of order (d/L) are neglected. The interference terms due to the presence of room boundaries measured at the observation point r are similar to those computed in the single source case, and become negligible sufficiently far from the room boundaries. If the magnitudes of the source strengths are Q1 and Q2 and if φ is the phase difference between the two source excitations, then the room-averaged power in the reverberant field far from the boundaries is proportional to Power ∼ Q12 + Q22 + 2Q1Q2 cos φ (sin kd/kd), where k is the wavenumber. The cross term is similar to the free-space mutual impedance term and vanishes when the spacing d is large compared to a wavelength. The spatial cross-correlation function R at two points in the reverberant field separated by a distance r has also been calculated. This function is R = (sin kr/kr), the same as for a single source, as long as R is averaged over all angular orientations of d. These results demonstrate that the sound power radiated from multiple sources or an extended structure is not simply additive. On the other hand, the statistical character of the sound field produced by multiple sources is very similar to the single source case.
Structure-function relationships and the role of experience in auditory system ontogeny
Authors: Rubel Edwin W.
Published: October 2005

Two structure-function relationships which influence the development of hearing will be discussed. First the evidence of a paradoxical relationship between the ontogeny of responsiveness as a function of frequency and developmental gradients seen in the inner ear and central nervous system will be considered. To account for this paradox, I will propose that the mechanical tuning properties of the basilar membrane are systematically changing during development. Two lines of indirect evidence, one plotting developmental changes in the position of damage produced by high-intensity pure tones and the other showing ontogenetic changes in the tonotopic map in the central nervous system, support the proposed interpretation. Second, the influence of afferent interactions on the development of hearing and of neuronal structure in the arian brainstem auditory pathways will be examined. Data will be presented to show that afferent integrity and activity profoundly influence the normal development of structure and function. [Work supported by NIH RCDA ♯00305-04 and grants NS15478 and NS15395.]
Performance characterization of a remote acoustic Doppler current profiling sonar
Authors: Williams R. G. , Huff L. C. , Pijanowski J. A.
Published: October 2005

Monostatic acoustic Doppler technology is being evaluated for application to NOAA's mission requirements for the measurement of upper ocean current profiles. As part of that evaluation, a shipboard current profiling sonar, developed in 1978 under contract to NOAA by Thomson-CSF, was tested on the Blake Plateau. The system includes a four-beam 300-kHz “Janus geometry” hull-mounted transducer, and associated microprocessor-based electronics. The system estimates vertical current profiles in the upper 100 m by detecting the mean Doppler shift in volume-backscattered pulses at multiple ranges. Although no “sea truth” was available, agreement between mean ship' speed inferred from the acoustic Doppler measurements and Loran-C was good. The variance in time series of orthogonal components of current at specified depths is discussed as a function of transmission characteristics and ship's speed. The variance reduction with averaging indicates a random noise-type dependence when averaging of up to 10–20 observations. As more observations are averaged, the decrease in variance is limited, suggesting that an optimum averaging window can be tailored to the operating environment.
Range-dependent sound-speed perturbations: Travel time approximations and ray geometry
Authors: Spiesberger John L. , Worcester Peter F.
Published: October 2005

A number of approximations, both linear and nonlinear, for computing the variations in acoustic travel time due to mesoscale eddies, have been examined. Such approximations are an alternative to fully range-dependent calculations and are necessary to linearize the problem of inverting travel-time variations to obtain sound-speed perturbations. Calculations were performed for a number of sound-speed profiles with source and receiver on the sound-channel axis separated by 300 km. A single mesoscale eddy was assumed to be present. It was found that: (i) no one of the approximations tested is uniformly the best, (ii) the eddy position relative to the ray path is quite significant, (iii) the approximate travel time perturbations can be in error by up to roughly 100% for large (3 °C) eddies in some situations, and (iv) the exact travel-time perturbations are not sensitive to whether the eddy boundaries are assumed sharp or gradual. Vertical displacements of the ray path due to a mesoscale eddy can be of order several hundred meters for large eddies.
Bounds on performance in tomographic estimates of currents
Authors: Porter David L. , Eisler Thomas J. , New Ronald , Calderone Denise
Published: October 2005

Measurements of travel time anomalies along the acoustic ray paths of a tomographic configuration can be inverted to obtain estimates of the ocean sound velocity profile. Estimates of current component profiles can also be obtained directly from measured data, without use of an intermediate step, such as one relating sound velocity, geostrophy, and satellite altimetry data. While direct estimates of current profiles are theoretically possible, their usefulness will depend on their accuracy in a practical context. This question is now being studied. The Backus-Gilbert theory provides a format in which performance bounds related to such estimates can be conveniently formulated in terms of resolution length, bias error, and variance. Statistical errors, such as those due to clock error, mooring motion, nonreciprocity, and microscale fluctuations, enter the analysis of performance bounds through the covariance matrix of the measured quantities. An example of this covariance matrix has been developed and applied to the configuration used in the 1981 tomography experiment in the MODE area [B. Cornuelle, J. Acoust. Soc. Am. Suppl. 1 70, S38 (1981)].
Wave theory approach to ocean acoustic tomography
Authors: Murphy Joseph E.
Published: October 2005

The proposal of monitor ocean basins for mesoscale fluctuations using acoustic inverse techniques consists of measuring perturbations in travel time between multiple fixed sources and receivers, and applying inverse theory of estimate sound speed structure along ray paths [W. Munk and C. Wunsch, Deep-Sea Res. 26A, 123–161 (1979)]. An acoustic inverse technique based on wave theory should make use of all pertinent observables: amplitude, phase, travel time, etc. We present results obtained within the context of a two-dimensional horizontal ocean model. Estimates of sound speed structure are obtained from rms amplitudes and an eikonal approximation to the solution of the Helmholtz equation. Extension to three dimensions using a normal mode expansion is outlined. [Supported by ONR.]
Near field inverse scattering for a stratified acoustic medium
Authors: Murphy Joseph E.
Published: October 2005

Most previous work on inverse scattering theory for stratified media has assumed incident plane waves, and generally yields impedance as a function of travel time, rather than velocity and density as functions of depth. Recently it was shown [S. Coen, J. Math. Phys. 22, 1127–1129 (1981)] that the inverse problem for the permittivity and permeability in stratified electromagnetic media is soluble, and by similar mathematical techniques the density and Lame' profiles of stratified elastic media can be determined [S. Coen, J. Acoust. Soc. Am. 70, 172–175 (1981)]. By adapting Coen's technique to the acoustic case, we first show that velocity and density profiles can be found as functions of depth from two plane wave reflection coefficients. Then we show that the same profiles can be found from measurements on the surface of the stratified half-space of the impulse response of a point source. A Fourier-Hankel transform of the normal velocity component of the reflected wave provides the reflection coefficients necessary for the inversion algorithm.
Eigenmodes and quality of violins
Authors: Moral Jesus Alonso , Janssen Erik V.
Published: October 2005

From a Scandinavian violinmakers' competition, a number of 24 violins of different qualities were selected. Input admittances as function of frequency were recorded perpendicularly to the top plate at two positions on top of the bridge. The admittance curves at the side of the bass bar show three resonances at approximately 400, 500, and 700 Hz and a broad resonance around 3 kHz. Three “acoustical” quality criteria were extracted from these curves: (1) the average level of the three resonance peaks (high is favorable), (2) the summed discrepancies between single peak levels and the average level (small is favorable), and (3) steepness of upwards slope from 1500 to 3000 Hz (steep is favorable). The levels of input admittances of the bass bar and sound post sides are approximately the same. A fourth acoustical quality criterion was extracted from the two curves: (4) the level discrepancies between the two curves (small is favorable). Calculated “acoustical” quality points correlate well with given tonal quality ratings (a correlation coefficient of 0.92 with five violins with singular faults excluded).
Computer-controlled violin mode measurements compatible with microbudgets
Authors: Arnold Eric B.
Published: October 2005

Control by a dedicated microcomputer has been applied to a system previously developed for violin normal mode measurement [Weinreich and Arnold, J. Acoust. Soc. Am. Suppl. 1 67, S84 (1980); Arnold and Weinreich, J. Acoust. Soc. Am. (to be published)], increasing its usefulness in several ways: (1) operator attention is required less frequently, enabling data to be collected more efficiently, (2) a sequence of operations may be repeated without error, (3) error conditions may be monitored and acted upon, (4) useful statistics may be compiled and displayed, and (5) the system behavior may be modified easily through program control. Present-generation microcomputers with internally-resident high-level language interpreters are nearly ideal for such purposes: the Zilog Z8671, used here, provides a crystal-controlled time base, frequency synthesizer control, data management, error monitor, and terminal interface. Potential future applications will be discussed. With component costs of about $100 and relatively little assembly and programming time, the computer may offer new possibilities within the constraints of microbudgets. [Work supported by NSF.]
Violin intonation problems caused by body resonances
Authors: Pickering Norman C.
Published: October 2005

Strong mechanical resonances in the body of a violin, coupled to the strings through the bridge, cause a shift in the actual frequency of the string which can be 30 cents or more away from the frequency which should exist at a given stopped length. Apparatus has been constructed which permits the detuning effect to be measured. It consists of means for exciting an electrically conducting violin string by the Lorenz force while precisely changing string length with a nylon roller moved along the fingerboard under control of an accurate leadscrew. String amplitude is measured by an optical sensor in the pole-pieces of the magnetic circuit. Results are shown for several instruments of differing characteristics.
Reflection from and transmission through a periodically stratified ideal fluid half-space
Authors: Schoenberg Michael , Sen Pabitra N.
Published: October 2005

The problem of the reflection of acoustic waves from a periodically layered acoustic half-space is solved exactly at all frequencies. Pass and stop bands and the associated complex slowness surfaces for propagation through the periodic medium are found. In the low-frequency limit, when the wavelength normal to the layering is much greater than one period, it is shown that there always exists a homogeneous ideal fluid with the same reflection properties as the layered medium. The effective acoustic medium that models transmission as well as reflection at low frequencies has a bulk modulus, Keff, given by 〈K−1〉−1, where the brackets denote a volume weighted average. However, for the inertial density appearing in the equations of motion, the effective medium has an anisotropic density tensor with ρ∥, the density component parallel to the layering, given by 〈1/ρ〉−1, and ρ⊥, the density component perpendicular to the layering given by 〈ρ〉. The slowness surface for such an anisotropic acoustic medium is the usual ellipse with a speed that is always greater parallel to the layering than normal to the layering.
Acoustical behavior of a submerged steel plate coated with an elastomer layer that contains perforations
Authors: Rudgers Anthony J. , Solvoid Christine A.
Published: October 2005

The reflection and transmission characteristics of an infinite steel plate submerged in water are analyzed for a normally incident plane acoustic wave. The plate is coated on one side by a layer of styrene-butadiene rubber (SBR) perforated by a doubly periodic array of rectangular holes. A second, thin, homogeneous SBR layer covers the perforated layer so as to exclude water from the holes. Numerical analyses are presented that compare two different models describing the perforated layer—the “effective-modulus” model and an alternative model derived using an approximate elasticity-theory analysis. In the effective-modulus model, only the volume concentration of the perforations in the SBR affects the elastic properties of the layer. However, in the alternative model, the layer elastic properties are affected by the size, shape, and pattern of the perforations, in addition to their concentration. The effects of perforation size, shape, and pattern are illustrated by comparing computed results for different perforation schemes having the same volume concentration of perforations. [This abstract appears in the program of the 102nd Meeting. The paper, which was to have been presented as paper HH3 at that Meeting, was cancelled.]
Reflection of Waterborne acoustic waves from a viscoelastic layer on a rigid hacking with perforations
Authors: Jarzynski J.
Published: October 2005

The reflection coefficient is calculated for a plane acoustic wave normally incident on a viscoelastic rubber cover layer submerged in water. The rubber layer is mounted on a rigid backing with air-filled cylindrical perforations. Acoustical losses are attributed to motion of the layer over the perforations. This motion is calculated by treating the layer above each perforation as a vibrating circular viscoelastic plate. Different boundary conditions are assumed, and in each case the sound reflection coefficient is calculated. The results are compared with the experimental data of R. Lane [Ultrason. 19, 28–30 (1981)].
Acoustic wave scattering by highway noise barriers
Authors: Varadan V. K. , Varadan V. V. , Hayek S.
Published: October 2005

Barriers are commonly constructed beside highways to screen residential areas from traffic noise. The effectiveness of the barrier depends on its shape and height, the material with which it is constructed and its distance from the source of noise. In this paper we wish to analyze acoustic wave scattering by highway barriers of different shape and height. The sources considered will be harmonic point and line sources. The T-matrix method and the finite element approach will be used to solve the scattering problem taking into consideration the effect of the ground. Comparisons with scale model experiments will be made.
An evaluation of the “leaky integration” model of Jeffress using reproducible noise maskers
Authors: Gilkey R. H , Hanna T. E. , Robinson D. E.
Published: October 2005

At the 1980 Los Angeles meeting we presented the results of an experiment which investigated the detectability of a 500-Hz tonal signal in the presence of each of 25 samples of reproducible Gaussian noise. The present paper reports on our attempts to predict these data using a model similar to that of Jeffress [J. Acoust. Soc. Am. 41, 480–488 (1967)]. The combination of a 50-Hz-wide, single-tuned filter, followed by a half-wave recitifier and an integrator with an integration time of 100 to 200 ms was found to fit the data of each of the four subjects relatively well. Small differences in the parameters of the best-fitting model were found across subjects. The proportion of variance explained by the model varied from 0.42 to 0.72 across subjects. Combining the output of several models which differed in center frequency or integration interval increased the proportion of predicted variance. Limitations of the present approach will be discussed and certain anomalies reported in previous attempts to model reproducible noise masking data [e.g., Ahumada and Lovell, J. Acoust. Soc. Am. 49, 1751–1756 (1967)] will be explained. [Work supported by NSF research grant BNS-77-17308 and by a Grant-in-Aid from Indiana University.]
Interaural-intensity discrimination
Authors: Yost William A. , Dye R. H.
Published: October 2005

The difference threshold for interaural intensity was measured at 200, 1000, and 5000 Hz for six different (0, 3, 6, 9, 12, 15 dB) interaural-intensity reference conditions. All tones were presented at an average level of 65 dB SPL and the duration of the tones was 200 ms. The interaural-intensity thresholds were measured in both a single-interval and in a two-alternative, forced-choice procedure. A random (4 dB) overall intensity variation was introduced from observation interval to observation interval in order to eliminate the use of monaural intensity cues as a basis for discrimination. The results will be discussed in terms of discrimination of interaural intensity for images off midline, and for tasks involving one or two observations per trial. [Research supported by the National Science Foundation.]
Interaction of masker and suppressor levels in forward masking
Authors: Weber Daniel L.
Published: October 2005

The interaction of masker and suppressor levels was investigated for a narrow-band noise masker (60 Hz wide centered at 1000 Hz) and sinusoidal suppressors at 500, 800, 1120, and 1400 Hz. Forward-masked threshold for a 10-ms, 1000-Hz sinusoidal signal was determined as a function of suppressor level (ranging from 30 to 90 dB SPL) for each of five masker levels (30, 40, 50, 60, and 70 dB SPL total noise power). The results for suppressors below the masker frequency are as predicted by the class of models based on bandpass nonlinearities. Although the form of the data is qualitatively the same for suppressors above the masker frequency, these data do not show a lower limit corresponding to the excitatory effect of the suppressor alone, as do the data for the lower frequency suppressors. [Research supported by NSF and NIH.]
Design and calibration of a portable high-frequency audiometer
Authors: Hsiao Henry S.
Published: October 2005

Assessment of high-frequency hearing in the frequency range from 8–20 kHz has been shown to have important clinical applications. It can be used to predict future hearing loss at lower speech frequencies, to monitor the effects of ototoxic drugs, and to assist in the use of speech translation hearing aids. Early detection and monitoring of high-frequency hearing can be used to prevent further hearing impairment. We have developed a unique, portable instrument which meets the technically difficult electroacoustic requirements. These include the design of an attenuator, amplifier, and oscillator with at least 120-dB signal-to-noise ratio, development of a pulse modulator circuit which can present tones with fixed rise and fall times, and calibration procedures for both the electronics and transducer. The transducer used in this unit is a professional earphone with 130-dB dynamic range but other transducers may be substituted. A second masking channel provides a warble tone which tracks the center frequency of the test stimuli. Preliminary testing with 25 young adults shows a test-retest repeatability of approximately 10 dB at each frequency over the entire frequency range.
Is the detection of a temporal gap frequency dependent?
Authors: Florentine Mary , Buus Søren
Published: October 2005

The minimal detactable gap, MDG, in a continuous noise was measured as a function of level. The MDG was produced by briefly turning off the low-frequency part (below 2 kHz), the high-frequency part (above 2 kHz), or all frequencies in a white noise. The rise and fall times were 1 ms. An adaptive two-interval, 2AFC paradigm with feedback was used. For three listeners the MDG decreased as level increased up to approximately 60 dB SPL, above which the MDG appeared to increase. The results were in good agreement with the data of Irwin et al. [Audiology 20, 234–243 (1981)]. For both the all-frequency and the high-frequency conditions the MDG decreased from 15 to 2.5 ms as level increased from 20 to 60 dB SPL; at 90 dB SPL the MDG was approximatey 3.5 ms. For the low-frequency condition, the MDG at all levels was three to seven times larger than in the other conditions. These results suggest that high frequencies are much more important for gap detection than low frequencies.