bluuebunny/crossref_metadata_2025 huggingface dataset:
Detection threshold for a two-tone complex
Authors: Hall J. L. , Sondhi Man Mohan
Published: October 2005

The absolute threshold for two-component tone bursts of 500-msec and 1-sec duration was measured as a function of the frequency spacing between the components. The average frequency of the two components was 700 Hz. When interpreted in terms of an energy-detector model (peripheral filter followed by squarer, integrator, and threshold detector), the measurements give an estimate of the time constant and window shape of the integrator. Our measurements on two subjects give a time constant on the order of 200 msec. A window which initially decreases more rapidly than exponentially fits the data better than an exponential window.
Sound absorption in sea water
Authors: Fisher F. H. , Simmons V. P.
Published: October 2005

An equation is presented for sound absorption in sea water as a function of frequency, temperature, and pressure based on laboratory data. The equation includes contributions to absorption due to boric acid, magnesium sulfate, and water. The effect of pressure on sound absorption due to magnesium sulfate and water has been treated differently than in the Schulkin and Marsh equation. At 4°C our results for absorption at frequencies from 10–400 kHz and pressures up to 500 atm are substantially lower than those calculated from the Schulkin and Marsh equation.
Sensitivity of piezoceramic tubes, with capped or shielded ends, above the omnidirectional frequency range
Authors: Trott W. James
Published: October 2005

The NRL computer program SHIP is used to compute the diffraction constants for finite-length cylindrical radiators and circular pistons in the end of finite-length cylindrical baffles. Radiation impedances are calculated. The diffraction constants can be used to calculate the sensitivity of piezoceramic tube elements above the omnidirectional range.
Procedure for calculating loudness of temporally variable sounds
Authors: Zwicker Eberhard
Published: October 2005

Data on loundness comparisons are complemented by additional measurements. Thus, temporal effects in loudness with respect to four parameters can be summarized: (a) phase effects of complex tones and the influence of physiological noise, both in the low-frequency range, (b) effects of amplitude modulation, (c) frequency modulation, and (d) bandwidth in the high-frequency range. Additionally, transient masking patterns and the corresponding specific loudness patterns produced by strongly time-varying sounds are discussed. A model for the loudness development of such sounds is designed and realized electronically as a loudness measuring device. The usefulness of this equipment is demonstrated for measuring loudness of the following six types of sounds that vary both temporally and spectrally: (a) single tone bursts as a function of duration, (b) sinusoidally amplitude modulated tones as a function of repetition rate, (c) bandpass noise with constant rms value as a function of bandwidth within the critical band, (d) strongly frequency modulated tones as a function of modulation frequency, (e) temporally partially masked tone bursts, and (f) continuous speech.
Locus of segmental cues for word juncture
Authors: Nakatani Lloyd H. , Dukes Kathleen D.
Published: October 2005

Listening experiments with spliced speech showed that cues for the perception of word juncture occurred always at word onset, at word offset only for /l/ and /r/, and never word medially. Spectrograms showed the cues to be bursts, aspiration, glottal stops, laryngealization, and distinct syllable-initial allophones of /l/ and /r/.
Measuring laterality effects in dichotic listening
Authors: Repp Bruno H.
Published: October 2005

This paper discusses methodological issues and problems related to measuring laterality effects in dichotic listening. Section I describes the standard dichotic two-response paradigm, as well as a number of indices of the degree of ear advantage proposed in the literature. The numerical range of most of these indices is constrained by performance level; only one particular index avoids these constraints. However, this does not make this index necessarily the optimal one. First, a correction for guessing is proposed. Then, analogies to signal-detection theory are discussed, as well as theoretical and empirical criteria for choosing the correct index of laterality. While this index is still unknown, the index called here eg is proposed as the best solution at the present state of knowledge. Section II discusses the phenomenon of dichotic fusion and the dichotic single-response paradigm, which offers many methodological advantages over the two-response paradigm. Section III discusses the factors of ear dominance and stimulus dominance in the perception of fused stimuli. An index of ear dominance is derived by again taking advantage of analogies to signal-detection theory. In Sec. IV, a number of remaining problems are discussed: stimulus intelligibility, guessing and selective attention, blend responses, test reliability, validity, and homogeneity.
Detection and recognition of pure tones in noise
Authors: Green David M. , Weber Daniel L. , Duncan Joseph E.
Published: October 2005

We examine the predictions of a new theorem relating signal identification (specifying a signal as a particular member of a set of potential signals) to signal detection (discriminating the presence of a signal). The theorem, derived in the context of signal-detection theory, requires that the signals be equally detectable and orthogonal. Our sinusoidal signals are partially masked by noise and their intensities adjusted to produce equal-signal detectability; we do not examine this assumption of the theorem. The theorem generally provides a reasonably accurate description of recognition performance for two-signal and four-signal conditions and is equally accurate for both the Yes–No and category-rating procedures. In a preliminary investigation of the orthogonality assumption, we varied the frequency separation between two signals. When the frequency separation between two signals is small (20 Hz near 1 kHz), the theorem fails to provide a good description of performance.
Effect of final-syllable position on vowel duration in infant babbling
Authors: Oller D. K. , Smith Bruce L.
Published: October 2005

Previous research has suggested possible speech-production and/or speech-perception-oriented causes for the temporal phenomenon referred to as final-syllable vowel lengthening, yet little conclusive evidence has been adduced for either possibility. The present study represents an attempt to provide additional information concerning the nature of this phenomenon by approaching the issue from a developmental perspective. A much smaller amount of final-syllable vowel lengthening was observed in the premeaningful vocalizations of a number of very young infants than in phonetically comparable utterances produced by adult speakers of English. It is concluded on the basis of this preliminary evidence that extensive final-syllable lengthening observed in the productions of adult speakers of English seemingly constitutes a learned behavior.
Effect of arbitrary temperature and flow profiles on the speed of sound in a pipe
Authors: Robertson Baldwin
Published: October 2005

An expression for the wave number of the fundamental mode in a uniform duct of arbitrary cross section is obtained correct to first order in V/c and in c1/c0, where V is the velocity of the fluid in the pipe and c=c0+c1 is the local sound speed with c0=constant. Correction terms are also obtained. The calculation applies to a fluid with the equation of state of an ideal gas or to a liquid and is valid for frequencies well below cutoff. The speed c and velocity V can be arbitrary functions of position across the cross section given only ∇⋅V=0. For the gas, the wave number, which is a constant, can be expressed in terms of the average density and the total mass flow rate.
Distinctive features and acoustic cues
Authors: Parker Frank
Published: October 2005

Recent findings in speech perception studies have been interpreted as indicating that distinctive features are not ’’real.’’ That is, they seem to be merely convenient descriptive devices which are imposed on the data rather than found in it. This conclusion results from a failure to distinguish between distinctive features and acoustic cues. Distinctive features and acoustic cues are different types of entities and are justified on different empirical grounds. Acoustic cues are properties of the speech signal which relate the acoustic stream to phonological segments. Distinctive features are the elemental units of phonology which govern the behavior of segments within language. Acoustic cues are determined by observation of the speech signal and distinctive features by observation of phonological rules and phonological change. The relation between distinctive features and acoustic cues is not 1 : 1, but rather 1 : many. Therefore, distinctive features cannot function as, nor be equated with, acoustic cues and vice versa. Moreover, confusion matrices, which are generated by masking the input stimulus with noise or filtering, are a direct function of the speech signal, and thus yield information concerning acoustic cues, not distinctive features. Therefore, this research does not disprove the empirical status of distinctive features; it corroborates the 1 : many relation between distinctive features and acoustic cues.
Measurement of acoustic intensity using the cross-spectral density of two microphone signals
Authors: Fahy Frank J.
Published: October 2005

A technique is presented for evaluating the acoustic-intensity vector in an arbitrary environment by measuring the imaginary part of the cross-spectral density between the output signals from two closely spaced, pressure microphones.
Reflection and radiation due to a quadrupole near a fluid interface
Authors: Dash R.
Published: October 2005

The reflexion of sound at an interface between two fluid half-space in relative motion (one in motion and the other at rest), but with different density and different sound speed, is considered. The reflexion coefficient is found in an explicitly closed form. A brief discussion of the effect of mean velocity, i.e., corresponding Mach number on different noise generating quadrupole directivities concludes the presentation of the paper. The graphs provided illustrate this aspect in a rather more convincing way.
Project TASMAN TWO: Low-frequency propagation measurements in the South Tasman Sea
Authors: Bannister R. W. , Denham R. N. , Guthrie K. M. , Browning D. G.
Published: October 2005

In February 1975, a low-frequency acoustic propagation experiment, Project TASMAN TWO, was conducted in the South Tasman Sea to the west of the South Island of New Zealand. The aim was to study low-frequency acoustic propagation in a region having considerable variations in oceanic environment. Sound signals, set to detonate at the SOFAR axis, were air dropped out to a range of 3000 km along paths chosen to sample three distinct water masses (Subtropical Water, Australasian Subantarctic Water, and Circumpolar Subantarctic Water) and to traverse a large bathymetric feature (the South Tasman Rise). In addition, convergence zone (RSR) propagation in subtropical water was investigated with the sound signals set to detonate at 18 m. The results show that the three individual water masses have significantly different attenuations at frequencies below 500 Hz. It was established that Circumpolar Subantarctic Water has an attenuation nearly five times greater than Subtropical Water. For SOFAR propagation conditions, major acoustic transmission discontinuities were not always observed at the boundaries between the water masses, but strong shadowing effects with level changes of as much as 15 dB were clearly associated with the bathymetric feature. The experimental data for both SOFAR and RSR propagation are compared with predictions made using the parabolic equation model. Although the predictions match most general trends observed in the data, poor-detailed agreement was achieved where rapid horizontal gradients in either sound speed or water depth were experienced.
Coherent ray propagation through a Gulf Stream ring
Authors: Weinberg N. L. , Zabalgogeazcoa X.
Published: October 2005

A model study using coherent ray-tracing methods was based on a cold-water eddy measured in the Altantic. The eddy, whose diameter is about 320 km was passed through the propagation path at a rate of 4 km/day between a fixed source and fixed receiver separated 445 km. A brief description of the range-dependent model required for this study is presented. The major effects of the eddy were in changing the ray type (number of cycles, RR–RSR, etc.) and in the travel time which had a major effect on the multipath resultant. Time series of amplitude and phase are presented with a qualitative comparison to previously measured data.
Spectrum of the lagged product in cross correlation
Authors: Beisner Henry M.
Published: October 2005

Cross correlation has been used for detection and parameter estimation of moving targets. Various correlation techniques consist, essentially, of methods to estimate the spectrum of the correlation product. The power spectrum of the lagged product is derived. The time-lag dependence of the spectrum is found to be proportional to the squared magnitude of the signal autocorrelation function. It is shown that, if the bandwidth of the modulation noise is small compared to the signal bandwidth, considerable gain can be obtained by correlation.
Probe-tube microphone for pressure-fluctuation measurements in harsh environments
Authors: Barton J. P. , Koester J. K. , Mitchner M.
Published: October 2005

A probe-tube microphone has been developed for use in the harsh experimental environment involved in studying small-scale pressure fluctuations in combustion magnetohydrodynamics. A smooth frequency response is obtained by a theoretically derived method of impedance matching where an acoustical resistance is placed midway within the length of the tube. The use of such probe-tube microphones under experimental conditions has proven very satisfactory.
Sound reflection from an absorbing sphere
Authors: Hasegawa Takahi , Kitagawa Yoshiko , Watanabe Yumiko
Published: October 2005

A discrepancy in the recent paper ’’Monostatic reflection of a plane wave from an absorbing sphere’’ [F.H. Vogt et al., J. Acoust. Soc. Am. 57, 558–561 (1975)] is investigated. Calculations are made by means of a modified method for lucite and polyethylene spheres in water. A serious disagreement between Vogt et al. and us is demonstrated in the case where no absorption is included.
Adaptive cross-sensor beam forming with planar arrays
Authors: Bucker Homer P.
Published: October 2005

In cross-sensor beamforming the narrow-band quadrature signal at one sensor is multiplied by the complex conjugate of the narrow-band quadrature signal at a second sensor to form a stable element of the cross-sensor field. After suitable time averaging, the beam response can be calculated as the weighted correlation between the cross-sensor field that is measured and the field that is expected. If N sensors form a sparse line array, then N lines form a sparse square array. Examples are given showing the performance of a sparse square array and a random planar array in resolving a realistic multiwave signal plus noise field. A simple adaptive algorithm is used to resolve weak signals close to strong signals and to reduce sidelobe problems associated with a random array.
Broadband target classification using a bionic sonar
Authors: Skinner D. P. , Altes R. A. , Jones J. D.
Published: October 2005

A recently proposed echo-analysis technique based on a power-series expansion of the target transfer function and an optimally Doppler-tolerant transmitted waveform is discussed. Specific problems with the technique including sensitivity of the extracted parameters to time delay and Doppler changes in the received waveform are identified. An analysis is conduced of relatively low-frequency echoes from a number of simple submerged targets, and the results are reported. An iterative generalization of the proposed technique is introduced which substantially improves its performance.
Compound actionpotential tuning curves in normal and pathological human ears
Authors: Eggermont J. J.
Published: October 2005

Using a tone-on-tone masking procedure to just mask a compound actionpotential (AP) evoked by a 10 dB SL short toneburst yields frequency-intensity combinations for the tonal masker called AP tuning curves. This procedure is used in addition to the standard electrocochleography procedure to obtain information about the peripheral frequency selectivity. Both methods were performed on a (normal) group of patients having normal or nearly normal (within 15 dB) thresholds for frequencies above and including 1 kHz, and in patients having hearing losses of sensorineural origin exceeding 40 dB HL. In normal ears, the characteristic two-segment tuning curves are obtained. For pathological ears having a hearing loss of cochlear origin, tuning curves broadening by the loss of their sharp tips are obtained. There is some indication that in predominant neural hearing loss most of the sharp tuning is preserved. The changes in tuning associated with recovery from sudden deafness to almost normal hearing are reported. The overall conclusion is that the results obtained are in agreement with those from AP tuning curves reported in animal studies [P. Dallos and M.A. Cheatham, ’’Compound action potential (AP) tuning curves,’’ J. Acoust. Soc. Am. 59, 591–597 (1976)] as well as with changes in single-fiber tuning in reversible hearing loss [E. F. Evans, ’’Auditory frequency selectivity and the cochlear nerve,’’ in Facts and Models in Hearing, edited by E. Zwicker and E. Terhardt (Springer–Verlag, New York, 1974)].
Transmission and reflection of ultrasonic waves in layered media
Authors: Folds D. L. , Loggins C. D.
Published: October 2005

The wave equation is solved to determine the transmission and reflection coefficients for plane waves at oblique incidence on a system of n layers of plane parallel plates. Both shear- and longitudinal-wave properties of the materials are included in the derivation. Equations are presented in a form which will facilitate adaptation to a digital computer. Data measured in the frequency range 100–700 kHz for one, two, and three solid layers immersed in water compare favorable with computer results.
Fluid mechanics of the edgetone
Authors: Holger David K. , Wilson Theodore A. , Beavers Gordon S.
Published: October 2005

A model is proposed to explain the means by which an edgetone transforms the energy of a fully developed plane jet into energy which is radiated as sound. The edgetone configuration considered consists of a flat plate located in the medial plane of a fully developed two-dimensional jet. The flow is modeled as follows. A periodic disturbance at the jet origin leads to the formation of an asymmetric vortex street which propagates downstream with a fixed convection velocity and wavelength. The vortex strength, convection velocity, and wavelength are determined as functions of the Strouhal number by applying conservation laws and kinematic relationships. A potential flow analysis of the interaction of the vortices with the edge is used to estimate the nearfield oscillating flow at the jet exit which, in turn, is used to calculate the phase of the feedback mechanism. The phase then determines the operating frequency as a function of jet velocity and edge stand-off distance. It is shown that the proposed model is capable of predicting the major observed features of edgetone operation. The frequency predictions of the theory are compared with experiments for a wide range of jet parameters in both air and water. The comparison indicates that the frequency predictions are as good or better than previous empirical or semiempirical formulas.
Simultaneous measurement of sound velocity and sound attenuation in liquids by a correlation method
Authors: Sedlacek Martin , Asenbaum Augustinus
Published: October 2005

The correlation between the input and output signals of an ultrasonic ransmitter–receiver system with two quartz transducers was used for the simultaneous measurement of sound speed and sound absorption in liquids. With a correlator built from a semiconductor heterodyne detector (active mixer) followed by a low-pass filter, the space-dependent cross-correlation function of the signals, which depicts the sound field in the liquid, was recorded on a x-t recorder by continuous variation of the transmitter–receiver distance. First tests with the apparatus yielded a reproducibility of the sound velocity of ±0.1%, that of the sound attenuation was within ±3%.
Subjective preference in relation to objective parameters of music sound fields with a single echo
Authors: Ando Y.
Published: October 2005

Subjective preference tests with a simulated single reflection in an anechoic chamber were conducted in order to get a knowledge of the preferred properties of sound fields. The degree of preference in relation to a long-time autocorrelation function of source signal and the interaural cross correlation of the sound field is discussed here. The preferred time delay gap between the direct sound and the first echo can be determined by the coherence of autocorrelation function and the amplitude of the echo. The preferred echo direction to a listener may be obtained by minimizing the interaural cross correlation which relates to the ’’subjective diffuseness.’’ Results of the autocorrelation function, which was measured with an A-weighting filter, and the interaural cross correlation are presented for several music motifs. convection velocity and wavelength. The vortex strength, convection
Harmonics of the difference frequency in saturation-limited parametric sources
Authors: Willette John G. , Moffett Mark B.
Published: October 2005

Data are presented for the spectra and waveforms generated by saturation-limited parametric acoustic sources. The primary source was a 10-cm-diam, 710-kHz projector driven with double side band and sine-wave amplitude modulation at peak primary source levels up to 246 dB//1μPa m. The data tend to confirm the theory of H. M. Merklinger [Ph. D. thesis, (Department of Electronic and Electrical Engineering, University of Birmingham, England, 1971) (unpublished)], namely, that the secondary pressure is proportional to ∂2‖E (t−x/c0) ‖/∂t2, where E is the primary envelope waveshape. A modified version of the theory provides a useful primary amplitude taper function for parametric source performance prediction.
Three-dimensional ray paths in basins, troughs, and near seamounts by use of ray invariants
Authors: Harrison C. H.
Published: October 2005

Horizontal curvature of long-range underwater sound rays can be caused by repeated reflection from a sloping or undulating sea bed. This paper uses ray invariants to derive analytical solutions for the horizontal projections of ray paths for many types of basins, troughs, seamounts, and ridges. The isovelocity invariants for elevation angle and ray heading are extended to cover a basin with rotational symmetry as well as a trough of constant cross section, and the additional effects of refraction in a stratified medium are considered. Rough figures for the geometrical spreading loss and reflection loss at the edge of a basin are derived.
Target strength of an individual fish at any aspect
Authors: Love Richard H.
Published: October 2005

A set of empirical equations has been developed for use in determining the target strength or acoustic cross section of an individual fish at any insonified aspect as a function of fish size and insonifying frequency in the range 1?L/λ? 100, where L is fish length and λ is acoustic wavelength. The equations were developed by interpolating experimental data obtained by insonifying individual fish as they were rotated about one of their principal axes. It was found that acoustic cross section σ is proportional to slightly less than L2 for each aspect, indicating that σ is approximately proportional to insonified area. Since σ is almost proportional to L2, a modified set of empirical equations was developed with σ exactly proportional to L2, thus eliminating the dependence of σ on frequency. The resulting errors are relatively minor and in some situations the modified equations lead to considerable simplifications which make their use quite convenient.
The effect of Doppler on long-range sound propagation
Authors: Neubert Jerome A.
Published: October 2005

In this sound propagation study of the effect of Doppler on source and/or receiver motion has been developed. It is based on modifying the inputs to existing normal-mode software so that the source and/or receiver trajectory and consequent Doppler effects of the given ocean experiment are properly modeled without requiring direct changes in the static softward. From this the effects of the received signal after long-range, multipath sound propagation from a moving source can be modeled and interpreted.
Sperm whale codas
Authors: Watkins William A. , Schevill William E.
Published: October 2005

Short series of 3 to 40 or more clicks are produced by sperm whales, Physeter catodon, in stereotyped repetitive sequences or codas. The temporal click patterns in codas appear to be unique to individual whales over at least a few hours. It is suggested that sperm whale codas serve as a means of individual acoustic identification. An apparent exchange of codas between two animals was analyzed and acoustical locations calculated for the four-hydrophone array data that changes in underwater meovement coincided with changes in the coda sequences.
Design method for ultrasound transducers using experimental data and computers
Authors: Sigelmann Rubens A. , Caprihan Arvind
Published: October 2005

An approach is described for designing thickness mode ultrasound transducers. A computer subroutine is used to simulate the frequency response of a transducer in the transmitting or receiving mode. The physical parameters of the piezoelectric ceramic required for the design are obtained with conventional instrumentation. Two of the parameters (e33 and an equivalent resistance to represent losses) are calculated with the aid of a computer program which makes use of the measured impedance versus frequency. An example of design is presented.
Acousto-optic effect in nematic liquid crystals
Authors: Letcher S. , Lebrun J. , Candau S.
Published: October 2005

Acoustically induced birefringence has been studied in homeotropic cells of nematic liquid crystals. Annular rings associated with the edge of the ultrasonic beam have been observed in agreement with the model based on acoustic streaming. Other observed features of the spatial distribution of the optical signal are not described by this theory. The increased sensitivity near the nematic-isotropic transition is shown to be due primarily to the increased sound absorption.
Scattering of longitudinal waves incident on a spherical cavity in a solid
Authors: Tittmann B. R. , Cohen E. Richard , Richardson John M.
Published: October 2005

Experimental data are compared with theoretical calculations for the scattering of ultrasonic pulses from a single spherical cavity embedded in a metallic solid. Except at high frequencies, the data are in reasonable agreement with theory, bearing out the notable features predicted for the angular dependence and the mode conversion between longitudinal and transverse waves. At high frequencies the disagreement can be accounted for by the lack of monochromicity in the ultrasonic pulse, and the technique for analyzing the data taking into account the broadband spectrum must be applid. The experimental parameters were chosen to span the regime where the wavelength is of the order of the size of the spherical cavity (0.8 mm) on samples of diffusion bounded Ti–6% Al–4% V.
On cochlear encoding: Potentialities and limitations of the reverse-correlation technique
Authors: de Boer E. , de Jongh H. R.
Published: October 2005

This paper presents a description of the interrelation between two major properties of the responses recordable from auditory nerve fibers: frequency selectivity and partial synchrony between stimulus and response. In the course of this work the influence of nonlinearity on the cochlear encoding process can be assessed. The theory of the reverse-correlation technique is derived in a most general way. It is based on a model in which a filter—assumed to be linear—is followed by a stochastic pulse generator—the probability of producing an output pulse being an instantaneous but nonlinear function of its input signal. Insofar as such a model represents stimulus transformations in a primary auditory neuron, the technique can be applied to the responses recorded from an auditory nerve fiber. Several illustrative examples of experimental reverse-correlation functions−abbreviated: revcor functions—are presented and discussed. These functions have the general character of impulse responses of sharp bandpass filters. They show very little phase modulation. For noise stimuli of up to 70 dB per third octave the revcor functions are almost invariant. Above that level some (but not all) of the revcor functions show a loss of frequency selectivity. If a nerve fiber can be contacted for a sufficiently long time, it is possible to compare the response with that of a model filter, in which the revcor function of that fiber is substituted as its impulse response. The output signal of the model filter is shown to be a very good predictor of the firing probability of the fiber under study. This property is demonstrated for noise as well as for tone stimuli. There is surprisingly little evidence of nonlinear filtering in these results. This so-called simulation method can also be applied when the stimulus is switched on and off. The results show, apart from effects due to filtering, clear manifestations of fast adaptation. Again, the filtering appears to be independent of the latter effect. It is concluded that for wide-band noise and single-tone signals the firing probability is predominantly controlled by a linearly filtered version of the acoustical stimulus; this constitutes the principle of specific coding. The conspicuous absence of nonlinear effects in the results can partly be explained in terms of the response properties of a class of networks in which sharp filtering occurs after the generation of nonlinear distortion products. It can then be predicted that this property will hold only for wide-band and tonal stimuli. That our results show so little evidence of cochlear distortion appears to be a property of signal transformations and is not due to linearization tendencies of the experimental method.
Coding of information in single auditory-nerve fibers of the goldfish
Authors: Fay Richard R.
Published: October 2005

Patterns of activity in single fibers of the saccular branch of the auditory nerve of goldfish were analyzed in response to acoustic stimulation. Neurons were categorized on the basis of differences in spontaneous activity patterns, rates of adaptation, and frequency response areas. The sensitivity and responsiveness of neurons are presented both in terms of impulse rate and synchronization (phase locking). Nonspontaneous neurons fall into two clear frequency response area categories based upon impulse rate criteria. Spontaneously active neurons have continuously distributed frequency response characteristics based upon synchronization criteria. Functions relating impulse rate responsiveness to frequency indicate that frequency is coded only crudely as an across-fiber pattern of impulse rates. Synchronization responsiveness functions show that frequency is coded temporally with the same precision in the goldfish auditory nerve that it is in mammals, at 1000 Hz and below.
Threshold and growth of the acoustic reflex
Authors: Wilson Richard H. , McBride Linda M.
Published: October 2005

Measurements of the threshold and growth function of the acoustic reflex in man were made utilizing a signal-averaging technique. Pure tones (250, 500, 1000, 2000, and 4000 Hz) and broadband noise served as the contralateral stimuli delivered at intensity levels from the reflex threshold to 116 dB SPL. The acoustic conductance and susceptance components of admittance, at 220 and 660 Hz, were used to measure the reflex activity. The results are reported as changes in conductance, susceptance, and admittance in cgs mmho. The acoustic reflex thresholds were similar to those reported in other studies, with the 220-Hz probe yielding thresholds that averaged 3.5 dB higher than those obtained with the 660-Hz probe. Broadband noise and 1000-Hz stimuli produced the largest reflex magnitudes, while the smallest were observed with 250- and 4000-Hz signals. The dynamic ranges of the restricted growth functions were frequency dependent for pure tones and ranged from ≳16 dB with 250 Hz to ≳28 dB with 1000 Hz, while that for noise was ≳50 dB. The first derivative of the best-fit third-degree polynomial was used to describe the slope characteristics of the growth functions, in which frequency and intensity effects were found. Relationships between the acoustic reflex and tympanometry were observed and are also discussed.
Influence of the precedence effect on word identification by normally hearing and hearing-impaired subjects
Authors: Náb?lek Anna K. , Robinette Larry
Published: October 2005

The influence of the precedence effect on word identification was investigated binaurally and monaurally with normally hearing and hearing-impaired subjects. The Modified Rhyme Test was processed through a PDP-12 computer to produce delay times of 0, 5, 10, 20, 40, 80, or 160 ms. The sounds were reproduced in a room by two loudspeakers positioned at ±30° azimuths in front of a subject at 50 dB SPL for normals and at the most comfortable level for impaireds. A babble of eight voices was added to reduce scores about 15% from the best values measured in quiet. Binaural and monaural word identification remained constant over a range of delays from 0 to 20 ms and declined for longer delays for both groups of subjects. The shapes of the word-identification curves were explained by self-masking (an overlap of consonants with their own repetitions) and masking (an overlap of consonants with preceding vowels or preceding and following words in sentence). Binaural responses for ten selected initial and final consonants showed various patterns of perception with delay. Some hearing impaireds showed more deterioration in word identification than others which might indicate that they experience more perceptual difficulties than normal listeners in places with reverberation or sound amplification.
A power law transformation resulting in a class of short-term integrators that produce time-intensity trades for noise bursts
Authors: Penner M. J.
Published: October 2005

Recent work on temporal masking and temporal resolution indicates that acoustic stimuli are combined to a degree determined by their temporal proximity [D. Ronken, J. Acoust. Soc. Am. 47, 1091–1099 (1970); J. H., Patterson, Jr., Ph.D thesis (1970) (unpublished); M. J. Penner, Percept. Psychophys. 18, 114–120 (1975)]. For broadband stimuli, the process of combining inputs has been modeled as resulting from an exponential integrator with a time constant of 2–4 ms. Such models seem to suggest that stimuli more than, say, 20 ms apart are treated largely as separate inputs. In contrast, the classical view, based on the results from time-intensity trades, holds that broadband noise stimuli are integrated together for 100–200 ms [W. R. Garner, J. Acoust. Soc. Am. 19, 808–815 (1947)]. This difference in the period over which stimuli are integrated therefore varies by about two orders of magnitude according to research in the two areas. It may be that the difference in the magnitude of the time constants reflects the plasticity of the auditory system. However, in this paper we show one way to eliminate the apparent discrepancy by demonstrating that there exists a class of short-term integrators, operating on some fractional power of the stimulus intensity, that can produce the time-intensity trade data.
Mathematical predictions of electroacoustic frequency response of i
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i
t
u hearing aids
Authors: Egolf David P. , Tree David R. , Feth Lawrence L.
Published: October 2005

The amplitude spectrum of an acoustic signal presented to the microphone of a hearing aid is altered drastically before it finally reaches the user’s eardrum. A major part of this alteration is due to the interaction of various mechanical and acoustic resonances which are characteristic of the hearing-aid receiver and the sound transmission system linking the receiver with the eardrum. Because of the complexity of this phenomenon, there is yet no means for predicting, a priori, the true shape of the sound spectrum that will occur at the user’s eardrum. This paper reports on the development and testing of just such a scheme. The accuracy of this scheme—a computer-aided mathematical technique—is measured in the laboratory on real and artificial ears. The results of those measurements show good agreement between experimental and computer-generated data below 5000 Hz.
Acoustic sidebands from cw sources towed at long ranges in the deep ocean
Authors: Ramsdale Dan J.
Published: October 2005

Three cw sources (9.8, 110, and 262 Hz) were towed at approximately 7 knots along a great circle track from Antigua, W.I., to the Grand Banks of Newfoundland. Acoustic data from each were recorded on a bottom-mounted hydrophone near Antigua, providing source-to-receiver distances of from 100 to 2800 km. High-resolution spectral analysis centered at each frequency showed that while no acoustic sidebands were discernible at 9.8 Hz, they were observable over the entire track for both the higher frequencies. Except for expected statistical fluctuations, the upper and lower sidebands were of equal amplitude and symmetrically placed about the carrier frequency. In regions of strong convergence zone activity the sideband level displayed similar peak-to-null variation to those of the carrier, although the peak-to-null ratio was smaller than for the carrier. Detailed environmental data were available only near the sources. A high degree of correlation was observed between the sideband levels and the wave and swell heights when the sources were towed through a storm which occurred some 2000 km from the receiver. Sideband levels computed from the single bounce sinusoidal surface theory of Roderick and Cron [J. Acoust. Soc. Am. 48, 759–766 (1970)] using swell amplitude data at the sources agreed well with the measured levels for both frequencies during the stormy period. The separation of the sidebands in frequency from the carrier was the same for both source frequencies, was not affected by the convergence zone behavior of the sideband levels, and decreased as the sources approached and transited the stormy area.
Ray theory for wide classes of sound-speed profiles with two-dimensional variation
Authors: White DeWayne
Published: October 2005

This paper presents closed-form ray-path and travel-time equations using solutions of the eikonal equation for wide classes of sound-speed profiles which vary with range as well as depth. The geometric intensity equation is also given. In the past, ray theory for two-dimensional sound-speed variation has been treated mainly by numerical methods. Closed-form solutions have been available for only a few profiles of a simple form. In this paper the sound-speed profile is expressed in terms of x and y of a transformed coordinate system in which x and y are functions of depth and range. This transformation and sound-speed function are such that the transformed eikonal equation reduces to a partial differential equation separable in x and y. The closed-form ray equations are calculated in terms of x and y, then the results are converted to and presented in depth and range coordinates. The general characteristics of large classes of allowable transformations are presented. Five specific examples of allowable transformation are presented. Three different profile forms are treated in detail for the polar coordinate transformation. Numerical results, including ray diagrams, are presented for these three forms. These three numerical examples provide controls suitable for test cases testing approximate numerical ray-trace methods.
Alternate derivation of the generalized beam pattern
Authors: Vasholz David P.
Published: October 2005

A derivation of the generalized beam pattern associated with approximate solutions to the source extraction integral equation is presented which has a number of advantages over the author’s original treatment. Specifically it is more direct, makes fewer assumptions regarding the algorithm employed, and makes explicit some interesting relationships with the local nature of the basic field equation.
Tympanic membrane perforations in cats: Configurations of losses with and without ear canal extensions
Authors: Kruger Barbara , Tonndorf Juergen
Published: October 2005

In cat, a small tympanic membrane (TM) perforation produces a low-frequency loss—in terms of sound pressure changes (ΔSP) in front of the TM re a 10-μV round window cochlear microphonic (RW CM) —that varies inversely with frequency at a rate of 12 dB/octave with a surgically shortened external auditory meatus (EAM). Losses were determined at the outer opening (ΔSP00) and at the TM (ΔSPTM) of four artificial EAM’s of various lengths, volumes, and leakiness. In the low-frequency region, a leaky EAM produced a flat loss. In the midfrequency region, the flatness of losses was attributable to (1) the length of the EAM and (2) the location at which the loss was determined. EAM volume was not related to the configuration of the loss. Losses, under all conditions, were always identical in shape and magnitude for the open and closed systems. Clinically, hearing losses due to TM perforations are essentially frequency independent, especially in the low frequencies. The relation between voltage changes (ΔV) across the transducer and losses with different EAM’s suggests that the discrepency between audiometric results and CM losses—at least in the high and midfrequencies—may be due to the use of precalibrated SPL’s in clinical audiometry.
Sound radiation from an accelerated or decelerated sphere
Authors: Akay A. , Hodgson T. H.
Published: October 2005

A careful review of the current literature has led to a more complete theoretical analysis of the sound radiation from an accelerated or decelerated sphere. The acoustic field has been calculated for an accelerated sphere in an arbitrary fluid medium, which shows the effect of the fluid density on the radiated sound pressure. The radiated sound pressure from an impulsively accelerated sphere has been compared with a finite acceleration case in order to emphasize the effect of the rate of change of velocity on the pressure waveform. Energy calculations have been made in both the time and frequency domains in order to identify the sources of radiated acoustic energy and the stored nearfield energy and also to demonstrate conclusively that the energy lost in the acceleration or deceleration is dissipated as sound.
Surface wave resonances in sound scattering from elastic cylinders
Authors: Dickey J. W. , Überall H.
Published: October 2005

It is shown that the elastic-type surface waves (Rayleigh wave, etc.) which enter in a description of sound scattering from elastic objects, exhibit resonances at the eigenfrequencies of the elastic body. These resonances can be interpreted in terms of Regge poles.
Design of a curved-face parametric projector
Authors: Bennett Mary Beth , Slack Charles M.
Published: October 2005

A transducer capable of penetrating marine sediments with multiple, rectangular beams which are broad (20°–30°) in one plane and narrow (2°–3°) in the other plane at frequencies of 10–20 kHz was desired. Transducer size constraints prohibited attaining such a beam conventionally; thus, parametric operation of a rectangular transducer was examined. A relatively high parametric source level of 190 dB re 1 μPa at 1 m was also desired, and the resulting cavitation and acoustic intensity considerations dictated a curved-face transducer design. Primary and parametric beam patterns and propagation data obtained for both a rectangular transducer and a curved-face transducer confirmed the prediction techniques being employed. Parametric beam patterns in the broad plane exhibited minor lobes with the minor-lobe structure of the curved-face transducer beam less pronounced than that experienced with the rectangular transducer. Sound pressure levels and beam patterns measured for the curved-face projector confirmed that a curved-face transducer can be operated parametrically to produce high-power, low-frequency rectangular beams.
Characterization and simulation of underwater acoustic signals reflected from the sea surface
Authors: Lord G. E. , Plemons T. D.
Published: October 2005

The properties of underwater acoustic signals scattered in the forward direction by the sea surface have been analyzed statistically. It is shown that the energy of the scattered signal is described adequately by a beta distribution. The beta parameters (α, β) can be estimated using ensemble estimates of the mean and variance of the normalized scattered energies. The mean scattered energy in turn can be related to the surface roughness parameter g=4πσsinϑ/λ, where σ is the rms surface wave height, ϑ is the grazing angle, and λ is the acoustic wavelength. For a wind driven, rough surface, the acoustic frequency and grazing angle were varied to obtain values of g from 0.5 to 1.4. The structural changes of pulses reflected by the surface are also treated statistically by means of a linear autoregressive model. It is shown that models of relatively low order (e.g., first or second, thus containing few parameters) provide a fairly complete description of forward-scattered signals. The converse problem of using these models to simulate data having the appropriate statistical properties is also discussed and examples are given.
Verification of the optimal probabilistic basis of aural processing in pitch of complex tones
Authors: Goldstein J. L. , Gerson A. , Srulovicz P. , Furst M.
Published: October 2005

Periodicity pitch for complex tones has been quantitatively accounted for by a two-stage process of Fourier-frequency analysis subject to random errors and significant nonlinearities, followed by an harmonic pattern recognizer that makes an optimum probabilistic estimate of the fundamental period of musical and speech sounds. The theory predicts that periodicity pitch is a multimodal probabilistic function of a given stimulus. A clear and empirically supported distinction is made between limitations on the pitch mechanism caused by the stochastic nature of aural frequency representation and by the deterministic resolution bandwidths of aural frequency analysis. This model was developed earlier [J. L. Goldstein, J. Acoust. Soc. Am. 54, 1496–1516 (1973)] to account for probabilistic data on pitch errors [A. J. M. Houtsma and J. L. Goldstein, J. Acoust. Soc. Am. 51, 520 (1972)] measured with periodic stimuli comprising two successive harmonics. This paper presents new predictions by the theory that were calculated, with computer simulation where needed, for known probabilistic pitch data from stimuli comprising three to six successive harmonics. Predicted pitch errors increase with increasing errors in estimating the frequencies of stimulus harmonics and decrease as more harmonics are added to the stimulus. Optimum processor theory fully accounts for the multicomponent pitch data on the basis of similar errors in estimating component stimulus frequencies as reported earlier, thus providing further evidence for the optimum probabilistic basis of aural signal processing in pitch of complex tones.