bluuebunny/crossref_metadata_2025 huggingface dataset:
Sensitivity of auditory-nerve fibers to changes in intensity: A dichotomy between decrements and increments
Authors: Smith R. L. , Brachman M. L. , Frisina R. D.
Published: October 2005

Adaptation of auditory-nerve responses was investigated by applying increments and decrements in intensity to an ongoing tonal background. The change in firing rate produced by a change in intensity was obtained as a function of the time delay from the onset of the background to the onset of the change in intensity. The initial change in firing rate was measured using both small (1 ms) and large (10 ms) time intervals in order to evaluate properties of rapid and short-term adaptation, respectively. Consistent with previous results, the incremental and decremental responses measured with large windows were independent of time delay and the amount of prior adaptation. A similar additivity was observed for the incremental response measured with a small time window. In contrast, the decremental response measured with a small window decreased with increasing time delay and in proportion to the decrease in firing rate produced by the background. A similar decrease was observed in the response modulation produced by sinusoidal amplitude modulation. It was concluded that sensitivity to decrements in intensity decreases during adaptation, so that this response component does not reflect the additivity inherent in other aspects of adaptation.
Sound velocity as a function of depth in marine sediments
Authors: Hamilton Edwin L.
Published: October 2005

Additional data from sonobuoys and the Deep Sea Drilling Project (DSDP) justify separating sound-velocity-depth functions and velocity gradients (in the first layer of soft marine sediments) into some geographic areas and sediment types. Based on sonobuoy and core measurements (where V is sound velocity in km/s, and h is depth in sediments in km), the following data are obtained: continental shelf basins off Sumatra and Java—V=1.484+0.710h−0.085h2; U. S. Atlantic continental rise—V=1.513+0.828h−0.138h2; deep-sea terrigenous sediments—V=1.519+1.227h−0.473h2; and siliceous sediments of the Bering Sea— V=1.509+0.869h−0.267h2. Selected DSDP data (through leg 74) in similar areas yield: continental terrace silt–clays—V=1.505+0.712h; deep-sea terrigenous sediments—V=1.510+1.019h; and deep-sea siliceous sediments—V=1.533+0.761h. Computed velocity gradients from sonobuoy measurements are generally supported by the DSDP gradients. Only DSDP data give the following: hemipelagic sediments—V=1.501+1.151h; deep-sea calcareous sediments—V=1.541+0.928h; and deep-sea pelagic clay—V=1.526+1.046h. Where fast sediment accumulation occurs, there has not been enough time to reduce sediment pore spaces under overburden pressure; areas of slow accumulation may have relatively high sediment structural strength. Both cases have lower velocity gradients because higher porosities and consequent lower velocities persist to deeper depths.
Sound propagation over a sloping bottom using rays with beam displacement
Authors: Tindle C. T. , Deane G. B.
Published: October 2005

Ray theory with beam displacement has been shown previously to be an accurate method of finding the acoustic field at low frequencies in shallow water by comparison with normal mode solutions. The method is here extended to the case of a uniformly sloping bottom. The extension requires only geometry and involves no approximations. It is not restricted to small angles. Calculations for a simple two-fluid (Pekeris) model show that even small bottom slopes have a dramatic effect on the details of the sound field. Comparison with the results of the adiabatic normal mode approximation shows good general agreement at higher frequencies. At lower frequencies, differences are attributed to normal modes passing through cutoff, a process which is ignored in simple adiabatic mode theory.
The back reflection effects of an ultrasonic beam with a Gaussian profile at the liquid–solid interface
Authors: Kim H. C. , Kwon Sung Duk
Published: October 2005

In the paper under discussion, Norris [J. Acoust. Soc. Am. 73, 427–434 (1983)] studied the dependence of the backscattered amplitude on the Schoch displacement. It has been found that there exist some faults in the author’s derivation of AB in Eq. (64) of his paper that consequently led him to an incomplete discussion. The present analysis rectifies a mathematical error and clarifies the resultant discrepancy in the discussion.
Modeling scatterers embedded in plane-layered media by a hybrid Haskell–Thomson and boundary integral equation method
Authors: Schuster Gerard T. , Smith Lance C.
Published: October 2005

A hybrid Haskell–Thomson and boundary integral equation (BIE) method is formulated which can model the acoustic or elastic response of scatterers embedded in plane-layered media. The scatterers can have an arbitrary smooth shape but must not intersect layer interfaces. The Green’s function of the scatterer is computed by BIEs in the (x,z,ω) domain and the Green’s function of the layers is computed by a Haskell–Thomson method in the (kx,z,ω) domain. Their fields are coupled by the appropriate combination of FFTs and extrapolation operators and are finally summed up in a Born series. For notational convenience this hybrid method will be called a generalized Born series (GBS) method. Two advantages of the GBS method are (1) it is more efficient than finite elements or finite differences for small scatterers embedded in thickly layered media, and (2) no artificial side reflections are generated from the infinitely extended plane interfaces. The disadvantages are (1) the convergence rate of the GBS depends on the model and is unknown a priori, and (2) the computation time increases with the size of the scatterer.
Nearfield acoustic holography: I. Theory of generalized holography and the development of NAH
Authors: Maynard J. D. , Williams E. G. , Lee Y.
Published: October 2005

Because its underlying principles are so fundamental, holography has been studied and applied in many areas of science. Recently, a technique has been developed which takes the maximum advantage of the fundamental principles and extracts much more information from a hologram than is customarily associated with such a measurement. In this paper the fundamental principles of holography are reviewed, and a sound radiation measurement system, called nearfield acoustic holography (NAH), which fully exploits the fundamental principles, is described.
The effect of segmental and suprasegmental corrections on the intelligibility of deaf speech
Authors: Maassen Ben , Povel Dirk-Jan
Published: October 2005

Three experiments were conducted to study the effect of segmental and suprasegmental corrections on the intelligibility and judged quality of deaf speech. By means of digital signal processing techniques, including LPC analysis, transformations of separate speech sounds, temporal structure, and intonation were carried out on 30 Dutch sentences spoken by ten deaf children. The transformed sentences were tested for intelligibility and acceptability by presenting them to inexperienced listeners. In experiment 1, LPC based reflection coefficients describing segmental characteristics of deaf speakers were replaced by those of hearing speakers. A complete segmental correction caused a dramatic increase in intelligibility from 24% to 72%, which, for a major part, was due to correction of vowels. Experiment 2 revealed that correction of temporal structure and intonation caused only a small improvement from 24% to about 34%. Combination of segmental and suprasegmental corrections yielded almost perfectly understandable sentences, due to a more than additive effect of the two corrections. Quality judgments, collected in experiment 3, were in close agreement with the intelligibility measures. The results show that, in order for these speakers to become more intelligible, improving their articulation is more important than improving their production of temporal structure and intonation.
Incidence of spontaneous otoacoustic emissions in children and infants
Authors: Strickland Elizabeth A. , Burns Edward M. , Tubis Arnold
Published: October 2005

Whereas some evidence indicates that spontaneous otoacoustic emissions (SOAEs) may be a manifestation of the normal functioning of an active feedback mechanism in the cochlea, other evidence suggests that emissions may be the result of the interaction of such a feedback mechanism with localized outer-hair-cell damage. The present study surveyed the incidence of SOAEs in children and infants. If SOAEs are correlated with outer-hair-cell damage, the incidence of SOAEs might be expected to be lower in these two groups than in adults. The results showed no difference in the incidence of SOAEs with age. They also showed a significant tendency for a higher incidence of SOAEs in females than in males. PACS numbers: 43.63.Kz, 43.63.La
Amplification of surface skimming S
H waves in rotated Y-cut quartz/dielectric film/semiconductor structure
Authors: Josse Fabien
Published: October 2005

A theory for the amplification of surface skimming SH waves, commonly known as surface skimming bulk waves (SSBW), in 90°-propagating, rotated Y-cut quartz is presented. In particular, the structure proposed utilizes a thin, continuous, isotropic dielectric film instead of an air gap as the medium separating the piezoelectric substrate and semiconductor. The effective permittivity function at the crystal surface, which contains all the necessary mechanical and electrical information about the structure, is derived to analyze the amplification coefficient. The results show that the amplification coefficient increases with film thickness. This is in contrast to the air gap separate piezoelectric/semiconductor configuration where the amplification coefficient decreases with increasing gap size. As a result, acoustoelectric devices, having the advantages of higher operational frequencies and better temperature stability characteristics of SSBW devices, might be realized.
The measurement of acoustic noise generated by moving artificial sediments
Authors: Thorne Peter D.
Published: October 2005

Laboratory measurements relating to the acoustic detection of marine sediment transport are reported. A series of underwater measurements have been conducted on agitated artificial sediments, and the acoustic noise generated by interparticle collisions monitored. Measurements of the total acoustic pressure and spectral pressure levels were made on a wide range of particle diameters for different values of the mass of agitated material, the collision velocities, and the swept bandwidth of the spectrum analyzer. The objective was to relate the total pressure level to the mass of mobile material and ascertain if there was an acoustic spectral signature unique to particle size. This information could then be used to guide the interpretation of acoustic measurements of bedload transport taken in the marine environment and provide specifications for the development of an acoustic system to monitor remotely the material moving along the seabed.
The Kirchhoff approximation and first-order perturbation theory for rough surface scattering
Authors: Berman David H. , Perkins John S.
Published: October 2005

The conventional Kirchhoff approximation for rough surface scattering does not reduce to perturbation results in the limit of small surface heights. It is shown here how to modify the conventional Kirchhoff approximation by using appropriate half-space Green’s functions. The resulting expressions for the differential cross section for scattering from rough surfaces reduce to the conventional Kirchhoff results and the perturbation results in the appropriate limits.
Backscattering from an elastic sphere: Sommerfeld–Watson transformation and experimental confirmation
Authors: Williams Kevin L. , Marston Philip L.
Published: October 2005

The Sommerfeld–Watson transformation (SWT) of the partial wave series for the acoustical scattering from a fluid-loaded elastic sphere is examined. This research specifically focuses on the specular reflection and Rayleigh wave contribution to scattering at small backscattering angles. In a previous paper the angular dependence of the Rayleigh contribution to near backward scattering was measured and modeled [Williams and Marston, J. Acoust. Soc. Am. 78, 722–728 (1985)]. The SWT confirms the physical picture used and, for the first time, predicts the absolute Rayleigh contribution associated with one or more circumnavigations of the sphere. To test the SWT, tungsten carbide spheres in water were ensonified by tone bursts having central frequencies in the range 24<ka<80. Measurements were made of the first and second Rayleigh contributions to the backscattered pulse train. Plots of these measured distinct Rayleigh amplitudes as a function of ka confirm the results of the SWT and illustrate the significance of radiation damping and axial focusing.
Perceptual learning in frequency discrimination
Authors: Demany Laurent
Published: October 2005

This study was concerned with the effects of training on the frequency discrimination ability of human listeners. Frequency discrimination at 200 Hz was tested before and after training. Four groups of listeners received training in four different frequency regions, 200, 360, 2500, and 6000 Hz. It was found that training at 200, 360, and 2500 Hz all provided comparable improvement in discrimination performance at 200 Hz whereas training at 6000 Hz provided less improvement. This result is consistent with the idea that frequency discrimination and pitch perception are mediated by different processes at high (>5000 Hz) and low (<5000 Hz) frequencies.
Effect of opening and draining the cochlea
Authors: Steele Charles R. , Zais Jeffrey G.
Published: October 2005

The WKB approximation was used in calculations of the pure-tone response of a two-dimensional inviscid model of the human cochlea and a three-dimensional inviscid model of the guinea pig cochlea. The common experimental procedure of opening the scala tympani was simulated. Basilar membrane displacement was unaffected at and beyond the peak, but was slightly lower pre-peak. The peak location shifted to a significant extent apically only when the fluid level in the scala tympani was lowered to less than 1/10 of normal depth.
Extraction of helicopter-radiated noise by frequency domain processing
Authors: Dwyer Roger F.
Published: October 2005

Real data observations of farfield radiated noise from an approaching UH-1 helicopter revealed that the received time-domain radiated noise contained impulses. The cited literature attributes these observed impulses to blade slap which is caused by, among other mechanisms, blade vortex interactions. This paper is concerned exclusively with extracting these measured impulses by a frequency-domain processing method. As is well known, the total radiated noise of a helicopter is quite complex. No attempt is made in the paper to discuss the full complexity of the radiated noise field. However, references are cited in the text which support our findings and give a more general treatment to helicopter-radiated noise. The method for extracting impulses generated by an approaching helicopter utilizes a nonlinearity implemented in the frequency domain. It is shown with real helicopter-radiated noise data that autocorrelation estimates of a signal, interfered with by additive helicopter-radiated noise, can be improved by extracting some of the interfering components. The extracted components are also available as an enhanced time-domain representation.
Masking-period patterns: Presentation of a model compatible with an enlarged set of psychophysical and physiological results
Authors: Schwartz Jean-Luc , Escudier Pierre
Published: October 2005

Masking-period patterns (MPP) have been regarded by Zwicker [J. Acoust. Soc. Am. 59, 166–175 (1976)] as psychoacoustic equivalents of period histograms (PH) measured in auditory neurons. Various models have been proposed in the literature to account for his results. We present here a set of results on the MPP produced by a 40-Hz triangular masker that cannot be reproduced by any of these models. This leads to the elaboration of a new model for predicting MPP assuming the existence of nonlinearities in the basilar membrane, and based on neural fast adaptation and rectification, and a simple detection device. This model is shown to be able to account for the whole set of available results, and thus to provide a good basis for the use of MPP as a psychoacoustic tool for the study of PH.
Ultrasonic backscatter from mammalian tissues
Authors: Fei D. Y. , Shung K. K.
Published: October 2005

Ultrasonic B-mode images are formed from echoes backscattered from tissue structures in the body. Quantitative analysis of this signal from tissues may provide additional information about the tissues which may be valuable for clinical diagnosis. Results on measurements of backscatter properties of tissues such as heart, liver, and blood have been reported by a number of investigators. Data on other tissues such as spleen, kidney, and pancreas, however, are still very scanty. In this paper, results on ultrasonic backscattering properties of bovine heart, liver, kidney, spleen, pancreas, and rat myocardium, recently obtained in our laboratory utilizing a computerized system over the frequency range of 2–7 MHz, are presented. The results show that for all the tissues investigated, backscatter from liver is the highest, while that from spleen is the lowest. Liver and pancreas exhibit frequency dependence distinctively different from other tissues. Moreover, backscatter from bovine myocardium is found to be higher than that from rat myocardium. The significance of these findings in relation to the histological composition of these tissues is discussed.
Addendum and Erratum: ‘‘Comparison of the T-matrix and Helmholtz integral equation methods for wave scattering calculations’’ [J. Acoust. Soc. Am. 7
7, 369–374 (1985)]
Authors: Tobocman W.
Published: October 2005

Certain errors appeared in our paper [J. Acoust. Soc. Am. 77, 369–374 (1985)]. In this letter we attempt to rectify and clarify the problem.
Theoretical study of a plane, uniform, piezoelectric polymer hydrophone element
Authors: Brigham Gerald A.
Published: October 2005

The three-dimensional elastodynamic model of the open-circuit voltage generated in an infinite, plane, uniform piezoelectric polymer sheet irradiated by a plane monochromatic acoustic wave is mathematically developed. The model is shown to be correct asymptotically by comparison to the solution for an unstretched sheet (i.e., an isotropic sheet). The low-frequency solution is expanded in a power series in frequency and truncated at  f2. Results indicate that the sheet thickness mode voltage is canceled at an angle close to longitudinal coincidence in the stretch direction by the voltage generated in that direction. Similar phenomena should be expected on small sheets, but at a different angle because the latter are stressed around their circumference as well as on the flat plated surfaces. The paper concludes with suggestions for realistic solutions to the problem for both large and small transducer elements.
Security by masking
Authors: Salmon Vincent
Published: October 2005

By radiating the proper amount of masking noise into the space between the leaves of boundary walls of an area to be kept secure, both acoustical privacy and the audibility of masking noise that flows back into the secure area can be controlled at the same time. This letter provides design relations and suggestions for system configuration.
Procedure-independent growth-of-masking functions
Authors: Weber Daniel L.
Published: October 2005

The forward-masked threshold for a 10-ms, 1-kHz sinusoidal signal was measured as a function of the level of a narrow-band (60-Hz wide) noise masker at five masker frequencies (0.6, 0.8, 1.0, 1.15, and 1.25 kHz) using both a fixed-masker procedure (determine the threshold level of the signal for a fixed level of the masker) and the converse procedure (determine the masker level necessary to just mask a given signal). A common growth-of-masking function describes the results of both procedures for a given masker frequency; i.e., an identical masker and signal lead to identical performance regardless of which is the dependent variable. The growth-of-masking functions for different masker frequencies show varying degrees of nonlinearity. The nonlinearity of the growth-of-masking functions underlies the discrepancies which arise between masking-pattern and tuning-curve data. These discrepancies do not arise because performance somehow depends upon whether the masker or signal is the dependent variable.
Diffraction correction for a radiation force measurement on an infinite plane target
Authors: Nagy Peter B.
Published: October 2005

A discussion is given of a rigorous diffraction correction for acoustic dosimetry by a radiation force measurement on an infinite plane target. As an example, analytical results are presented for circular radiators of different velocity distributions and diameter-to-wavelength ratios, including baffled rigid piston, simply supported piston, clamped piston, and Gaussian radiators.
High-resolution beamforming by fitting a plane-wave model to acoustic data
Authors: Hebbert R. S. , Barkakati L. T.
Published: October 2005

The problem addressed in this paper is the representation of the acoustic field at an array of hydrophones as a background plus a small number of plane waves. As data, assume that a narrow-band covariance matrix has been observed. The covariance matrix implied by the model (i.e., background plus small number of plane waves) is adjusted to obtain the least-squares fit to the observed covariance matrix. Since the number of plane waves is not known, one plane wave is initially assumed and others added in succession until the error is no longer reduced. Each plane wave is described by two parameters: power and bearing. However, the power may be eliminated formally. The problem remaining is one of multidimensional optimization with bearings as unknowns.
Acoustic comparison of voice use in solo and choir singing
Authors: Rossing Thomas D. , Sundberg Johan , Ternström Sten
Published: October 2005

An experiment was carried out in which eight bass/baritone singers were recorded while singing in both choral and solo modes. Together with their own voice, they heard the sound of the rest of the choir and a piano accompaniment, respectively. The recordings were analyzed in several ways, including computation of long-time-average spectra for each passage, analysis of the sound levels in the frequency ranges corresponding to the fundamental and the ‘‘singer’s formant,’’ and a comparison of the sung levels with the levels heard by the singers. Matching pairs of vowels in the two modes were inverse filtered to determine the voice source spectra and formant frequencies for comparison. Differences in both phonation and articulation between the two modes were observed. Subjects generally sang with more power in the singer’s formant region in the solo mode and with more power in the fundamental region in the choral mode. Most singers used a reduced frequency distance between the third and fifth formants for increasing the power in the singer’s formant range, while the difference in the fundamental was mostly a voice source effect. In a choral singing mode, subjects usually adjusted their voice levels to the levels they heard from the other singers, whereas in a solo singing mode the level sung depended much less on the level of an accompaniment.
Application of an acoustic model to determine i
n s
i
t
u permeability of a borehole
Authors: Hsui Albert T. , Toksöz M. N.
Published: October 2005

A simple acoustic model has been developed to study the attenuation of a tube wave due to fluid flow from a borehole into its surrounding porous formation. It is found that attenuation increases with increasing porosity, with increasing frequency, and with decreasing borehole radius. Comparison with field data indicates that this attenuation mechanism can be significant for formations with a permeability exceeding about 100 millidarcy (md). Utilizing an appropriate correction for intrinsic attenuation, it is also demonstrated that tube wave attenuation data obtained through full waveform acoustic logs can be used to estimate in situ formation permeability.
Methods of measuring the attenuation of hearing protection devices
Authors: Berger E. H.
Published: October 2005

The published literature describing three real-ear-attenuation-at-threshold (REAT), nine above-threshold, and four objective methods of measuring hearing protector attenuation is reviewed and analyzed with regard to the accuracy, practicality, and applicability of the various techniques. The analysis indicates that the REAT method is one of the most accurate available techniques since it assesses all of the sound paths to the occluded ear and, depending upon the experimenter’s intention, can reflect actual in-use attenuation as well. An artifact in the REAT paradigm is that masking in the occluded ear due to physiological noise can spuriously increase low-frequency (≤500 Hz) attenuation, although the error never exceeds approximately 5 dB, regardless of the device, except below 125 Hz. Since the preponderance of available data indicates that attenuation is independent of sound level for intentionally linear protectors, the use of above-threshold procedures to evaluate attenuation is not a necessity. An exception exists in the case of impulsive noises, for which the existing data are not unequivocal with regard to hearing protector response characteristics. Two of the objective methods (acoustical test fixture and microphone in real ear) are considerable time savers. All objective procedures are lacking in their ability to accurately determine the importance of the flanking bone-conduction paths, although some authors have incorporated this feature as a post-measurement correction. The microphone in real-ear approach is suggested to be one of the most promising for future standardization efforts and research purposes, and the acoustical test fixture technique is recommended (with certain reservations) for quality control and buyer acceptance testing.
Surface velocity, shadowing, multiple scattering, and curvature on a sinusoid
Authors: McCammon Diana F. , McDaniel Suzanne T.
Published: October 2005

The Kirchhoff approximation is frequently invoked in the solution of scattering problems because it greatly reduces the computational complexity. This paper compares the actual surface velocity distribution on a sinusoidal pressure release surface to that assumed by the Kirchhoff approximation and examines more closely the reasons for its successes and failures. Corrections designed to improve the result by including the effects of shadowing, surface curvature, and multiple scattering are also investigated. In the cases examined, curvature correction appears to offer the most improvement while the multiple scattering contribution is practically negligible.
The constant-volume-velocity nature of hearing aids: Conclusions based on computer simulations
Authors: Egolf David P. , Haley Brett T. , Larson Vernon D.
Published: October 2005

In the literature there are several references which imply that various parts of a hearing aid are sources of constant volume velocity. Reported herein are the findings of an investigation of the validity of such statements. A computer scheme, referenced elsewhere, for modeling in situ hearing aids was utilized to test the constant-volume-velocity hypothesis. In particular, capabilities of the receiver, ear hook, and earmold tip to deliver constant volume velocity were investigated via a computer. To facilitate such an investigation, a universal receiver/earmold model was created. This model was broken down into ‘‘source’’ and ‘‘load’’ at three locations: the receiver output, output of the ear hook, and medial tip of the earmold. At each location comparisons were made between computed values of source and load impedance. The constant-volume-velocity hypothesis was assumed to be valid for those cases where source impedance was much, much greater than load impedance. Plots of such impedances show that, for the cases investigated, this rarely occurred, except over certain frequency bands. With the exception of in-the-ear hearing aids, these results appear to contradict inferences made in the literature about the constant-volume-velocity nature of hearing aids.
Reply to ‘‘Comments on ‘Transverse vibrations of composite piezoelectric polymer plates’ ’’ [J. Acoust. Soc. Am. 7
9, 1181 (1986)]
Authors: Ricketts Donald
Published: October 2005

The author takes this opportunity to reply to Laura and Gelos [J. Acoust. Soc. Am. 79, 1181 (1986)] and to express his appreciation for their comments. He completes the orthogonal set of characteristic functions φi given in his paper and obtains a single-term Rayleigh solution for the first six modes of the completely free composite piezoelectric polymer plate. The accuracy of these results for the case of an isotropic square plate is evaluated by direct comparison to the 36-term Rayleigh–Ritz solution obtained by Leissa [J. Sound Vib. 31, 257–293 (1973)].
Standing wave patterns in the human ear canal used for estimation of acoustic energy reflectance at the eardrum
Authors: Lawton B. W. , Stinson Michael R.
Published: October 2005

Standing wave patterns were measured in the unoccluded ear canals of 13 human subjects, for applied pure tones of 3 to 13 kHz. Measurements were made, using a probe microphone technique, over a region which could be approximated as a duct of constant cross-sectional area. Analysis of the patterns allowed the reflective properties of the middle ear to be determined in terms of an acoustic energy reflection coefficient, or reflectance, at the eardrum. Over all subjects the trend of the results was for the energy reflection coefficient to rise from about 0.3 at 4 kHz up to 0.8 at 8 kHz, and continue at this value to 13 kHz. There was, however, significant intersubject variation, especially at frequencies greater than 7 kHz.
Auditory profile analysis of irregular sound spectra
Authors: Kidd Gerald , Mason Christine R. , Green David M.
Published: October 2005

The discrimination of changes in the shapes of sound spectra is reported. The change was always an intensity increment to the 948-Hz component of a multitone complex. First, the ability of naive listeners to learn to discriminate a change in a ‘‘regular’’ background or reference spectrum (equal-level tones equally spaced in logarithmic frequency) was measured as a function of the number of trials. On the average, threshold improved about 10 dB over 3000 trials, with about 50% of the decrease in threshold occurring during the first 750 trials. In a subsequent series of experiments, the overall pattern of spectral shape of the background was varied randomly. Two kinds of perturbations in spectral shape were employed: (1) Randomly choosing the frequencies of the reference spectra and (2) randomly choosing the amplitudes of the components of the reference spectra. The experimental manipulations involved fixing the random spectra across a block of trials, varying the reference spectra from interval to interval of each trial, and providing extensive practice in discriminating specific randomly perturbed reference spectra. The results of the spectrum-learning and random perturbation experiments provide insight into the roles of critical band filtering, sensory variability, and short-term and long-term memory representations in auditory profile analysis. Further, the appropriateness of the generalization of a simple energy detection model is discussed
Envelope detection of amplitude-modulated high-frequency sinusoidal signals by skin mechanoreceptors
Authors: Lamoré P. J. J. , Muijser H. , Keemink C. J.
Published: October 2005

High-frequency (1000–2000 Hz) sinusoidal vibrations of the skin, which are normally imperceptible, induce distinct sensations when amplitude modulation is applied in the frequency region around 200 Hz. This phenomenon appears to be initiated in the mechanoreceptor, as a result of rectification in the mechanoelectrical transduction process. The curve for sensitivity to modulation frequency resembles the frequency-sensitivity curve of the Pacini receptor system. The low-frequency slope is flatter than that of comparable psychophysical frequency-threshold curves for sinusoidal stimuli. This finding suggests that mechanical filtering (in the capsule of the Pacinian corpuscle and the surrounding skin tissue) contributes to the detection threshold. The characteristics of such a mechanical filter are estimated.
Resonances of a bent vocal tract
Authors: Sondhi Man Mohan
Published: October 2005

Analyses of wave propagation in a vocal tract invariably assume the tract to be a variable area tube with a straight axis. No estimates appear to be available of the effect of curvature of the tract on its resonances (or, equivalently, on its transfer function). For arbitrarily varying cross section, the computation is difficult. However, one can choose an idealized bent vocal tract with a uniform cross section for which the wave equation is separable. The resonance frequencies for such a bent tract are computed and compared to those of the corresponding straight tract. The comparison shows that for typical dimensions of the tract the shift in the resonance frequencies below 4 kHz is in the range of 2%–8%.
A practical evaluation method for the effects of meter characteristics of sound and vibration level meters on the output fluctuation probability under the random input of an arbitrary frequency spectrum
Authors: Ohta Mitsno , Nishimura Kiminobu
Published: October 2005

This article theoretically considers how the fundamental mechanism of a mean-squaring operation existing in sound level or vibration level meters affects the probability distribution form of the output level fluctuation in direct connection with the probabilistic evaluation problem, by applying the well-known residue theorem to its moment generating function. More specifically, the explicit expression for the output level distribution is theoretically proposed in a general expansion form, after introducing the so-called Parseval’s relation at the starting point of theoretical analysis, in the case when a Gaussian random wave with arbitrary frequency characteristic is measured through usual sound or vibration level meters. The effect of the time constant and the frequency characteristic of the indicating system and the frequency spectrum of input random noise on the output probability distribution is concretely reflected in each parameter of the output probability distribution expression. The validity of the above theoretical result is confirmed experimentally by applying it to the actual random noise data observed by a usual sound level meter.
The use of ultrasonics for gauging and proximity sensing in air
Authors: Hickling Robert , Marin Samuel P.
Published: October 2005

The use of ultrasonics is investigated for gauging and proximity sensing of distances of about 1 m and less in air. Because strong attenuation due to absorption in air limits usable frequencies to less than about 1 MHz, ultrasonic methods are inherently less accurate than optical methods. However, in tests reported here with a commercially available ultrasonic system, it is shown that perpendicular distances up to 250 mm can be measured with an accuracy of ±0.1 mm, provided there is adequate compensation for changes in the speed of sound due to temperature variation. This accuracy in distance measurement, coupled with the fact that it is possible to have a minimum beam diameter, or spot size, as small as 1 mm, means that ultrasonic methods are sufficiently accurate for many applications in manufacturing and robot control. In addition, ultrasonic systems are generally cheaper, lighter, more compact, and more durable than equivalent optical systems. Results are reported here on the effect of air currents, surface temperature, and background noise. Different aspects of ultrasonic gauging are discussed, including absorption in air and beam forming and focusing. Factors affecting the precision of ultrasonic gauging are emphasized.
Recognition of previously unfamiliar speakers as a function of narrow-band processing and speaker selection
Authors: Schmidt-Nielsen A. , Stern Karen R.
Published: October 2005

The effect of narrow-band digital processing, using a linear predictive coding (LPC) algorithm at 2400 bits/s, on the recognition of previously unfamiliar speakers was investigated. In two experiments, rated voice distinctiveness was used to select three sets of five speakers (two sets of males and one set of females). The more distinctive male speakers and the females were better recognized than the less distinctive males for unprocessed speech. With LPC processed speech, there were large losses in speaker recognition for the more distinctive males and the females, whereas the less distinctive males showed no recognition loss. This interaction is discouraging to prospects for developing practical procedures for comparing speaker recognition over various voice communication systems.
Propagation of sound in the presence of gradients and turbulence near the ground
Authors: Daigle G. A. , Embleton T. F. W. , Piercy J. E.
Published: October 2005

Sound-pressure levels of pure tones between 1 and 16 kHz, generated by a point source on hard ground, were measured as a function of height at horizontal distances up to 21 m. In another experiment, measurements were made above hard ground and ground of finite impedance at horizontal distances up to 250 m using frequencies between 250 and 4000 Hz. Five frequencies were generated simultaneously and measured at four (and sometimes five) heights. The sound-pressure levels below the refractive shadow boundary are compared with a simple theory that assumes a linear change of sound speed with height. This vertical gradient was obtained by approximating the temperature and wind velocity profiles measured during the acoustical experiment. Good agreement between theory and experiment was obtained at all distances and frequencies. However, at the largest distances and highest frequencies, there was evidence of additional energy penetrating the refractive shadow from scattering by atmospheric turbulence. Therefore, in addition to their vertical gradients, the temperature and wind velocity fluctuations were also recorded. These were used to obtain the strength and scale of turbulence, and the analysis of these results is summarized. The amplitude and phase fluctuations predicted from a simple theory that approximates the source region of the turbulence by a Gaussian spectrum were compared with measurements. In particular, transverse coherence length decreases deep within the refractive shadow compared with its predicted values and with values measured above the shadow boundary.
Simulation of mechanical to neural transduction in the auditory receptor
Authors: Meddis Ray
Published: October 2005

A probabilistic model is described for transmitter release from hair cells, auditory neuron EPSP’s, and discharge patterns. The model assumes that the release fraction of the transmitter is a function of stimulus intensity. It further assumes that some of this transmitter substance is taken back into the cell while some is irretrievably lost from the cleft. These assumptions differ from other recent models which propose multiple release sites, fixed release fractions, and no transmitter reuptake. The model produces realistic mammalian rate intensity functions, interval and period histograms, incremental responses, and adaptation effects. It mimics successfully the adaptation of successive EPSP amplitudes of the afferent neuron of the goldfish sacculus and offers a reinterpretation of the implications of these studies for hair cell synaptic mechanism.
Onset and equilibration of oscillations in general Rijke devices
Authors: Bayly B. J.
Published: October 2005

Oscillations in Rijke devices of general shape are investigated with a model in which the relation between the acoustic motion and the heat transfer from the gauze is nonlinear. In addition to corroborating existing results on necessary conditions for the growth of small disturbances, the model predicts the observed finite range of blowing speeds that allow oscillation. The nonlinear theory determines the amplitude at which the oscillation saturates. Under some circumstances, the equilibrium amplitude is a multivalued function of the parameters, and hysteresis is possible.
Log-linear modeling of consonant confusion data
Authors: Bell Theodore S. , Dirks Donald D. , Levitt Harry , Dubno Judy R.
Published: October 2005

Log-linear models, in conjunction with the G2 statistic, were developed and applied to several existing sets of consonant confusion data. Significant interactions of consonant error patterns were found with signal-to-noise ratio (S/N), presentation level, vowel context, and low-pass and high-pass filtering. These variables also showed significant interactions with error patterns when categorized on the basis of feature classifications. Patterns of errors were significantly altered by S/N for place of articulation (front, middle, back), voicing, frication, and nasality. Low-pass filtering significantly affected error patterns when categorized by place of articulation, duration, or nasality; whereas, high-pass filtering only affected voicing and frication error patterns. This paper also demonstrates the utility of log-linear modeling techniques in applications to confusion matrix analysis: specific effects can be tested; variant cells in a matrix can be isolated with respect to a particular model of interest; diagonal cells can be eliminated from the analysis; and the matrix can be collapsed across levels of variables, with no violation of independence. Finally, log-linear techniques are suggested for development of parsimonious and predictive models of speech perception.
Influence of errors on the two-microphone method for measuring acoustic properties in ducts
Authors: Bodén Hans , Åbom Mats
Published: October 2005

Using the two-microphone method, acoustic properties in ducts, as, for example, reflection coefficient and acoustic impedance, can be calculated from a transfer function measurement between two microphones. In this paper, a systematic investigation of the various measurement errors that can occur and their effect on the calculated quantities is made. The input data for the calculations are the measured transfer function, the microphone separation, and the distance between one microphone and the sample. First, errors in the estimate of the transfer function are treated. Conclusions concerning the most favorable measurement configuration to avoid these errors are drawn. Next, the length measurement errors are treated. Measurements were made to study the question of microphone interference. The influence of errors on the calculated quantities has been investigated by numerical simulation. From this, conclusions are drawn on the useful frequency range for a given microphone separation and on the magnitude of errors to expect for different cases.
Broadband noise propagation in a Pekeris waveguide
Authors: Vianna Marcio L. , Soares-Filho W.
Published: October 2005

A theory of broadband noise propagation from a point source in shallow water is developed by use of a Pekeris model with a lossy bottom. The broadband interference pattern in the power spectrum is calculated analytically and numerically including both the proper mode and the virtual mode fields. It is shown that the interference maxima of the proper mode spectrum describe straight lines in the range-frequency plane and that the virtual mode fields (branch-line integral) are localized and decay slowly with a range around the cutoff frequencies of the proper modes. It is also shown that bottom attenuation does not influence the form of the power spectrum in any significant way up to ranges of 100 water depths.
Inverse elastic scattering in three dimensions
Authors: Boyse William E. , Keller Joseph B.
Published: October 2005

It is shown how to find the density and the elastic constants in the half-space x3≥0 from the value of the scattered displacement field us on the plane x3=0. The source of the field is a time-harmonic force applied at a source point xs on x3=0, and the field is measured at a geophone position xg on this plane. The medium is assumed to differ slightly from a uniform medium so that us(xg, xs, ω) can be calculated by the single scattering or Born approximation. As is to be expected, us contains more than enough information for the desired reconstruction. Therefore, a subset of the data, involving only longitudinal waves, is used. From it the density and the elastic constants are determined explicitly. A similar problem in which the elastic medium occupies all of space, with perturbations confined to a half-space, is treated also.
Acoustic reciprocal transmission experiments, Florida Straits
Authors: DeFerrari H. A. , Nguyen H. B.
Published: October 2005

An acoustic approach for the measurement of range- and depth-averaged current and temperature is successfully demonstrated for the bottom-limited acoustic transmission of the Florida Straits. The shallow water environment prohibits the use of deep ocean tomography methods since there are usually no separable arrivals associated with eigenrays. Instead, multipath groupings of arrivals are shown to have stable envelopes if averaged sufficiently long to eliminate effects of interference. The shape of the envelope is controlled to some extent by the source–receiver depth and has characteristics which can be used for very precise travel time measurements. Ray models predict a unique relation between ray height above the bottom and arrival time allowing for unambiguous inversion. Two three-point reciprocal transmission experiments were conducted in the Florida Straits (ranges approx. 25 and 45 km). Two-way channel pulse responses are analyzed to give travel times which are then inverted to give depth averages of temperature and current; the depth and extent of the average is determined by ray models. The method is shown to be precise in resolving variations in temperature of 0.002 °C and current of 2 cm/s. The spatially averaged tomographic results are compared with point measurements of current and temperature from current meter moorings along the path of propagation.
Coupled mode theory of intrinsic modes in a wedge
Authors: Arnold J. M. , Felsen L. B.
Published: October 2005

Recent theoretical studies of acoustic wave propagation in a model waveguide consisting of a homogeneous wedge with one reflecting and one penetrable boundary have established the utility of the concept of an intrinsic mode, which generalizes for nonseparable problems the normal mode of separable configurations. In this paper, it is shown by explicit calculations on the same model problem that direct orthogonal expansion (in local normal modes) of the intrinsic mode produces the same expansion coefficients as those obtained by a perturbation analysis of the coupled mode equations. The perturbation method used is that of renormalization, in which the mode coupling operator is iteratively diagonalized up to a certain order in the nonseparability parameter, which, in this case, is the wedge angle α.
Prediction of tissue composition from ultrasonic measurements and mixture rules
Authors: Apfel Robert E.
Published: October 2005

A methodology is presented for predicting the composition of tissues from measurements of the density, sound velocity, and acoustic nonlinear parameter, using mixture laws for the density, compressibility, and nonlinear parameter. It is shown that the mixture law for the nonlinear parameter plays an essential part in this methodology, which leads to the prediction of the volume fractions of water, protein, and fat in a given tissue. Data from the literature for solutions, blood, normal tissue, and cancerous tissue are investigated, and predicted fractions are consistent with tissue compositional information available in handbooks. More experimental work is needed with tissues of known composition in order to more fully test the proposed methodology.