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Journal of the Acoustical Society of America

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Apr 1983

Volume 73, Issue 4, pp. 1105-1416

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Rays and local modes in a wedge‐shaped ocean

J. M. Arnold and L. B. Felsen

J. Acoust. Soc. Am. Volume 73, Issue 4, pp. 1105-1119 (1983); (15 pages) | Cited 2 times

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Conventional normal mode theory cannot be applied to the nonseparable problem of wave propagation in an ocean with sloping bottom. For small bottom slopes, the sound field may be expressed approximately in terms of adiabatic modes, but this description fails when a mode propagating upslope passes through cutoff. An alternative solution by ray acoustics, valid at high frequencies, contains many multiply reflected contributions, and also undergoes difficult trapped to leaky ray transitions upslope. To address these transition problems, the conventional ray solution is used here as a convenient starting point for collective treatment of ray fields and their conversion into local modes. First, the ray fields are generalized by associating with each ray trajectory from source to observer a bundle of local plane waves that is multiply reflected between the boundaries and remains valid also in the transition regions. When the generalized ray series is subjected to Poisson summation and subsequent asymptotics on the transform integrals, it is found to furnish local modes which coincide with the conventional adiabatic modes where these exist. The local mode integrals also yield transition functions which smoothly continue an originally trapped adiabatic mode through cutoff to the leaky regime. The transition behavior agrees with that found by Pierce [J. Acoust. Soc. Am. 72, 523–531 (1982)] by an entirely different approach, and with that predicted by the spectral Green’s function method of Kamel and Felsen [J. Acoust. Soc. Am. 73 xxx–xxx (1983)]. The ultilization of rays and local modes in each step of the analysis here grants physical insight and therefore clarifies the mechanism of propagation in this range‐dependent environment.
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43.20.Dk Ray acoustics
43.20.Bi Mathematical theory of wave propagation
43.30.Bp Normal mode propagation of sound in water
43.30.Jx Radiation from objects vibrating under water, acoustic and mechanical impedance

Spectral theory of sound propagation in an ocean channel with weakly sloping bottom

A. Kamel and L. B. Felsen

J. Acoust. Soc. Am. Volume 73, Issue 4, pp. 1120-1130 (1983); (11 pages) | Cited 3 times

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Spectral representations based on the theory of characteristic Green’s functions (resolvents) have been used effectively for studying sound propagation in a coordinate separable ocean environment. Such representations are here generalized to accommodate weak nonseparability as represented by a homogeneous water channel separated from a homogeneous sediment by a gradually and monotonically sloping bottom. The generalization involves the use of adiabatic invariants for the spectral integration variable and of symmetrizing factors in order to insure that the Green’s function, so expressed, reduces by residue calculus to the conventional adiabatic trapped mode expansion whenever that is valid. However, subject to ignoring coupling between the adiabatic modes, the generalized Green’s function contains all of the spectral information (discrete and continuous) for upslope propagation from a source to arbitrary observation points in the water or the bottom, and it can be used to derive ray, hybrid ray‐mode, and other formulations in this configuration. Numerical evaluation of the spectral integral and comparison with results obtained independently by the parabolic equation algorithm have confirmed its validity for a typical range of observer locations. Asymptotic considerations have been employed to clarify the mechanism of adiabatic mode transition from trapped to radiating in terms of lateral and leaky waves, and to reduce the spectral integral to a simpler canonical transition function similar to those of Pierce [J. Acoust. Soc. Am. 72, 523–531 (1982)] and of Arnold and Felsen [J. Acoust. Soc. Am. 73, xxx–xxx (1983)] which were derived by entirely different methods.
Show PACS
43.20.Bi Mathematical theory of wave propagation
43.30.Bp Normal mode propagation of sound in water
92.10.Vz Underwater sound
43.30.Jx Radiation from objects vibrating under water, acoustic and mechanical impedance

Propagation of sound in highly porous open‐cell elastic foams

Robert F. Lambert

J. Acoust. Soc. Am. Volume 73, Issue 4, pp. 1131-1138 (1983); (8 pages) | Cited 2 times

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This work presents both theoretical predictions and experimental measurements of attenuation and progressive phase constants of sound in open‐cell, highly porous, elastic polyurethane foams. The foams are available commercially in graded pore sizes for which information about the static flow resistance, thermal time constant, volume porosity, dynamic structure factor, and speed of sound is known. The analysis is specialized to highly porous foams which can be efficient sound absorbers at audio frequencies. Negligible effect of internal wave coupling on attenuation and phase shift for the frequency range 16–6000 Hz was predicted and no experimentally significant effects were observed in the bulk samples studied. The agreement between predictions and measurements in bulk materials is excellent. The analysis is applicable to both the regular and compressed elastic open‐cell foams.
Show PACS
43.20.Fn Scattering of acoustic waves
43.20.Hq Velocity and attenuation of acoustic waves
43.35.Bf Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in liquids, liquid crystals, suspensions, and emulsions
43.20.Bi Mathematical theory of wave propagation

Surface acoustic admittance of highly porous open‐cell, elastic foams

Robert F. Lambert

J. Acoust. Soc. Am. Volume 73, Issue 4, pp. 1139-1146 (1983); (8 pages) | Cited 1 time

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This work presents a comprehensive study of the surface acoustic admittance properties of graded sizes of open‐cell foams that are highly porous and elastic. The intrinsic admittance as well as properties of samples of finite depth were predicted and then measured for sound at normal incidence over a frequency range extending from about 35–3500 Hz. The agreement between theory and experiment for a range of mean pore size and volume porosity is excellent. The implications of fibrous structure on the admittance of open‐cell foams is quite evident from the results.
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43.20.Rz Steady-state radiation from sources, impedance, radiation patterns, boundary element methods
43.20.Hq Velocity and attenuation of acoustic waves
43.58.Bh Acoustic impedance measurement
43.20.Bi Mathematical theory of wave propagation

Target strength of liquid‐filled spheres

Don L. Folds and Chester D. Loggins

J. Acoust. Soc. Am. Volume 73, Issue 4, pp. 1147-1151 (1983); (5 pages) | Cited 1 time

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The liquid‐filled target sphere is a high target strength reflector which, since its first use in 1971, has proven to be of great utility in sonar research. The spherical metal shell filled with a low‐velocity liquid is being used as a calibrated, passive, aspect‐independent target. To date, the characteristics of this target have only been described in a narrow ka range by simple ray theory models. In this paper, a comprehensive treatment for 0<ka<100 for various shell materials and filling fluid refractive indices is presented, using results from wave theory analyses. Comparisons are made with air‐filled and water‐filled spheres and with solid spheres. Form function versus ka plots, echo time history, and target strength versus frequency are presented. Results show good agreement between computed and measured target strengths and permit an accurate prediction of target strength over a wide range of frequency and fluid velocities.
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43.20.Fn Scattering of acoustic waves
43.30.Gv Backscattering, echoes, and reverberation in water due to combinations of boundaries

Doubly asymptotic approximations for vibration analysis of submerged structures

Thomas L. Geers and Carlos A. Felippa

J. Acoust. Soc. Am. Volume 73, Issue 4, pp. 1152-1159 (1983); (8 pages) | Cited 4 times

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Doubly Asymptotic Approximations (DAAs) are differential equations for boundary‐element analysis of the interaction between a complex structure and a surrounding infinite medium. In this paper, the use of first‐ and second‐order DAAs for steady‐state vibration analysis of submerged structures is examined. First, the governing discrete‐element equations for the general problem are set down and discussed. Then the accuracy of three DAA forms is studied through the generation of numerical results for a submerged spherical shell. Although the first‐order DAA is found to be inadequate, the two second‐order forms show considerable promise.
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43.20.Fn Scattering of acoustic waves
43.40.At Experimental and theoretical studies of vibrating systems
43.20.Tb Interaction of vibrating structures with surrounding medium

The scattering of ultrasonic waves by polycrystals. II. Shear waves

Sigrun Hirsekorn

J. Acoust. Soc. Am. Volume 73, Issue 4, pp. 1160-1163 (1983); (4 pages) | Cited 4 times

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The theory of ultrasonic propagation in polycrystals presented in a previous paper is used to calculate the scattering coefficient and the phase and group velocities of plane shear waves in polycrystals of cubic symmetry with randomly orientated grains. The calculation was done in second‐order perturbation theory using the assumption that the changes in the elastic constants and in the density from grain to grain are small. The asymptotic values at low κa (Rayleigh scattering) are exactly the same as the well‐known results from Bhatia and Moore. Numerical calculations are carried out for some examples.
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43.20.Fn Scattering of acoustic waves
43.35.Cg Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in solids; elastic constants
62.30.+d Mechanical and elastic waves; vibrations
43.20.Bi Mathematical theory of wave propagation

Multiple scattering with applications to fish‐echo processing

T. K. Stanton

J. Acoust. Soc. Am. Volume 73, Issue 4, pp. 1164-1169 (1983); (6 pages) | Cited 4 times

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A general expression has been derived and evaluated for the backscattered echo energy of an acoustic pulse due to a collection of identical randomly distributed isotropic scatterers. Excess attenuation of the signal due to the extinction cross section of the scatterers as well as second‐order scattering have been taken into account. Special attention is focused toward the numerical evaluation of second‐order scattering effects. The expression is evaluated for three scattering geometries. It is shown in each geometry that when the absorption cross section of the scatterers is small, second‐order scattering can be a factor in the backscattered energy. In this case, second‐order scattering at least partially offsets effects due to excess attenuation in the low‐to‐moderate attenuation region. When applied to fish‐echo processing, it was shown that in most cases the results represent an upper bound for the processed signal from a school of fish. The directional characteristics, acoustic frequency of the pulse in relation to the resonance frequency of the swimbladder (if any), and degree of randomness of the spatial distribution of the fish determine the degree to which second‐order scattering plays a role in this area.
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43.20.Fn Scattering of acoustic waves
43.30.Gv Backscattering, echoes, and reverberation in water due to combinations of boundaries
43.80.Ev Acoustical measurement methods in biological systems and media

Cavity resonances in engine combustion chambers and some applications

Robert Hickling, Douglas A. Feldmaier, Francis H. K. Chen, and Josette S. Morel

J. Acoust. Soc. Am. Volume 73, Issue 4, pp. 1170-1178 (1983); (9 pages) | Cited 2 times

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Cavity resonances in engine cylinders are caused by combustion events such as the rapid rate of pressure rise that occurs during compression ignition in diesels or from knock in gasoline engines. These resonances generally occur at frequencies greater than 4 to 5 kHz where the engine structure is not an efficient acoustical radiator. However, when they occur at lower frequencies such as in engines with a large bore or in indirect injection diesels, they can be important in the noise generation process. They are also important for knock detection in gasoline engines. Current knock detection systems are tuned to the frequency band of the lowest cavity resonance in the combustion chamber. It is shown in the paper that higher order resonances can also be detected by a knock vibration sensor on the surface of the engine. Another use for the cavity resonances is to determine the bulk temperature of the gas in the combustion chamber as a function of crank angle. This technique is demonstrated in the paper for a heavy‐duty two‐stroke diesel. Also, the results of several fundamental investigations of cavity resonances in engine combustion chambers are reported briefly. Good agreement is obtained between theoretical prediction of the resonant frequencies and experimental observation. The splitting of degenerate modes into two components is discussed.
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43.20.Mv Waveguides, wave propagation in tubes and ducts
43.20.Ks Standing waves, resonance, normal modes
43.50.Lj Transportation noise sources: air, road, rail, and marine vehicles
43.28.Ra Generation of sound by fluid flow, aerodynamic sound and turbulence

Inverse methods in the reconstruction of acoustical impedance profiles

Horst Schwetlick

J. Acoust. Soc. Am. Volume 73, Issue 4, pp. 1179-1186 (1983); (8 pages)

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Three methods for the reconstruction of inhomogeneities in a one‐dimensional lossless medium from incident and reflected wave signals are presented in this paper: the method of characteristics, the Gel’fand–Levitan method, and the newly developed method of iterative local regulization. Reconstructed results from numerical experiments are compared with emphasis on inversion in the presence of noise, and on general excitations. An error analysis and a study of computation requirements are also presented.
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43.20.Rz Steady-state radiation from sources, impedance, radiation patterns, boundary element methods
43.20.Bi Mathematical theory of wave propagation

Intensity variance of spherical waves in anisotropic media

Morris Schulkin

J. Acoust. Soc. Am. Volume 73, Issue 4, pp. 1187-1191 (1983); (5 pages)

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The solution to the problem of determining the intensity variance in the forward direction for spherical waves propagating in an anisotropic medium of Gaussian correlation oblate spheroids has not yet been reduced to elementary functions. However, the solution is known for asymptotic limits at zero range and at very long range where the anisotropic terms are separable in both cases. The author shows that anisotropic terms are also separable for the intensity variance of plane waves at the point where the variance depends on the square of the range. A new anisotropic component is found in this way. He also computes the ratio of the intensity variance for plane waves to that of spherical waves at all ranges in a random medium of Gaussian correlation spheres. Applying this ratio to the plane‐wave anisotropic solution yields useful estimates for the variance of spherical waves in Gaussian anisotropic media in the region where the variance depends on the square of the range for both small and large anisotropy.
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43.30.Bp Normal mode propagation of sound in water
43.20.Fn Scattering of acoustic waves
43.60.Cg Statistical properties of signals and noise

Coherent modes and boundary waves in a rough‐walled acoustic waveguide

I. Tolstoy

J. Acoust. Soc. Am. Volume 73, Issue 4, pp. 1192-1199 (1983); (8 pages)

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The theory of Biot scatter was generalized to acoustically rough interfaces between fluids of differing densities and sound velocities by Tolstoy [J. Acoust. Soc. Am. 72, 960–972 (1982)] for the case kh≤1, k being the wavenumber and h the mean spacing between roughness elements. The present paper applies this approach to a harmonic point acoustic source in a fluid layer of thickness H and sound velocity c1, with: (1) a rigid floor with hard pebbles and (2) a soft floor of sound velocity c2≥c1 (Pekeris waveguide) with a monolayer of hard pebbles at the interface. For a ratio H/h=102 it is shown that: (a) pebbles have a marked influence on the usual coherent acoustic waveguide modes. This effect is best understood in terms of an alteration of the smooth‐walled phase shift suffered by sound totally reflected from the bottom. This is particularly obvious for the Pekeris waveguide, for which the net effect on individual modes, for tightly packed spherical pebbles and for typical bottom acoustic parameters, is to increase their excitation amplitudes by factors approaching 2 near the limit of validity of the scatter theory (kh=1). (b) Pebbles may bring about the existence of a subsonic branch of the lowest mode, corresponding to a wall roughness boundary mode carried by the rough boundary. In the hard‐bottomed model this branch always exists for k≥(ϵH)−1/2, where ϵ is a scattering parameter determined by the shape and volume per unit area of the scatterers. When combined with the criterion kh≤1 this condition yields a definite boundary wave passband. In the case of the Pekeris waveguide the passband is quite restrictive, being very sensitive to the ratio c2/c1; the boundary mode exists only for c2/c1≂1+δ, where δ≲0.008. For the special case c2=c1 the boundary wave is strongest and allows for an entirely subsonic mode having no analog in the smooth‐walled model. The c2/c1 restriction being fairly stringent one must expect the chief practical effect of this kind of bottom roughness to be of the type (a).
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43.30.Gv Backscattering, echoes, and reverberation in water due to combinations of boundaries
43.30.Bp Normal mode propagation of sound in water
43.20.Mv Waveguides, wave propagation in tubes and ducts
68.03.-g Gas-liquid and vacuum-liquid interfaces
68.05.-n Liquid-liquid interfaces

Low‐frequency propagation in almost fluid sediments: Role of gravity and other stresses

I. Tolstoy

J. Acoust. Soc. Am. Volume 73, Issue 4, pp. 1200-1204 (1983); (5 pages)

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Relatively unconsolidated sediments of low rigidity μ are common in oceans. Shear modes of low velocity cs(cs≲100 ms−1) then exist in sea floor sediments, as well as slow boundary waves of velocity v<cs at the water–sediment interface (Stoneley modes). Both have been observed in shallow water experiments at frequencies in the 1–5 Hz band [Rauch, Bottom‐Interacti ng Acoustics (Plenum, New York, 1980)]. In poorly consolidated sediments of this kind ( μ<109 dyn cm−2) gravity and other stresses introduce small corrections to the propagation velocities. The role of gravity is of two sorts. On the one hand it introduces buoyancy forces and internal gravity waves—these are negligible for frequencies above 10−1 Hz; on the other, it introduces hydrostatic stresses which primarily affect the velocity of shear modes in the sediment—leading to corrections of order ρgz/μ (for an overburden of height z in a sediment or sediment+water column of mean density ρ). While the latter measurably affects propagation speeds in sediments, it is an isotropic effect which, in practice, finds itself lumped with other mechanisms of velocity stratification. Interesting and in principle more easily diagnosed in experiments are the effects of anisotropic stress fields—e.g., tensions and compressions associated with gravity slumping mechanisms on slopes and, for deeper and somewhat more consolidated sediments, with forces of local origin such as island loading or tectonic stresses. These can introduce measurable anisotropies into the propagation of various low‐frequency bottom associated modes.
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43.30.Bp Normal mode propagation of sound in water
92.10.Vz Underwater sound
43.40.Ph Seismology and geophysical prospecting; seismographs

Measurement of fish target strength and associated directivity at high frequencies

P. H. Dahl and O. A. Mathisen

J. Acoust. Soc. Am. Volume 73, Issue 4, pp. 1205-1211 (1983); (7 pages) | Cited 5 times

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A technique for measuring fish target strength and directivity in the yaw (coronal) plane is described. Measurements were made at 420 kHz on 40‐ to 60‐cm‐long salmonids, these are expressed through polar plots. Since fish‐length‐to‐wavelength ratios generally were greater than 100, the estimated square root of backscattering cross section, or its equivalent peak envelope voltage, approaches a Rayleigh distribution. This was verified experimentally. Expressions for the expected value of target strength and its variance were derived.
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43.30.Gv Backscattering, echoes, and reverberation in water due to combinations of boundaries
43.20.Fn Scattering of acoustic waves
43.80.Jz Use of acoustic energy (with or without other forms) in studies of structure and function of biological systems

Automated digital benchtop calibration system for hydrophone arrays

L. Dwight Luker, Joseph F. Zalesak, Craig K. Brown, and Richard E. Scott, Jr.

J. Acoust. Soc. Am. Volume 73, Issue 4, pp. 1212-1216 (1983); (5 pages)

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A calibration system is described which can measure the complex sensitivity and directivity patterns of hydrophone arrays, such as sonobuoy arrays, in which the hydrophone elements are individually accessible. These arrays are often deployed over a great distance in the ocean. Calibrating them under free‐field conditions would be an extremely difficult task. The system described here allows for their calibration on a benchtop. The entire calibration system is controlled by a computer and requires minimal operator intervention. The computer algorithm is also applicable to hydrophone arrays which do not have individually accessible elements. Results are presented which compare measured directivity patterns with theoretical directivity patterns calculated from the measured complex sensitivities of the individual array elements.
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43.30.Sf Acoustical detection of marine life; passive and active
43.30.Yj Transducers and transducer arrays for underwater sound; transducer calibration
43.58.Ta Computers and computer programs in acoustics

Acoustic emission measurements of a shape‐memory alloy

Rong S. Geng, Bryan Britton, and Raymond W. B. Stephens

J. Acoust. Soc. Am. Volume 73, Issue 4, pp. 1217-1222 (1983); (6 pages)

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A description is given of a systematic study of the acoustic emission (AE) characteristics of a specific shape‐memory alloy, a copper‐based Betalloy. Using a narrow‐band AE measuring system, a considerable change in AE signals was observed in the different phase states of the Betalloy, the changes being particularly significant in the slope changes of the amplitude‐distribution curves. By careful correlation of AE signals with the stress‐induced martensitic transformation, it was found, in repetition cycles, that a reversible AE energy release accompanied the austenite–martensite transition process, which is in direct conflict with the ‘‘Kaiser effect.’’ This observation implies that caution is necessary in applying the AE technique for evaluating failure in shape‐memory alloys. The values derived from the AE data for the stress required to induce martensitic transformation and for the temperature at which the transformation is initiated are in good agreement with those obtained from stress–strain measurements.
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43.40.Le Techniques for nondestructive evaluation and monitoring, acoustic emission

Progressive phase trends in multi‐degree‐of‐freedom systems

Richard H. Lyon

J. Acoust. Soc. Am. Volume 73, Issue 4, pp. 1223-1228 (1983); (6 pages) | Cited 2 times

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The relative phase of the response of a dynamical system to its excitation has been largely ignored in problems dealing with noise response of such systems. This is because mean‐square amplitude functions are able to predict many of the quantitites that one is interested in such as crack growth, noise radiation, and clearance impact probabilities without concern for phase. But phase has an essential role in other cases, such as phase coherence of vibration fields, or the design of filters to ‘‘dereverberate’’ a received signal. This paper describes some early results of the analysis of phase response of multi‐degree‐of‐freedom systems, using ideas that are closely related to statistical energy analysis, until now, used exclusively for the kinds of problems listed above that tend to ignore phase. The present results show good agreement between simple theory and experiments, but more importantly, they suggest directions for further work that should have significant payoff in the future.
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43.55.Ka Computer simulation of acoustics in enclosures, modeling
43.30.Nb Noise in water; generation mechanisms and characteristics of the field

An analysis of community complaints to noise

George A. Luz, Richard Raspet, and Paul D. Schomer

J. Acoust. Soc. Am. Volume 73, Issue 4, pp. 1229-1235 (1983); (7 pages) | Cited 4 times

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Noise complaints received Army‐wide for a one‐year period were analyzed (a) to determine the relationship between the nature of the complaint and the type of noise and (b) to determine the relationship between complaints and the day–night level (DNL). For blast noise, 77% of complaints mentioned vibration or physical damage or both, thus confirming the validity of the C‐weighted DNL as a better measure of blast noise than the A‐weighted DNL. The relationship between DNL and complaints, however, was a very weak one. Instead, the data confirmed an independent finding of a recent study of Air Force noise complaints—that complaints are generated by unusual rather than typical noise levels. Since a valid measure of community response to noise should be functionally relatable to the noise dose, complaints do not appear to be a good measure of the community response. To deal with the wide variability in the emotional tone of the complaints a psychological model was developed and tested. The implications of this model for how an airport or Army base should deal with complaints are discussed.
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43.50.Qp Effects of noise on man and society
43.50.Sr Community noise, noise zoning, by-laws, and legislation

Assessment of significant acoustical parameters for rating sound insulation of party walls

Jean‐Paul Vian, William F. Danner, and Jay W. Bauer

J. Acoust. Soc. Am. Volume 73, Issue 4, pp. 1236-1243 (1983); (8 pages) | Cited 3 times

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To test the adequacy of French regulations for sound isolation in buildings, subjects were asked to rate their annoyance with samples of music filtered by electronic ‘‘insulation curves’’ representing different party walls. The insulation curves differed in their shape but all provided an A‐weighted level difference of 51 dB with a pink noise source, measured over a 1/3‐octave bandwidth of 40 Hz–10 kHz. However, the different insulation curves did not provide the same degree of sound isolation with various music samples due to source spectral differences. A statistically significant correlation was observed between annoyance and the A‐weighted level difference ratings of the insulation curves when bandlimited pink noise (125 Hz–4 kHz) was used as a source. This correlation was not present when broadband (40 Hz–10 kHz) pink noise was used for the performance rating. Subjects showed a preference for insulation curves with steeper slopes (9 and 12 dB/oct), thus preferring a greater relative attenuation at higher frequencies. Additionally, the presence of coincidence dips was found to have an effect on subject preference that appeared to depend upon both the frequency range at which they occurred and the slope. The bandwidth of the music signals and the intelligibility of speech in the intruding sounds were also found to influence the annoyance ratings. These results indicate that the level difference method for rating sound insulation could better predict occupant response if the above results were accounted for in the procedure.
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43.55.Rg Sound transmission through walls and through ducts: theory and measurement
43.55.Ti Sound-isolating structures, values of transmission coefficients

Frequency‐domain investigations of cochlear stability in the presence of active elements

Shozo Koshigoe and Arnold Tubis

J. Acoust. Soc. Am. Volume 73, Issue 4, pp. 1244-1248 (1983); (5 pages) | Cited 1 time

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For a linear, time‐invariant cochlear response function, the requirements of causality and stability imply the absence of poles of the spectral response function g(ω) for Im ω>0, with e−iωt as the time‐dependence factor. The existence of such poles invalidate conventional Hilbert transform (dispersion) relations. The testing of these dispersion relations provides a frequency‐domain check of system stability for cochlear models which contain active elements such as negative resistance. The stability of several one‐ and two‐dimensional cochlear models with active elements is checked using these dispersion relations. A simple circuit analog of the cochlea, which contains active elements, is used to illustrate the relationship between the pole locations of g(ω) and the strength of active elements.
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43.64.Bt Models and theories of the auditory system
43.64.Ri Evoked responses to sounds

Growth of forward masking for sinusoidal and noise maskers as a function of signal delay; implications for suppression in noise

Brian C. J. Moore and Brian R. Glasberg

J. Acoust. Soc. Am. Volume 73, Issue 4, pp. 1249-1259 (1983); (11 pages) | Cited 22 times

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The first two experiments were designed to determine whether mutual suppression in broadband noise increases in strength with increasing overall level. In experiment I masking functions (signal threshold versus masker level) were measured in forward masking as a function of the delay time of a 10‐ms signal, both for a broadband noise masker (low‐pass filtered at 8 kHz) and for sinusoidal maskers at 1, 2, and 4 kHz. In the latter case the signal frequency equaled the masker frequency. For short signal delays the masking functions were steeper for the sinusoidal masker than for the noise masker. At longer delays the slopes for both masker types decreased and the slopes for the two masker types became more nearly equal. In experiment II we investigated the effect of gating a low‐level noise cue with the sinusoidal masker. At the longer signal delays the masking functions had equal slopes for the broadband noise masker and the sinusoidal masker with cue. At short signal delays the masking functions for sinusoidal maskers may be ‘‘artificially’’ steepened, since the subject lacks an effective cue to distinguish the signal from the masker. The equal slopes at longer delays indicate that mutual suppression of the components within a broadband noise does not increase in strength with increasing overall level. In experiment III we attempted to estimate the magnitude of mutual suppression in a broadband noise by comparing masking functions for a broadband noise and for a noise whose bandwidth was 20% of the center frequency. The suppression was estimated to be about 2 dB at 4 kHz and 8 dB at 2 kHz. A simple mathematical expression, suggested by Jesteadt et al. [J. Acoust. Soc. Am. 71, 950–962 (1982)], was found to give an accurate description of the amount of masking produced by the broadband masker as a function of masker level and signal delay.
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43.66.Dc Masking
43.66.Mk Temporal and sequential aspects of hearing; auditory grouping in relation to music

Further studies of auditory profile analysis

David M. Green and Gerald Kidd, Jr.

J. Acoust. Soc. Am. Volume 73, Issue 4, pp. 1260-1265 (1983); (6 pages) | Cited 17 times

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The discrimination of a change in the intensity of a component or components of a multitone complex is reported as a function of a number of experimental variables. In one experiment, changes in the shape of the spectrum were explored to determine which kinds of changes are more easily detected. Although different signal spectra produced different thresholds, the change in a single component produced the lowest threshold on an energy basis. Various binaural conditions were tested to determine if the shape or profile of the stimulus could be supplied by the ear opposite the one in which the signal was presented. Conditions where spectral contrasts were available to both ears simultaneously (diotic conditions) were much more sensitive than conditions where the spectral contrasts occurred for opposite ears (dichotic conditions). Finally, the level of the component at the signal frequency was varied relative to the other, equal amplitude, components to form a ‘‘pedestal’’ upon which the signal was added. Detection of the signal was roughly the same for pedestal levels within about ±12 dB of the background except for conditions where masking was apparent.
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43.66.Fe Discrimination: intensity and frequency
43.66.Dc Masking
43.66.Ba Models and theories of auditory processes

A central spectrum model: A synthesis of auditory‐nerve timing and place cues in monaural communication of frequency spectrum

P. Srulovicz and J. L. Goldstein

J. Acoust. Soc. Am. Volume 73, Issue 4, pp. 1266-1276 (1983); (11 pages) | Cited 29 times

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A probabilistic psychophysical model for monaural communication from the auditory nerve to the brain is given in the form of a tonotopic display of stimulus spectrum, termed central spectrum. The model builds upon prior research demonstrating the potential of neural timing cues from the auditory nerve for conveying information on complex spectra, and was designed to meet the quantified demands of the psychophysics of frequency measurement. The central spectrum magnitude at each frequency is determined by the response of the auditory‐nerve fiber with characteristic frequency matching that frequency. An interval histogram from each fiber is passed through a filter matched to the characteristic frequency of the fiber. This output versus characteristic frequency defines the central spectrum. Detailed analysis demonstrates that efficient probabilistic processing of the central spectrum describes known psychophysical properties of frequency measurement in discrimination and periodicity pitch experiments. Psychophysical models based upon the central spectrum model followed by optimum probabilistic pattern recognition are potentially relevant for predicting human communication limits in response to arbitrary sounds of speech and music.
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43.66.Hg Pitch
43.66.Ba Models and theories of auditory processes
43.66.Nm Phase effects

The ear effect as a function of age and hearing loss

David Y. Chung, Keith Mason, R. Patrick Gannon, and Glenn N. Willson

J. Acoust. Soc. Am. Volume 73, Issue 4, pp. 1277-1282 (1983); (6 pages)

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Many studies have shown that the right ear statistically is slightly more sensitive than the left ear, particularly in the male adult population. In this study, we examined the lateral difference in hearing sensitivity, termed the ear effect here, in an industrial noise‐exposed, nonshooting population, by sex, age, and hearing level. It was found that the male population had a larger ear effect (right ear being more sensitive) than the female population. The magnitude of the ear effect was found to be significantly related to the hearing threshold level. The ear effect was highest when the threshold was between 30‐ and 40‐dB HL. Several possible causes for the ear effect are discussed.
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43.66.Sr Deafness, audiometry, aging effects
43.66.Cb Loudness, absolute threshold

Intensity discrimination with cochlear implants

Bryan E. Pfingst, Patricia A. Burnett, and Dwight Sutton

J. Acoust. Soc. Am. Volume 73, Issue 4, pp. 1283-1292 (1983); (10 pages) | Cited 4 times

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Intensity difference limens were measured for various frequencies and intensities of sinusoidal and pulsatile electrical stimulation in monkeys with electrodes implanted in the scala tympani, scala vestibuli, modiolus, or middle ear. Difference limens decreased, as a function of initial stimulus intensity, from values of 1.5–3 dB near threshold to as low as 0.5 dB near the upper limit of the dynamic range. If sensation level was held constant, difference limens decreased as a function of frequency up to about 500 Hz, and then remained constant. They were similar across a variety of electrode placements and separations if differences in threshold and dynamic range were taken into account. However, difference limens measured in severely damaged ears were slightly smaller than those in moderatly damaged ears. The near miss to Weber’s law, characteristic of acoustic difference limens, was not seen with electrical stimuli. Difference limens for electrical stimuli were roughly one‐half those for acoustic stimuli; thus, part of the deficit in dynamic range for electrical stimulation compared with acoustic stimulation is countered by the smaller intensity difference limens for electrical stimuli.
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43.66.Ts Auditory prostheses, hearing aids
43.66.Gf Detection and discrimination of sound by animals
43.66.Fe Discrimination: intensity and frequency
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