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Journal of the Acoustical Society of America

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Jun 1982

Volume 71, Issue 6, pp. 1321-1632

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Auditory perception of radio‐frequency electromagnetic fields

Chung‐Kwang Chou, Arthur W. Guy, and Robert Galambos

J. Acoust. Soc. Am. Volume 71, Issue 6, pp. 1321-1334 (1982); (14 pages) | Cited 1 time

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Absorption of pulsed microwave energy can produce an auditory sensation in human beings with normal hearing. The phenomenon manifests itself as a clicking, buzzing, or hissing sound depending on the modulatory characteristics of the microwaves. While the energy absorbed (∠10 μJ/g) and the resulting increment of temperature (∠10−6 °C) per pulse at the threshold of perception are small, most investigators of the phenomenon believe that it is caused by thermoelastic expansion. That is, one hears sound because a miniscule wave of pressure is set up within the head and is detected at the cochlea when the absorbed microwave pulse is converted to thermal energy. In this paper, we review literature that describes psychological, behavioral, and physiological observations as well as physical measurements pertinent to the microwave‐hearing phenomenon.
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43.10.Ln Surveys and tutorial papers relating to acoustics research; tutorial papers on applied acoustics
43.64.Bt Models and theories of the auditory system
43.66.Ba Models and theories of auditory processes

Acoustic propagation in a rigid torus

Michael El‐Raheb and Paul Wagner

J. Acoust. Soc. Am. Volume 71, Issue 6, pp. 1335-1346 (1982); (12 pages) | Cited 1 time

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The acoustic propagation in a rigid torus is analyzed using a Green’s function method. Three types of surface elements are developed; a flat quadrilateral element used in modeling polygonal cavities, a curved conical element appropriate for surfaces with one curvature, and a toroidal element developed for such doubly curved surfaces as the torus. Curved elements are necessary since the acoustic pressure is sensitive to slope discontinuities between consecutive surface elements especially near cavity resonances. The acoustic characteristics of the torus are compared to those of a bend of square cross section for a frequency range that includes the transverse acoustic resonance. Two equivalences between the different sections are tested; the first conserves curvature and cross‐sectional dimension while the second matches transverse resonance and duct volume. The second equivalence accurately matches the acoustic characteristics of the torus up to the cutoff frequency corresponding to a mode with two circumferential waves.
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43.20.Bi Mathematical theory of wave propagation
43.20.Fn Scattering of acoustic waves
43.40.Ey Vibrations of shells

Torsional dispersion relations of waves in an infinitely long clad cylindrical rod

R. Parnes

J. Acoust. Soc. Am. Volume 71, Issue 6, pp. 1347-1351 (1982); (5 pages) | Cited 1 time

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The dispersion relations of torsional waves propagating in a system consisting of an elastic rod of radius a embedded in a linear elastic medium are investigated. Phase speeds of waves of wavelength λ which propagate under steady‐state conditions are determined. The dispersion relations are found to be dependent on the geometric ratio a/λ, as well as on nondimensional ratios of the rod‐medium properties. The frequency equation obtained is analyzed and upper and lower bounds on the phase speed are determined. It is shown that torsional waves can propagate freely only if the propagation speed of torsional waves in the corresponding free rod is less than that of shear waves propagating in the medium. Results are presented by means of dispersion curves and surfaces.
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43.20.Bi Mathematical theory of wave propagation
43.20.Hq Velocity and attenuation of acoustic waves
62.30.+d Mechanical and elastic waves; vibrations
43.40.Cw Vibrations of strings, rods, and beams

Resolution of the discrepancies between different physical optics solutions for rough surface scattering

Ezekiel Bahar

J. Acoust. Soc. Am. Volume 71, Issue 6, pp. 1352-1358 (1982); (7 pages)

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The analysis presented here resolves the discrepancies between the different high‐frequency, physical optics expressions for the scattered field derived by several researchers in the field. On applying the divergence theorem (in two dimensions) the term associated with the edge effect is shown to vanish identically for all scatter directions. Thus it is also shown that the so‐called edge effect which appears in earlier derivations of the physical optics solution for rough surface scattering is a result of premature truncation of the closed surface integral expression for the scattered fields. Therefore this term must be suppressed even when it is not very small compared to the scattered field in the off specular direction. Since the Kirchhoff approximations for the surface fields are used in the physical optics approach, it cannot account for wave diffraction by edges. The physical optics solution derived here for arbitrary source excitation is shown to satisfy reciprocity and realizability relationships in electromagnetic theory. The integrand in the integral expression for the scattered field is identified with the specific reflectance (per unit area) of the rough surface. Although the scalar acoustic problem is considered here in detail, the results are also applicable to electromagnetic scattering.
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43.20.Fn Scattering of acoustic waves
43.20.Bi Mathematical theory of wave propagation

Coherence and multiple scattering effects on acoustic backscattering from linear arrays of gas‐filled bubbles

Daniel R. Bruno and Jorge C. Novarini

J. Acoust. Soc. Am. Volume 71, Issue 6, pp. 1359-1367 (1982); (9 pages) | Cited 1 time

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Acoustic backscattering of spherical waves from finite linear arrays of gas‐filled bubbles, both regular and randomly spaced, is studied numerically including coherence and acoustic interaction to all orders between bubbles. Coherence effects are first examined neglecting multiple scattering. Large effects are observed and the single bubble resonance can be appreciably distorted. The combined effect of coherence and multiple scattering is studied through an interaction parameter which relates the total scattered field intensity and the single scattering incoherent intensity. Regular arrays resonate at the single bubble resonance frequency and when the bubble spacing is a multiple of the incident wavelength. Close to the array, coherence is predominant over multiple scattering. In the farfield, multiple scattering causes an enhancement of the intensity, depending on the bubble spacing. For random arrays only the single bubble resonance subsists and multiple scattering produces a decrement of the field intensity for any average bubble spacing.
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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
43.20.Bi Mathematical theory of wave propagation

Acoustic wave scattering from a fluid/solid periodic rough surface

Shun‐Lien Chuang and Richard K. Johnson

J. Acoust. Soc. Am. Volume 71, Issue 6, pp. 1368-1376 (1982); (9 pages) | Cited 2 times

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A rigorous theory based on the extended boundary condition method is proposed to solve the problem of elastic wave scattering from a periodic fluid/solid interface. The diffraction efficiencies of the reflected compressional wave in the fluid and the transmitted shear and compressional waves are calculated. The energy conservation criterion is used to check the accuracy of the numerical results. The effect of loss (viscoelasticity) in the solid is also included. The wave diffraction from a water and acrylic rough surface is measured. Good agreement between the theory and the experiment is obtained.
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43.20.Fn Scattering of acoustic waves
62.30.+d Mechanical and elastic waves; vibrations
68.35.Gy Mechanical properties; surface strains
68.35.Iv Acoustical properties
43.20.Bi Mathematical theory of wave propagation

Comparison of sound scattering by rigid and elastic obstacles in water

V. K. Varadan, V. V. Varadan, J. H. Su, and T. A. K. Pillai

J. Acoust. Soc. Am. Volume 71, Issue 6, pp. 1377-1383 (1982); (7 pages) | Cited 4 times

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Acoustic wave scattering by prolate and oblate spheroids and finite cylinders immersed in water is compared when rigid body and elastic boundary conditions, respectively, are satisfied at the fluid–scatterer interface. The frequency dependence of the scattered farfield is obtained for various angles of incidence for both types of boundary conditions using the null field or T‐matrix approach. From our computations it is concluded that only for restricted materials properties of the scatterer, scattering geometry and scatterer shape, the scattering characteristics of an elastic obstacle, and a rigid obstacle of the same shape are comparable up to wavelengths comparable to the size of the obstacle.
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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
43.20.Bi Mathematical theory of wave propagation

Elastic wave scattering from surface breaking cylindrical cracks: SH waves

V. V. Varadan, D. J. N. Wall, S. J. Tsao, and V. K. Varadan

J. Acoust. Soc. Am. Volume 71, Issue 6, pp. 1384-1390 (1982); (7 pages)

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The diffraction of SH waves by a crack breaking the surface of a homogeneous half‐space is considered. By the use of image theory, this problem is reduced to consideration of a cavity in an infinite homogeneous space. The null field or T‐matrix method is used to obtain a system of algebraic equations which are solved by a numerical scheme. The scattered field is then calculated. Numerical results are presented for the angular and frequency dependence of the scattered field from cracks of various shapes.
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43.20.Fn Scattering of acoustic waves
68.35.Gy Mechanical properties; surface strains
68.35.Iv Acoustical properties
62.30.+d Mechanical and elastic waves; vibrations
43.20.Bi Mathematical theory of wave propagation

Exact solutions of the one‐dimensional acoustic wave equations for several new velocity profiles: Transmission and reflection coefficients

P. B. Abraham and H. E. Moses

J. Acoust. Soc. Am. Volume 71, Issue 6, pp. 1391-1399 (1982); (9 pages) | Cited 1 time

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After reviewing the relationship of the acoustic equation to the Schrödinger equation, solutions of the latter are used to construct new indices of refraction [or equivalently sound velocity profiles (SVP)] for which the solutions of the acoustic equation are expressed in terms of elementary functions. The new indices of refraction can be used to form layers to model more general inhomogeneous media, just as piecewise constant slabs or other indices have been used in the past. Four of the new indices of refraction also provide especially simple closed‐form examples which can be used to describe how waves are scattered in media with such indices. More general scattering problems are discussed. In particular, the notion of outgoing wave is gone into. The five indices given in the present paper are the first of several which have been obtained from Schrödinger equations with potentials for which the eigenfunctions can be found in closed form. Others will be given in later papers.
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43.20.Hq Velocity and attenuation of acoustic waves
43.20.Fn Scattering of acoustic waves
43.20.Bi Mathematical theory of wave propagation

Sound propagation in a pipe containing a liquid of comparable acoustic impedance

M. P. Horne and R. J. Hansen

J. Acoust. Soc. Am. Volume 71, Issue 6, pp. 1400-1405 (1982); (6 pages) | Cited 2 times

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A detailed experimental study of sound propagation in liquids contained by pipes constructed of polymeric materials is discussed. Experiments were conducted with vertically aligned cylinders containing water ensonified at one end by a piston‐driven sound source. Significant sound attenuation (as much as 60 dB) was observed in pipes made of flexible polymeric materials, the effect increasing with frequency and loss tangent. Sound propagation in more rigid polymeric pipes exhibited similar characteristics to that in metallic pipe in that negligible attenuation was observed. In this latter case, a comparison was made with recent analytical work for which excellent agreement was obtained.
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43.20.Mv Waveguides, wave propagation in tubes and ducts
43.30.Bp Normal mode propagation of sound in water
43.20.Hq Velocity and attenuation of acoustic waves

On the plane‐wave approximation of acoustic intensity

K. Beissner

J. Acoust. Soc. Am. Volume 71, Issue 6, pp. 1406-1411 (1982); (6 pages) | Cited 3 times

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The acoustic intensity is given by the product of acoustic pressure p and particle velocity v, but in the literature, expressions like p2/ρc or ρcv2 are often quoted. These are plane‐wave approximations and are not in general valid. Assuming continuous‐wave operation, the relations between the approximate formulas and the exact one are discussed in terms of the specific acoustic impedance. Further remarks deal with the vector character of the acoustic intensity and its connection with heat generation in the medium, as considered in a recent paper by Nyborg [J. Acoust. Soc. Am. 70, 310–312 (1981)].
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43.20.Rz Steady-state radiation from sources, impedance, radiation patterns, boundary element methods
43.20.Tb Interaction of vibrating structures with surrounding medium
43.20.Bi Mathematical theory of wave propagation

Thermal hysteresis in acoustic resonators

Lee W. Casperson, Lloyd M. Davis, and John D. Harvey

J. Acoust. Soc. Am. Volume 71, Issue 6, pp. 1412-1416 (1982); (5 pages)

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In some applications of piezoelectrically driven acoustic resonators, the power dissipated in the resonating material may be sufficient to significantly change the temperature and hence the resonance frequency. A straightforward analysis shows that this effect can lead to severe hysteresis and thermal bistability. This model is in agreement with experiments that have been performed using a fused silica acousto‐optic modulator.
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43.25.Gf Standing waves; resonance
43.58.Kr Spectrum and frequency analyzers and filters; acoustical and electrical oscillographs; photoacoustic spectrometers; acoustical delay lines and resonators
43.38.Fx Piezoelectric and ferroelectric transducers

Shallow‐water transmission loss prediction using the Biot sediment model

J. H. Beebe, S. T. McDaniel, and L. A. Rubano

J. Acoust. Soc. Am. Volume 71, Issue 6, pp. 1417-1426 (1982); (10 pages) | Cited 4 times

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Experimental data and predicted propagation loss from three shallow‐water test sites with highly varied sediments are compared for frequencies from 25 to 800 Hz. The predicted loss was obtained using normal‐mode and adiabatic normal‐mode models with the sediment absorption calculated using the theory of Biot. The theory predicted a linear variation of absorption with frequency for a site off Corpus Christi, Texas, having a mud bottom (the mean grain size was 6.37 phi). The absorption was predicted to vary as frequency raised to the 1.76 power for a site off Daytona Beach, Florida having a medium‐to‐coarse sand bottom (the mean grain size was 0.85 phi). Range‐independent propagation was assumed for the sites just noted and the agreement between measured and predicted loss was good for frequencies from 100 to 600 Hz. Range‐dependent conditions existed for the third site, off the coast of Nova Scotia, where the sound‐speed profile, bottom sediments, and depth varied with range. Good agreement was obtained between measured, 1/3‐octave transmission loss values and predicted values for frequencies of 25, 80, and 250 Hz.
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43.30.Bp Normal mode propagation of sound in water
43.30.Dr Hybrid and asymptotic propagation theories, related experiments
92.10.Vz Underwater sound
43.30.Jx Radiation from objects vibrating under water, acoustic and mechanical impedance

Application of the WKBJ Green’s function to acoustic propagation in horizontally stratified oceans

Michael G. Brown

J. Acoust. Soc. Am. Volume 71, Issue 6, pp. 1427-1432 (1982); (6 pages) | Cited 2 times

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The Green’s function (response to an impulsive point source) for ocean acoustic propagation is found using the WKBJ seismogram technique [Chapman, Geophys. J. R. Astron. Soc. 54, 481–518 (1978)]. It is shown that the WKBJ Green’s function reduces to geometric ray theory; in the vicinity of caustics it gives the well‐known Airy function range dependence of each harmonic component of the acoustic field. Arrival patterns constructed using the WKBJ Green’s function are in excellent agreement with a solution to the parabolic equation (PE) except when the source and/or receiver depth is near the turning depth of a geometric ray. Agreement with a measured arrival pattern is also found to be good.
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43.30.Bp Normal mode propagation of sound in water
92.10.Vz Underwater sound
43.20.Bi Mathematical theory of wave propagation
43.20.Dk Ray acoustics

Nature of the lateral wave effect on bottom loss measurements

Stanley A. Chin‐Bing, James A. Davis, and Richard B. Evans

J. Acoust. Soc. Am. Volume 71, Issue 6, pp. 1433-1437 (1982); (5 pages) | Cited 1 time

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The lateral wave is examined for the Sommerfeld model with respect to its effect on bottom loss measurement. Some inconsistencies between existing results are resolved and a numerical example is given.
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43.30.Bp Normal mode propagation of sound in water
43.30.Dr Hybrid and asymptotic propagation theories, related experiments
91.50.Ey Seafloor morphology, geology, and geophysics
92.10.Vz Underwater sound

Analysis of deep ocean sound attenuation at very low frequencies

Karl C. Focke, S. K. Mitchell, and C. W. Horton, Sr.

J. Acoust. Soc. Am. Volume 71, Issue 6, pp. 1438-1444 (1982); (7 pages)

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The attenuation coefficient of low‐frequency, deep ocean acoustic waves is computed for various assumptions regarding the depth profile and the frequency dependence of the scatterers. The calculations are made for a realistic velocity profile by means of a perturbation technique proposed by Guthrie [Ph. D. dissertation, The University of Auckland (1975)]. It is shown that excellent agreement with experimental data is obtained when the attenuation function is independent of frequency and decreases exponentially with depth with a characteristic depth of 200 to 500 m. A surface value of 0.11 dB/km gives good agreement with the data. At frequencies below 50 Hz the attenuation in the water column is comparable to the attenuation in the sediments for the lowest order normal modes.
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43.30.Bp Normal mode propagation of sound in water
92.10.Vz Underwater sound
43.30.Cq Ray propagation of sound in water

On the ray equivalent of a group of modes

A. Kamel and L. B. Felsen

J. Acoust. Soc. Am. Volume 71, Issue 6, pp. 1445-1452 (1982); (8 pages) | Cited 2 times

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The raylike behavior of a cluster of normal modes furnishes a useful concept for determining the interference properties of a normal‐mode pressure field. In previous investigations, a selected group of modes has been heuristically smeared out into a continuum, and it has been established that the interference maximum lies along a path traversed by the ’’modal ray’’ for the central mode in the group. This approximate analysis does not quantify the corresponding amplitude behavior of the mode cluster. A rigorous basis may be provided by Poisson summation of the group of modes, which procedure incorporates systematically not only the transition to the continuum but also the effect of truncation of the mode bundle. As a result, a mode cluster may be shown to be completely equivalent, in phase and amplitude, to a ray field plus a remainder. The equivalence remains intact even in convergence zones and other transition regions where simple ray acoustics must be corrected by uniform asymptotic treatment. The remainder can be minimized by an appropriate ’’optimum’’ choice of the number of modes in the bundle, and by weighting the first and last included modes. Numerical calculations for a simple ducting environment are presented in support of these conclusions.
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43.30.Bp Normal mode propagation of sound in water
43.30.Jx Radiation from objects vibrating under water, acoustic and mechanical impedance
43.20.Dk Ray acoustics

Correlation measurements of surface‐reflected underwater acoustic signals at several sea states

J. R. Olson and R. H. Nichols

J. Acoust. Soc. Am. Volume 71, Issue 6, pp. 1453-1457 (1982); (5 pages)

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A coherent wavefront which strikes the rough and moving surface of the ocean is expected to suffer some degree of decorrelation. Two exploratory experiments were performed to investigate the effect of sea state on decorrelation for acoustical wavelengths of the order of the ocean wave heights and signal durations comparable to the ocean wave periods. In the first, 10‐s pulses of random noise signal of 300‐Hz bandwidth centered at 750 Hz were generated by a bottomed omnidirectional sound source, reflected once from the surface at a grazing angle of 31° and received on two bottomed omnidirectional hydrophones spaced 500 ft apart, approximately broadside to the sound path. Cross‐correlation coefficients for the last 5 s of each pulse were measured at several sea states. In the second experiment, the output of one hydrophone was cross correlated with a replica of the pseudo‐random signal which drove the sound source. Cross‐correlation coefficients between the two receivers decreased with increasing sea state to a value of about 0.4 at 20‐ft wave height. Replica‐correlation coefficients with a single receiver also decreased, but to only about 0.8 at 20‐ft wave height. These values are higher than values presented in other publications of theoretical and experimental results obtained under other conditions. One reason for the difference may lie in the shorter duration of our signals relative to the ocean wave periods.
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43.30.Dr Hybrid and asymptotic propagation theories, related experiments
43.30.Bp Normal mode propagation of sound in water
92.10.Vz Underwater sound

Effects of partial water saturation on attenuation in Massilon sandstone and Vycor porous glass

William F. Murphy, III

J. Acoust. Soc. Am. Volume 71, Issue 6, pp. 1458-1468 (1982); (11 pages) | Cited 33 times

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The advent of new high resolution seismic reflection and borehole sonic techniques has stimulated renewed interest in what information stress wave propagation may carry about rock properties and pore fluids in situ. We have measured extensional and shear wave velocities. Ve and Vs, and their specific attenuation, Q−1e and Q−1s, in Massilon sandstone and Vycor porous glass as a function of continuously varying partial water saturation and relative humidity. Measurements were made at frequencies from 300 Hz to 14 kHz using a resonant bar technique and from 25–400 Hz using a torsional pendulum technique. Energy loss is very sensitive to partial water saturation. In Massilon sandstone, Q−1s is maximum and greater than Q−1e only at full saturation. Q−1e rises to a strong peak at 85% water saturation. Energy loss drops significantly as the Massilon becomes ’’very dry.’’ Q−1e and Q−1s in partially saturated Massilon and Vycor are strongly frequency dependent throughout the acoustic range, exhibiting peaks between 1–10 kHz. Q−1 in dry Massilon and Vycor is independent of frequency, at least in the acoustic range. Two pore fluid mechanisms absorb energy. Viscous dissipation due to fluid flow in pores dominates in fully and partially water saturated materials. A surface capillary film mechanism dominates at low moisture contents. Nonlinear frame mechanisms such as frictional grain sliding are not signficant at normal acoustic strains, even in ’’dry’’ rocks. Compressional wave velocity and specific attenuation, Vp and Q−1p, and bulk compressional specific attenuation, Q−1k, were calculated at given frequencies. While the dependence of velocities on water saturation agrees well with a very simple explanation, there is no satisfactory theory yet available for attenuation. Vp/Vs and Q−1p/Q−1s provide sufficient information to distinguish between fully and partially water saturated Massilon sandstones, yet are insufficient to resolve the degree of partial water saturation.
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43.35.Cg Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in solids; elastic constants
91.60.-x Physical properties of rocks and minerals
43.40.Ph Seismology and geophysical prospecting; seismographs

Grüneisen numbers in hexagonal crystals

Manik Nandanpawar and S. Rajagopalan

J. Acoust. Soc. Am. Volume 71, Issue 6, pp. 1469-1472 (1982); (4 pages) | Cited 2 times

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Grüneisen numbers, which relate the change in the phonon mode frequency to the applied strain, can be estimated if all the second‐order and third‐order elastic moduli are known. Expressions for Grüneisen numbers are normally found in the literature for cubic and trigonal crystals only. In the present work, for the first time, expressions for Grüneisen numbers for both longitudinal and shear wave propagation along the (0 0 0 1) axis in hexagonal materials have been derived, considering 41 modes of pure elastic wave propagation affected by a longitudinal strain and 16 pure modes affected by a shear strain. The average of the Grüneisen numbers for longitudinal wave propagation along the hexagonal axis in magnesium is close to the Grüneisen constant determined from the thermal expansivities and specific heat, while the average for shear wave propagation along the c axis is zero, as expected. The expressions derived here can be used to estimate phonon viscosity losses in hexagonal materials.
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43.35.Cg Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in solids; elastic constants
43.35.Gk Phonons in crystal lattices, quantum acoustics
63.20.kg Phonon-phonon interactions
62.20.D- Elasticity
65.40.De Thermal expansion; thermomechanical effects

On the evolution, generation, and regeneration of gas cavitation nuclei

David E. Yount

J. Acoust. Soc. Am. Volume 71, Issue 6, pp. 1473-1481 (1982); (9 pages) | Cited 2 times

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Recently a new cavitation model has been proposed in which bubble formation in aqueous media is initiated by spherical gas nuclei stabilized by surface‐active membranes of varying gas permeability. By tracking the changes in nuclear radius that are caused by increases or decreases in ambient pressure, the varying‐permeability model has provided precise quantitative descriptions of several bubble counting experiments carried out with supersaturated gelatin. The model has also been used to calculate diving tables and to predict levels of incidence for decompression sickness in a variety of animal species, including salmon, rats, and humans. Although the phenomena involved are in some sense dynamic, the model equations, in their present form, are essentially static and can be derived by requiring mechanical or chemical equilibrium at each setting in a rudimentary pressure schedule. In this paper, we examine the time dependence of the evolution of an individual nucleus from one equilibrium state to another, and we then investigate a statistical process by which the equilibrium size distribution of an entire population of nuclei may be generated or regenerated.
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43.35.Ei Acoustic cavitation in liquids
43.25.Yw Nonlinear acoustics of bubbly liquids
43.30.Nb Noise in water; generation mechanisms and characteristics of the field

Measurement of vibrational relaxation time of oxygen between 475° and 675°K using an acoustic resonant technique

I‐an Feng and Mark C. Lee

J. Acoust. Soc. Am. Volume 71, Issue 6, pp. 1482-1486 (1982); (5 pages)

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Vibrational relaxation times of O2–He, O2–CO2, and O2–H2 mixtures have been measured using a resonant chamber method between 475° and 675°K. This temperature range lies in the gap between the bulks of previous data obtained using acoustic and shock tube methods. Data analyses were carried out by a novel computer techique. Data for pure O2 were obtained by extrapolating that of mixtures to zero impurity concentrations. Our data agree with previous acoustic results at 473° and 573°K and shock tube results at 700°K. The temperature dependence of the vibrational relaxation time for pure O2 was compared to the theories of Landau and Teller [Physik. Z. Sowjetunion 10, 34 (1936)]; Schwartz et al. (SSH) [J. Chem. Phys. 20, 1591 (1952)]; and Parker [J. Chem. Phys. 34, 1763 (1961); 41, 1600 (1964)]. The simple Landau–Teller theory has shown better agreement with experimental data than that of SSH and Parker for the case of O2–O2, O2–He, and O2–H2 collisions.
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43.35.Fj Ultrasonic relaxation processes in gases, liquids, and solids
51.40.+p Acoustical properties
43.35.Ae Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in gases

Generalized Kirchhoff approach to the ocean surface‐scatter communication channel. Part II: Second‐order functions

Lawrence J. Ziomek

J. Acoust. Soc. Am. Volume 71, Issue 6, pp. 1487-1495 (1982); (9 pages) | Cited 2 times

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Three second‐order functions which characterize the ocean surface‐scatter communication channel are derived from the transfer function of the ocean surface. These second‐order functions include the two‐frequency correlation function or the two‐frequency mutual coherence function, the scattering function, and the power spectral density function of the scattered acoustic pressure field. These functions are shown to be dependent upon the general form of the directional wavenumber spectrum. Both the slightly rough and very rough surface cases are included. The interrelationships which exist amongst these functions are demonstrated. As an example, the power spectral density function is computed for the very rough surface case using the Neumann–Pierson directional wavenumber spectrum.
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43.60.Cg Statistical properties of signals and noise
43.60.Gk Space-time signal processing, other than matched field processing
43.30.Gv Backscattering, echoes, and reverberation in water due to combinations of boundaries
43.20.Bi Mathematical theory of wave propagation

Correspondence principle in cochlear mechanics

E. de Boer

J. Acoust. Soc. Am. Volume 71, Issue 6, pp. 1496-1501 (1982); (6 pages)

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When only long waves play the most important part in the cochlea, the response can be described by a most simplified model, the one‐dimensional model. When short waves are to be included, a more complex model is needed. The response then depends on the dimensionality of the model and is much harder to obtain. This applies especially to the region in the neighborhood of the point where the basilar membrane shows resonance. Both two‐ and three‐dimensional models have been studied to assess the effects of short and long waves. The relative importance of the part played by short waves depends on the damping constant (or loss factor) δ associated with the resonance of the basilar membrane (BM). For very small δ a three‐dimensional model is really necessary, it cannot be replaced by a model of lower dimensionality. When δ is small, but not too small, the three‐dimensional model can be made equivalent to a two‐dimensional one, provided the latter is modified in a specific manner. This paper shows why this is so and which conditions have to be met. The two‐dimensional model must undergo two modifications to effect this equivalence. The first modification ensures that the model has the same long‐wave behavior. In the second place, a specific additional mass (’’added mass’’) reactance should be added to Z(x). An expression for the limiting value of δ, above which this correspondence is valid, is given in the paper. A second, larger, limit is presented as well: when δ is above this limit, the responses of both the three‐dimensional and the two‐dimensional model are equivalent to that of an appropriately chosen one‐dimensional model. In this case too, long‐wave behavior must be matched and an ’’added mass’’ reactance must be included in Z(x). This holds true for the entire cochlea including the region of resonance. For both types of transition the amount of ’’added mass’’ is given.
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43.64.Bt Models and theories of the auditory system
43.64.Kc Cochlear mechanics

Forward masking by enhanced components in harmonic complexes

Neal F. Viemeister and Sid P. Bacon

J. Acoust. Soc. Am. Volume 71, Issue 6, pp. 1502-1507 (1982); (6 pages) | Cited 15 times

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The audibility of a given target component in certain spectral complexes can be considerably increased by exposure to the complex with the target component deleted. This ’’enhancement effect’’ can be observed under a wide variety of conditions and presumably reflects frequency‐specific adaptation: the frequency region around the target frequency is not adapted during the exposure and hence is relatively more sensitive. Data from the present study indicate that an enhanced component in a harmonic complex produces more forward masking of a sinusoidal probe than when that component is not enhanced, i.e., an enhanced component behaves as if it were physically more intense. This suggests that the adaptation process underlying the enhancement effect produces an increase in gain in the unadapted frequency region. This increase might result from a decrease, due to adaptation, of suppression of the unadapted region.
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43.66.Dc Masking
43.66.Ed Auditory fatigue, temporary threshold shift
43.66.Ki Subjective tones
43.66.Fe Discrimination: intensity and frequency
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