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Dec 1989

Volume 86, Issue 6, pp. 2063-2482

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Light diffraction by two spatially separated ultrasonic waves

P. Kwiek

J. Acoust. Soc. Am. Volume 86, Issue 6, pp. 2261-2272 (1989); (12 pages) | Cited 2 times

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A theoretical model of light diffraction by two sinusoidal and spatially separated ultrasonic waves of frequency ratio 1:n is presented. Experimental verification of the model is shown for ultrasonic waves having frequency ratio 1:1 and 1:2, and the agreement between results, both theoretical and experimental, is very good. The investigation was performed for the near‐ (Fresnel) and far‐ (Fraunhofer) fields of the light diffracted by two ultrasonic waves.
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43.35.Sx Acoustooptical effects, optoacoustics, acoustical visualization, acoustical microscopy, and acoustical holography

Theory of acoustic radiation in corners with homogeneous and mixed perfectly reflecting boundaries

Michael J. Buckingham

J. Acoust. Soc. Am. Volume 86, Issue 6, pp. 2273-2291 (1989); (19 pages) | Cited 3 times

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An exact solution in the form of uncoupled normal modes is derived for the harmonic field from a point monopole source in a corner with perfectly reflecting boundaries (either homogeneous Dirichlet, homogeneous Neumann, or mixed Dirichlet–Neumann). Each mode coefficient is the sum of two integrals, representing the image and diffraction components of the field, neither of which can be expressed explicitly. The image mode integral shows a highly oscillatory spatial dependence in the ensonified region of the mode, a domain that is bounded by a hyperbolic caustic beyond which lies a shadow zone. First‐ and second‐order asymptotic approximations are developed for the image mode integral that are matched in the vicinity of the caustic and that give an extremely accurate representation of the image mode field throughout the ensonified region, across the caustic, and into the shadow. The diffraction mode integral shows a relatively slow spatial dependence. A uniform asymptotic approximation is developed that provides an accurate representation of the diffraction mode integral throughout the domain of the corner. Both the matched and uniform asymptotic approximations are very fast to evaluate compared with numerical computations of the respective integrals. The mode sum yields an expression for the velocity potential consisting of a finite number of image terms plus an intractable integral for the diffracted component of the field, for which an accurate first‐order stationary phase approximation is developed.
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43.30.Es Velocity, attenuation, refraction, and diffraction in water, Doppler effect
43.30.Bp Normal mode propagation of sound in water

Stochastic geometrical theory of diffraction

R. Mazar and L. B. Felsen

J. Acoust. Soc. Am. Volume 86, Issue 6, pp. 2292-2308 (1989); (17 pages) | Cited 5 times

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The localization of high‐frequency sound‐wave propagation around ray trajectories, and the reflection and(or) diffraction of these local plane‐wave fields by boundaries, inhomogeneities, and(or) scattering centers has been combined via the geometrical theory of diffraction (GTD) into one of the most effective means of analyzing high‐frequency wave phenomena in complex deterministic environments. These constructs are here incorporated into a stochastic propagation and diffraction theory for statistical moments of the high‐frequency field when the propagation medium has weak random fluctuations superimposed upon an inhomogeneous background profile, subject to the assumption that the correlation length ln of the fluctuations is small compared with the scale of variation, but large compared with the local wavelength λ=2π/k=2πv/ω, in the fluctuation‐free background, with k being the local wavenumber, v the local wave speed, and ω the radian frequency. Canonical problems of deterministic GTD furnish the propagators and, in the presence of interfaces, boundaries, or other types of scatterers, the local reflection, refraction, and diffraction coefficients that relate incoming to outgoing wave fields.
The major analytical building blocks include propagators described in local coordinates centered on the curved GTD ray trajectories in the deterministic inhomogeneous background environment; multiscale expansions in these coordinates to chart and solve for the propagation properties of statistical measures of the parabolically formulated ray fields; Kirchhoff or physical optics (PO) approximations, generated by stochastic GTD incident fields, to establish initial conditions for fields reflected from, or transmitted across, extended smooth surfaces; and ‘‘point scatterer’’ solutions to establish GTD initial conditions for small scatterers and edges. In addition to the conventional second‐ and higher‐order coherence functions, there are introduced as appropriate statistical objects two‐point random functions and corresponding higher‐order functions which are useful in treating correlation of incident and of backward reflected or diffracted fields that traverse the same propagation volume. By this solution strategy, one gains access to a much larger class of high‐frequency problems in a random medium than at present. Expressions for the average field and higher moments have been obtained for forward propagation in a fluctuating medium with inhomogeneous and caustic‐forming background, for reflection and refraction due to a plane or smoothly curved interface in such a medium, and for diffraction due to a wedge and a small scatterer.
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43.30.Es Velocity, attenuation, refraction, and diffraction in water, Doppler effect
43.30.Cq Ray propagation of sound in water
43.30.Dr Hybrid and asymptotic propagation theories, related experiments

Directional spectra observations of seafloor microseisms from an ocean‐bottom seismometer array

Dean Goodman, Tokuo Yamamoto, Mark Trevorrow, Chuck Abbott, Altan Turgut, Mohsen Badiey, and Koichi Ando

J. Acoust. Soc. Am. Volume 86, Issue 6, pp. 2309-2317 (1989); (9 pages) | Cited 1 time

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Observations of the directional spectra of seabed motion in shallow water were conducted off the New Jersey coast during the summer of 1987. Using a six‐point ocean‐bottom seismometer array, each instrument supporting a pressure transducer, and two horizontal and vertical accelerometers, measurements of gravity and seismic waves across the ULF/VLF band were collected in 12.5 m of water. Array dimensions were tuned particularly for directional spectra observations of short‐period seafloor microseisms. Directional spectra analysis indicates that in the short‐period microseismic band, 1.5–2.5 s, motion of the seafloor is primarily a result of slow seismic waves traveling at apparent velocities near 200 m/s. These propagation velocities for the microseismic band in shallow water are an order of magnitude less than microseismic velocities from similar studies on land. Contemporaneous measurements of the directional spectra of long‐period ocean gravity waves, 15–85 s, show an eastern direction of origin; short‐period ocean gravity waves, 5–9 s, measured using particle motion analysis, are from the south. The direction of propagation of the microseisms, found from the maximum response of the array, is shown to be approximately N150E—a direction midway between long‐ and short‐period ocean‐wave propagation directions. Correlation of particle motion and directional spectra analysis indicates that microseisms have retrograde motion. These results suggest that the microseisms are most likely Scholte interface waves.
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43.30.Nb Noise in water; generation mechanisms and characteristics of the field
43.30.Ma Acoustics of sediments; ice covers, viscoelastic media; seismic underwater acoustics
43.40.Ph Seismology and geophysical prospecting; seismographs

Measurements of ambient seabed seismic levels below 1.0 Hz on the shallow eastern U.S. continental shelf

Mark V. Trevorrow, Tokuo Yamamoto, Altan Turgut, and Dean Goodman

J. Acoust. Soc. Am. Volume 86, Issue 6, pp. 2318-2327 (1989); (10 pages) | Cited 1 time

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Measurements of ambient seismic noise levels in the range 0.03–1.0 Hz were made using ocean‐bottom seismometers (OBS) at four shallow‐water (<100 m) locations on the New Jersey Shelf and George’s Bank. Surface gravity‐wave‐induced seabed motion (single‐frequency microseism) was found to be dominant in the frequency range 0.03–0.3 Hz, with the high‐frequency cutoff strongly dependent on water depth. The peak seismic level in the water wave band was measured at 2.0×10−8 (m/s2)2/Hz in 12 m of water. This level was observed to decrease rapidly with greater water depth. Seismic interface waves (microseisms) of power level approximately 5×10−10 (m/s2)2/Hz were observed in the range 0.25–1.0 Hz. This microseism power level was found to be roughly constant in water depths from 12 to 70 m. A quiet ‘‘notch’’ between the two wave bands, in the range 0.15–0.3 Hz, was observed. The background seismic level in this notch was determined to be less than 5×10−12 (m/s2)2/Hz. Extrapolations of the observed pressures and seabed motions into deeper water conditions are made.
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43.30.Nb Noise in water; generation mechanisms and characteristics of the field
43.40.Ph Seismology and geophysical prospecting; seismographs

Test results using a prototype synthetic aperture sonar

Peter T. Gough and Michael P. Hayes

J. Acoust. Soc. Am. Volume 86, Issue 6, pp. 2328-2333 (1989); (6 pages)

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In this paper, the operation is described of a prototype coherent synthetic aperture sonar (SAS) based on continuous transmission frequency modulation that covers a 1‐octave bandwidth. Images calculated from real data (collected from a sonar range in Loch Linnhe, Scotland) show that it is now possible to produce high‐quality images of the seafloor at realistic mapping rates. An air‐filled steel buoy was used as a test target, and several images are shown of this target using a variety of reconstruction algorithms.
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43.30.Pc Ocean parameter estimation by acoustical methods; remote sensing; imaging, inversion, acoustic tomography
43.30.Vh Active sonar systems

An exact solution for finite‐amplitude plane sound waves in a dissipative fluid

Hideto Mitome

J. Acoust. Soc. Am. Volume 86, Issue 6, pp. 2334-2338 (1989); (5 pages) | Cited 1 time

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The propagation of finite‐amplitude plane sound waves in a dissipative fluid can be described by Burgers’ equation, and its exact solution obtained. In this paper, an exact solution for the sound pressure, which is suitable for direct numerical computation of the waveform in the time domain, is derived. Numerical results illustrate that this solution describes the entire propagation process, including shock formation and decay. Computation limits are determined in connection with the computational system. It is found that computation is possible for D0>0.0114 and any value of X with the present system, where D0 indicates the importance of dissipation relative to nonlinearity and X is distance normalized by the lossless shock formation distance. It is also found that the solution for the limiting value of D0 connects smoothly with the Fubini solution for X<1 and with the Fay solution for X>3.5. Since the present solution is exact and yields the waveform at any distance without introducing the Fourier series expansion of finite terms, it can serve as a standard solution for various approximate methods. As examples, changes in the energy density and the saturation phenomena are shown.
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43.25.Cb Macrosonic propagation, finite amplitude sound; shock waves

Finite‐amplitude effects on ultrasound beam patterns in attenuating media

Clarence R. Reilly and Kevin J. Parker

J. Acoust. Soc. Am. Volume 86, Issue 6, pp. 2339-2348 (1989); (10 pages) | Cited 1 time

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Some problems relevant to medical ultrasonics are addressed through experimental measurements of focused, pure‐tone beam patterns under quasilinear conditions where significant nonlinearities are manifested. First, measurements in water provide a comparison of the beam patterns of the fundamental and nonlinearly generated harmonics against recent theoretical predictions of others. The radial beamwidths, presence and spacing of sidelobes, axial distances to peak pressures, focal shock parameter, time‐domain waveform asymmetry, and post‐focal falloff of the fundamental through fifth harmonics are discussed relative to various models under preshock conditions (σ<1). Second, the focused sources are placed in a more attenuating fluid to mimic the behavior of these fields in tissue. The changes in beam characteristics are examined relative to measurements at the same intensities in water, and relative to theoretical predictions. The results suggest that, given a known linear(low‐intensity) focused beam pattern in water, guidelines can be followed to predict the beam pattern of the fundamental and higher harmonics at higher intensities in water, and then in attenuating media such as tissue.
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43.25.Jh Reflection, refraction, interference, scattering, and diffraction of intense sound waves
43.80.Sh Medical use of ultrasonics for tissue modification (permanent and temporary)
43.30.Qd Global scale acoustics; ocean basin thermometry, transbasin acoustics

Effects of bubbly layers on wave propagation

Michael J. Miksis and Lu Ting

J. Acoust. Soc. Am. Volume 86, Issue 6, pp. 2349-2358 (1989); (10 pages) | Cited 2 times

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The transmission and reflection of an acoustic wave through a bubbly layer are investigated. Nonlinear model equations for the bubbly liquid are used. These equations first linearized and solved exactly for a time‐harmonic incident wave. Then, numerical solutions of the nonlinear system are found. It is found that even for a small amplitude incident pressure wave, it is possible to have nonlinear transmitted and reflected waves. The limit where the bubbly layer is thin relative to the incident wavelength is also considered. By using the method of matched asymptotic expansions, it is found that the bubbly layer can be replaced by an interface subject to the continuity of pressure and an effective nonlinear jump condition. The latter involves the internal effects of the layer. Solutions of this limiting case are compared with the numerical results and good agreement is found even when the ratio of the bubbly layer thickness to the incident wavelength is of order 1.
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43.25.Yw Nonlinear acoustics of bubbly liquids

An upper bound on acoustic reflectivity, and the Rayleigh approximation

John Lekner

J. Acoust. Soc. Am. Volume 86, Issue 6, pp. 2359-2362 (1989); (4 pages) | Cited 2 times

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Reflection of plane acoustic compressional waves at a stratified transitional layer between two fluid media is treated by means of a nonlinear differential equation for the reflection amplitude. When the normal component of the wave vector divided by the local density changes monotonically, the reflectance is shown to be no greater than that at a sharp transition between the same two media (at the same angle of incidence). A related Riccati‐type differential equation for the reflection amplitude leads to the Rayleigh (or weak‐reflection) approximation. This approximation is simple, easy to evaluate, and works well at all wavelengths provided that the reflection is weak.
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43.20.Fn Scattering of acoustic waves
43.20.Bi Mathematical theory of wave propagation
43.30.Bp Normal mode propagation of sound in water

Sound scattering of a plane wave obliquely incident on a cylinder

Tai‐bao Li and Mitsuhiro Ueda

J. Acoust. Soc. Am. Volume 86, Issue 6, pp. 2363-2368 (1989); (6 pages) | Cited 3 times

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The solution of sound scattering of a plane wave obliquely incident on an isotropic elastic cylinder of infinite length is obtained and verified by experiment. The solution is expressed in terms of phase angles associated with partial scattered waves. It is found that, when the angle of incidence is small, supplementary resonances, which are not present in the case of normal incidence, are excited. The peaks and dips resulting from the resonances appear in the farfield form function ‖f∞‖. Experimental results for several different metals show good agreement with the calculated ones.
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43.20.Fn Scattering of acoustic waves

Floquet wave properties in a periodically layered medium

M. Rousseau

J. Acoust. Soc. Am. Volume 86, Issue 6, pp. 2369-2376 (1989); (8 pages) | Cited 6 times

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In a periodically stratified medium, the acoustic propagation for wavelength of the order of the period is conveniently described by Floquet waves. A first part of this paper is concerned with a fluid medium and it completes previous results showing the existence of a pseudocritical angle. The extension to an elastic medium allows the introduction of the shear effects inside the layers. Several properties of Floquet waves are exhibited; the particular case of a medium composed of fluid and solid layers is also studied.
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43.20.Hq Velocity and attenuation of acoustic waves
43.20.Bi Mathematical theory of wave propagation

Shape perturbation and inertial mode coupling in cavities

P. Herzog and M. Bruneau

J. Acoust. Soc. Am. Volume 86, Issue 6, pp. 2377-2384 (1989); (8 pages) | Cited 3 times

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The influences of shape perturbation and inertial effects on the modal structure of acoustic fields are studied inside small cavities, taking into account dissipative phenomena near the walls. Both are shown to have similar effects on the acoustic field, leading to coupling and energy transfers between modes. Validity of the analytical model is discussed and compared with accurate experimental results for the lower‐order modes. Discrepancies are found to be less than 0.1 dB for small shape perturbations, as well as for rotations up to 1000°/s, which shows a very good agreement between the theoretical and experimental results. Qualitative aspects of the perturbed problem are also discussed and illustrated experimentally.
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43.20.Ks Standing waves, resonance, normal modes
43.20.Ye Measurement methods and instrumentation

Sound propagation in a waveguide with finite thermal conduction at the boundary

M. J. Anderson and P. G. Vaidya

J. Acoust. Soc. Am. Volume 86, Issue 6, pp. 2385-2396 (1989); (12 pages)

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The modal theory of sound propagation in an acoustic waveguide is extended to include the effect of finite heat conduction at the boundaries. A thermal‐impedance equation is derived that controls the conduction of heat from the acoustic medium to the waveguide boundary. The thermal impedance is characterized by a single dimensionless parameter that measures dynamic thermal impedance as it ranges continuously from infinitely conducting to fully insulated boundaries. The boundary‐value problem in the waveguide is then solved for rigid, no‐slip, and finite conducting boundaries. Perturbations from inviscid mode shapes and axial attenuation rates are calculated for the acoustic mode as well as the modal coefficients of the vorticity and entropy modes as they depend upon the thermal‐impedance parameter. It is found that the dependence of the preceding quantities on the thermal‐impedance parameter is described for the most part by one continuous function of this parameter.
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43.20.Mv Waveguides, wave propagation in tubes and ducts

Acoustic multipole logging in transversely isotropic poroelastic formations

Denis P. Schmitt

J. Acoust. Soc. Am. Volume 86, Issue 6, pp. 2397-2421 (1989); (25 pages) | Cited 11 times

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The properties of the modes generated by multipole sources in a fluid‐filled borehole embedded in (radially layered) formations that include transversely isotropic poroelastic layers are investigated. These layers are modeled following Biot’s and homogenization theories, under the assumption that the principal axes of symmetry of both the transversely isotropic skeleton and the complex permeability tensor are parallel to the vertical axis of the borehole. A general formulation based on the Thomson–Haskell method accounts for any combination of fluid, elastic, and poroelastic layers, either isotropic or transversely isotropic. The investigation is achieved through the computation of dispersion and attenuation curves, and frequency‐dependent sensitivity coefficients with respect to the parameters. In the presence of a fast or slow radially semi‐infinite transversely isotropic poroelastic formation with an impermeable borehole wall, the shear‐wave transverse isotropy of the skeleton can be determined using the low‐frequency parts of the fundamental modes generated by a monopole source and one of higher order. With a permeable interface, the fluid flow effects refer to the horizontal mobility (horizontal permeability/saturant fluid viscosity) and disables the determination of the shear‐wave transverse isotropy. Without this information, any horizontal mobility determination is incorrect. Whatever the nature of any fluid–poroelastic interface, the presence of radial layering decreases the reliability of any estimation of parameter related to the virgin formation except for the velocity and attenuation of the vertically propagating SV wave. Whatever the configuration, the transverse isotropy of the compressional wave velocity cannot be determined nor can that of the complex permeability tensor or the anelastic attenuation due to the polarization of the (quasi) body waves involved. The results of this work also show that, in contrast to the pure elastic situation, a transverse isotropy of the complex permeability tensor leads to slightly different quasi‐SV‐wave velocities along the principal directions of propagation at ultrasonic frequencies.
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43.20.Mv Waveguides, wave propagation in tubes and ducts

Method for computing spatial pulse response: Time‐domain approach

B. Piwakowski and B. Delannoy

J. Acoust. Soc. Am. Volume 86, Issue 6, pp. 2422-2432 (1989); (11 pages) | Cited 3 times

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The computer‐aided, time‐domain method is a proposal to determine the spatial pulse response for an arbitrarily shaped source and for arbitrary aperture velocity and delay distributions. The computational procedure ‘‘generates’’ the pulse response function by directly repeating the physical stages that accompany the creation of this phenomenon, such as radiation from the surface element, and propagation and summation in the observation point. The method is very simple mathematically, employing a simple algorithm, and can be easily implemented—even on a small minicomputer. The mathematical work required prior to the computation has been greatly simplified; the commonly studied behavior of the derivatives (arrival time/source point), as well as the exact temporal limits of the pulse response occurrence, need not be analyzed. The Dirac‐type free‐space Green’s function, as well as other arbitrary types of the causal Green’s function, can also be considered. The obtainable results are approximate, but computational precision depends only on the number of the elementary surfaces used to model the aperture, and, therefore, can be obtained practically, as desired. The method can also be easily used for computations of the transducer coupling functions and of the transient field diffracted by an arbitrary object. The nonplanar sources and objects can also be considered.
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43.20.Px Transient radiation and scattering

A method for computing acoustic fields based on the principle of wave superposition

Gary H. Koopmann, Limin Song, and John B. Fahnline

J. Acoust. Soc. Am. Volume 86, Issue 6, pp. 2433-2438 (1989); (6 pages) | Cited 28 times

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A method for computing the acoustic fields of arbitrarily shaped radiators is described that uses the principle of wave superposition. The superposition integral, which is shown to be equivalent to the Helmholtz integral, is based on the idea that the combined fields of an array of sources interior to a radiator can be made to reproduce a velocity prescribed on the surface of the radiator. The strengths of the sources that produce this condition can, in turn, be used to compute the corresponding surface pressures. The results of several numerical experiments are presented that demonstrate the simplicity of the method. Also, the advantages that the superposition method has over the more commonly used boundary‐element methods are discussed. These include simplicity of generating the matrix elements used in the numerical formulation and improved accuracy and speed, the latter two being due to the avoidance of uniqueness and singularity problems inherent in the boundary‐element formulation.
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43.20.Rz Steady-state radiation from sources, impedance, radiation patterns, boundary element methods

Nonlinearity, chaos, and the sound of shallow gongs

K. A. Legge and N. H. Fletcher

J. Acoust. Soc. Am. Volume 86, Issue 6, pp. 2439-2443 (1989); (5 pages) | Cited 2 times

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Experimental studies on several orchestral gongs of the tamtam and cymbal families suggest that two separate nonlinear mechanisms contribute to the evolution of the sound. The first mechanism is an upward cascade of energy from the low‐frequency modes initially excited into high‐frequency modes, caused by coupling between tension and shear stresses at regions of sharp change in shape of the gong. The second is a transition from simple periodic nonlinear modal motion to multiple fractional subharmonics, or even chaotic motion, which fills out the radiated spectrum at frequencies between those of the normal linear modes. Each of these mechanisms has considerable hysteresis, so that the spectrum of the radiated sound evolves over a period of several seconds. Measurements using high‐level sinusoidal excitation have elucidated some of the features of this behavior.
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43.75.Kk Bells, gongs, cymbals, mallet percussion, and similar instruments
43.40.Ey Vibrations of shells

Determining the extent of coarticulation: Effects of experimental design

Carole E. Gelfer, Fredericka Bell‐Berti, and Katherine S. Harris

J. Acoust. Soc. Am. Volume 86, Issue 6, pp. 2443-2445 (1989); (3 pages) | Cited 1 time

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The purpose of this letter is to explore some reasons for what appear to be conflicting reports regarding the nature and extent of anticipatory coarticulation, in general, and anticipatory lip rounding, in particular. Analyses of labial electromyographic and kinematic data using a minimal‐pair paradigm allowed for the differentiation of consonantal and vocalic effects, supporting a frame versus a feature‐spreading model of coarticulation. It is believed that the apparent conflicts of previous studies of anticipatory coarticulation might be resolved if experimental design made more use of contrastive minimal pairs and relied less on assumptions about feature specifications of phones.
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43.70.Bk Models and theories of speech production
43.70.Aj Anatomy and physiology of the vocal tract, speech aerodynamics, auditory kinetics

Comments on ‘‘Acoustic transfer characteristics in human middle ears studied by a SQUID magnetometer method’’ [J. Acoust. Soc. Am. 82, 1646–1654 (1987)]

Richard L. Goode, Koshiro Nakamura, Kiyofumi Gyo, and Hiroshi Aritomo

J. Acoust. Soc. Am. Volume 86, Issue 6, pp. 2446-2449 (1989); (4 pages) | Cited 3 times

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The study by Brenkman et al. [J. Acoust. Soc. Am. 82, 1646–1654 (1987)] of malleus umbo and anterior crus of stapes displacement in 14 human temporal bones shows a mean −7.3‐dB/oct slope above 1.0 kHz for stapes displacement in response to a 80‐dB SPL input at the eardrum. The slope they obtained for midfrequency (1.0–4.0 kHz) stapes displacement is significantly flatter than what was found previously [Gyo et al., Acta Otolaryngol. 103, 87–95 (1987); Gundersen, Prostheses in the Ossicular Chain (University Park, Baltimore, MD, 1971); Kringlebotn and Gundersen, J. Acoust. Soc. Am. 77, 159–164 (1985); Vlaming and Feenstra, Clin. Otolaryngol. 11, 353–363 (1986a)]; in these studies, stapes displacement rolled off at −12.0 to −14.9 dB/oct above 1.0 kHz. It appears that their mean midfrequency stapes displacement slope has been flattened by some unusual results in a small number of ears. Possible reasons for these results are discussed.
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43.64.Ha Acoustical properties of the outer ear; middle-ear mechanics and reflex
43.64.Yp Instruments and methods

Correction for an auditory periphery model

C. David Covington

J. Acoust. Soc. Am. Volume 86, Issue 6, pp. 2450-2451 (1989); (2 pages)

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Payton [K. L. Payton, J. Acoust. Soc. Am. 83, 145–162 (1988)] constructed a model of the auditory periphery including a simulation of basilar membrane (BM) mechanics based on the numerical solution of the differential equation relating membrane displacement to stapes velocity, membrane compliance, and membrane damping. Payton indicated that the model membrane length parameter was arbitrarily doubled to 5.0 cm in order to avoid what appeared to be reflections. Even with this compensation, Payton relied on the fact that the middle‐ear model essentially removed frequency components significantly below 1000 Hz, thereby attenuating the reverse traveling waves before they reached the region of the basilar membrane being modeled. In using the model, an error in the basilar membrane simulation module was isolated due to a data mapping discrepancy. Correcting this error eliminates the spurious response, restores the model to physiological dimensions, improves the execution speed versus resolution trade‐off in the membrane component, and corrects a phase error introduced to the model.
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43.64.Kc Cochlear mechanics
43.64.Bt Models and theories of the auditory system

Notions of conventional stereo in ‘‘Interaural cross‐correlation coefficients in stereo‐reproduced sound fields’’ [J. Acoust. Soc. Am. 85, 780–786 (1989)]

Duane H. Cooper

J. Acoust. Soc. Am. Volume 86, Issue 6, pp. 2452-2454 (1989); (3 pages)

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Characterizations of stereo systems in Tohyama and Suzuki [J. Acoust. Soc. Am. 85, 780–786 (1989)] appear to be largely limited to diagrams of loudspeaker layout, including one for a so‐called conventional stereo. Because of this, many readers may be unaware that the conclusions drawn are not generally applicable without further qualification. Omission of signal‐format characterizations could, in principle, require the exclusion of certain stereo systems. In particular, one four‐channel system could be regarded as excluded because it overturns a conclusion of Tohyama and Suzuki. Further, one stereo system that uses a conventional two‐loudspeaker layout, but uses particularly apt signal formats, also overturns a conclusion.
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43.55.Br Room acoustics: theory and experiment; reverberation, normal modes, diffusion, transient and steady-state response
43.38.Vk Stereophonic reproduction
43.66.Pn Binaural hearing

Range‐dependent extensions to Munk’s canonical sound‐speed profile

J. S. Robertson

J. Acoust. Soc. Am. Volume 86, Issue 6, pp. 2454-2456 (1989); (3 pages)

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Range‐dependent extensions to Munk’s canonical deep water sound‐speed profile are discussed. A formalism is presented which ensures that the main properties of the profile are preserved even as the profile changes from place to place in the ocean. These extensions permit one straightforward way to formulate relatively simple analytical expressions for these profiles useful as inputs to propagation models.
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43.30.Es Velocity, attenuation, refraction, and diffraction in water, Doppler effect

Surface waves on a solid half‐space

Giacomo Caviglia, Angelo Morro, and Enrico Pagani

J. Acoust. Soc. Am. Volume 86, Issue 6, pp. 2456-2459 (1989); (4 pages) | Cited 1 time

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Inhomogeneous waves in viscoelastic solids are considered with the aim of a thorough characterization of surface waves in a solid half‐space. To ascertain the existence of surface waves and to investigate their properties, a general scheme is established that is appropriate for numerical developments. Viscoelastic and elastic solids are examined in detail and previous results on admissible surface waves are generalized.
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43.20.Bi Mathematical theory of wave propagation
43.35.Mr Acoustics of viscoelastic materials
43.35.Pt Surface waves in solids and liquids

Erratum: ‘‘Finite element solution to the parabolic wave equation’’ [J. Acoust. Soc. Am. 84, 1405–1413 (1988)]

Dehua Huang

J. Acoust. Soc. Am. Volume 86, Issue 6, pp. 2460-2460 (1989); (1 page)

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Abstract Unavailable
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43.30.Bp Normal mode propagation of sound in water
43.30.Hw Rough interface scattering
43.20.Bi Mathematical theory of wave propagation
99.10.Cd Errata
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