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Jan 1991

Volume 89, Issue 1, pp. 1-497

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Temporal response of coupled one‐dimensional dynamic systems

J. Dickey and G. Maidanik

J. Acoust. Soc. Am. Volume 89, Issue 1, pp. 1-9 (1991); (9 pages) | Cited 1 time

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A formalism is presented that describes the response of a complex of coupled one‐dimensional dynamic systems to an impulse drive. The formalism is based on an impulse response operator that relates a drive applied to one point in the complex to the response at any point in the complex. The formalism is derived directly in the time domain and the impulsive drives which can be accommodated must be finite in time and applied at a spatial point. The constituent systems must be one‐dimensional and possess a pulse propagation velocity that is not a function of position within the system. Systems interact through junctions that also define their spatial extents. The junctions are characterized by reflection and transmission coefficients that modulate the amplitude of reverberant components and by delays in the reflections and transmissions. Propagation in the systems is characterized by losses. Several simplistic examples are calculated and presented to illustrate the type of information that the formalism can provide.
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43.20.Bi Mathematical theory of wave propagation
43.20.Fn Scattering of acoustic waves
43.20.Mv Waveguides, wave propagation in tubes and ducts
43.40.At Experimental and theoretical studies of vibrating systems

Calculation of the impulse response of a rigid sphere using the physical optic method and modal method jointly

Zhigang Sun, Gérard Gimenez, Didier Vray, and Florence Denis

J. Acoust. Soc. Am. Volume 89, Issue 1, pp. 10-18 (1991); (9 pages) | Cited 2 times

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In this paper a practical method is proposed to calculate the acoustical response of a rigid sphere. This method combines the physical optic method, which gives good results at high frequencies, with the modal method, which is suitable at low frequencies. This gets around the problems that arise when only one of these methods is used, namely the failure of the physical optic method at low frequencies and the convergence difficulties of the modal method at high frequencies. Here, the impulse response (response to a Dirac pressure transmission) of a rigid sphere for a backscattering situation is calculated.
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43.20.Dk Ray acoustics
43.20.Fn Scattering of acoustic waves
43.20.Px Transient radiation and scattering
43.30.Jx Radiation from objects vibrating under water, acoustic and mechanical impedance

Acoustic scattering by two‐dimensionally rough interfaces between dissipative acoustic media—Full wave, physical acoustics, and perturbation solutions

Ezekiel Bahar

J. Acoust. Soc. Am. Volume 89, Issue 1, pp. 19-26 (1991); (8 pages)

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Explicit expressions for the acoustic pressure and velocity scattered by two‐dimensionally rough surfaces are derived using a full‐wave approach. The conditions under which these solutions merge with the physical acoustic and small perturbation solutions in the high‐ and low‐frequency limits are given. The acoustic media on both sides of the rough interface are characterized by their bulk modulus, equilibrium density, and relaxation time (to account for dissipation); the Dirichlet and Neumann boundary conditions are treated as special cases. The closed‐form full‐wave expressions for the surface element scattering coefficients are significantly different for these special cases. However, the corresponding physical optics solutions differ only in the sign of the acoustic reflection coefficient. The full‐wave solution can be applied to composite surfaces with a broad range of roughness scales. Since it accounts for specular point and diffuse scattering in a unified self‐consistent manner, there is no need to adopt a two‐scale model of the rough surface. Thus the full‐wave expressions for the rough surface scattered fields are also more suitable for application to broadband (transient) excitation problems and for the solution of inverse problems.
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43.20.Fn Scattering of acoustic waves
43.20.Dk Ray acoustics
43.20.Mv Waveguides, wave propagation in tubes and ducts
43.30.Hw Rough interface scattering

Propagation, generation, and detection of SAW in a multiperiodic system of metal strips on a piezoelectric substrate

Eugeniusz Danicki and Dariusz Gafka

J. Acoust. Soc. Am. Volume 89, Issue 1, pp. 27-38 (1991); (12 pages)

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An infinite periodic system of groups of equidistant metal strips deposited on a piezoelectric half‐space is considered. Such a system may be useful for analyzing a single group of strips if the period of the groups is sufficiently large. A dispersion relation for generally slanted surface acoustic wave (SAW) propagation with respect to electrodes is derived and analyzed. Numerical examples are given for a wave propagating along, and perpendicular to the electrodes. A functional relationship for strip currents dependent on strip potentials has been derived. This can be applied for analyzing interdigital transducers (IDT) having a finite number of periodic fingers. Bragg’s reflection of SAW from metal strips is also analyzed.
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43.20.Mv Waveguides, wave propagation in tubes and ducts
43.20.Fn Scattering of acoustic waves
43.35.Pt Surface waves in solids and liquids
43.38.Rh Surface acoustic wave transducers

A wave‐vector–time‐domain technique to determine the transient acoustic radiation loading on cylindrical vibrators in an inviscid fluid with axial flow

D. D. Ebenezer and Peter R. Stepanishen

J. Acoust. Soc. Am. Volume 89, Issue 1, pp. 39-51 (1991); (13 pages)

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A wave‐vector–time‐domain method that was used to obtain the transient acoustic radiation loading on vibrating finite cylinders is extended to include the effects of the presence of inviscid axial flow. The method is based on the use of the in vacuo modes of vibration of the shell which have infinite rigid extensions. The solution to the boundary value problem for the pressure is first obtained in wave‐vector–time space. The time‐dependent modal forces are then expressed as a sum of the modal radiation impulse responses of the finite cylinder convolved with the time‐dependent modal velocities. The modal radiation impulse responses are obtained by using the impulse responses of an infinite cylinder and the modes in wave‐vector space. The approach can thus be easily used to obtain the radiation impulse responses for various boundary conditions, length to radius ratios, and arbitrary space‐ and time‐dependent surface velocities. Numerical results are presented for a wide range of Mach numbers and for length to radius ratios of simply supported cylindrical shells.
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43.20.Tb Interaction of vibrating structures with surrounding medium
43.20.Px Transient radiation and scattering
43.20.Rz Steady-state radiation from sources, impedance, radiation patterns, boundary element methods
43.28.Py Interaction of fluid motion and sound, Doppler effect, and sound in flow ducts

Simulation of the propagation of an acoustic wave through a turbulent velocity field: A study of phase variance

M. Karweit, Ph. Blanc‐Benon, D. Juvé, and G. Comte‐Bellot

J. Acoust. Soc. Am. Volume 89, Issue 1, pp. 52-62 (1991); (11 pages) | Cited 10 times

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A numerical technique for simulating the behavior of an acoustic wave propagating through a turbulent medium is introduced. The technique involves two elements: the generation of 3‐D, random, hypothetical, isotropic velocity fields in terms of a collection of discrete Fourier velocity modes; and the integration of the ray‐trace equations to describe the trajectories of points tagging an acoustic wave front. The propagation times for these points to travel fixed distances through each of an ensemble of random velocity fields are recorded, and the variance of travel time (or acoustic phase) over the ensemble is calculated. In numerical ray‐trace experiments through fields having average perturbation indices ≊0.01, acoustic travel‐time variances are obtained that have a higher‐order dependence on travel distance R than the classical Chernov prediction—a linear increase with R. The Chernov result is obtained, however, when the rays are confined to axial trajectories. Additional numerical experiments integrating the stochastic Helmholtz equation and its parabolic approximation yield time‐variance estimates consistent with the ray‐trace results. Predictions from these simulations are then applied to the laboratory experiments of Blanc‐Benon and found to be in qualitative agreement. Finally, a set of 2‐D travel‐time experiments are presented to identify differences between source–receiver eigenray propagation and preassigned initial direction ray propagation.
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43.20.Wd Analogies
43.20.Fn Scattering of acoustic waves
43.28.Py Interaction of fluid motion and sound, Doppler effect, and sound in flow ducts
43.20.Dk Ray acoustics

Source field modeling by self‐consistent Gaussian beam superposition (two‐dimensional)

L. B. Felsen, J. M. Klosner, I. T. Lu, and Z. Grossfeld

J. Acoust. Soc. Am. Volume 89, Issue 1, pp. 63-72 (1991); (10 pages) | Cited 2 times

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Gaussians are useful models for high‐frequency source field inputs into complex environments because they approximate the outputs of certain transducers, have favorable spectral and filtering properties, and can be propagated similar to ray fields. By recent analytic developments, any source field can be expressed exactly as a self‐consistent superposition of Gaussians on a discretized (configuration)–(wave number) phase space lattice. This extends the use of Gaussians systematically to realistic transducer outputs. The method is already being applied to electromagnetic and acoustic propagation. It is here extended to modeling the radiation from transducers into an elastic solid. Restricting to the two‐dimensional case, a distribution of forces over a finite, one‐dimensional planar aperture is expanded self‐consistently into Gaussian basis elements, which are then propagated into the unbounded medium. Numerical results reveal how successive addition of Gaussians for the compressional and shear potentials, as well as the displacements, homes in systematically on the assumed aperture profile, and on an independently generated numerical reference solution for the radiated near and far fields. Moreover, it is demonstrated how different self‐consistent choices of beams affect the convergence. Furthermore, the validity of complex‐source‐point modeling of the Gaussians is explored for later applications where the input will be required to propagate across interfaces, as in a layered medium.
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43.20.Ye Measurement methods and instrumentation
43.20.Wd Analogies
43.60.Qv Signal processing instrumentation, integrated systems, smart transducers, devices and architectures, displays and interfaces for acoustic systems

A small volume thermodynamic system for B/A measurement

Jian Zhang and Floyd Dunn

J. Acoust. Soc. Am. Volume 89, Issue 1, pp. 73-79 (1991); (7 pages) | Cited 1 time

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A thermodynamic method capable of determining the B/A value of 4‐ml sample volumes is described. The method involves a procedure in which the static pressure of the sample is altered in a short period of time, to approximate an adiabatic process, during which the ultrasonic velocity is measured. The velocity change so determined is used to calculate the B/A value. The B/A measurement error is less than 0.7%.
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43.25.Zx Measurement methods and instrumentation for nonlinear acoustics

Influences of structural factors of biological media on the acoustic nonlinearity parameter B/A

Jian Zhang, Mark S. Kuhlenschmidt, and Floyd Dunn

J. Acoust. Soc. Am. Volume 89, Issue 1, pp. 80-91 (1991); (12 pages) | Cited 2 times

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The influence of structural factors of biological media on the acoustic nonlinearity parameter B/A have been studied at the tissue, cellular, and molecular levels, using the thermodynamic and finite amplitude methods. B/A was determined as the structural factors of the media were altered physically and biochemically, while chemical composition was maintained unchanged. Significant structural dependencies of B/A were observed at all three levels; 26% of the dry weight contribution to the total B/A (the B/A value with water contribution subtracted) is due to the cell–cell adhesive force in liver tissue, 20% is due to the hepatocyte cellular structure, and 15% is due to secondary and tertiary protein structure.
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43.25.Ba Parameters of nonlinearity of the medium
43.80.Cs Acoustical characteristics of biological media: molecular species, cellular level tissues

Propagation of the difference frequency wave generated by a truncated parametric array through a water–sediment interface

Wen‐sen Liu and Zhen‐xia Xu

J. Acoust. Soc. Am. Volume 89, Issue 1, pp. 92-97 (1991); (6 pages)

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Muir et al. [T. G. Muir, C. W. Horton, Sr., and L. A. Thompson, J. Sound Vib. 64, 539–551 (1979)] observed that the propagation direction of the sound wave in the sediment insonified by a parametric array departed significantly from the prediction of Snell’s law. The wave fronts penetrated more steeply into the sediment and the attenuation at postcritical incidence was less than that predicted by the plane wave theory. It was found that mainly due to the variation of the length of the parametric array, the direction of the refracted sound wave occurs at or near the line‐of‐sight between the projector and the hydrophone. It has been proved, both theoretically and experimentally, that Snell’s law is still valid when the length of parametric array is kept constant. At postcritical incidence, the penetration of a parametric array can be deeper due to the contribution of the lateral wave and secondary sources close to the boundary.
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43.25.Jh Reflection, refraction, interference, scattering, and diffraction of intense sound waves
43.30.Ma Acoustics of sediments; ice covers, viscoelastic media; seismic underwater acoustics

An acoustical investigation method for a bar with nonlinear inclusions

A. A. Lokshin, M. A. Itskovits, and V. E Rok

J. Acoust. Soc. Am. Volume 89, Issue 1, pp. 98-100 (1991); (3 pages)

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In this paper an acoustical investigation method based on the nonlinear interaction of waves is proposed. It is assumed that only the ends of the bar are accessible for investigation.
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43.25.Zx Measurement methods and instrumentation for nonlinear acoustics
43.35.Zc Use of ultrasonics in nondestructive testing, industrial processes, and industrial products
43.40.Cw Vibrations of strings, rods, and beams

Dispersion of impulse sound above a curved surface

Gilles A. Daigle and Richard Raspet

J. Acoust. Soc. Am. Volume 89, Issue 1, pp. 101-106 (1991); (6 pages)

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Controlled experiments made indoors above a carefully constructed curved surface using pure tones have shown that the magnitude of the diffracted sound energy deep within the acoustic shadow can be accurately calculated from a residue series solution [Berry and Daigle, J. Acoust. Soc. Am 83, 2047 (1988)]. The theory also predicts dispersion, however, this aspect was not verified by the pure tone experiments. When the theory was used to predict impulse sound propagation in a refractive atmosphere the measured waveforms appeared to show considerably less dispersion than predicted [Don and Cramond, J. Acoust. Soc. Am. 80, 302 (1986)]. In this paper, impulse sound measurements made indoors above the same carefully constructed curved surface are described as well as outdoors measurements above a grass‐covered curved surface. In particular, the measured pulse shapes are compared with the theoretical waveforms in order to verify the predicted dispersion. The outdoor experiments investigate the potential effects of atmospheric turbulence on the predicted dispersion. Satisfactory agreement between the measured and predicted pulse shapes is found in both the indoor and outdoor experiments.
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43.28.Fp Outdoor sound propagation through a stationary atmosphere, meteorological factors
43.20.Hq Velocity and attenuation of acoustic waves
43.20.Fn Scattering of acoustic waves

The relationship between upward refraction above a complex impedance plane and the spherical wave evaluation for a homogeneous atmosphere

Richard Raspet, Gordon E. Baird, and Wenliang Wu

J. Acoust. Soc. Am. Volume 89, Issue 1, pp. 107-114 (1991); (8 pages) | Cited 6 times

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An investigation has been carried out on the relationship between the residue series method for the prediction of sound propagation in an upward refracting atmosphere and the spherical wave analysis of sound propagation in a homogeneous atmosphere. It is shown that, in the limit of small sound velocity gradients, the Airy function solution developed by Pierce for sound propagation over the earth’s surface does approach the Sommerfeld integral for spherical wave reflection in a homogeneous atmosphere for a limited range of values of wave number. For complex impedance with phases greater than π/3, it is found that the surface wave pole identified for sound propagation in a homogeneous atmosphere is present in the upward refracting atmosphere. This pole arises from the residue series. Methods suggested in the literature for searching for the poles will fail for impedances with phase angles greater than π/3.
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43.28.Fp Outdoor sound propagation through a stationary atmosphere, meteorological factors
43.20.Bi Mathematical theory of wave propagation
43.20.Fn Scattering of acoustic waves

Evaluations of the analytic solution for the acoustic field in an ideal wedge and the approximate solution in a penetrable wedge

Lian Sheng Wang and Nicholas G. Pace

J. Acoust. Soc. Am. Volume 89, Issue 1, pp. 115-124 (1991); (10 pages) | Cited 1 time

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Uniform asymptotic approximations to the analytic solution for the acoustic field of a cw point source in an ideal wedge [M. J. Buckingham, Proceedings of the NATO Advanced Research Workshop on Hybrid Formulation of Wave Propagation and Scattering (Nijhoff, Dordrecht, The Netherlands, 1984), pp. 77–105] and to the approximate solution in a penetrable wedge [M. J. Buckingham, J. Acoust. Soc. Am. 82, 198–210 (1987)] are obtained by a stationary phase method (SPM). Comparisons of the solutions are made. Very good agreements are found in the bright zones, the caustics, and the shadow zones of the sustained normal modes in small angle wedges, provided that the source is at a range that is not shorter than the range at which the lowest mode can be excited, or the source and the receiver are well separated. One of the major advantages of the present representations is that, in comparison with numerical integration, the results can be generated rapidly with a satisfactory accuracy.
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43.30.Bp Normal mode propagation of sound in water
43.30.Dr Hybrid and asymptotic propagation theories, related experiments
43.20.Fn Scattering of acoustic waves

Rapid computation of acoustic fields in three‐dimensional ocean environments

W. A. Kuperman, Michael B. Porter, John S. Perkins, and Richard B. Evans

J. Acoust. Soc. Am. Volume 89, Issue 1, pp. 125-133 (1991); (9 pages) | Cited 10 times

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Adiabatic and coupled‐mode theory is amenable to precalculations that can subsequently be used in a nonredundant manner to perform rapid three‐dimensional acoustic field computations for a complex ocean environment. Algorithms have been developed to take advantage of both horizontal and vertical precalculated quantities. Complex three‐dimensional field computations are then reduced to ‘‘spreadsheet’’ type manipulations of partial solutions to the wave equation. The method is illustrated by applying it to a Gulf Stream environment near the continental shelf. Results from adiabatic, coupled‐mode, and parabolic‐equation computations are compared.
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43.30.Bp Normal mode propagation of sound in water
43.20.Ks Standing waves, resonance, normal modes
92.10.Vz Underwater sound

An energy‐conserving parabolic equation incorporating range refraction

I. W. Schurman, W. L. Siegmann, and M. J. Jacobson

J. Acoust. Soc. Am. Volume 89, Issue 1, pp. 134-144 (1991); (11 pages)

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A new parabolic equation (PE) is presented that is independent of k0 and capable of handling relatively large range variations in the index of refraction. This equation is similar to, and ostensibly simpler than, an earlier range refraction PE (RAREPE). The modified range refraction parabolic equation (MOREPE) is obtained by a transformation approach, and operator and multiscale formalisms are described to validate the equation. Principal properties of MOREPE are developed, including energy conservation and possession of the correct (Helmholtz) rays in the high‐frequency, small‐angle limit. Exact solutions with range variation in sound speed are presented to illustrate differences between standard PE (SPE) and MOREPE. Propagation examples in range‐independent environments demonstrate close agreement between MOREPE and SPE, while examples with strong range dependence exhibit significant differences between the two equations in their predictions of acoustic intensity. Analytical and numerical comparisons of solutions to the one‐way Helmholtz equation (HE1), MOREPE, and SPE demonstrate the increased accuracy of MOREPE over SPE in range‐dependent environments.
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43.30.Bp Normal mode propagation of sound in water

Coupled ocean‐acoustic model studies of sound propagation through a front

A. D. Heathershaw, C. E. Stretch, and S. J. Maskell

J. Acoust. Soc. Am. Volume 89, Issue 1, pp. 145-155 (1991); (11 pages)

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A three‐dimensional (3‐D) numerical ocean model has been used to study sound propagation through an ocean front. The model has been used to provide environmental data for input to a range‐dependent acoustic model to study the effect of eddies that form at the front on sound propagation characteristics. The model was set up in an idealized ocean domain but with the model physics and the temperature contrast across the front configured so as to represent the polar front east of Iceland. Acoustic ray tracing was carried out to illustrate the effect of frontal eddy features on sound propagation paths, and propagation loss calculations were performed to quantify their effect acoustically. It was found that dependent upon sound source/receiver depth combinations, the effect of the front and the eddies was to increase propagation loss by as much as 10–20 dB. This is comparable with the magnitude of the frontal effect that is seen in studies using analytical models of ocean fronts and with acoustic calculations that are based on measured environmental data. However, the results of this study have also shown that the acoustic predictions may be sensitive to the choice of ocean model parameter, in particular the horizontal eddy viscosity coefficient.
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43.30.Cq Ray propagation of sound in water
43.30.Zk Experimental modeling

The duct leakage relation for the surface sound channel

D. E. Weston, C. G. Esmond, and A. Ferris

J. Acoust. Soc. Am. Volume 89, Issue 1, pp. 156-164 (1991); (9 pages) | Cited 2 times

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The leakage attenuation from a duct is simply related to the field level outside the duct, and the relation can be applied to the surface sound channel. High‐frequency measurements over the Biscay Abyssal Plain support the predicted relation and indicate that the loss is mainly due to scattering at very shallow angles, presumably from the surface waves. Similarly low‐frequency measurements in the same area show a diffraction loss occurring with effective angles that are again very shallow. Measurements by Reynolds and Pryce at 7.5 kHz are also shown to correspond very closely to low‐angle scattering, ruling out any large contribution from entrained bubbles. In addition, it is possible to estimate the residual bulk absorption. But their results at 3.25 kHz show marked additional effects that are interpreted as wide‐angle scattering and absorption due to small fish, and the existence of such deep‐water fish attenuation is thought to be both novel and important. Use of our leakage relation has helped to identify and to disentangle five separate loss mechanisms.
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43.30.Dr Hybrid and asymptotic propagation theories, related experiments
43.30.Ft Volume scattering
43.20.Mv Waveguides, wave propagation in tubes and ducts

Plane‐wave analysis of acoustic signals in a sandy sediment

Robert A. Altenburg, Nicholas P. Chotiros, and Carl M. Faulkner

J. Acoust. Soc. Am. Volume 89, Issue 1, pp. 165-170 (1991); (6 pages) | Cited 3 times

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A weighted least‐squares algorithm was developed to fit a plane wave to arrival time differences yielding wave front direction and speed estimates. The algorithm was applied to acoustic pulses entering a sandy sediment through the water–sediment interface. An acoustic projector in the water column was used to insonify an array of sensors embedded in the sediment. Pulsed carriers, from 5 to 80 kHz, were projected toward the sediment interface at grazing angles below, near, and above the critical value. The plane‐wave fit was found to be good in all cases.
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43.30.Ma Acoustics of sediments; ice covers, viscoelastic media; seismic underwater acoustics

Phase conjugation in underwater acoustics

Darrell R. Jackson and David R. Dowling

J. Acoust. Soc. Am. Volume 89, Issue 1, pp. 171-181 (1991); (11 pages) | Cited 76 times

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Phase‐conjugate mirrors are used in optics to compensate for aberrations caused by inhomogeneities in the propagation medium and by imperfections in optical components. In acoustics, analogous behavior can be achieved by a time‐reversed retransmission of signals received by an array. Compensation for multipath propagation and array imperfections is automatic and does not require knowledge of the detailed properties of either the medium or the array. The behavior of acoustic phase‐conjugate arrays is illustrated in several examples, some highly idealized and some more realistic. The effects of aperture size and inhomogeneities in the propagation medium are treated for both the near‐field and far‐field regions. It is concluded that phase‐conjugate arrays offer an attractive approach to some long‐standing problems in underwater acoustics.
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43.30.Yj Transducers and transducer arrays for underwater sound; transducer calibration
43.30.Vh Active sonar systems
43.30.Bp Normal mode propagation of sound in water
43.20.Fn Scattering of acoustic waves

A model for the propagation and scattering of ultrasound in tissue

Jørgen Arendt Jensen

J. Acoust. Soc. Am. Volume 89, Issue 1, pp. 182-190 (1991); (9 pages) | Cited 11 times

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An inhomogeneous wave equation is derived describing propagation and scattering of ultrasound in an inhomogeneous medium. The scattering term is a function of density and propagation velocity perturbations. The integral solution to the wave equation is combined with a general description of the field from typical transducers used in clinical ultrasound to yield a model for the received pulse‐echo pressure field. Analytic expressions are found in the literature for a number of transducers, and any transducer excitation can be incorporated into the model. An example is given for a concave, nonapodized transducer in which the predicted pressure field is compared to a measured field.
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43.35.Bf Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in liquids, liquid crystals, suspensions, and emulsions
43.80.Qf Medical diagnosis with acoustics

A study of a vehicle ground speed sensor using the ultrasonic wave doppler effect

Hiroshi Kobayashi, Toshiya Kimura, and Masami Negishi

J. Acoust. Soc. Am. Volume 89, Issue 1, pp. 191-195 (1991); (5 pages)

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The Doppler effect is composed of two phenomena, the propagation in the air and the reflection from the road surface of the ultrasonic wave signal. A detailed investigation was made of the relation between these two phenomena and the S/N and frequency bandwidth of the Doppler signal. It was clarified that the best transmission conditions were achieved with a wavelength of 3 mm and a directivity angle of 5 deg. The best reception condition was attained with a new method for sensing the Doppler signal. This method involves setting the reception frequency at a level determined by the optimum transmission conditions.
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43.35.Yb Ultrasonic instrumentation and measurement techniques
43.28.Bj Mechanisms affecting sound propagation in air, sound speed in the air
43.38.Fx Piezoelectric and ferroelectric transducers

Wave propagation in a piezoelectric human bone of arbitrary cross section with a circular cylindrical cavity

H. S. Paul and M. Venkatesan

J. Acoust. Soc. Am. Volume 89, Issue 1, pp. 196-199 (1991); (4 pages) | Cited 1 time

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A theoretical study of wave propagation in a piezoelectric cylinder of infinite length of arbitrary cross section with a circular cylindrical cavity of class 6 is investigated. The frequency equations are obtained by using the Fourier expansion collocation method and are analyzed numerically. The frequencies are evaluated for circular, elliptic, and cardioidal sections of bone and are tabulated. A plot of frequency spectrum is also presented for the cardioidal cross‐section bar.
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43.40.Cw Vibrations of strings, rods, and beams

Active control of total vibratory power flow in a beam. I: Physical system analysis

Jie Pan and Colin H. Hansen

J. Acoust. Soc. Am. Volume 89, Issue 1, pp. 200-209 (1991); (10 pages) | Cited 7 times

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Excitation of a beam may produce a combination of longitudinal, flexural, and torsional waves. The active control of one kind of wave by an actuator may create waves of the other kinds which may not be excited under the uncontrolled conditions. The generation and propagation of each wave in the beam depend upon the distribution of the forces, the geometrical shape and prestress condition of the beam, and the discontinuity and boundary conditions. This paper concentrates on the effect of the excitation and control forces on these waves and the control of the total power flow along a beam of infinite length and rectangular cross section. An expression for the power flow for an arbitrary distributed point excitation force and an arbitrary distributed point control force is obtained. This expression allows a study of the nature of the power flow for each wave under an excitation force and the effect of the control forces on these waves when the total power flow is minimized.
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43.40.Yq Instrumentation and techniques for tests and measurement relating to shock and vibration, including vibration pickups, indicators, and generators, mechanical impedance
43.40.Cw Vibrations of strings, rods, and beams

Modeling of shape memory alloy hybrid composites for structural acoustic control

C. A. Rogers, C. Liang, and C. R. Fuller

J. Acoust. Soc. Am. Volume 89, Issue 1, pp. 210-220 (1991); (11 pages)

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Experimental demonstration of active vibration and structural acoustic control using shape memory alloy (SMA) hybrid composites [C. A. Rogers, in Proceedings of the International Congress on Recent Developments in Air and Structure Borne Sound and Vibration (to be published)] has provided the motivation for investigating new control schemes and developing more accurate models. This paper will briefly describe newly developed constitutive models for shape memory alloy actuators and the hybrid material system. A general dynamical model for laminated SMA hybrid composite beams and plates will be presented with several theoretical results. A new structural acoustic model for laminated composite plates [Liang et al., J. Sound Vib. (to be published)] will be briefly described and the potential for active structural acoustic control using SMA hybrid composites demonstrated by numerical simulation.
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43.40.Yq Instrumentation and techniques for tests and measurement relating to shock and vibration, including vibration pickups, indicators, and generators, mechanical impedance
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