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Aug 1989

Volume 86, Issue 2, pp. 463-868

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Attenuation of sound in marine sediments: A review with emphasis on new low‐frequency data

Alick C. Kibblewhite

J. Acoust. Soc. Am. Volume 86, Issue 2, pp. 716-738 (1989); (23 pages) | Cited 29 times

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In many situations, the acoustic properties of the bottom are important, and considerable effort has been directed at their elucidation over the whole frequency range of interest to underwater acoustics. At low frequencies, experimental measurement of these properties is particularly difficult and uncertainty exists in the values of some key parameters. The determination of compressional and shear wave attenuation has been especially challenging and it is not surprising that debate has persisted as to the magnitude of this property and its overall dependence on frequency at low frequencies. This paper attempts to examine this question through a review of the relevant literature from rock mechanics and underwater acoustics, with a special emphasis on low‐frequency data.
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43.30.Ma Acoustics of sediments; ice covers, viscoelastic media; seismic underwater acoustics

Instrumentation for in situ acoustical measurements of bubble spectra under breaking waves

Nigel Breitz and Herman Medwin

J. Acoust. Soc. Am. Volume 86, Issue 2, pp. 739-743 (1989); (5 pages) | Cited 12 times

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A floating acoustical resonator has been developed to determine numbers and sizes of bubbles in the region of spilling breakers in the open sea. The change of Q of several modes of the one‐dimensional resonator has been used to infer, simultaneously, bubble populations of nine radii between 30 and 270 μm; smaller radii bubbles can also be studied. To demonstrate the accuracy of the technique, theoretical predictions of resonance broadening due to bubbles were compared with measured broadening for a known bubble population in the laboratory. Statistics of bubble densities under and near spilling breakers were then obtained at a depth of 25 cm below the ocean surface. These ocean data compare very well with recently published laser measurements in a water–wind tunnel over radius range 30<a<270 μm, but agree with older photographically obtained values at sea only for radii 50<a<100 μm.
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43.30.Pc Ocean parameter estimation by acoustical methods; remote sensing; imaging, inversion, acoustic tomography
43.30.Ft Volume scattering
43.30.Lz Underwater applications of nonlinear acoustics; explosions
43.30.Sf Acoustical detection of marine life; passive and active

Matched field processing in shallow water for range, depth, and bearing determination: Results of experiment and simulation

John M. Ozard

J. Acoust. Soc. Am. Volume 86, Issue 2, pp. 744-753 (1989); (10 pages) | Cited 12 times

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Recent theoretical studies have investigated high‐resolution methods for estimating source position in a shallow‐water waveguide. In this paper, an eigenvector method and a geophysical model based on several types of seismic data are used to estimate the bearing, depth, and range of a moving submerged source in the presence of an interfering surface source at the same range and bearing. The receiver was a sparse horizontal array of four sensors on the bottom (depth 82 m). A variant of the eigenvector method known as the MUSIC method was employed for measured and test field matching and a normal mode model was employed to calculate the test field. The data analyzed were obtained by towing a submerged source directly below the stern of the CFAV Endeavour, so that the surface and submerged sources were essentially at the same range and bearing. Source bearing estimates for the data showed that source bearings were usually well defined although somewhat ambiguous. The presence of the deep source was indicated at 15 and 19.5 Hz but the ranges were completely ambiguous. Simulations produced similar results for the same small number of sensors and a small number of propagating modes. However, simulations also showed that, with a horizontal array of 15 hydrophones and a signal‐to‐noise ratio of 10 dB, unambiguous resolution of depth, bearing, and range would be obtained.
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43.30.Wi Passive sonar systems and algorithms, matched field processing in underwater acoustics
43.60.Gk Space-time signal processing, other than matched field processing
43.40.Ph Seismology and geophysical prospecting; seismographs

Application of synthetic‐aperture processing to towed‐array data

Nai‐Chyuan Yen and William Carey

J. Acoust. Soc. Am. Volume 86, Issue 2, pp. 754-765 (1989); (12 pages) | Cited 2 times

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A synthetic‐aperture processing technique has been applied to towed‐array hydrophone data and has demonstrated that significant increase in signal gain, improved angular resolution, and improved peak‐to‐sidelobe level ratios can be achieved. The synthetic aperture was formed by the coherent sum of subaperture beams at successive time intervals. When the signal spatial coherence was greater than the synthetic‐aperture length and the signal stationary over the synthetic‐aperture processing time, 85% of the achievable coherent processing gain was realized. This gain was described by (x−1)10 log(NTF), with x the coherent gain factor and NTF the number of sequential time samples. The coherent gain factor was found at 175 Hz to be 1.7±0.3 for synthetic‐aperture lengths between 192 and 962 m, formed from subaperture lengths between 5 and 80 m over coherent processing times of less than 9 min. Beamwidths were found to be comparable to 58°, divided by the effective aperture length in wavelengths. Synthetic apertures, formed from subaperture lengths of 160 and 640 m, showed improvement when a tow‐ship phase reference was employed and yielded x=1.4, compared to a maximum value of 2. The synthetic processing technique was also shown to function as a velocity filter sensitive to the relative velocity of the source and receiver. These results demonstrate that the formation of midfrequency synthetic‐aperture arrays in the deep‐ocean environment is feasible.
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43.30.Wi Passive sonar systems and algorithms, matched field processing in underwater acoustics
43.60.Gk Space-time signal processing, other than matched field processing

Pressure variation above a layer of absorbing material and impedance measurement at oblique incidence and low frequencies

Jean F. Allard, Yvan Champoux, and Jean Nicolas

J. Acoust. Soc. Am. Volume 86, Issue 2, pp. 766-770 (1989); (5 pages) | Cited 5 times

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Measurements of the ratio of the acoustical pressures at two points above a sample of typical glass wool are performed for various angles of incidence and various distances from the sound source to the sample. The measurements are compared with predictions made using a recent model, and are used to estimate the surface impedance of the material at oblique incidence. It appears that, for the material studied, surface impedance measurements are possible for frequencies as low as 300 Hz and angles of incidence between 0° and 75°, as long as the source–sample distance is larger than half the sound wavelength in air.
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43.28.Fp Outdoor sound propagation through a stationary atmosphere, meteorological factors
43.20.Ye Measurement methods and instrumentation
43.58.Bh Acoustic impedance measurement
43.55.Ev Sound absorption properties of materials: theory and measurement of sound absorption coefficients; acoustic impedance and admittance

Ray theory solution for finite amplitude effects in a two‐dimensional hard‐walled waveguide

Kun‐Tien Shu and Jerry H. Ginsberg

J. Acoust. Soc. Am. Volume 86, Issue 2, pp. 771-776 (1989); (6 pages) | Cited 1 time

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Ray theory and perturbation analysis are combined to analyze the cumulative growth of nonlinear effects resulting from excitation of a single nonplanar mode in a two‐dimensional waveguide whose walls are rigid. The first‐order (linear) signal is decomposed into a pair of obliquely propagating planar waves. The signal associated with each ray is required to satisfy the inhomogeneous second‐order wave equation. A single ray emanating from its source is followed to its first incidence at one wall, and the reflection of such a ray is determined by requiring that incident and reflected rays combine to satisfy the hard‐wall boundary condition. The method of images then leads to a generalization of the result to the case of a ray that undergoes multiple reflections. Nonuniform validity of the ray signal determined in this manner is corrected by the method of renormalization, which leads to the conclusion that a ray behaves like a simple nonlinear planar wave, except that the propagation distance is measured by tracing the ray back to its source. The overall signal at a specified field point is determined by superposing the signals associated with the two rays that intersect at that location. The result is shown to be in complete agreement with earlier modal analyses of the same problem, provided that the frequency is sufficiently low to inhibit resonant energy transfer between nearly parallel rays. Although the analysis is less direct than that used previously, it yields physical insight into the distortion process not previously available.
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43.25.-x Nonlinear acoustics
43.20.Dk Ray acoustics
43.20.Mv Waveguides, wave propagation in tubes and ducts

Acoustic levitation in the presence of gravity

P. Collas, M. Barmatz, and C. Shipley

J. Acoust. Soc. Am. Volume 86, Issue 2, pp. 777-787 (1989); (11 pages) | Cited 5 times

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The method of Gor’kov has been applied to derive general expressions for the total potential and force on a small spherical object in a resonant chamber in the presence of both acoustic and gravitational force fields. The levitation position is also determined in rectangular resonators for the simultaneous excitation of up to three acoustic modes, and the results are applied to the triple‐axis acoustic levitator. The analysis is applied to rectangular, spherical, and cylindrical single‐mode levitators that are arbitrarily oriented relative to the gravitational force field. Criteria are determined for isotropic force fields in rectangular and cylindrical resonators. It is demonstrated that an object will be situated within a volume of possible levitation positions at a point determined by the relative strength of the acoustic and gravitational fields and the orientation of the chamber relative to gravity. Trajectories of an object from an arbitrary starting position to a final equilibrium position are also discussed.
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43.25.Qp Radiation pressure
43.25.Uv Acoustic levitation
43.25.Gf Standing waves; resonance

Assessment of a new radiation damping model for structural acoustic interactions

Gregory A. Kriegsmann and Clyde L. Scandrett

J. Acoust. Soc. Am. Volume 86, Issue 2, pp. 788-794 (1989); (7 pages) | Cited 2 times

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The equations that govern the scattering of acoustic waves from a baffled membrane strip couple the fluid pressure and the membrane displacement in an intimate way. The equations cannot be decoupled and consequently analytical solutions cannot be found. Approximate methods are often used to decouple the system. A new approximate method is presented, which can be classified as an ‘‘impedance approximation,’’ in that it relates the membrane displacement to a differential operator applied to the fluid pressure at the membrane surface. The differential operator arises from applying a radiation condition, which is strictly valid far away from the structure, to the pressure on the membrane’s surface. This new technique is compared to the plane‐wave approximation method and to a finite difference solution of the fully coupled system. It is found that the new approximation method improves upon the plane‐wave approximation method, particularly near the in vacuo eigenfrequencies of the membrane.
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43.20.Fn Scattering of acoustic waves
43.20.Tb Interaction of vibrating structures with surrounding medium
43.40.Dx Vibrations of membranes and plates

Variational principle for scattering by a baffled cavity‐backed membrane

G. L. Lamb, Jr.

J. Acoust. Soc. Am. Volume 86, Issue 2, pp. 795-801 (1989); (7 pages)

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The reflection of a plane sound wave by an infinite plane baffle containing a circular aperture spanned by a membrane that is backed by a closed cylindrical cavity is investigated theoretically. A variational expression for the amplitude of backscattered radiation at normal incidence is derived and results based upon this expression are compared with those obtained by others using the method of matched asymptotic expansions.
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43.20.Fn Scattering of acoustic waves
43.40.Dx Vibrations of membranes and plates
43.30.Gv Backscattering, echoes, and reverberation in water due to combinations of boundaries

Transient elastic wave scattering by a rigid spherical inclusion

Anil C. Wijeyewickrema and Leon M. Keer

J. Acoust. Soc. Am. Volume 86, Issue 2, pp. 802-809 (1989); (8 pages)

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The transient scattering of a stress wave by a rigid spherical inclusion embedded in an infinite elastic medium is considered. The Fourier synthesis technique is used to calculate the response of the inclusion and the interfacial stresses. This method of solution yields an exact solution for the inclusion response. The interfacial stresses are obtained in the form of an infinite series that is suitable for the long‐time response but that does not converge rapidly for early time. Hence, an early time analysis is performed by reformulating the problem in the Laplace transform domain; by utilizing Watson’s transformation, the early time stress response in the shadow region is obtained. Results in the shadow region using both techniques emphasize the importance of carrying out the early time analysis. The interfacial stresses in the illuminated zone using only the Fourier synthesis method are also given.
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43.20.Fn Scattering of acoustic waves
43.20.Px Transient radiation and scattering
43.20.Bi Mathematical theory of wave propagation

Transient generation of elastic waves in solids by a disk‐shaped normal force source

L. F. Bresse and D. A. Hutchins

J. Acoust. Soc. Am. Volume 86, Issue 2, pp. 810-817 (1989); (8 pages) | Cited 8 times

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A method for computing the transient radiation from a wide circular source, acting at a solid surface, is given for two different normal force apodizations. This method, based on a double Laplace–Hankel transform and a Cagniard inversion, allows an exact formulation of the impulse response to be obtained for two components of the displacement at any point inside the solid and is amenable to computing the field for an arbitrary time excitation. Numerical results are presented and are compared with experimental results for generation by a piezoelectric transducer.
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43.20.Px Transient radiation and scattering

Determination of the shear impedance of viscoelastic liquids using Love and Bleustein–Gulyaev surface waves

P. Kiełczyński and R. Płowiec

J. Acoust. Soc. Am. Volume 86, Issue 2, pp. 818-827 (1989); (10 pages) | Cited 4 times

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This paper presents a new method, using shear SH (shear horizontal) surface waves in solids, to determine the rheological parameters of viscoelastic liquids. Appropriate analytical formulas have been derived for Love and Bleustein–Gulyaev surface waves. The sensitivity of the proposed method is compared to that of the classical Mason method employing SH bulk waves. The measuring range of the proposed and classical methods is discussed in detail. Preliminary measurements are performed for typical mineral oil. The measured quantities agree very well with those obtained theoretically. The proposed method can be a few orders of magnitude more sensitive than the bulk wave method.
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43.20.Ye Measurement methods and instrumentation
43.35.Mr Acoustics of viscoelastic materials

Forward‐masking properties of multicomponent signals in normal and hearing‐impaired subjects

Munah Kim, Christopher W. Turner, and Evan M. Relkin

J. Acoust. Soc. Am. Volume 86, Issue 2, pp. 828-831 (1989); (4 pages)

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The forward‐masking properties of inharmonic complex stimuli were measured both for normal and hearing‐impaired subjects. The signal threshold for a 1000‐Hz pure‐tone probe was obtained for six different maskers, which varied in the number of pure‐tone components. The masking stimuli consisted of 1, 3, 5, 7, 9, or 11 components, logarithmically spaced in frequency surrounding the signal and presented at a fixed level of 80 dB SPL per component. In most normal‐hearing subjects, the threshold for the probe decreased as the number of masking components was increased, demonstrating that stimuli with more components tended to be less effective maskers. Results from hearing‐impaired subjects showed no decrease in threshold with increasing number of masking components. Instead, the thresholds increased as more components were added to the first masker. These results appear to be consistent with suppression effects within the multicomponent maskers for the normal subjects and a lack of suppression effects for the hearing‐impaired subjects. The results from the normal‐hearing subjects are also consistent with ‘‘across‐channel’’ cuing.
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43.66.Dc Masking

Analysis of a hybrid noise control system for a duct

M. L. Munjal and L. J. Eriksson

J. Acoust. Soc. Am. Volume 86, Issue 2, pp. 832-834 (1989); (3 pages)

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This letter proposes the combination of a passive muffler and an active noise control system for the control of very high‐level noise in ducts used with large industrial fans and similar equipment. The analysis of such a hybrid system is presented making use of electroacoustic analogies and the transfer matrix method. It turns out that a passive muffler upstream of the input microphone can indeed lower the acoustic pressure and, hence, the power requirement of the auxiliary source. The parameter that needs to be optimized (or maximized) for this purpose is a certain velocity ratio that can readily be evaluated in a closed form, making it more or less straightforward to synthesize the configuration of an effective passive muffler to go with the active noise control system.
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43.50.Ki Active noise control

On a theoretical interpretation of the prevalence rate of noise‐induced annoyance in residential populations—High‐amplitude impulse‐noise environments

Paul D. Schomer

J. Acoust. Soc. Am. Volume 86, Issue 2, pp. 835-836 (1989); (2 pages) | Cited 1 time

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In a recent paper, Fidell et al. [J. Acoust. Soc. Am. 84, 2109–2113 (1988)] have introduced a theoretical interpretation of the prevalence rate of noise‐induced annoyance in residential populations exposed to common environments consisting of sources such as aircraft, motor vehicles, etc. Their model assumes a compressive transformation of DNL, and they assert that ‘‘the quantity that engenders annoyance must be strongly related to the apparent magnitude of noise exposure.’’ Thus they use the well‐known finding that apparent loudness is proportional to the 0.3 root of acoustic energy. High‐amplitude impulse noise has been shown to be different from typical community noise, in part because it induces vibrations and rattles in structures. So the annoyance response is due both to the audible sound and to the induced vibrations and rattles; the latter should be proportional to the 0.5 power of DNL. In this letter, a compressive transformation coefficient of 0.4 (midway between 0.3 and 0.5) is used for high‐amplitude impulse sound. The results show excellent fit between theory and results. On the one hand, this fit supports the view of the Committee on Hearing Bioacoustics and Biomechanics (CHABA), a view that induced vibrations and rattles (and not only loudness) determine annoyance to high‐amplitude impulse noise, and, on the other hand, this close fit lends further credence to the Fidell model.
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43.50.Qp Effects of noise on man and society
43.50.Pn Impulse noise and noise due to impact

Measurements of acoustic phase stability in Loch Linnhe, Scotland

Peter T. Gough and Michael P. Hayes

J. Acoust. Soc. Am. Volume 86, Issue 2, pp. 837-839 (1989); (3 pages) | Cited 2 times

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The temporal phase stability of the acoustic environment is vital to the formation of a synthetic aperture. Acoustic phase stability measurements were made of the water in Loch Linnhe, Scotland over a period of several days. The phase stability was estimated from a sequence of phase measurements made over periods of 1 and 15 min. Over periods of a minute, it was found that the standard deviation of the fluctuations around the mean phase was 10°. Moreover, for frequencies in the band 15–30 kHz, the standard deviation was independent of frequency. This implies that the standard deviation measured is limited by the measurement accuracy of the experiment rather than a measure of the actual acoustic stability of the medium. Consequently, it is concluded that the acoustic phase stability is better than 10° for all frequencies and that the path‐length variation due to medium fluctuations is smaller than 6 mm in a total acoustic path of 130 m.
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43.30.Ft Volume scattering

The fictitious eigenvalue difficulty in the T‐matrix and the BEM methods for exterior wave scattering

Richard Paul Shaw and S.‐C. Huang

J. Acoust. Soc. Am. Volume 86, Issue 2, pp. 839-842 (1989); (4 pages) | Cited 1 time

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Exterior time‐harmonic wave scattering by finite obstacles in infinite domains has been studied extensively by both boundary element methods (BEM) and transfer‐matrix (T‐matrix) methods. The former is essentially a local discretization numerical approach, while the latter is basically a global ‘‘eigenfunction’’ expansion approach and thus these two approaches represent in some sense an ‘‘alpha and omega’’ of approximation solution method. Since these are both based on a Helmholtz integral equation formulation, which is known to fail at certain eigenvalues of a related interior problem, one could expect corresponding failures in these approximate methods. Such failures are well known in the BEM literature; they are recognized in principle but are essentially ignored in practice in the T‐matrix literature. This paper studies this disparity through a simple example where the T‐matrix approach is seen to fail over such a narrow frequency band near the interior eigenvalues that finding such failures in a standard solution procedure using discrete frequency values is highly unlikely. However, a related eigenfunction expansion method yields the same broadband failure as found in BEM indicating that this is not simply a result of eigenfunction versus element accuracy.
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43.20.Fn Scattering of acoustic waves

Active control of boundary‐layer transition and turbulence

J. Acoust. Soc. Am. Volume 86, Issue 2, pp. 843-843 (1989); (1 page)

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Abstract Unavailable
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43.28.Vd Measurement methods and instrumentation to determine or evaluate atmospheric parameters, winds, turbulence, temperatures, and pollutants in air

Technical report: ‘‘Analysis of flow across cylinders’’

J. Acoust. Soc. Am. Volume 86, Issue 2, pp. 843-843 (1989); (1 page)

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Abstract Unavailable
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43.28.Ra Generation of sound by fluid flow, aerodynamic sound and turbulence

Free NTIS catalog lists bibliographic searches of NTIS and 23 other technical databases

J. Acoust. Soc. Am. Volume 86, Issue 2, pp. 844-844 (1989); (1 page)

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Abstract Unavailable
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01.30.Tt Bibliographies
43.10.Jk Bibliographies

Advanced‐degree dissertations in acoustics— 86 (2,4,6), 844 (T), 1613 (T), 2462 (T)

J. Acoust. Soc. Am. Volume 86, Issue 2, pp. 844-844 (1989); (1 page)

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Abstract Unavailable
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43.10.Sv Education in acoustics, tutorial papers of interest to acoustics educators

Thresholds of transient cavitation produced by pulsed ultrasound in a controlled nuclei environment

Christy Katherine Smith Holland

J. Acoust. Soc. Am. Volume 86, Issue 2, pp. 844-844 (1989); (1 page)

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Abstract Unavailable
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43.25.Yw Nonlinear acoustics of bubbly liquids
43.80.Ev Acoustical measurement methods in biological systems and media

Micro‐mechanics of granular fluid‐saturated porous media using the finite element method

B. Yavari

J. Acoust. Soc. Am. Volume 86, Issue 2, pp. 844-844 (1989); (1 page)

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Abstract Unavailable
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43.20.Bi Mathematical theory of wave propagation
43.30.Ma Acoustics of sediments; ice covers, viscoelastic media; seismic underwater acoustics
43.35.Bf Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in liquids, liquid crystals, suspensions, and emulsions
47.56.+r Flows through porous media

Acoustic transmission in the respiratory system

George Robert Wodicka

J. Acoust. Soc. Am. Volume 86, Issue 2, pp. 844-845 (1989); (2 pages)

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Abstract Unavailable
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43.80.Jz Use of acoustic energy (with or without other forms) in studies of structure and function of biological systems
43.80.Qf Medical diagnosis with acoustics

Sound propagation under the Arctic ice canopy

David Glen Wegmann

J. Acoust. Soc. Am. Volume 86, Issue 2, pp. 845-845 (1989); (1 page)

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Abstract Unavailable
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43.30.Ma Acoustics of sediments; ice covers, viscoelastic media; seismic underwater acoustics
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