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Jan 1986

Volume 79, Issue 1, pp. 1-210

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Acoustic pulse scattering by baffled membranes

Gregory A. Kriegsmann, Andrew N. Norris, and Edward L. Reiss

J. Acoust. Soc. Am. Volume 79, Issue 1, pp. 1-8 (1986); (8 pages) | Cited 1 time

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Asymptotic expansions as ϵ→0 that are uniformly valid in t are obtained for the membrane’s motion and the scattered acoustic pressure field. The small parameter ϵ is the density ratio of the acoustic fluid and the membrane. For simplicity of presentation, only plane, compact incident pulses are considered. The scattered field depends on the pulse’s structure. If it is a sufficiently narrow bandwidth pulse which contains none of the in vacuo natural frequencies of the membrane, then it is essentially reflected as though the baffled plane is completely rigid. However, if the pulse spectrum is sufficiently broad so that it contains one or more of the in vacuo natural frequencies of the membrane, an additional scattered field is produced. This scattered field insonifies distant observation points after the rigidly reflected pulse has arrived. It is the sum of slightly damped and oscillating outgoing spherical waves that represents the ‘‘decayed ringing’’ of the membrane. Application is given to the baffled circular membrane which is insonified by a normally incident pulse. Graphs of the membrane’s motion and the farfield acoustic pressure are given. They demonstrate the importance of the incident pulse width on the qualitative features of the response.
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43.20.Fn Scattering of acoustic waves
43.40.Dx Vibrations of membranes and plates

Numerical studies of acoustic pulse scattering by baffled two‐dimensional membranes

G. A. Kriegsmann and C. L. Scandrett

J. Acoust. Soc. Am. Volume 79, Issue 1, pp. 9-17 (1986); (9 pages) | Cited 1 time

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A new method for solving the scattering problem of acoustic pulses by baffled membranes is described. It is an adaptation of the finite difference technique which uses an ‘‘artificial’’ boundary condition to mimic an infinite region. The numerical method is used on several problems involving a plane compact pulse. It is also used on a time‐harmonic pulse of infinite extent. This pulse generates a time‐harmonic response as t→∞; this is proved in the Appendix. The numerical scheme is marched out in time until the transients have decayed away and a time‐harmonic solution has been established. This ‘‘relaxation’’ scheme yields accurate solutions in a reasonable amount of time without requiring heavy or light fluid loading assumptions.
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43.20.Fn Scattering of acoustic waves
43.40.Dx Vibrations of membranes and plates

Antireflective materials at ultrasound frequencies

Tibor Sajo

J. Acoust. Soc. Am. Volume 79, Issue 1, pp. 18-25 (1986); (8 pages)

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This paper describes the acoustic behavior of polyurethane base, microballoon filler composites for echo‐reduction applications in water‐filled tanks. The approach is similar to that of Corsaro et al. [J. Acoust. Soc. Am. 68, 655 (1980)] for silicon rubber, three‐component anechoic systems with the additional study of off‐normal incidence. Depending on the way the mixtures are cured, the surface echo reduction of the resulting composites can be improved by 13 dB at normal incidence. For the case of oblique incidence, the sound speed in these compounds is relatively close to that in water; this optimizes their surface echo reduction once the condition of impedance match is reached. Measurements reveal a front echo reduction better than 35 dB at 45° of incidence. A formula to estimate the ‘‘Net Echo Reduction’’ of an anechoic water‐filled tank is also given.
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43.20.Fn Scattering of acoustic waves
43.30.Ky Structures and materials for absorbing sound in water; propagation in fluid-filled permeable material

Spectral analysis of numerical solutions to the Burgers–Korteweg–DeVries equation

Kodali V. Rao

J. Acoust. Soc. Am. Volume 79, Issue 1, pp. 26-30 (1986); (5 pages) | Cited 1 time

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Finite amplitude acoustic wave propagation through bubbly liquids is studied by using the Burgers–Korteweg–DeVries model equation. Numerical solutions are obtained using a pseudospectral method. Spectral analysis of the numerical solutions is performed to study the spectral energy transfer due to nonlinearity. Numerical solutions of the two limiting cases obtained by neglecting either the dissipation or dispersion term of the Burgers–Korteweg–DeVries equation are also analyzed. In nonlinear wave propagation, short waves are generated by long waves due to nonlinearity. In bubbly media, these short waves may undergo strong resonance absorption due to the presence of bubbles, even if other mechanisms of dissipation are negligible. The effect of such an absorption is simulated by applying a low‐pass filter on the results obtained with the dissipation term neglected. The filter eliminates the short waves generated after each time step. It is shown that such resonance absorption corrections may be necessary for any quantitative comparisons of computed results with experiment.
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43.25.Yw Nonlinear acoustics of bubbly liquids

Coupled mode theory of intrinsic modes in a wedge

J. M. Arnold and L. B. Felsen

J. Acoust. Soc. Am. Volume 79, Issue 1, pp. 31-40 (1986); (10 pages) | Cited 3 times

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Recent theoretical studies of acoustic wave propagation in a model waveguide consisting of a homogeneous wedge with one reflecting and one penetrable boundary have established the utility of the concept of an intrinsic mode, which generalizes for nonseparable problems the normal mode of separable configurations. In this paper, it is shown by explicit calculations on the same model problem that direct orthogonal expansion (in local normal modes) of the intrinsic mode produces the same expansion coefficients as those obtained by a perturbation analysis of the coupled mode equations. The perturbation method used is that of renormalization, in which the mode coupling operator is iteratively diagonalized up to a certain order in the nonseparability parameter, which, in this case, is the wedge angle α.
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43.30.Bp Normal mode propagation of sound in water
43.20.Bi Mathematical theory of wave propagation

Deep sound channel noise from high‐latitude winds

R. W. Bannister

J. Acoust. Soc. Am. Volume 79, Issue 1, pp. 41-48 (1986); (8 pages) | Cited 5 times

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The contribution to underwater ambient noise from the persistent winds which blow at high latitude is discussed and estimated. Energy is ducted into low‐loss paths in the deep sound channel by favorable horizontal sound‐speed gradients. A concept of ‘‘wind‐noise lanes’’ is developed into a simple model which is used to predict the resulting underwater ambient noise levels as a function of season and latitude. Three main oceans are considered—the Pacific, Atlantic, and Indian Oceans. In general terms, predicted omnidirectional levels at 50 Hz lie between 65 and 75 dB re: 1 μPa2/Hz and are comparable to those generally associated with light‐to‐moderate ship traffic. The spectral shape of high‐latitude wind noise is also similar to that associated with ships. High‐latitude wind noise arrives within ±15° of horizontal, and the predicted magnitude of this low‐angle component also matches measurements well. It is concluded that the component of noise associated with high‐latitude winds can be significant at low frequencies. Properties of omnidirectional noise, as well as vertical and horizontal directivity, may be dominated by this component under some conditions. It appears, however, to have been often overlooked in the interpretation of data.
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43.30.Bp Normal mode propagation of sound in water
43.30.Nb Noise in water; generation mechanisms and characteristics of the field
92.10.Vz Underwater sound

Measurement of down‐slope sound propagation from a shallow source to a deep ocean receiver

William M. Carey

J. Acoust. Soc. Am. Volume 79, Issue 1, pp. 49-59 (1986); (11 pages) | Cited 1 time

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An experiment has been performed to investigate the coupling of surface–ship noise to the deep ocean sound channel. These calibrated measurements of sound propagation from the 18‐m, 135‐Hz source were obtained at a deep ocean receiver while the source tow proceeded from deep water up the Sable Island Bank at ranges between 730 and 910 km. The sound propagation path was from the cold slope waters over the bank through the Gulf Stream and to the edge of the Sargasso Sea. The mean value of the transmission loss was 110 dB with a down‐slope enhancement estimated to be 4 dB resulting from the combined effects of trapping in the strong shallow sound channel and reflections from the slope. Comparisons with calculated results using the parabolic equation method were good and demonstrate coupling to the deep ocean sound channel. The acoustic field, sampled by 16 transverse hydrophone groups with a 4.75‐m center spacing over six consecutive (12.5 s, 0.08 Hz) samples, yielded a mean standard deviation of 1.7 dB (6≤S/N≤20 dB) corresponding to a coefficient of variation of 0.6. Coherent summation of slope‐reflected and deep‐refracted hydrophone signals yielded estimated mean values of the spatial coherence of 0.89 and an estimated spatial coherence length of 460 m, when multipath effects were not dominant; however, these estimates were found to range as low as 0.63 and 150 m. These results facilitate the interpretation of the spatial coherence of the ship‐induced, ‘‘slope‐enhanced’’ contribution to deep ocean ambient noise.
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43.30.Bp Normal mode propagation of sound in water
43.30.Nb Noise in water; generation mechanisms and characteristics of the field
92.10.Vz Underwater sound

Intensity decay laws for near‐surface sound sources in the ocean

R. N. Denham

J. Acoust. Soc. Am. Volume 79, Issue 1, pp. 60-63 (1986); (4 pages)

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Expressions derived for the acoustic intensity decay with range in shallow water by Marsh and Schulkin [J. Acoust. Soc. Am. 34, 863–864 (1962)] and Weston [J. Sound Vib. 18, 271–287 (1971)] have been adapted to describe the intensity‐range variation in the deep water situation, where the sound speed at the surface is equal to the sound speed at the base of the water column. The modified equations take account of the surface decoupling loss which occurs at frequencies below 100 Hz for source depths less than 25 m. The levels predicted by these equations are compared with experimental data obtained in deep water in the Indian Ocean. It is found that the mean difference in measured and predicted levels at frequencies of 25 and 50 Hz is less than 2 dB, and rms level differences are within 4 dB.
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43.30.Es Velocity, attenuation, refraction, and diffraction in water, Doppler effect
92.10.Vz Underwater sound

Surface reflection: On the convergence of a series solution to a modified Helmholtz integral equation and the validity of the Kirchhoff approximation

Diana F. McCammon and Suzanne T. McDaniel

J. Acoust. Soc. Am. Volume 79, Issue 1, pp. 64-70 (1986); (7 pages) | Cited 2 times

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In the problem of scattering from a pressure release boundary, the Helmholtz integral equation may be expressed as a Fredholm equation of the second kind with the unknown surface velocity as the independent variable. The method of successive approximations was employed by Meecham [J. Ration. Mech. Anal. 5, 323–333 (1956)] to obtain a series solution to this equation, where the first term of this series is, in fact, the unshadowed Kirchhoff approximation to the solution. Meecham attempted to formulate the region of validity of the Kirchhoff approximation by determining when the remaining terms of the series could be neglected, however, his arguments used to select ‘‘smallness’’ have been questioned. An exact solution to the integral equation for a sinusoidal boundary is employed to examine the series, term by term, for convergence; and it is found that (1) the alternating nature of the series does not bring convergence when the series diverges absolutely, and (2) the absence of any propagating side orders and reflection anomalies is not a sufficient condition for convergence. Finally, to highlight the extent of the error made when using the Kirchhoff approximation, comparisons are made between reflection coefficients computed using the exact solution and several terms of the series. It is found that in the shadowed regions, the Kirchhoff approximation is in reasonable agreement with the exact solution, even when Meecham’s series diverges.
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43.30.Bp Normal mode propagation of sound in water
43.30.Es Velocity, attenuation, refraction, and diffraction in water, Doppler effect
43.20.Bi Mathematical theory of wave propagation
02.30.Rz Integral equations

Low‐frequency rolloff in the response of shallow‐water channels

P. W. Smith, Jr.

J. Acoust. Soc. Am. Volume 79, Issue 1, pp. 71-75 (1986); (5 pages) | Cited 1 time

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Propagation in a shallow‐water channel of constant sound speed, overlying a homogeneous viscoelastic half‐space with frequency‐independent loss factors, is examined as a function of range, frequency, water depth, and a parameter representing the initial rate of increase of bottom reflection loss with increasing grazing angle. Particular attention is focused on the ‘‘transition’’ frequency below which the transmission loss increases rapidly. It is found to separate a ray‐theoretical domain, where the directional spectrum of transmitted sound is quasicontinuous, from a modal domain where, in fact, only the first mode carries significant energy. A simple algebraic formula is derived for this transition frequency that also yields good estimates of both the ‘‘optimum frequency’’ of Jensen and Kuperman [J. Acoust. Soc. Am. 73, 813 (1983)] and the low‐frequency rolloff observed in some data.
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43.30.Bp Normal mode propagation of sound in water
43.20.Bi Mathematical theory of wave propagation

Broadband noise propagation in a Pekeris waveguide

Marcio L. Vianna and W. Soares‐Filho

J. Acoust. Soc. Am. Volume 79, Issue 1, pp. 76-83 (1986); (8 pages) | Cited 1 time

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A theory of broadband noise propagation from a point source in shallow water is developed by use of a Pekeris model with a lossy bottom. The broadband interference pattern in the power spectrum is calculated analytically and numerically including both the proper mode and the virtual mode fields. It is shown that the interference maxima of the proper mode spectrum describe straight lines in the range‐frequency plane and that the virtual mode fields (branch‐line integral) are localized and decay slowly with a range around the cutoff frequencies of the proper modes. It is also shown that bottom attenuation does not influence the form of the power spectrum in any significant way up to ranges of 100 water depths.
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43.30.Bp Normal mode propagation of sound in water

The detection of liquids and viscoelastic substances trapped under solid surfaces

H. W. Jones, H. W. Kwan, T. Hayman, and E. M. Yeatman

J. Acoust. Soc. Am. Volume 79, Issue 1, pp. 84-90 (1986); (7 pages) | Cited 1 time

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This paper describes theoretical and experimental aspects of a method of detecting, by acoustical means, a layer of oil trapped under ice. Previous work directed to this end is briefly reviewed. A new method of detection is outlined. The theory of mode conversion at the surface of a solid and a viscoelastic layer is discussed in detail. The use of the reflected and mode‐converted acoustical signals for detection is described in some detail. Physical data collected for crude oil, sea water, and fresh water ice are presented. The theoretical predictions of acoustical mode conversion theory are compared with experimental results obtained from salt water ice and fresh water ice scenarios. A comment on the more general applicability of the method to other circumstances is given.
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43.35.Zc Use of ultrasonics in nondestructive testing, industrial processes, and industrial products
43.30.-k Underwater sound

Factor inverse matched filtering

Theodore G. Birdsall and Kurt Metzger, Jr.

J. Acoust. Soc. Am. Volume 79, Issue 1, pp. 91-99 (1986); (9 pages) | Cited 8 times

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Factor inverse matched filtering (FIMF) and factor inverse filtering (FIF) are signal processing techniques used to obtain desired signal responses. Both are especially useful procedures for ‘‘pulse‐compression’’ processing and channel measurements. The theory is developed for a simple channel and known noise power spectral density so that comparison may be made with matched filtering. Expressions for the pulse‐compression energy gain, nonflatness loss NFL, and total performance are derived. The NFL is useful in selecting the best among practical pulse‐compression modulations, and with FIMF and FIF, has been used extensively since 1974 by the authors and their co‐workers in underwater acoustic propagation measurements and ocean acoustic tomography.
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43.60.Gk Space-time signal processing, other than matched field processing
43.30.Bp Normal mode propagation of sound in water
43.30.Pc Ocean parameter estimation by acoustical methods; remote sensing; imaging, inversion, acoustic tomography

The representation of steady‐state vowel sounds in the temporal discharge patterns of the guinea pig cochlear nerve and primarylike cochlear nucleus neurons

A. R. Palmer, I. M. Winter, and C. J. Darwin

J. Acoust. Soc. Am. Volume 79, Issue 1, pp. 100-113 (1986); (14 pages) | Cited 7 times

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We have recorded the responses of fibers in the cochlear nerve and cells in the cochlear nucleus of the anesthetized guinea pig to synthetic vowels [i], [a], and [u] at 60 and 80 dB SPL. Histograms synchronized to the pitch period of the vowel were constructed, and locking of the discharge to individual harmonics was estimated from these by Fourier transformation. In cochlear nerve fibers from the guinea pig, the responses were similar in all respects to those previously described for the cat. In particular, the average‐localized‐synchronized‐rate functions (ALSR), computed from pooled data, had well‐defined peaks corresponding to the formant frequencies of the three vowels at both sound levels. Analysis of the components dominating the discharge could also be used to determine the voice pitch and the frequency of the first formants. We have computed similar population measures over a sample of primarylike cochler nucleus neurons. In these primarylike cochlear nucleus cell responses, the locking to the higher‐frequency formants of the vowels is weaker than in the nerve. This results in a severe degradation of the peaks in the ALSR function at the second and third formant frequencies at least for [i] and [u]. This result is somewhat surprising in light of the reports that primarylike cochlear nucleus cells phaselock, as well as do cochlear nerve fibers.
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43.64.Pg Electrophysiology of the auditory nerve
43.64.Qh Electrophysiology of the auditory central nervous system
43.71.Qr Neurophysiology of speech perception

Rate discrimination of high‐pass‐filtered pulse trains

John K. Cullen, Jr. and Glenis R. Long

J. Acoust. Soc. Am. Volume 79, Issue 1, pp. 114-119 (1986); (6 pages) | Cited 10 times

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Difference limens for trains of 30‐μs pulses were determined for repetition rates of 50, 100, 200, 400, and 800 pulses per second under conditions of no filtering and high‐pass filtering (115 dB/oct) with corner frequencies of 2.5, 5.0, 7.5, and 10 kHz. Low‐pass‐filtered noise was mixed with the trains of impulses to preclude discrimination on the basis of potential low‐frequency signal components. Measures were obtained from four trained listeners at a signal level of 30 dB SL relative to individually determined thresholds for each filter condition and repetition rate. The data support the hypothesis that resolution of pulse‐train repetition rate involves both temporal‐ and frequency‐based processes—the latter becoming ineffective when frequency resolution of the ear is insufficient to resolve separate harmonics of the signal. Inter‐ and intra‐individual differences are interpreted as reflecting frequency resolution capacity.
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43.66.Fe Discrimination: intensity and frequency
43.66.Hg Pitch
43.66.Mk Temporal and sequential aspects of hearing; auditory grouping in relation to music

NBS‐9A coupler‐to‐eardrum transformation: TDH‐39 and TDH‐49 earphones

Robyn M. Cox

J. Acoust. Soc. Am. Volume 79, Issue 1, pp. 120-123 (1986); (4 pages) | Cited 3 times

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A transformation was derived to convert sound‐pressure levels referenced to an NBS‐9A coupler to corresponding eardrum sound‐pressure levels. It was found that the same transformation may be used for male and female adults and for both TDH‐39 and TDH‐49 earphones in MX‐41/AR supra‐aural cushions. It was determined that from 250–2000 Hz the transformation provides an eardrum sound‐pressure level estimate that is within 6 dB of the actual eardrum level for 95% of individuals. However, in the 4000–6300‐Hz range, the accuracy deteriorates to ±12 dB of actual eardrum level for 95% of individuals.
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43.66.Yw Instruments and methods related to hearing and its measurement
43.58.Vb Calibration of acoustical devices and systems
43.64.Ha Acoustical properties of the outer ear; middle-ear mechanics and reflex
43.66.Cb Loudness, absolute threshold

Intelligibility of vowels sung by a countertenor

Terry L. Gottfried and Stephen L. Chew

J. Acoust. Soc. Am. Volume 79, Issue 1, pp. 124-130 (1986); (7 pages) | Cited 2 times

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Ten American English vowels were sung in a /b/–vowel–/d/ consonantal context by a professional countertenor in full voice (at F0=130, 165, 220, 260, and 330 Hz) and in head voice (at F0=220, 260, 330, 440, and 520 Hz). Four identification tests were prepared using the entire syllable or the center 200‐ms portion of either the full‐voice tokens or the head‐voice tokens. Listeners attempted to identify each vowel by circling the appropriate word on their answer sheets. Errors were more frequent when the vowels were sung at higher F0. In addition, removal of the consonantal context markedly increased identification errors for both the head‐voice and full‐voice conditions. Back vowels were misidentified significantly more often than front vowels. For equal F0 values, listeners were significantly more accurate in identifying the head‐voice stimuli. Acoustical analysis suggests that the difference of intelligibility between head and full voice may have been due to the head voice having more energy in the first harmonic than the full voice.
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43.71.Es Vowel and consonant perception; perception of words, sentences, and fluent speech
43.71.Gv Measures of speech perception (intelligibility and quality)
43.75.Rs Singing

Vibrotactile perception of suprasegmental features of speech: A comparison of single‐channel and multichannel instruments

Arlene Earley Carney and Cindy R. Beachler

J. Acoust. Soc. Am. Volume 79, Issue 1, pp. 131-140 (1986); (10 pages)

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The recognition of three suprasegmental aspects of speech—the number of syllables in a word, the stress pattern of a word, and rising or falling intonation patterns—through a single‐channel tactile device and through a 24‐channel tactile vocoder, using two groups of normal‐hearing subjects, was compared. All subjects received an initial pretest on three recognition tasks, one for each prosodic feature. Half the subjects from each group then received 12 h of training with feedback on the tasks and stimuli used in the pretest. All subjects received a post‐test which contained physically different stimuli from those previously tested. Performance was significantly better on the syllable‐number and syllabic stress tasks with the single‐channel than with the multichannel device on both the pre‐ and post‐tests; no difference was found for the intonation task. Performance on the post‐test was poorer for all trained subjects compared to their final training results, suggesting that cues learned in training were not readily transferable to new stimuli, even those with similar prosodic characteristics. Overall, the results provide support for the notion that certain prosodic features of speech may be conveyed more readily when the waveform envelope is preserved.
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43.71.Rt Sensory mechanisms in speech perception
43.71.Ky Speech perception by the hearing impaired
43.66.Wv Vibration and tactile senses

Piano string excitation in the case of small hammer mass

Donald E. Hall

J. Acoust. Soc. Am. Volume 79, Issue 1, pp. 141-147 (1986); (7 pages) | Cited 4 times

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When a hammer of mass m strikes a string of mass M, it is dependent on the string for the force which will finally cause it to rebound. They remain in contact for a finite time, and this makes a general solution for the resulting string motion rather complicated. In the limit m≪M for a very stiff hammer the solution is relatively simple, but has some features that seem not to have been noted before. If the original hammer kinetic energy is E0, then 0.865 E0 is ultimately transferred to the string. Most interesting is that the normal modes with antinodes at the striking point receive only about two‐thirds as much energy as certain other modes. Analytic expressions are also given for hammer masses which are finite but still small enough that the solution involves only the first reflection from the near end of the string. These apply to cases with m as large as 0.463 M, and show how the larger values of m affect the relative amplitude of the high‐frequency modes. The mode energy spectrum level rolls off at 6 dB/oct above a mode number nmax∼0.73 M/m. Modes with either a node or an antinode at the striking point become missing modes for high frequencies.
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43.75.Mn Pianos and other struck string instruments
43.40.Cw Vibrations of strings, rods, and beams

Prediction of tissue composition from ultrasonic measurements and mixture rules

Robert E. Apfel

J. Acoust. Soc. Am. Volume 79, Issue 1, pp. 148-152 (1986); (5 pages) | Cited 2 times

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A methodology is presented for predicting the composition of tissues from measurements of the density, sound velocity, and acoustic nonlinear parameter, using mixture laws for the density, compressibility, and nonlinear parameter. It is shown that the mixture law for the nonlinear parameter plays an essential part in this methodology, which leads to the prediction of the volume fractions of water, protein, and fat in a given tissue. Data from the literature for solutions, blood, normal tissue, and cancerous tissue are investigated, and predicted fractions are consistent with tissue compositional information available in handbooks. More experimental work is needed with tissues of known composition in order to more fully test the proposed methodology.
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43.80.Cs Acoustical characteristics of biological media: molecular species, cellular level tissues
43.80.Ev Acoustical measurement methods in biological systems and media
43.80.Jz Use of acoustic energy (with or without other forms) in studies of structure and function of biological systems

Acoustic surface wave measurements on live bottlenose dolphins

W. M. Madigosky, G. F. Lee, J. Haun, F. Borkat, and R. Kataoka

J. Acoust. Soc. Am. Volume 79, Issue 1, pp. 153-159 (1986); (7 pages)

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The surface wave velocity and absorption constant were determined on live bottlenose dolphins as a function of position, propagation direction, and frequency. A surface wave was propagated on the outer skin of a dolphin by an electromagnetic shaker driven by a noise source. Two miniature accelerometers were attached to the skin at a distance of 3.2 cm apart. The output signals from the accelerometers were analyzed by a dual‐channel fast Fourier transform spectrum analyzer. The data acquisition was further automated by a minicomputer. The surface wave velocities were the highest below the dorsal fin area and the lowest at an area around the posterior insertion of the pectoral fin. Generally, the velocity and absorption constant were independent of the propagation direction (anterior, posterior, dorsal, and ventral) except near the dorsal fin. Over most of the regions measured, the surface wave velocity ranged from 4 to 14 m/s over the frequency range of 20 to 1000 Hz. The attenuation α (dB/m) was assumed to be α=Af, where A is the absorption constant and f is the frequency. The absorption constant was the highest around a line at the posterior insertion of the pectoral fin, 1.5 dB s/m, and the lowest just below the dorsal fin, 0.5 dB s/m.
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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.Cs Acoustical characteristics of biological media: molecular species, cellular level tissues
43.80.Ev Acoustical measurement methods in biological systems and media

Substrate thickness dependence of SH wave propagation characteristics in rotated Y‐cut X‐propagation LiNbO3

Kohji Toda and Koichi Mizutani

J. Acoust. Soc. Am. Volume 79, Issue 1, pp. 160-163 (1986); (4 pages)

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Shear horizontal (SH) waves in rotated Y‐cut X‐propagation LiNbO3 plates are numerically analyzed. The phase velocity, displacement distribution, and electromechanical coupling constant are presented as a parameter of the product of the frequency and the substrate thickness, including the rotation angle dependences. Some experimental configurations on the numerical results are fairly good.
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43.38.Ar Transducing principles, materials, and structures: general
43.58.Dj Sound velocity
43.35.Cg Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in solids; elastic constants
62.30.+d Mechanical and elastic waves; vibrations

On the tangentially and radially polarized piezoceramic thin cylindrical tube transducers

Hong‐zhang Wang

J. Acoust. Soc. Am. Volume 79, Issue 1, pp. 164-176 (1986); (13 pages) | Cited 5 times

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The electric admittance equations of the tangentially and radially polarized piezoceramic thin circular cylindrical tube in the unloaded case have been derived approximately. On the basis of these equations, a method to calculate the main electromechanical parameters is suggested. With the same assumptions, the equations of vibration of the tube in water and the formulas for the responses of the radiation and receiving corresponding to a wider frequency range have also been derived. A further discussion about the influence of radiation impedance, Poisson’s ratio, piezoelectric constant ratio, and coupling coefficient to the response of receiving sensitivity of the piezoceramic thin circular cylindrical tube has been given.
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43.38.Ar Transducing principles, materials, and structures: general
43.38.Fx Piezoelectric and ferroelectric transducers
43.20.Ks Standing waves, resonance, normal modes

Comments on ‘‘Theory, ingenuity, and wishful wizardry in loudspeaker design—A half‐century of progress?’’ [J. Acoust. Soc. Am. 77, 1303–1308 (1985)]

Edgar Villchur

J. Acoust. Soc. Am. Volume 79, Issue 1, pp. 177-179 (1986); (3 pages)

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Some of Augspurger’s statements about the acoustic‐suspension speaker system are questioned. These concern the nonlinearity of the air spring in the enclosure, FM distortion, the definition of the acoustic‐suspension principle as the use of a heavy cone, and the effect of the acoustic‐suspension design on electroacoustic efficiency.
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43.10.Ln Surveys and tutorial papers relating to acoustics research; tutorial papers on applied acoustics
43.38.Ja Loudspeakers and horns, practical sound sources
43.38.Tj Public address systems, sound-reinforcement systems

Reply to ‘‘Comments on ‘Theory, ingenuity, and wishful wizardry in loudspeaker design—A half‐century of progress?’ ’’ [J. Acoust. Soc. Am. 77, 1303–1308 (1985)]

G. L. Augspurger

J. Acoust. Soc. Am. Volume 79, Issue 1, pp. 179-179 (1986); (1 page) | Cited 1 time

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In this letter, the author responds to comments on a former article.
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43.10.Ln Surveys and tutorial papers relating to acoustics research; tutorial papers on applied acoustics
43.38.Ja Loudspeakers and horns, practical sound sources
43.38.Tj Public address systems, sound-reinforcement systems
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