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Dec 1988

Volume 84, Issue 6, pp. 1975-2310

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Methods of chaos physics and their application to acoustics

W. Lauterborn and U. Parlitz

J. Acoust. Soc. Am. Volume 84, Issue 6, pp. 1975-1993 (1988); (19 pages) | Cited 17 times

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This article gives an introduction to the research area of chaos physics. The new language and the basic tools are presented and illustrated by examples from acoustics: a bubble in water driven by a sound field and other nonlinear oscillators. The notions of strange attractors and their basins, bifurcations and bifurcation diagrams, Poincaré maps, phase diagrams, fractal dimensions, scaling spectra, reconstruction of attractors from time series, winding numbers, as well as Lyapunov exponents, spectra, and diagrams are addressed.
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43.10.Ln Surveys and tutorial papers relating to acoustics research; tutorial papers on applied acoustics
05.45.-a Nonlinear dynamics and chaos
43.25.Yw Nonlinear acoustics of bubbly liquids
43.50.Yw Instrumentation and techniques for noise measurement and analysis

Velocity control and the mechanical impedance of single degree of freedom electromechanical vibrators

Michael P. Johnson

J. Acoust. Soc. Am. Volume 84, Issue 6, pp. 1994-2001 (1988); (8 pages) | Cited 2 times

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Most of the transducer devices used in present day sonar arrays are usefully approximated as single degree of freedom devices. Such devices exhibit a minimum in their mechanical input impedance to their radiating face at the fundamental resonance frequency. This minimum in impedance, leading to possible wide fluctuations in velocity across the array, can result in deterioration of electroacoustic performance and possibly disastrous results to hardware if left unchecked. The standard technique used to prevent this is attributed to D. L. Carson [J. Acoust. Soc. Am. 34, 1191–1196 (1962)] and essentially provides an electrically induced antiresonance near the mechanical resonance frequency. It is shown that this technique results in two minima, one residing on each side of the previous minimum. The resulting bandwidth over which velocity control of the array can be achieved is closely tied to the bandwidth between these minima. The relative locations of these minima are dependent only on effective electromechanical coupling coefficients and the ratio of the electrical antiresonance to mechanical resonance frequencies. This bandwidth appears to have a practical limit of approximately an octave.
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43.38.Ar Transducing principles, materials, and structures: general
43.38.Fx Piezoelectric and ferroelectric transducers
43.30.Yj Transducers and transducer arrays for underwater sound; transducer calibration

Detection of fluid velocity and hydroacoustic particle velocity using a temperature autostabilized nonlinear dielectric element (TANDEL)

Kurt M. Rittenmyer, George C. Alexandrakis, and Pieter S. Dubbelday

J. Acoust. Soc. Am. Volume 84, Issue 6, pp. 2002-2006 (1988); (5 pages)

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A ferroelectric sensor operated in the temperature autostabilized mode was developed for the measurement of the particle motion in hydroacoustic fields. The sensor is a capacitorlike element constructed from antimony sulfur iodide (SbSI) single crystals and SbSI–polymer composites. The device is operated slightly above the Curie point of SbSI, which is approximately 20 °C. Using a Schering bridge, the element is heated by driving it through the hysteresis cycle. The heat transferred to the surrounding fluid is related to the motion of the fluid. The technique was applied to the measurement of a constant velocity flow field and to a low‐frequency acoustic field. In the case of the constant velocity flow field, an exponential relationship between fluid velocity and sensor voltage was observed. For acoustic fields, the response of the sensor decreased sharply with frequency above 100 Hz. The acoustic particle velocity could be measured to a frequency around 1 kHz.
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43.58.Vb Calibration of acoustical devices and systems
43.38.Ar Transducing principles, materials, and structures: general
43.38.Pf Hydroacoustic and hydraulic transducers
47.80.-v Instrumentation and measurement methods in fluid dynamics

Fast search strategy in a large vocabulary word recognizer

V. N. Gupta, M. Lennig, and P. Mermelstein

J. Acoust. Soc. Am. Volume 84, Issue 6, pp. 2007-2017 (1988); (11 pages)

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In this article, a fast search algorithm is presented for generating word hypotheses for a 75 000‐word vocabulary, speaker‐trained, isolated word recognizer. The algorithm is envisioned as the first pass of a total recognition system generating a small number of hypotheses with rough likelihood estimates, to be followed by more detailed hypothesis evaluation. The possible word choices are restricted by estimating the number of syllables in the unknown word using a hidden Markov model (HMM) for syllables. A heuristic search algorithm then searches through a sequence of syllable networks to find the most likely word candidates. Arcs in the syllable network correspond to phonemes. The assumption that the likelihoods of these phoneme arcs are independent of the phonetic context allows us to convert the search through a large tree into a search through a much smaller network or graph. The computational requirements are reduced by roughly a factor of 70 compared to estimating the exact likelihood scores for the 75 000 words. This fast search algorithm is called the syllabic graph search. The recognition accuracy obtained for the syllabic graph search approaches that obtained using the exact likelihood scores for the phoneme sequences.
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43.72.Ne Automatic speech recognition systems

A search for a word‐beginning superiority effect

S. G. Nooteboom and M. J. van der Vlugt

J. Acoust. Soc. Am. Volume 84, Issue 6, pp. 2018-2032 (1988); (15 pages)

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This article reports two experiments examining whether or not auditory word recognition is more sensitive to word‐initial than to word‐final stimulus information. In the first experiment the contributions of prefixes and suffixes to word recognition were compared. These affixes carried widely varying amounts of lexical information and were added to somewhat degraded monomorphematic word stems in Dutch synthetic speech. Although there was a strong effect of lexical information on word recognition, no difference was found between the contributions of prefixes and suffixes. In the second experiment the effects of masking with noise of either initial or final parts of polysyllabic and monomorphematic synthesized Dutch words were compared. The amount of lexical redundancy carried by initial and final parts of words was the same. Again no difference was found. We conclude that the process of lexical activation during spoken‐word recognition is equally sensitive to word‐initial and word‐final stimulus information. A special role of word onsets remains because the onsets can ensure proper temporal alignment between stimulus and candidate word forms.
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43.71.An Models and theories of speech perception
43.71.Es Vowel and consonant perception; perception of words, sentences, and fluent speech

Speech masking. II: Simultaneous masking thresholds under ‘‘naturalistic’’ listening conditions

Murray Spiegel

J. Acoust. Soc. Am. Volume 84, Issue 6, pp. 2033-2044 (1988); (12 pages) | Cited 2 times

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This article investigates the role of listening conditions in determining thresholds for probe tones masked by natural speech. These thresholds are of interest because they are a sensitive probe of the activity profile, or spectrum, of sounds such as speech in the auditory system. Most human performance tests are carried out under highly artificial listening conditions, which may not reflect how people listen to speech in common listening environments. In this study, reference conditions (similar to minimal uncertainty listening conditions used in many performance tests) were compared to a ‘‘naturalistic’’ listening condition and to another, intermediate, condition. In the naturalistic listening condition, listeners did not know the frequency or the position of probe tones; additionally, they were required to attend to the semantic content of sentences. In the reference condition, listeners knew the frequency and position of probe tones masked by single syllables. Average thresholds were elevated by 4 dB in the naturalistic listening condition with respect to the reference condition, and thresholds tended to be elevated more for higher‐frequency probe tones. The results provide previously unknown information about the resolution of speech sounds in the auditory system during speech comprehension.
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43.71.Qr Neurophysiology of speech perception
43.71.Es Vowel and consonant perception; perception of words, sentences, and fluent speech
43.66.Dc Masking

Detection of linear frequency glides as a function of frequency and duration

Gary J. Dooley and Brian C. J. Moore

J. Acoust. Soc. Am. Volume 84, Issue 6, pp. 2045-2057 (1988); (13 pages) | Cited 10 times

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This article compares frequency discrimination thresholds for four conditions, using a two‐interval forced‐choice task: (1) discrimination of a difference in center frequency for two pulsed tones (DLF); (2) discrimination of a steady tone from an up‐frequency glide with the same mean frequency (UP‐DL); (3) discrimination of a steady tone from a down‐frequency glide with the same mean frequency (DOWN‐DL); (4) discrimination of an up‐frequency glide from a down‐frequency glide with the same mean frequency (UPVSDOWN‐DL). All glides were linear in Hz/s. Experiment 1 measured thresholds as a function of center frequency over the range 500–8000 Hz in 1‐oct steps, for a fixed duration of 500 ms. The variation of glide thresholds with frequency was similar to that for the DLFs. Experiment 2 measured thresholds as a function of duration over the range 50–750 ms, for a fixed center frequency of 2000 Hz. The DLFs decreased monotonically with increasing duration. The glide thresholds decreased as duration increased from 50 to 100 ms, but did not change markedly beyond that. In both experiments, DLFs and UPVSDOWN‐DLs were similar. UP‐DLs and DOWN‐DLs were typically two to three times greater than DLFs and UPVSDOWN‐DLs, and UP‐DLs tended to be larger than DOWN‐DLs at center frequencies up to 2000 Hz. Experiments 3 and 4 measured thresholds for detecting glides in frequency when fixed glides in level were superimposed on all stimuli. The glides in level had only a small effect on the frequency‐glide thresholds. The results are discussed in terms of their compatibility with Zwicker’s [Acustica 6, 365–381 (1956)] excitation‐pattern model of modulation detection and in terms of their implications for sampling theories of glide detection.
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43.66.Fe Discrimination: intensity and frequency
43.66.Mk Temporal and sequential aspects of hearing; auditory grouping in relation to music
43.66.Ba Models and theories of auditory processes

Broadband repetition pitch: Spectral dominance or pitch averaging?

Richard M. Warren and James A. Bashford, Jr.

J. Acoust. Soc. Am. Volume 84, Issue 6, pp. 2058-2062 (1988); (5 pages) | Cited 1 time

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Repetition pitch (RP) produced by mixing noise with its restatement was studied under a variety of delays and filtering conditions. Both normal or cophasic mixtures (RP+) and polarity inverted or antiphasic mixtures (RP−) were used. In keeping with earlier reports, RP+ having a delay of t seconds produced a pitch of 1/t Hz for all spectral regions examined. Broadband RP− diverged from 1/t Hz in keeping with the literature, but the pitches heard under novel filtering conditions indicated that (contrary to some current theories) RP− is a weighted average of the different pitches contributed by different spectral regions. Polarity inversion of an echo introduces additional frequency‐dependent delays, and it is suggested that the corresponding RP− at local regions of the basilar membrane reflects a temporal domain analysis based on the sum of these two types of delays.
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43.66.Hg Pitch
43.66.Ki Subjective tones

Discrimination of interaural differences of time in the envelopes of high‐frequency signals: Integration times

Thomas N. Buell and Ervin R. Hafter

J. Acoust. Soc. Am. Volume 84, Issue 6, pp. 2063-2066 (1988); (4 pages) | Cited 10 times

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Listeners detected interaural differences of time in trains of high‐frequency clicks. The manipulated variables were the number of clicks in the train and the period between clicks. Thresholds were compared to an optimal integrator, where the binaural information accrued from each click in the stimulus train is equivalent. In agreement with data reported in the past, integration is optimal only when the period between clicks exceeds approximately 10 ms and when the duration of the entire stimulus train is less than about 250 ms. The first constraint represents a limitation due to a form of ‘‘binaural adaptation’’ and the second is due to a limited ‘‘integration period.’’
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43.66.Pn Binaural hearing
43.66.Mk Temporal and sequential aspects of hearing; auditory grouping in relation to music

Morphology of the cochlear nerve in Sprague‐Dawley and Brown Norway rats

Virginia Hoeffding and Martin L. Feldman

J. Acoust. Soc. Am. Volume 84, Issue 6, pp. 2067-2069 (1988); (3 pages)

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Cochlear nerve morphology was studied in young adult albino (Sprague‐Dawley) and pigmented (Brown Norway) rats. Analysis of the material included counts of normal and degenerating fibers and of glial cell nuclei, and measurements of vascularity and of the nerves’ cross‐sectional areas. The median number of normal fibers in the Sprague‐Dawley rats was 21 216, and, in the Brown Norway rats, it was 20 186. There were no statistically significant differences between the two strains in numbers of normal fibers, degenerating myelin sheaths, or glial cell nuclei, or in the cross‐sectional areas of the nerves. The area density of blood vessels was significantly higher in nerves from the Sprague‐Dawley rats. The median area density in that strain was 0.0149, while in the Brown Norway rats the median area density was 0.0105.
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43.64.Dw Anatomy of the cochlea and auditory nerve
43.64.Tk Physiology of sound generation and detection by animals

High‐frequency plane waves in the ear canal: Application of a simple asymptotic theory

R. D. Rabbitt

J. Acoust. Soc. Am. Volume 84, Issue 6, pp. 2070-2080 (1988); (11 pages) | Cited 3 times

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An asymptotic theory describing the propagation of plane waves in a variable cross‐section ear canal is combined with pressure measurements in order to determine the energy reflection coefficient at the eardrum and the standing wave patterns along the length of the canal. The relative phase of the reflected wave, and the cross‐sectional area function of the ear canal, are also determined from the noninvasive pressure measurements. The theory is based on a high‐frequency multiscale solution of the one‐dimensional horn equation and is shown to agree well with the phase and amplitude of experimental measurements in human replica ear canals.
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43.64.Ha Acoustical properties of the outer ear; middle-ear mechanics and reflex
43.64.Bt Models and theories of the auditory system

Masking patterns in the bullfrog (Rana catesbeiana). II: Physiological effects

Edward G. Freedman, Michael Ferragamo, and Andrea Megela Simmons

J. Acoust. Soc. Am. Volume 84, Issue 6, pp. 2081-2091 (1988); (11 pages) | Cited 1 time

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Responses of individual eighth‐nerve fibers in the bullfrog (Rana catesbeiana) were measured to tone bursts at best frequency against a background of continuous, broadband masking noise. These data were used to calculate critical masking ratios to describe the fibers’ responses to tones embedded in noise. In the frequency response range of the amphibian papilla (100–1000 Hz), critical ratios increase with tone frequency. Critical ratios of basilar papilla fibers (1000–2000 Hz) are generally higher than those of amphibian papilla fibers. Critical ratios are also significantly related to fiber threshold such that fibers with high thresholds, regardless of their best frequencies, have higher critical ratios and are thus less selective to signals embedded in noise. Critical ratios based on neural responses show a somewhat different frequency‐dependent trend than do critical ratios based on psychophysical data presented previously for this species [A. M. Simmons, J. Acoust. Soc. Am. 83, 1087–1092 (1988a)]. In addition, these neural critical ratios do not appear to be level independent, as are psychophysical critical ratios. The data suggest that frequency selectivity of hearing in the bullfrog as measured behaviorally is probably not mediated solely by spectral filtering in the auditory periphery.
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43.64.Pg Electrophysiology of the auditory nerve
43.64.Tk Physiology of sound generation and detection by animals
43.66.Dc Masking

Synchrony‐dependent autocorrelation in eighth‐nerve‐fiber response to rippled noise

Jaap H. ten Kate and Marc F. van Bekkum

J. Acoust. Soc. Am. Volume 84, Issue 6, pp. 2092-2102 (1988); (11 pages)

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Autocorrelograms and interval and delay histograms of the eighth‐nerve‐fiber response in cats to cosine noise were recorded. A good detectability level for the delay oscillations in the autocorrelograms was always found, when the fiber had a high value of the synchronization index at characteristic frequency (CF). In order to study their relationship, autocorrelograms for cosine noise stimulation were computed by the substitution of synchronization indices in the Poisson distribution formulas for higher‐order intervals. The approach was made possible through a further exploration of Johnson’s synchronization theory [D. H. Johnson, ‘‘The response of single auditory‐nerve fibers in the cat to single tones: synchrony and average discharge rate,’’ Ph. D. thesis, MIT, Cambridge, MA (1974)]. It was shown that computed autocorrelograms somewhat resembled experimental ones. The differences between them concerned the envelopes of the ‘‘onset’’ and ‘‘delay’’ oscillations, viz., in their constrictions and amplitudes. These constrictions were shown to be significant only in recordings at delays ≥4/CF, corresponding to the dominant region for human repetition pitch.
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43.64.Pg Electrophysiology of the auditory nerve
43.64.Bt Models and theories of the auditory system
43.66.Hg Pitch

Formulation for quantitative performance evaluation of holographic imaging

Hua Lee

J. Acoust. Soc. Am. Volume 84, Issue 6, pp. 2103-2108 (1988); (6 pages) | Cited 1 time

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In this article, an alternative approach is proposed to quantitatively evaluate image quality of holographic reconstructions. Instead of the conventional approach outlined by the Rayleigh resolution criterion, this approach describes the image quality in terms of the certainty of the estimation of the source distribution. Given the classical imaging parameters, this formulation gives results in exact agreement with the Rayleigh criterion. In addition, this formulation can be extended to quantitatively evaluate the degradation factors such as aperture offset, wave field sampling, quantization error, noise level, and phase‐only data acquisition that are not considered in the formulation of Rayleigh resolution criterion. This approach can be also used for quantitative performance evaluation of enhancement algorithms for comparison purposes.
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43.60.Sx Acoustic holography

A theoretical interpretation of the prevalence rate of noise‐induced annoyance in residential populations

Sanford Fidell, Theodore Schultz, and David M. Green

J. Acoust. Soc. Am. Volume 84, Issue 6, pp. 2109-2113 (1988); (5 pages) | Cited 9 times

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A simple statistical model containing only one free parameter is proposed to account for the variability observed in a dosage–effect relationship between an integrated metric of noise exposure and the prevalence of annoyance in a community as synthesized by Schultz [J. Acoust. Soc. Am. 64, 377–405 (1978)]. The model assumes that a community’s noise dose is produced by long‐term noise exposure acting through a compressive transformation of the day–night average sound level (DNL). Individual reactions to this noise dose are characterized by a random variable. Individuals are assumed to report a consequential degree of annoyance when the value of this random variable exceeds a criterion level that is not a function of acoustic factors.
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43.50.Ba Noisiness: rating methods and criteria
43.50.Qp Effects of noise on man and society
43.50.Sr Community noise, noise zoning, by-laws, and legislation
43.66.Ba Models and theories of auditory processes

The time‐domain solution of the wide‐angle parabolic equation including the effects of sediment dispersion

Michael D. Collins

J. Acoust. Soc. Am. Volume 84, Issue 6, pp. 2114-2125 (1988); (12 pages) | Cited 6 times

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The wide‐angle time‐domain parabolic equation (TDPE), which is the inverse Fourier transform of the wide‐angle parabolic equation (PE), is derived. A numerical solution for the model is described and a benchmark calculation is presented. The narrow‐angle TDPE is also considered and its error is analyzed and compared with the error of the narrow‐angle PE. The TDPE is compared with the progressive wave equation, which is shown to be restricted to narrow‐angle propagation for practical purposes. In the sediment, attenuation is assumed to depend linearly on frequency and the corresponding causal dispersion law is assumed. The model is used to show that the effect of sediment dispersion on pulse propagation in the ocean can be significant.
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43.30.Bp Normal mode propagation of sound in water
43.30.Ma Acoustics of sediments; ice covers, viscoelastic media; seismic underwater acoustics
43.20.Bi Mathematical theory of wave propagation

Acoustical absorption and scattering cross sections of spherical bubble clouds

Luca d’Agostino and Christopher E. Brennen

J. Acoust. Soc. Am. Volume 84, Issue 6, pp. 2126-2134 (1988); (9 pages) | Cited 12 times

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The present work investigates the acoustical absorption and scattering cross sections of spherical bubble clouds subject to harmonic farfield pressure excitation. Bubble dynamics effects and energy dissipation due to viscosity, heat transfer, liquid compressibility, and relative motion of the two phases are included. The equations of motion for the average flow and for the bubble radius are linearized and a closed‐form solution is obtained. Due to the presence of natural oscillatory modes and frequencies, the acoustical cross sections of the cloud are very different from those of each individual bubble in the cloud, as well as from the acoustical cross sections of a single large bubble with the same volume of vapor and gas. In general, the acoustical properties of any given volume of the dispersed phase depend strongly on the degree of dispersion because of the complex interactions of the dynamics of the bubbles with the whole flow.
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43.30.Ft Volume scattering
43.30.Gv Backscattering, echoes, and reverberation in water due to combinations of boundaries

Sound transmission experiments from an impulsive source near rigid wedges

Saimu Li and C. S. Clay

J. Acoust. Soc. Am. Volume 84, Issue 6, pp. 2135-2143 (1988); (9 pages) | Cited 2 times

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Experimental sound transmissions in air from a spark source to a small microphone were made near rigid wedges. Two types of experiments were made. The first experiments were transmissions within an approximately 12° wedge and a 52° wedge. The Biot–Tolstoy exact wedge solution [I. Tolstoy and C. S. Clay, Ocean Acoustics (American Institute of Physics, New York, 1987), 2nd ed.] was used to calculate the theoretical impulse responses. Within the 12° and 52° wedge, the solution gives a finite set of images and a diffraction arrival. Theory and experiments matched. The second type of experiments measured the image or ‘‘optical’’ reflection as the reflection point was moved to the edge of a half‐plane and tested a Fresnel–Kirchhoff solution. The exact wedge solution gives a relative reflection amplitude of 1 compared to the reflection from an infinite plane. The Fresnel–Kirchoff solution of Trorey [A. W. Trorey, Geophysics 35, 762–784 (1970)] gives a relative signal of 1/2. Experiments were made near vertical incidence over a 270° wedge. They confirmed the correctness of the exact wedge solution and the incorrectness of the Trorey solution.
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43.30.Gv Backscattering, echoes, and reverberation in water due to combinations of boundaries
43.20.Fn Scattering of acoustic waves
43.20.Bi Mathematical theory of wave propagation

Generation of underwater sound by colliding spheres

Peter D. Thorne and Derek J. Foden

J. Acoust. Soc. Am. Volume 84, Issue 6, pp. 2144-2152 (1988); (9 pages) | Cited 2 times

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A laboratory examination of the acoustic field generated by spheres impacting underwater has been carried out. Records of the sound arising from collisions were taken and analyzed in the time and frequency domain. The transient radiated had the approximate form of a 1 1/2 ‐cycle sinusoid that, in some cases, had superimposed a high‐frequency ripple. A theoretical analysis of the signal in terms of rigid body radiation has been conducted. For such cases the sphere is treated as rigid and the motion of the sphere itself during impact generates a pressure wave that propagates out into the fluid. Using the Hertz law of contact to describe the acceleration time history of the spheres during impact, predictions for the underwater rigid body radiation were obtained and comparisons made with laboratory data. Also the natural modes of vibration of the sphere are considered to explain the high‐frequency component of the signal.
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43.30.Jx Radiation from objects vibrating under water, acoustic and mechanical impedance
43.20.Px Transient radiation and scattering
43.40.Kd Impact and impact reduction, mechanical transients

Estimation of surface noise source level from low‐frequency seismoacoustic ambient noise measurements

Henrik Schmidt and W. A. Kuperman

J. Acoust. Soc. Am. Volume 84, Issue 6, pp. 2153-2162 (1988); (10 pages) | Cited 5 times

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The waveguide nature of a shallow water environment bounded below by a viscoelastic medium permits noise to couple into seismic waves. Geophone and hydrophone measurements have shown that below a threshold frequency of about 10 Hz in 100 m of water, there is a large increase in the measured noise levels, with a peak at approximately 0.25 Hz. A previously developed wave theory of distributed noise in a waveguide has been combined with a full wave solution technique for stratified elastic media and used for numerical modeling and analysis of this phenomenon. It is demonstrated that this low‐frequency increase in noise level is only partly due to an increase in the source spectral level. At these frequencies, seismic interface waves become important propagation paths for the ambient noise, leading to a significant magnification of the observed noise levels. This strongly suggests that propagation effects have to be accounted for when evaluating source theories by comparison to experimental data.
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43.30.Nb Noise in water; generation mechanisms and characteristics of the field
43.30.Bp Normal mode propagation of sound in water

Signal attenuation due to cavity leakage

Max H. Sherman and Mark P. Modera

J. Acoust. Soc. Am. Volume 84, Issue 6, pp. 2163-2169 (1988); (7 pages)

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The propagation of sound waves in fluids requires information about three properties of the system: capacitance (compressibility), resistance (friction), and inductance (inertia). Acoustical design techniques to date have tended to ignore the frictional effects associated with airflow across the envelope of the acoustic cavity (e.g., resistive vents). Since such leakage through the cavity envelope is best expressed with a power law dependence on the pressure, standard Fourier techniques that rely on linearity cannot be used. In this article, the theory relevant to nonlinear leakage is developed and equations presented. Potential applications of the theory to techniques for quantifying the leakage of buildings are presented. Experimental results from pressure decays in a full‐scale test structure are presented and the leakage so measured is compared with independent measurements to demonstrate the technique.
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43.25.Ed Effect of nonlinearity on velocity and attenuation
43.25.Zx Measurement methods and instrumentation for nonlinear acoustics
43.55.Br Room acoustics: theory and experiment; reverberation, normal modes, diffusion, transient and steady-state response

Equivalent temperature of sonoluminescence by steady and pulsed ultrasound irradiation for different gas–water systems

G. K. Johri, P. Ciuti, G. Iernetti, and F. Tomasini

J. Acoust. Soc. Am. Volume 84, Issue 6, pp. 2170-2178 (1988); (9 pages)

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The equivalent temperature of sonoluminescence is analyzed by focused steady and pulsed ultrasonic irradiation at 0.7 MHz for different monoatomic and diatomic gases saturating the distilled water. Transducer voltage, pulse time, total excitation time, and pulse duty ratio have been varied. The intensities of sonoluminescence in a yellow, a blue, and an ultraviolet wavelength range are measured using corresponding filters and three photomultiplier tubes viewing a cell of 160 cm3 in volume. The data are taken near the threshold and well inside the region of developed cavitation. The equivalent temperature decreases by decreasing the inverse pulse duty ratio from the threshold value down to the steady irradiation; it increases by increasing the sound pressure amplitude and decreases by increasing the pulse time and the excitation time. The equivalent temperature increases by increasing the atomic weight of the monoatomic gas saturating the water when the cavitation zone is in a nonsaturated condition, i.e., near the incipient threshold of the pulsed irradiation. The equivalent temperature of the sonoluminescence is analyzed in the initial and final stages of development of the cavitation zone, which correspond to bubble densities different by many orders of magnitude.
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43.25.Yw Nonlinear acoustics of bubbly liquids
43.35.Ei Acoustic cavitation in liquids
43.35.Sx Acoustooptical effects, optoacoustics, acoustical visualization, acoustical microscopy, and acoustical holography

Reexamination of dynamic problems of elasticity for negative Poisson’s ratio

A. William Lipsett and Abraham I. Beltzer

J. Acoust. Soc. Am. Volume 84, Issue 6, pp. 2179-2186 (1988); (8 pages) | Cited 2 times

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Recently, isotropic elastic materials with a negative Poisson’s ratio have been manufactured. Since most of the theoretical results of linear elasticity focus on a positive Poisson’s ratio, the need arises for their extension and reexamination. The above materials may have a variety of technological applications so the motivation for this study is not purely academic. The article deals first with some of the limit cases arising when Poisson’s ratio takes on an extreme value. For models represented by these limit cases, the material and structure responses may not be treated independently from each other. Then such basic dynamic elasticity problems as reflection from a free surface, propagation of Rayleigh waves, and lateral vibrations of beams and plates are reconsidered for the case of a negative Poisson’s ratio. It is shown, in particular, that the static definition of the shear factor in Timoshenko beam theory may not be satisfactory in all cases. Extensive numerical results are also given.
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43.20.Bi Mathematical theory of wave propagation
43.40.Cw Vibrations of strings, rods, and beams
43.40.Dx Vibrations of membranes and plates

Surface wave characteristics of fluid‐loaded multilayered media

Adnan H. Nayfeh and Timothy W. Taylor

J. Acoust. Soc. Am. Volume 84, Issue 6, pp. 2187-2191 (1988); (5 pages) | Cited 4 times

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Theoretical analyses are presented for the interaction of ultrasonic waves with multilayered media. The wave is supposed to be incident from a liquid, at an arbitrary angle, upon a plate consisting of an arbitrary number of different material layers. The composite plate is supported from the bottom by a solid half‐space. It is assumed that all solid interfaces are either rigidly or smoothly bonded. Reflection and transmission coefficients are derived for the total system. By examining the behavior of the reflection coefficient, all of the propagation characteristics are identified. Numerical results are given in order to delineate the influence of the plate material orderings on the propagation process. Included are also comparisons of results obtained under the rigid and the smooth bonding assumptions.
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43.20.Hq Velocity and attenuation of acoustic waves
43.35.Bf Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in liquids, liquid crystals, suspensions, and emulsions

Active control of low‐frequency harmonic sound radiated by a finite panel

C. Deffayet and P. A. Nelson

J. Acoust. Soc. Am. Volume 84, Issue 6, pp. 2192-2199 (1988); (8 pages) | Cited 7 times

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Quadratic optimization theory is applied to determine the minimum sound power output of a simply supported panel in a baffle when the radiation is controlled with additional ‘‘secondary’’ monopole sources. The theory presented produces analytical results for the optimal complex strengths of the secondary sources and the resulting value of minimum power output. The results are valid in the low‐frequency limit when the panel dimensions are much smaller than the wavelength of the radiated sound. The results demonstrate the importance of matching the secondary source distribution to the type of panel mode and can be explained using Maidanik’s modal radiation classification scheme.
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43.20.Ks Standing waves, resonance, normal modes
43.50.Ki Active noise control
43.20.Rz Steady-state radiation from sources, impedance, radiation patterns, boundary element methods
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