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Journal of the Acoustical Society of America

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Nov 1984

Volume 76, Issue 5, pp. 1293-1604

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Acoustic injury and the physiology of hearing

Richard A. Schmiedt

J. Acoust. Soc. Am. Volume 76, Issue 5, pp. 1293-1317 (1984); (25 pages) | Cited 3 times

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A critical bibliography of published articles concerning the effects of noise exposure on hearing has been compiled for the NIH. The review concentrated on articles published over the last 14 years; however, historical highlights of the past 50 years or so were included for continuity. This paper attempts to summarize in tutorial fashion the results of that review with regard to auditory physiology in general and explores some of the current issues with specific reference to acoustic injury. To date, most of the effort toward understanding acoustic injury has been focused on the auditory periphery; the emphasis is clear simply from the number of papers published in that area. On the other hand, the response of the central nervous system to noise exposure or to any type of damage in the periphery is essentially unknown. It would seem that it is now time to assume a more balanced approach and recognize the importance of the CNS with regard to understanding the overall consequences of acoustic injury.
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43.10.Ln Surveys and tutorial papers relating to acoustics research; tutorial papers on applied acoustics
43.64.-q Physiological acoustics
43.50.Qp Effects of noise on man and society
01.30.Rr Surveys and tutorial papers; resource letters

Noise‐induced hearing loss as influenced by other agents and by some physical characteristics of the individual

Larry E. Humes

J. Acoust. Soc. Am. Volume 76, Issue 5, pp. 1318-1329 (1984); (12 pages)

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The interaction of noise with a variety of other agents and with some physical characteristics of the individual to produce noise‐induced hearing loss is reviewed critically. The review is restricted, for the most part, to publications since 1970. Other agents interacting with steady‐state noise that are reviewed here include: (1) ototoxic drugs (kanamycin, neomycin, ethacrynic acid, furosemide, and salicylates), (2) impulse noise, and (3) whole‐body vibration. Physical characteristics of the individual that are reviewed are: (1) age, (2) presence of previous hearing loss from prior noise exposure, (3) eye color, and (4) race. Suggestions for future research in this general area are also made. Some of these suggestions are as follows: (1) to extend studies of the interaction of steady‐state noise with impulse noise, salicylates, and whole‐body vibration to encompass a broader range of exposure conditions, including exposure conditions typically encountered by the worker, (2) to develop an animal model of presbycusis to explore the interactions of noise‐induced hearing loss and presbycusis, and (3) to explore the potential interactions resulting from concurrent exposure to multiple agents, such as impulse noise and ototoxic drugs, in younger, more susceptible animals.
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43.10.Ln Surveys and tutorial papers relating to acoustics research; tutorial papers on applied acoustics
43.50.Qp Effects of noise on man and society
43.66.Sr Deafness, audiometry, aging effects

Biomolecular absorption of ultrasound. I: Molecular weight

Frederick W. Kremkau and Robert W. Cowgill

J. Acoust. Soc. Am. Volume 76, Issue 5, pp. 1330-1335 (1984); (6 pages) | Cited 1 time

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Amino acid solutions have absorptions which are generally small compared to those for proteins. Proteolytic enzyme treatment of proteins in solution reduces their absorption. These observations suggest that absorption increases with molecular weight. However, measurements of sugars, polysaccharides, amino acids, and proteins yield no correlations of absorption with molecular weight within these groups. Therefore, it is concluded that absorption increases in these molecules with increasing molecular weight only in a threshold sense, with absorption increasing significantly only in a restricted molecular weight range. This range may approximate that observed for polyethylene glycol and dextran, viz., 1 to 100 monomer units. However, there is some indication that the transition range may be narrower than a factor of 100 in molecular weight.
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43.80.Cs Acoustical characteristics of biological media: molecular species, cellular level tissues
43.35.Bf Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in liquids, liquid crystals, suspensions, and emulsions
87.15.-v Biomolecules: structure and physical properties

Effects of air loading on timpani membrane vibrations

Richard S. Christian, Robert E. Davis, Arnold Tubis, Craig A. Anderson, Ronald I. Mills, and Thomas D. Rossing

J. Acoust. Soc. Am. Volume 76, Issue 5, pp. 1336-1345 (1984); (10 pages) | Cited 10 times

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Measurements and theoretical calculations of timpani modal frequencies and decay times are made for the cases of no kettle enclosure and kettle enclosures of varying volume. For the calculations, the timpani membrane is assumed to be ideal and the kettle is assumed to be a rigid cylinder which is volume equivalent to the actual kettle. A Green function method is used for calculating the effects of air loading. The calculated modal frequencies and decay times are generally in good agreement with the experimental measurements. In particular, for typical kettle enclosures, the frequency ratios f11 : f21 : f31 ; f41 are found to be close to the harmonic ratios 2 : 3 : 4 : 5 over the normal playing range 100 Hz≲f11≲175 Hz.
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43.75.Hi Drums
43.40.At Experimental and theoretical studies of vibrating systems

Vocal cues to speaker affect: Testing two models

Klaus R. Scherer, D. Robert Ladd, and Kim E. A. Silverman

J. Acoust. Soc. Am. Volume 76, Issue 5, pp. 1346-1356 (1984); (11 pages) | Cited 2 times

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We identified certain assumptions implicit in two divergent approaches to studying vocal affect signaling. The ‘‘covariance’’ model assumes that nonverbal cues function independently of verbal content, and that relevant acoustic parameters covary with the strength of the affect conveyed. The ‘‘configuration’’ model assumes that both verbal and nonverbal cues exhibit categorical linguistic structure, and that different affective messages are conveyed by different configurations of category variables. We tested these assumptions in a series of two judgment experiments in which subjects rated recorded utterances, written transcripts, and three different acoustically masked versions of the utterances. Comparison of the different conditions showed that voice quality and F0 level can convey affective information independently of the verbal context. However, judgments of the unaltered recordings also showed that intonational categories (contour types) conveyed affective information only in interaction with grammatical features of the text. It appears necessary to distinguish between linguistic features of intonation and other (paralinguistic) nonverbal cues and to design research methods appropriate to the type of cues under study.
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43.70.Fq Acoustical correlates of phonetic segments and suprasegmental properties: stress, timing, and intonation
43.71.Gv Measures of speech perception (intelligibility and quality)

Late‐onset auditory deprivation: Effects of monaural versus binaural hearing aids

Shlomo Silman, Stanley A. Gelfand, and Carol Ann Silverman

J. Acoust. Soc. Am. Volume 76, Issue 5, pp. 1357-1362 (1984); (6 pages) | Cited 3 times

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Performance on tests of pure‐tone thresholds, speech‐recognition thresholds, and speech‐recognition scores for the two ears of each subject were evaluated in two groups of adults with bilateral hearing losses. One group was composed of individuals fitted with binaural hearing aids, and the other group included persons with monaural hearing aids. Performance prior to the use of hearing aids was compared to performance after 4–5 years of hearing aid use in order to determine whether the unaided ear would show effects of auditory deprivation. There were no differences over time for pure‐tone thresholds or speech‐recognition thresholds for both ears of both groups. Nevertheless, the results revealed that the speech‐recognition difference scores of the binaurally fitted subjects remained stable over time whereas they increased for the monaurally fitted subjects. The findings reveal an auditory deprivation effect for the unfitted ears of the subjects with monaural hearing aids.
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43.71.Gv Measures of speech perception (intelligibility and quality)
43.66.Ts Auditory prostheses, hearing aids
43.66.Sr Deafness, audiometry, aging effects
43.66.Pn Binaural hearing

Auditory filter asymmetry in the hearing impaired

Richard S. Tyler, Joseph W. Hall, Brian R. Glasberg, Brian C. J. Moore, and Roy D. Patterson

J. Acoust. Soc. Am. Volume 76, Issue 5, pp. 1363-1368 (1984); (6 pages) | Cited 11 times

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Thresholds for 2‐kHz sinusoidal signals were determined in the presence of a notched‐noise masker, for six normal‐hearing listeners and 12 listeners with cochlear hearing losses. Following Patterson and Nimmo Smith [J. Acoust. Soc. Am. 67, 229–245 (1980)], conditions were used where the notch was placed both symmetrically and asymmetrically about the signal frequency. The auditory filter shape for both the low‐ and high‐frequency side of the filter was calculated using the rounded‐exponential form of the filter. In six hearing‐impaired listeners, the auditory filter shape showed a shallow low‐frequency skirt indicating pronounced susceptibility to the upward spread of masking. In two hearing‐impaired listeners, the filter shape showed a shallow high‐frequency skirt, indicating pronounced susceptibility to the downward spread of masking. Two other listeners with mild threshold losses had steeper and more symmetric filters than normal, suggesting either a small conductive loss or an attenuation factor of sensorineural origin not associated with a degradation of frequency resolution. In the remaining two listeners, the auditory filter had too little selectivity for its shape to be reliably determined.
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43.66.Dc Masking
43.66.Sr Deafness, audiometry, aging effects

Intensity discrimination: A severe departure from Weber’s law

Robert P. Carlyon and Brian C. J. Moore

J. Acoust. Soc. Am. Volume 76, Issue 5, pp. 1369-1376 (1984); (8 pages) | Cited 16 times

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These experiments were designed to assess the importance of different types of information which might be used in detecting intensity changes for pure tones. Thresholds for detecting an intensity change, expressed as 10 log (ΔI/I), were measured over a wide range of frequencies and levels under conditions where one or more sources of information was either present or was removed. Spread of excitation was restricted by using bandstop noise centered at the signal frequency. Information conveyed by dynamic responses to signal onsets and offsets was eliminated by masking onsets and offsets with bursts of bandpass noise. Phase‐locking information was eliminated by using high‐frequency signals (above 5 kHz). Dynamic responses to signal onsets and offsets appear to play little role in intensity discrimination. Phase locking does appear to be important since Weber’s law or a near‐miss to it was observed at low frequencies, whereas at high frequencies performance deteriorated at moderate sound levels, and improved again at high levels. A preliminary experiment, using 225‐ms stimuli revealed only a small midlevel deterioration at high frequencies. However, when 30‐ms stimuli were used a large deterioration was observed, performance being worse when bandstop noise was presented with the tone. Hence at short durations and high frequencies spread of excitation seems to be important: When it is restricted by bandstop noise values of 10 log (ΔI/I) observed at moderate levels it can be as large as 14 dB. The results of the experiments are consistent with a bimodal distribution of thresholds in primary auditory neurons; at intermediate levels neither population will operate effectively. The absence of a level effect at low frequencies can be explained by phase‐locking cues extending the range over which VIIIth‐nerve fibers can signal changes in intensity.
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43.66.Fe Discrimination: intensity and frequency
43.64.Pg Electrophysiology of the auditory nerve

The precedence effect: Revisited

William A. Yost and David R. Soderquist

J. Acoust. Soc. Am. Volume 76, Issue 5, pp. 1377-1383 (1984); (7 pages) | Cited 19 times

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The precedence effect, as investigated by Wallach et al. [Am. J. Psychol. 62, 324–336 (1949)] was studied in three experiments. Experiment I was a replication of the original work of Wallach et al. Although the first click pair appears to dominate the perception of the position of the lateral image, the effect of the first click pair does not appear to ‘‘offset’’ or ‘‘cancel’’ the effect of the second click pair in terms of producing a lateral image at midline. The data are consistent with Zurek’s [J. Acoust. Soc. Am. 67, 952–964 (1980)] proposal that the binaural system is less sensitive to the interaural temporal difference of the second click pair. Experiment II indicated that the effect of the first click pair on lateral judgments still dominates that of the second click pair when the images are judged to be off midline. In all of these studies, the variability of the data is quite high. Experiment III showed that the first click pair also led to a larger change in masked thresholds (masking‐level differences, MLDs) than does the second click pair. These data reconfirm the use of two‐click stimuli for demonstrations of the precedence effect and they describe some of the limitations of the procedure and the generalities of the effect.
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43.66.Pn Binaural hearing
43.66.Mk Temporal and sequential aspects of hearing; auditory grouping in relation to music
43.66.Qp Localization of sound sources

The vertebrate ear as an exquisite seismic sensor

Peter M. Narins and Edwin R. Lewis

J. Acoust. Soc. Am. Volume 76, Issue 5, pp. 1384-1387 (1984); (4 pages) | Cited 1 time

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The neotropical frog Leptodactylus albilabris exhibits the greatest sensitivity to substrate‐borne vibrations (seismic stimuli) reported to date for any terrestrial animal. Nerve fibers from the source of this extraordinary sensitivity in the ear show clear stimulus‐evoked modulations of their resting discharge rates in response to sinusoidal seismic stimuli with peak accelerations less than 0.001 cm/s2 (10−6 g). Evidence indicates that its source is the saccule, an organ of hearing in fish and of balance in man. We report that single vibration‐sensitive fibers in the white‐lipped frog saturate at (whole animal) displacements of 10 Å peak to peak [Fig. 1(b)]. Assuming a conservative 20‐dB dynamic range for these fibers, the in vivo frog saccule and the mammalian cochlea exhibit roughly equal sensitivities to displacement.
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43.64.Ld Physiology of hair cells
43.64.Tk Physiology of sound generation and detection by animals
43.66.Wv Vibration and tactile senses

Group delay measurement from spiral ganglion cells in the basal turn of the guinea pig cochlea

Anthony W. Gummer and Brian M. Johnstone

J. Acoust. Soc. Am. Volume 76, Issue 5, pp. 1388-1400 (1984); (13 pages) | Cited 4 times

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Measurements of group delay were made extracellularly from spiral ganglion cells in the 3.7 to 5.0‐mm region of the guinea pig cochlea, using sinusoidally amplitude modulated tones with constant modulating frequency (100 Hz) and depth of modulation (0.19). Threshold cochlear tuning was accompanied by frequency‐dependent group delays. The group delay on the low‐frequency tail was independent of carrier frequency; the interunit variation was 0.28–1.28 ms. The difference in group delay between CF and the low‐frequency tail decreased as the CF threshold increased (−0.09±0.02 ms per 10 dB, beginning at 0.62±0.07 ms at 0 dB SPL). The group delay decreased above CF; at the units’ maximum frequency it was less than the low‐frequency tail value, and was sometimes negative. Following arterial injections of furosemide the CF threshold increased and the group delay peak decreased; the low‐frequency tail was unaffected. The group delay decreased with increasing intensity; the reduction near and above CF was not only larger than that on the low‐frequency tail, but also the change at 5–10 dB above threshold was far greater than expected from the Q10 dB of the suprathreshold iso‐rate tuning curves. A minimum‐phase analysis suggested that the group delay response above CF, together with its nonlinear behavior, can be accounted for by a high‐frequency, level‐independent, amplitude plateau, in combination with the single unit, amplitude nonlinearity which is known to exist above CF.
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43.64.Pg Electrophysiology of the auditory nerve
43.64.Nf Cochlear electrophysiology
43.64.Tk Physiology of sound generation and detection by animals
43.80.Lb Sound reception by animals: anatomy, physiology, auditory capacities, processing

Interaural time sensitivity of high‐frequency neurons in the inferior colliculus

Tom C. T. Yin, Shigeyuki Kuwada, and Yasumasa Sujaku

J. Acoust. Soc. Am. Volume 76, Issue 5, pp. 1401-1410 (1984); (10 pages) | Cited 2 times

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Recent psychoacoustic experiments have shown that interaural time differences provide adequate cues for lateralizing high‐frequency sounds, provided the stimuli are complex and not pure tones. We present here physiological evidence in support of these findings. Neurons of high best frequency in the cat inferior colliculus respond to interaural phase differences of amplitude modulated waveforms, and this response depends upon preservation of phase information of the modulating signal. Interaural phase differences were introduced in two ways: by interaural delays of the entire waveform and by binaural beats in which there was an interaural frequency difference in the modulating waveform. Results obtained with these two methods are similar. Our results show that high‐frequency cells can respond to interaural time differences of amplitude modulated signals and that they do so by a sensitivity to interaural phase differences of the modulating waveform.
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43.64.Qh Electrophysiology of the auditory central nervous system
43.66.Pn Binaural hearing
43.66.Qp Localization of sound sources

Short‐latency auditory responses obtained by cross correlation

Robert A. Dobie and Michael J. Wilson

J. Acoust. Soc. Am. Volume 76, Issue 5, pp. 1411-1421 (1984); (11 pages) | Cited 1 time

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Short‐latency auditory responses were derived by cross correlation of pseudorandom white noise with averaged scalp potentials in guinea pigs. The cross‐correlation functions were characterized by distinct cochlear microphonic and neural components, as distinguished by susceptibility to hypothermia and masking noise. This technique detects only linear, frequency‐following responses of the auditory system, and demonstrated neural frequency following up to 3–4 kHz; thresholds were about 30–40 dB spectrum level. While conventional auditory brain stem responses reflect onset neural activity and are most responsive to high‐frequency stimuli, cross‐correlation responses reflect frequency‐following activity, primarily to low frequencies, and thus may represent a complementary method of electrophysiologic assessment of the auditory system. Data are very rapidly acquired, and estimation of responses of limited areas of the cochlea may be possible by off‐line digital filtering of cross‐correlation functions obtained with broadband noise stimuli.
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43.64.Ri Evoked responses to sounds
43.64.Tk Physiology of sound generation and detection by animals

Spectral model and time‐varying covariance functions for the nonstationary processes

Y. H. Tsao

J. Acoust. Soc. Am. Volume 76, Issue 5, pp. 1422-1426 (1984); (5 pages) | Cited 1 time

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A stochastic (random) process may be nonstationary if its stochastic features vary with a shift of time. For the most practical processes, although more or less nonstationary, the generalized harmonics representation still makes sense; so does the spectral density function which is now defined as being ‘‘evolutionary’’ in view of the time dependency. The present paper briefly reviews this spectral description for a nonstationary process and further models it as the output from a white‐noise excited time‐variant shaping filter. With this model the nonstationary processes X(t) and Y(t) are denoted as ∫∞−∞Ax,t(ω)ejωt dW(ω) and ∫∞−∞Ay,t(ω)ejωt dW(ω), respectively, where Ax,t(ω) and Ay,t(ω) are the so‐called modulation functions (MFs) and dW(ω) is a random variable which retains the orthogonality. Previous papers have investigated and shown some advantage of using such a modulation function (MF) description in solving many practical nonstationary problems which hinged on the concept of the evolutionary auto/cross‐spectral density (EASD/ECSD). In this paper an attempt is made to apply further this MF model to describe the time‐varying auto/cross‐covariance functions (ACVF/CCVF) for the nonstationary processes and it is found that they are closely related to the relevant MFs but not to the EASD/ECSD in the Fourier transform sense, as has been summarized in the well‐known Wiener–Khintchine (W–K) relationship for the stationary processes. The new relationship has effectively generalized the W–K theorem in a special way, which has been proven efficient and accurate to both the synthetic signals such as the uniformly amplitude‐modulated process, the uniformly frequency‐modulated process and random‐phase process, and to the practical signals such as the nonstationary acoustic processes.
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43.60.Cg Statistical properties of signals and noise
43.60.Gk Space-time signal processing, other than matched field processing
43.58.Kr Spectrum and frequency analyzers and filters; acoustical and electrical oscillographs; photoacoustic spectrometers; acoustical delay lines and resonators

Tomographic observation of flow in a water tank

Takuso Sato and Makoto Shiraki

J. Acoust. Soc. Am. Volume 76, Issue 5, pp. 1427-1432 (1984); (6 pages)

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A tomographic method flow distribution estimation from the data of time of flight of pulsed sound waves among fixed stations is examined for the case of plane flow detection in a water tank. The errors due to the limited number of stations and the effects of the use of a pseudoinverse method are examined under practical conditions. Experimental results showed the usefulness of the method in these cases.
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43.60.Gk Space-time signal processing, other than matched field processing
47.80.-v Instrumentation and measurement methods in fluid dynamics

Range and frequency dependence of transfer function phase

Richard H. Lyon

J. Acoust. Soc. Am. Volume 76, Issue 5, pp. 1433-1437 (1984); (5 pages) | Cited 2 times

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The phase trend in multi‐degree‐of‐freedom systems can be determined by an algorithm that tracks the relative signs of adjacent resonances in a modal expansion of transfer functions. This algorithm is expressed in analytical form for two‐dimensional systems. The analytical expression shows the transition from input function phase to the reverberant phase limit. The phase trend for two‐dimensional systems greatly exceeds that of the average response of such systems and the reason for this difference is analyzed.
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43.55.Ka Computer simulation of acoustics in enclosures, modeling
43.40.Cw Vibrations of strings, rods, and beams
43.40.Dx Vibrations of membranes and plates

Rayleigh wave velocity and displacement in orthorhombic, tetragonal, hexagonal, and cubic crystals

D. Royer and E. Dieulesaint

J. Acoust. Soc. Am. Volume 76, Issue 5, pp. 1438-1444 (1984); (7 pages) | Cited 10 times

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The analysis of Rayleigh wave propagation in crystals is carried out in the cases for which, on the one hand, Christoffel equations split into two parts providing a Rayleigh wave polarized in the sagittal plane, and on the other hand, boundary conditions simplify under the conditions that some elastic constants vanish. It is shown that these requirements are satisfied by 16 configurations in crystals belonging to the orthorhombic, tetragonal, cubic, and hexagonal symmetry systems. The three particular cases solved by Stoneley [R. Stoneley, Proc. R. Soc. London, Ser. A 232, 447–458 (1955)] are included. The equations giving the velocity and the mechanical displacement are established. The influence of the anisotropy factor on the decay constant is emphasized for crystals belonging to the cubic or tetragonal systems. Curves showing the decrease of the longitudinal and transverse components of the mechanical displacement are given for YAG, Si, GaAs, TiO2, and TeO2. Oscillations and a very slow decrease versus depth of the mechanical displacement components were observed for TeO2. These are ascribed to the strong anisotropy of this crystal.
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43.35.Cg Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in solids; elastic constants
43.35.Pt Surface waves in solids and liquids
68.35.Gy Mechanical properties; surface strains
68.35.Iv Acoustical properties

Influence of horizontal random bottom structure on acoustic intensity in a shallow ocean

C. E. Ashley, M. J. Jacobson, and W. L. Siegmann

J. Acoust. Soc. Am. Volume 76, Issue 5, pp. 1445-1455 (1984); (11 pages)

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Effects of random bottom structure on acoustic intensity in isospeed shallow water are studied. The randomness is due to stochastic variations in the bottom density and sound speed in the horizontal direction beneath a plane water–bottom interface. Ray geometry, spreading loss, and bottom loss and phase shift are examined in order to derive formulas for mean intensity and the variance of intensity. The expressions obtained are sufficiently general to permit their use with different bottom‐acoustic models of sound reflection. In this paper, for illustrative and comparative purposes, two such models, one developed by Mackenzie and the other by Rayleigh, are considered. The distinctive acoustic consequences of bottoms of different density mean, variance, and horizontal correlation are discussed, as are comparisons of results for the two bottom‐reflection models. Intensity moments are obtained also for differing source–receiver range and water depth.
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43.30.Cq Ray propagation of sound in water
43.20.Dk Ray acoustics
43.20.Fn Scattering of acoustic waves
43.60.Cg Statistical properties of signals and noise

Propagation of sound out of a fluid wedge into an underlying fluid substrate of greater sound speed

Alan B. Coppens, M. Humphries, and James V. Sanders

J. Acoust. Soc. Am. Volume 76, Issue 5, pp. 1456-1465 (1984); (10 pages)

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A Green’s function extension of image theory allows the sound field in an absorbing fluid substrate underlying a fluid wedge of slower sound speed to be evaluated on a desktop computer. (1) Solutions based on an end‐point approximation, valid at great distances from the apex of the wedge and for absorptions representative of sedimentarylike materials, show a beam peaking at a depth close to that predicted by more complicated models. An additional random‐phase assumption provides a functional dependence for this angle identical with that obtained by a more elaborate procedure. (2) Solutions based on a saddle‐point approximation are valid below the apex and for arbitrary absorption. At moderate absorption, these solutions are consistent with those observed in the farfield. For small absorption, the sound field displays a heretofore unnoticed structure that is consistent with the mutual interference of sound beams entering the substrate at various distances from the apex. Some previously unreported measurements of the sound field in the substrate support the predictions of the saddle‐point approximation.
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43.30.Cq Ray 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

The probability distribution of intensity for acoustic propagation in a randomly varying ocean

C. Macaskill and T. E. Ewart

J. Acoust. Soc. Am. Volume 76, Issue 5, pp. 1466-1473 (1984); (8 pages) | Cited 2 times

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Probability distributions of intensity fluctuations from the MATE, AFAR, and S. W. Bermuda underwater acoustics experiments are compared with recently derived theoretical expressions. The limitations and strengths of these expressions are discussed. In particular, it is found that the work of Furutsu [J. Math. Phys. 17, 1252–1263 (1976)] gives a good description of the probability distribution function of intensity or log intensity, requiring only a knowledge of the second‐ and third‐order intensity moments. Furutsu’s description is not asymptotically correct at large range, so a modified form is proposed for the moments of intensity that reduce analytically to the log‐normal distribution at short range and to the exponential distribution at large range. This new form also predicts the higher moments well but cannot be inverted analytically. A numerical inversion is used, and the ensuing distribution agrees well with the analytical result of Furutsu. It is expected that the new expression will be applicable at all ranges.
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43.30.Bp Normal mode propagation of sound in water
43.60.Cg Statistical properties of signals and noise

Parametric acoustic array formation in dispersive fluids

Mark F. Hamilton and Francis H. Fenlon

J. Acoust. Soc. Am. Volume 76, Issue 5, pp. 1474-1492 (1984); (19 pages) | Cited 3 times

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The effect of dispersion on parametric arrays formed by Gaussian beams is investigated via solutions of the nonlinear paraxial wave equation. Analytical solutions are obtained by employing the quasilinear approximation; the results are thus restricted to weak nonlinear interactions. Axial field curves, farfield directivity patterns, and three‐dimensional field plots are presented for the difference‐frequency signal. The combined effects of dispersion, dissipation, and diffraction are considered in detail. Discrepancies with previous work are discussed. Solutions for the sum‐frequency and second‐harmonic components are also presented. A transformation is given to make the various solutions apply to arrays formed by primaries from a circular piston.
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43.25.Lj Parametric arrays, interaction of sound with sound, virtual sources
43.25.Cb Macrosonic propagation, finite amplitude sound; shock waves

Effects of noncollinear interaction on parametric acoustic arrays in dispersive fluids

Mark F. Hamilton

J. Acoust. Soc. Am. Volume 76, Issue 5, pp. 1493-1504 (1984); (12 pages) | Cited 1 time

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The effect of noncollinear interaction on radiation of the difference‐frequency signal from a parametric array is analyzed for small angles of intersection formed by two primary beams radiated from the same source. Although variations in the angle of intersection affect the phasing of the array, it is shown that for no practical situations can noncollinear interaction be used to offset detrimental effects due to dispersion. Instead, reduction in length of the interaction region as a result of noncollinear interaction adversely affects the farfield radiation. Length reduction is avoided when one primary beam completely overlaps the other, which is the situation encountered with the parametric receiving array.
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43.25.Lj Parametric arrays, interaction of sound with sound, virtual sources

Minimum target size in radiation force measurements

K. Beissner

J. Acoust. Soc. Am. Volume 76, Issue 5, pp. 1505-1510 (1984); (6 pages) | Cited 5 times

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The necessary target size in acoustic radiation force measurements has not, up to now, been discussed in the literature in a systematic and quantitative manner. Making use of recent progress in the theoretical treatment of the radiation force of three‐dimensional sound fields, this paper gives an assessment formula involving the target’s radius and distance from the source which is valid for the field of a baffled, circular, continuously vibrating piston source.
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43.25.Qp Radiation pressure

A microscopic investigation of bubble formation nuclei

D. E. Yount, E. W. Gillary, and D. C. Hoffman

J. Acoust. Soc. Am. Volume 76, Issue 5, pp. 1511-1521 (1984); (11 pages) | Cited 3 times

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Numerous experiments suggest that bubble formation in aqueous media is initiated by stable gas nuclei. Although attempts have been made both to detect and to describe these entities, their very existence is still controversial. This paper reports a detailed investigation using light and electron microscopes. The objects identified as nuclei are found in both distilled water and gelatin, and they resemble ordinary gas bubbles. Radii are on the order of 1 μm or less and can be three orders of magnitude smaller. The number density decreases exponentially with increasing radius. A gas filling is implied by the observation that nuclei expand when the pressure decreases and contract when it rises. The occurrence of nuclear clusters and of binary or osculating nuclei suggests that stabilization is achieved via surfactant films. The monolayer thickness of these films, estimated from the thicknesses of bilayer septa, is (20±7) Å. Many nuclei are embedded in reservoirs of surface‐active material made visible by osmium–tetroxide staining. Electron microscope sections are hardened by infiltrating gelatin with epoxy. Reservoirs, encased in epoxy, form microbubble chambers in which the coalescence and bursting of nuclei can be studied during extended exposures to the electron beam.
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43.25.Yw Nonlinear acoustics of bubbly liquids

The magnetospatial and electrospatial dispersion effects on elastic wave propagation in crystals

K. Kumaraswamy and N. Krishnamurthy

J. Acoust. Soc. Am. Volume 76, Issue 5, pp. 1522-1526 (1984); (5 pages)

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The effect of electric and magnetic fields on elastic wave propagation is studied for all crystal classes. Similarities in the propagation characteristics of electromagnetic and elastic waves in crystals are brought out. In the S4 type of crystals, there is a rotation of the major and minor axes of the elliptical state of polarization which depends on magnetospatial and electrospatial dispersion terms in the respective fields. A birefringence depending quadratically on an applied electric field is induced in the Th type of crystals for parallel field configurations. In perpendicular field configurations the longitudinal and transverse modes are coupled, exhibiting an elliptical state of polarization.
Show PACS
43.20.Bi Mathematical theory of wave propagation
43.35.-c Ultrasonics, quantum acoustics, and physical effects of sound
72.50.+b Acoustoelectric effects
73.50.Rb Acoustoelectric and magnetoacoustic effects
77.65.Dq Acoustoelectric effects and surface acoustic waves (SAW) in piezoelectrics
43.35.Rw Magnetoacoustic effect; oscillations and resonance
62.30.+d Mechanical and elastic waves; vibrations
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