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Journal of the Acoustical Society of America

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Oct 1985

Volume 78, Issue 4, pp. 1163-1459

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Passive acoustic location of bowhead whales in a population census off Point Barrow, Alaska

W. C. Cummings and D. V. Holliday

J. Acoust. Soc. Am. Volume 78, Issue 4, pp. 1163-1169 (1985); (7 pages) | Cited 5 times

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A sonobuoy array placed in the nearshore lead was used for locating bowhead whale sounds to determine if whales migrated past census stations beyond visual range and were uncounted. Based on a sample of 182 whale sounds (over 48 h) from closest point of approach (CPA) distances out to more than 10 km, 68% originated beyond 2 km (CPA), where only 1% of the 242 whales were sighted. No whales were sighted beyond 3 km during this time, but 53% of the located sounds originated that far and beyond. Thirty‐seven other bowhead sounds over 15 h were distributed out to 6 km. Two tracked whales moved at average speeds of 1.5 and 1.8 kn. Maximum location error was 1%–25% in a sector of 120° × 5–10 km, depending upon bearing and range. Most whale sounds were low‐frequency moans, trumpeting roars, and repetitive sequences (songs) with peak spectrum source level up to 189 dB re: 1 μPa, 1 m. Lack of correlations between numbers of sounds and sighted whales precluded using bowhead sounds to count individuals or even to extrapolate ratios of unseen to observed whales.
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43.80.Nd Effects of noise on animals and associated behavior, protective mechanisms

Colony differences in auditory thresholds in the canary (Serinus canarius)

Kazuo Okanoya and Robert J. Dooling

J. Acoust. Soc. Am. Volume 78, Issue 4, pp. 1170-1176 (1985); (7 pages) | Cited 1 time

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Adult canaries (Serinus canarius) from a closebred colony of the Belgian ‘‘Waterslager’’ strain were trained with operant techniques to respond to pure tones. A psychophysical tracking procedure was used to measure absolute auditory thresholds in quiet and in noise. Absolute thresholds in the middle‐ to high‐frequency region of the audiogram were between 30 and 40 dB higher (4–5 standard deviations) than those typically reported for other song birds including canaries of other strains and Waterslagers tested some years ago from another colony. Thus the Millbrook colony of domestic canary—an oscine songbird which learns its vocalizations by reference to auditory information—shows unusually high absolute thresholds for pure tones.
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43.80.Nd Effects of noise on animals and associated behavior, protective mechanisms
43.80.Jz Use of acoustic energy (with or without other forms) in studies of structure and function of biological systems
43.80.Lb Sound reception by animals: anatomy, physiology, auditory capacities, processing
43.66.Cb Loudness, absolute threshold

Perceptual aspects of synthesized approximations to melody

Anthony J. Watkins

J. Acoust. Soc. Am. Volume 78, Issue 4, pp. 1177-1186 (1985); (10 pages)

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A procedure is described for synthesizing tone sequences that contain a high proportion of events that are likely to be found in melodies that occur in music. This is done by using a random‐number generator with probability weightings that favor the selection of certain notes and intervals. The form of the probability weightings derives from constraints on the ‘‘semitone span’’ of the intervals, the ‘‘fifth span’’ of the intervals, and the occurrence of ‘‘scale’’ notes. The role of ‘‘redundancy’’ is also considered. In this way it is possible to obtain melodies that obey various combinations of the different constraints. Other melody variables are either fixed, randomized, or controlled. These experimental melodies were used in a test of the hypothesis that the more melodious tone sequences will be easier to organize perceptually and remember than less melodious sequences of equal redundancy. A psychophysical scaling procedure confirmed that the constraints generated tone sequences bearing degrees of perceptual similarity to ‘‘real’’ melodies. Melody discrimination was also measured. The ‘‘fifth span’’ and ‘‘scale’’ constraints increased the melodiousness of tone sequences. They also improved performance on tasks requiring the discrimination of unfamiliar, untransposed melodies, and the discrimination of transposed melodies after some familiarization. It is argued that general perceptual principles do not give a complete account of the perception of melody: A full description requires consideration of the listener’s tacit musical ‘‘knowledge’’ and its interaction with perceptual processes.
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43.75.Bc Scales, intonation, vibrato, composition
43.75.Wx Electronic and computer music
43.66.Fe Discrimination: intensity and frequency
43.66.Lj Perceptual effects of sound

Perceptual equivalence of acoustic cues that differentiate /r/ and /l/

Linda Polka and Winifred Strange

J. Acoust. Soc. Am. Volume 78, Issue 4, pp. 1187-1197 (1985); (11 pages) | Cited 4 times

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The perceptual effects of orthogonal variations in two acoustic parameters which differentiate American English prevocalic /r/ and /l/ were examined. A spectral cue (frequency onset and transition of F2 and F3) and a temporal cue (relative duration of initial steady state and transition of F1) were varied in synthetic versions of ‘‘rock’’ and ‘‘lock.’’ Four temporal variations in each of ten stimuli of a spectral‐cue continuum were generated. Phonetic identification and oddity discrimination tasks with the four series showed systematic displacement of perceptual boundaries and discrimination peaks, thus reflecting a trading relation between the two cues. The perceptual equivalence of spectral and temporal cues was investigated by comparing the accuracy of discrimination of three types of stimulus comparisons: phonetically facilitating two‐cue pairs, one‐cue pairs, and phonetically conflicting two‐cue pairs. As predicted, discrimination accuracy was ordered: facilitating cues > one cue > conflicting cues, indicating that perceivers discriminated on the basis of an integrated phonetic perception.
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43.71.Es Vowel and consonant perception; perception of words, sentences, and fluent speech

Consonant recognition in quiet as a function of aging among normal hearing subjects

Stanley A. Gelfand, Neil Piper, and Shlomo Silman

J. Acoust. Soc. Am. Volume 78, Issue 4, pp. 1198-1206 (1985); (9 pages) | Cited 4 times

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Consonant recognition in quiet using the Nonsense Syllable Test (NST) [Resnick et al., J. Acoust. Soc. Am. Suppl. 1 58, S114 (1975)] was investigated in 62 normal hearing subjects 20 to 65 years of age at their most comfortable listening levels (MCLs) and at 8 dB above and below MCL. Although overall consonant recognition performance was high (as expected for normal listeners), the effects of age decade, relative presentation level, and NST subsets were all significant, as was the interaction of age × level. The interactions of age × NST subset, and age × subset ×level were nonsignificant. These findings suggest that consonant recognition decreases with normal aging, particularly below MCL. However, the relative perceptual difficulty of the seven subtests is the same across age groups. Confusion matrices were similar across levels and age groups. Percent information transmitted for several consonant features was calculated from the confusion matrices. Older subjects showed decrements in performance primarily for the features recognized relatively less accurately by the younger subjects. The results suggest that normal hearing older individuals listening in quiet have decreased consonant recognition ability, but that their confusions are similar to those of younger persons.
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43.71.Gv Measures of speech perception (intelligibility and quality)
43.71.Es Vowel and consonant perception; perception of words, sentences, and fluent speech
43.66.Sr Deafness, audiometry, aging effects

Effects of masker waveform and signal‐to‐masker phase relation on diotic and dichotic masking by reproducible noise

Robert H. Gilkey, Donald E. Robinson, and Thomas E. Hanna

J. Acoust. Soc. Am. Volume 78, Issue 4, pp. 1207-1219 (1985); (13 pages) | Cited 11 times

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The proportions of hits and false alarms were estimated for the detection of a 500‐Hz sinusoidal signal in each of 25, reproducible samples of wideband, white, Gaussian noise. The effects of signal phase were investigated under diotic (MoSo) and dichotic (MoSπ) conditions and compared to the predictions of two major models of binaural hearing. Averaging the data over samples obscured important across‐sample and across‐subject differences in performance. The proportions of hits and false alarms for individual noise samples presented under the MoSo condition were highly correlated with those for the same noise samples under the dichotic MoSπ condition, suggesting that the cues determining performance under these conditions are related. Signal‐to‐masker phase had a large effect on the proportion of hits under the MoSo condition, but only a small effect under the MoSπ condition. The Vector model predicts a large effect of signal phase under the MoSπ condition, and is, therefore, imcompatible with this aspect of the data. The expected value of the decision variable of the EC model is independent of signal phase. However, when the variance of the decision variable is also considered, the EC model does predict changes in the proportion of hits with the phase of the signal, comparable to those observed here. Further, it was shown that, if minor changes in the form of the EC model’s decision variable or in the distribution of the internal noise parameters are assumed, the expected value of the decision variable also changes with the phase of the signal.
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43.66.Ba Models and theories of auditory processes
43.66.Dc Masking
43.66.Pn Binaural hearing

Simultaneous masking by gated and continuous sinusoidal maskers

Sid P. Bacon and Neal F. Viemeister

J. Acoust. Soc. Am. Volume 78, Issue 4, pp. 1220-1230 (1985); (11 pages) | Cited 16 times

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Simultaneous masking of a 20‐ms, 1‐kHz signal was investigated using 50‐ms gated and continuous sinusoidal maskers with frequencies below, at, and above 1 kHz. Gated maskers can produce considerably (5–20 dB) more masking than continuous maskers, and this difference does not appear to result from the spread of energy produced by gating either the masker or the signal. For masker frequencies below the signal frequency, this difference in masking is primarily due to the detection of the cubic difference tone in the continuous condition. For masker frequencies at and above the signal frequency, the difference appears to be an important property of masking. Implications of this frequency‐dependent effect for measures of frequency selectivity are discussed.
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43.66.Dc Masking
43.66.Mk Temporal and sequential aspects of hearing; auditory grouping in relation to music

The temporal course of simultaneous tone‐on‐tone masking

Sid P. Bacon and Neal F. Viemeister

J. Acoust. Soc. Am. Volume 78, Issue 4, pp. 1231-1235 (1985); (5 pages) | Cited 14 times

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Threshold for a 20‐ms, 1‐kHz signal was measured as a function of its temporal position within a longer duration gated masker; masker frequencies were below, at, and above 1 kHz. For a masker frequency above the signal frequency, there is a sizable temporal effect: As the onset of the signal is delayed, threshold decreases rapidly but then increases again as the signal approaches masker offset. Similar results can be observed for a masker frequency below the signal frequency, but that temporal effect is due to the detection of the cubic difference tone. The implication of this frequency‐dependent temporal effect for measuring psychophysical tuning curves is discussed.
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43.66.Dc Masking
43.66.Mk Temporal and sequential aspects of hearing; auditory grouping in relation to music

Behavioral audiograms of the bullfrog (Rana catesbeiana) and the green tree frog (Hyla cinerea)

Andrea Megela‐Simmons, Cynthia F. Moss, and Kimberly M. Daniel

J. Acoust. Soc. Am. Volume 78, Issue 4, pp. 1236-1244 (1985); (9 pages) | Cited 1 time

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Reflex modification was used in a psychophysical technique to measure absolute auditory sensitivity of two species of anurans. Behavioral audiograms for these animals reveal that the bullfrog can detect sounds from 100 Hz to 3.2 kHz and the green tree frog from 100 Hz to 5 kHz. The shape and the sensitivity of these behavioral audiograms are similar to those of neural evoked‐response audiograms of these animals. Absolute auditory sensitivity of anurans is only partially related to the spectral composition of their species‐specific vocalizations.
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43.66.Gf Detection and discrimination of sound by animals
43.64.Tk Physiology of sound generation and detection by animals
43.80.Lb Sound reception by animals: anatomy, physiology, auditory capacities, processing

Cancellation level and phase of the ( f2−f1) distortion product

Larry E. Humes

J. Acoust. Soc. Am. Volume 78, Issue 4, pp. 1245-1251 (1985); (7 pages) | Cited 2 times

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The cancellation level and phase were measured for the (f2−f1) distortion product in six normal‐hearing ears as a function of input level (L1,L2) and the frequency separation of the two input signals (f1, f2, where f2>f1). The effects of input level were examined for L1 and L2, varied together (L1=L2) and separately. Typically, f1 was 1500 Hz while f2/f1 was either 1.16, 1.32, 1.44, or 1.68. For L1=L2, the median data indicate that the (f2−f1) level grows at a rate of approximately 1.1 dB/dB when averaged across all stimulus conditions. This slope tended to be higher (∼1.6 dB/dB) for L1=L2>80 dB. Slopes for some subjects also increase as f2/f1 increases. The cancellation phase increases slightly (50°–100°) with an increase in L1=L2. With L1 at 75 to 80 dB, L2 ranging from 65 to 95 dB, and f2/f1=1.16, (f2−f1) increases monotonically with L2 up to L1=L2. As L2 increases further (L2>L1), the slopes for the growth of (f2−f1) decrease. For f2/f1=1.44, on the other hand, (f2−f1) appears to grow monotonically at a rate of approximately 0.5 dB/dB throughout the range of L2 values. The cancellation phase increases with L2 (approximately 100°) only for the wider frequency separation of the two input signals (f2/f1=1.44). There are, however, sizable individual differences in the behavior of the (f2−f1) distortion product.
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43.66.Ki Subjective tones
43.66.Ba Models and theories of auditory processes

An excitation‐pattern algorithm for the estimation of (2f1−f2) and (f2−f1) cancellation level and phase

Larry E. Humes

J. Acoust. Soc. Am. Volume 78, Issue 4, pp. 1252-1260 (1985); (9 pages) | Cited 1 time

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An excitation‐pattern algorithm is described which provides an estimate of cancellation level and phase for the (2f1−f2) and (f2−f1) distortion products. An experiment is first conducted to demonstrate the need for such an algorithm for (f2−f1) level predictions. The results of this experiment, which employed three pairs of primaries having complementary input levels (L1=65, L2=85 dB; L1=85, L2=65 dB), do not agree with the predictions of another similar algorithm [E. Zwicker, J. Acoust. Soc. Am. 69, 1410–1413 (1981)]. A new excitation‐pattern algorithm is then described. The predicted level behavior for (f2−f1) and (2f1−f2) is more accurate for the proposed algorithm. In addition, an accurate phase estimate is also provided by the new algorithm.
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43.66.Ki Subjective tones
43.66.Ba Models and theories of auditory processes

Relations between psychophysical data and speech perception for hearing‐impaired subjects. II

Wouter A. Dreschler and Reinier Plomp

J. Acoust. Soc. Am. Volume 78, Issue 4, pp. 1261-1270 (1985); (10 pages) | Cited 15 times

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Twenty‐one sensorineurally hearing‐impaired adolescents were studied with an extensive battery of tone‐perception, phoneme‐perception, and speech‐perception tests. Tests on loudness perception, frequency selectivity, and temporal resolution at the test frequencies of 500, 1000, and 2000 Hz were included. The mean values and the gradient across frequencies were used in further analysis. Phoneme‐perception data were gathered by means of similarity judgments and phonemic confusions. Speech‐reception thresholds were determined in quiet and in noise for unfiltered speech material, and with additional low‐pass and high‐pass filtering in noise. The results show that hearing loss for speech is related to both the frequency resolving power and temporal processing by the ear. Phoneme‐perception parameters proved to be more related to the filtered‐speech thresholds than to the thresholds for unfiltered speech. This finding may indicate that phoneme‐perception parameters play only a secondary role, and for that reason their bridging function between tone perception and speech perception is only limited.
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43.66.Sr Deafness, audiometry, aging effects
43.70.Dn Disordered speech

Relations among some psychoacoustic parameters in normal and cochlearly impaired listeners

Carl Ludvigsen

J. Acoust. Soc. Am. Volume 78, Issue 4, pp. 1271-1280 (1985); (10 pages) | Cited 7 times

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Frequency resolution (viz., masking by low‐pass‐filtered noise and broadband noise) and temporal resolution (viz., masking by interrupted noise) were compared with hearing thresholds and acoustic reflex thresholds for four normally hearing and 13 cochlearly impaired subjects. Two models, one for frequency resolution (model I) and one for temporal resolution (model II), were introduced, and these provided a means of predicting individual frequency and temporal resolution from hearing thresholds for both normal‐hearing and hearing‐impaired listeners. Model I is based on the assumption that the upward spread of masking increases in cochlearly impaired hearing with an amount proportional to the hearing threshold in dB HL. Model II is based on the assumption that the poststimulatory masked thresholds return to the level of the hearing threshold within a duration of 200 ms, independent of the level of the masker and the amount of cochlear hearing loss. Model parameters were determined from results from other studies. Although some discrepancies between measured and predicted values were observed, the model predictions generally agree with measurements. Thus, to a first‐order approximation, it seems possible to predict individual frequency and temporal resolution of cochlearly hearing‐impaired listeners solely on the basis of their hearing thresholds.
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43.66.Sr Deafness, audiometry, aging effects
43.66.Ba Models and theories of auditory processes
43.66.Dc Masking
43.66.Cb Loudness, absolute threshold

Effects of normal and pathologic eardrum impedance on sound pressure in the aided ear canal: A computer simulation

David P. Egolf, Lawrence L. Feth, William A. Cooper, and John R. Franks

J. Acoust. Soc. Am. Volume 78, Issue 4, pp. 1281-1285 (1985); (5 pages)

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Reported herein are results of computer simulations of aided sound spectra in ears with normal and pathologic eardrum impedance. The computer technique used in this study has been reported elsewhere [D. P. Egolf, D. R. Tree, and L. L. Feth, J. Acoust. Soc. Am. 63, 264–271 (1978)]. Consequently, to develop reader confidence in the computer scheme, its application to real ears was first tested. This was accomplished by (1) comparing computed spectral data with in‐the‐ear measurements and (2) comparing real ear minus 2‐cc coupler data—both computer generated—with an idealized difference curve published elsewhere [R. M. Sachs and M. D. Burkhard, unpublished rep. no. 20022‐1, Industrial Research Products, Inc., Elk Grove Village, IL (1972)]. Results indicate that the wide variation in eardrum impedance among normals evidenced in other studies produces a corresponding wide variation in aided spectrum shape. Likewise, simulations utilizing two sets of pathologic eardrum impedance data obtained from the literature show that aided sound spectra in such ears are likely to be significantly different from those occurring in normal ears. These findings suggest, as others have concluded, that there may be a substantial variation in spectrum shape among individuals wearing identically the same hearing aid—even if those individuals have normal hearing. In conclusion, questions are raised about the use of real‐ear simulators and the need for a comprehensive computer‐based model of an entire hearing aid.
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43.66.Ts Auditory prostheses, hearing aids

High‐synchrony cochlear compound action potentials evoked by rising frequency‐swept tone bursts

Susan E. Shore and Alfred L. Nuttall

J. Acoust. Soc. Am. Volume 78, Issue 4, pp. 1286-1295 (1985); (10 pages) | Cited 15 times

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The auditory compound action potential (CAP) represents synchronous VIIIth nerve activity. Clicks or impulses have been used in the past to produce this synchrony under the assumption that the wide spectral spread inherent in transient signals will activate a large portion of the cochlear partition. However, the observation that only auditory nerve units tuned above 3 kHz contribute to synchronous activity in the N1P1 complex of the CAP [Dolan et al., J. Acoust. Soc. Am. 73, 580–591 (1983)] suggests that temporal delays imposed by the traveling wave result in an asynchronous pattern of VIIIth nerve activation. In order to determine if units tuned below 3 kHz could be recruited into the CAP response, the present study uses tone bursts of exponentially rising frequency to hypothetically activate synchronous discharges of VIIIth nerve fibers along the length of the cochlear partition. The equations defining the frequency sweeps are calculated to be the inverse of the delay‐line characteristics of the guinea pig cochlear partition.
The resultant sweeps theoretically cause a constant phase displacement of a large portion of the cochlear partition at one time. Compound action potentials recorded in response to the rising frequency sweeps were compared to CAPs evoked by corresponding falling frequency sweeps and clicks. Analysis of the CAP waveforms showed narrower N1 widths and larger N1 and P1 amplitudes for rising sweeps when compared to falling sweeps. This is consistent with the hypothesis of increased synchrony. A further test of the hypothesis was made by using high‐pass masking noise to evaluate the contributions of discrete cochlear locations to the CAP (‘‘derived’’ CAP). Latency functions of the derived CAPs for clicks and falling frequency sweeps showed progressive increases in latency as the cutoff frequency of the high‐pass filter was lowered. The latency of the derived CAP for these stimulus conditions reflects traveling wave delays [Aran and Cazals, ‘‘Electrocochleography: Animal studies,’’ in Evoked Electrical Activity in The Auditory Nervous System (Academic, New York, 1978)]. In contrast, derived CAPs obtained from rising sweeps showed no change in latency for any cutoff frequencies, indicating a constant delay of response for fibers with different characteristic frequencies (CFs). These results support the theoretical premise underlying the derivation of the rising sweep: Spectral energy with the appropriate temporal organization, dictated by basilar membrane traveling wave properties, will increase CAP synchrony.
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43.64.Nf Cochlear electrophysiology

Sound intensity processing by the goldfish

Richard R. Fay

J. Acoust. Soc. Am. Volume 78, Issue 4, pp. 1296-1309 (1985); (14 pages) | Cited 1 time

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Capacities of the goldfish for intensity discrimination were studied using classical respiratory conditioning and a staircase psychophysical procedure. Physiological studies on single saccular (auditory) nerve fibers under similar stimulus conditions helped characterize the dimensions of neural activity used in intensity discrimination. Incremental intensity difference limens (IDLs in dB) for 160‐ms increments in continuous noise, 500‐ms noise bursts, and 500‐ms, 800‐Hz tone bursts are 2 to 3 dB, are independent of overall level, and vary with signal duration according to a power function with a slope averaging −0.33. Noise decrements are relatively poorly detected and the silent gap detection threshold is about 35 ms. The IDLs for increments and decrements in an 800‐Hz continuous tone are about 0.13 dB, are independent of duration, and are level dependent. Unlike mammalian auditory nerve fibers, some goldfish saccular fibers show variation in recovery time to tonal increments and decrements, and adaptation to a zero rate. Unit responses to tone increments and decrements show rate effects generally in accord with previous observations on intracellular epsp’s in goldfish saccular fibers. Neurophysiological correlates of psychophysical intensity discrimination data suggest the following: (1) noise gap detection may be based on spike rate increments which follow gap offset; (2) detection of increments and decrements in continuous tones may be determined by steep low‐pass filtering in peripheral neural channels which enhance the effects of spectral ‘‘splatter’’ toward the lower frequencies; (3) IDLs for pulsed signals of different duration can be predicted from the slopes of rate–intensity functions and spike rate variability in individual auditory nerve fibers; and (4) at different sound pressure levels, different populations of peripheral fibers provide the information used in intensity discrimination.
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43.64.Pg Electrophysiology of the auditory nerve
43.64.Tk Physiology of sound generation and detection by animals
43.80.Lb Sound reception by animals: anatomy, physiology, auditory capacities, processing
43.80.Nd Effects of noise on animals and associated behavior, protective mechanisms

Sensitivity of auditory‐nerve fibers to changes in intensity: A dichotomy between decrements and increments

R. L. Smith, M. L. Brachman, and R. D. Frisina

J. Acoust. Soc. Am. Volume 78, Issue 4, pp. 1310-1316 (1985); (7 pages) | Cited 9 times

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Adaptation of auditory‐nerve responses was investigated by applying increments and decrements in intensity to an ongoing tonal background. The change in firing rate produced by a change in intensity was obtained as a function of the time delay from the onset of the background to the onset of the change in intensity. The initial change in firing rate was measured using both small (1 ms) and large (10 ms) time intervals in order to evaluate properties of rapid and short‐term adaptation, respectively. Consistent with previous results, the incremental and decremental responses measured with large windows were independent of time delay and the amount of prior adaptation. A similar additivity was observed for the incremental response measured with a small time window. In contrast, the decremental response measured with a small window decreased with increasing time delay and in proportion to the decrease in firing rate produced by the background. A similar decrease was observed in the response modulation produced by sinusoidal amplitude modulation. It was concluded that sensitivity to decrements in intensity decreases during adaptation, so that this response component does not reflect the additivity inherent in other aspects of adaptation.
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43.64.Pg Electrophysiology of the auditory nerve

Track segment association with a distributed field of sensors

R. Mucci, J. Arnold, and Y. Bar‐Shalom

J. Acoust. Soc. Am. Volume 78, Issue 4, pp. 1317-1324 (1985); (8 pages)

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A performance prediction procedure is developed for geographical localization of targets traversing through a distributed field of sensors. The analysis is based on a tracking scheme where targets are detected and tracked locally by as few as two sensors. Target estimates from adjacent sensor sets are extrapolated to an estimated time of intersection, and the hypothesis is made that the two segments have a common origin (i.e., that the two tracks have emanated from a single target). Through a statistical test based on a maximum likelihood ratio, this hypothesis is either accepted or rejected. It is then shown that associated target track segments can be reestimated using the combined set of measurements. The theoretical results have been corroborated by applying a maximum likelihood tracking algorithm to simulated data and observing the results for a series of Monte Carlo simulations. The actual and expected statistics on the probability of correctly associating target segments, along with the localization ellipses, are displayed.
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43.60.Gk Space-time signal processing, other than matched field processing

Acoustic propagation over an impedance plane

Matthew A. Nobile and Sabih I. Hayek

J. Acoust. Soc. Am. Volume 78, Issue 4, pp. 1325-1336 (1985); (12 pages) | Cited 10 times

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A new solution is obtained for the acoustic pressure field generated by a point source and scattered by a locally reacting impedance covered plane. The new solution is obtained in the form of an asymptotic series which has been shown to agree well with other studies. One of the most important features of this solution is that higher‐order terms can be calculated from preceding terms in the series by the use of recursion formulas. Comparing data predicted from this solution with that from a numerical integration of the exact expression shows the asymptotic series to be extremely accurate, even for relatively low values of the parameter kR. Not surprisingly, the plane‐wave solution often shows major deviations from the exact integral solution.
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43.50.Vt Topographical and meteorological factors in noise propagation
43.28.Fp Outdoor sound propagation through a stationary atmosphere, meteorological factors
43.20.Bi Mathematical theory of wave propagation

Investigation of the amplitude distribution of AT‐cut quartz crystals

S. Hertl, L. Wimmer, and E. Benes

J. Acoust. Soc. Am. Volume 78, Issue 4, pp. 1337-1343 (1985); (7 pages) | Cited 2 times

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The three‐dimensional equations of linear piezoelectricity are used to compute the mechanical vibration amplitude distributions, as well as the resonance frequencies of plano‐convex circular AT‐cut quartz crystal resonators. These computations are compared with vibration amplitude measurements employing a new technique that utilizes the speckle effect. Very good agreement has been found between the measured and the computed vibration amplitude distributions.
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43.40.Dx Vibrations of membranes and plates
43.38.Fx Piezoelectric and ferroelectric transducers

A general normal mode solution for the free vibration of the rectangular parallelepiped

Eric v. K. Hill

J. Acoust. Soc. Am. Volume 78, Issue 4, pp. 1344-1347 (1985); (4 pages)

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A general normal mode solution is presented for the free vibration of the rectangular parallelepiped with arbitrary, static boundary conditions and body forces. This is followed by three examples of the solution procedure. Dynamic body forces and boundary conditions are also mentioned.
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43.40.Dx Vibrations of membranes and plates
43.40.Cw Vibrations of strings, rods, and beams

Sound velocity as a function of depth in marine sediments

Edwin L. Hamilton

J. Acoust. Soc. Am. Volume 78, Issue 4, pp. 1348-1355 (1985); (8 pages) | Cited 3 times

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Additional data from sonobuoys and the Deep Sea Drilling Project (DSDP) justify separating sound‐velocity‐depth functions and velocity gradients (in the first layer of soft marine sediments) into some geographic areas and sediment types. Based on sonobuoy and core measurements (where V is sound velocity in km/s, and h is depth in sediments in km), the following data are obtained: continental shelf basins off Sumatra and Java—V=1.484+0.710h−0.085h2; U. S. Atlantic continental rise—V=1.513+0.828h−0.138h2; deep‐sea terrigenous sediments—V=1.519+1.227h−0.473h2; and siliceous sediments of the Bering Sea— V=1.509+0.869h−0.267h2. Selected DSDP data (through leg 74) in similar areas yield: continental terrace silt–clays—V=1.505+0.712h; deep‐sea terrigenous sediments—V=1.510+1.019h; and deep‐sea siliceous sediments—V=1.533+0.761h. Computed velocity gradients from sonobuoy measurements are generally supported by the DSDP gradients. Only DSDP data give the following: hemipelagic sediments—V=1.501+1.151h; deep‐sea calcareous sediments—V=1.541+0.928h; and deep‐sea pelagic clay—V=1.526+1.046h. Where fast sediment accumulation occurs, there has not been enough time to reduce sediment pore spaces under overburden pressure; areas of slow accumulation may have relatively high sediment structural strength. Both cases have lower velocity gradients because higher porosities and consequent lower velocities persist to deeper depths.
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43.30.Ma Acoustics of sediments; ice covers, viscoelastic media; seismic underwater acoustics
43.30.Es Velocity, attenuation, refraction, and diffraction in water, Doppler effect
43.35.Bf Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in liquids, liquid crystals, suspensions, and emulsions

Acoustic normal mode propagation through a three‐dimensional internal wave field

Cecile Penland

J. Acoust. Soc. Am. Volume 78, Issue 4, pp. 1356-1365 (1985); (10 pages) | Cited 8 times

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In describing the effects of internal waves on acoustic normal modes excited by a time‐harmonic point source, all previous descriptions have neglected the existence of azimuthal fluctuations in the acoustic field. This study compares this azimuthally symmetric case with the case where azimuthal fluctuations in the acoustic field are taken into account. Although azimuthal variations can enhance the randomization of interference effects so that different depth modes decorrelate more quickly in range, this enchancement is generally small. The autocorrelation functions of the depth modes approach equipartition at long ranges as in the azimuthally symmetric case, as long as each range function is interpreted as a sum of all the azimuthal modes. The mean energy flux vector 〈j〉 becomes radial at long ranges. Integral expressions for the scattering coefficients and interference terms have been derived so that these quantities can be calculated without having to perform an infinite sum.
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43.30.Bp Normal mode propagation of sound in water
43.20.Bi Mathematical theory of wave propagation

Sound propagation over a sloping bottom using rays with beam displacement

C. T. Tindle and G. B. Deane

J. Acoust. Soc. Am. Volume 78, Issue 4, pp. 1366-1374 (1985); (9 pages) | Cited 4 times

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Ray theory with beam displacement has been shown previously to be an accurate method of finding the acoustic field at low frequencies in shallow water by comparison with normal mode solutions. The method is here extended to the case of a uniformly sloping bottom. The extension requires only geometry and involves no approximations. It is not restricted to small angles. Calculations for a simple two‐fluid (Pekeris) model show that even small bottom slopes have a dramatic effect on the details of the sound field. Comparison with the results of the adiabatic normal mode approximation shows good general agreement at higher frequencies. At lower frequencies, differences are attributed to normal modes passing through cutoff, a process which is ignored in simple adiabatic mode theory.
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43.30.Cq Ray propagation of sound in water
43.30.Bp Normal mode propagation of sound in water
43.20.Bi Mathematical theory of wave propagation

Direct acoustic scattering for one‐dimensional lossy media

Jing Bai, Chris Rorres, Peder C. Pedersen, and Oleh J. Tretiak

J. Acoust. Soc. Am. Volume 78, Issue 4, pp. 1375-1383 (1985); (9 pages)

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The scattering of acoustic waves by inhomogeneities within a one‐dimensional lossy medium is investigated. The inhomogeneities may be spatial variations in the attenuation coefficient of the lossy medium and/or variations in its density and wave velocity. The frequency dependence of the attenuation coefficient is modeled after loss mechanisms governed by viscosity, heat conduction, and single and multiple relaxation processes. Two methods previously developed for lossless media—the transmission matrix method and the forward scattering or impediography method—are extended to treat the determination of the reflection and transmission coefficients of an inhomogeneous lossy medium. These scattering coefficients are numerically determined for several one‐dimensional media with varying density and attenuation profiles.
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43.20.Fn Scattering of acoustic waves
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