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Journal of the Acoustical Society of America

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Oct 1982

Volume 72, Issue 4, pp. 1105-1334

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Diffraction constants for pressure gradient transducers

Ralph S. Woollett

J. Acoust. Soc. Am. Volume 72, Issue 4, pp. 1105-1113 (1982); (9 pages) | Cited 2 times

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Conventionally the diffraction constant D of a receiving transducer (microphone or hydrophone) is defined as the ratio of the average sound pressure acting on the blocked diaphragm to the free‐field sound pressure. This definition is inadequate for transducers that have complex vibration patterns, and, in the absence of ad hoc modifications, it will fail to give the correct results for pressure gradient transducers. A new definition based on the general theory of transducers with fixed velocity distributions is therefore introduced. The diffraction constant is assigned not only the function of accounting for scattered wave effects but also the function of extracting from the surface pressure distribution the component that drives the velocity distribution (or vibration pattern) of the transducer. The diffraction constant depends on the choice of the reference velocity that is associated with the acoustic port of the transducer. A spatial rms reference velocity is defined, and it is shown to be a suitable reference for pressure gradient transducers. Calculation of the diffraction constant is carried out for the following piezoelectric pressure gradient hydrophones: a flexural disk supported inside an annular mass, an end supported flexural bar, a cantilever bar, an oscillating rigid cylinder, and an oscillating rigid sphere. The use of the diffraction constant in conjunction with the electroacoustic circuit of the hydrophone to calculate voltage receiving response is described, and the circuit information needed to illustrate the procedure is given for the flexural disk hydrophone.
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43.38.Ar Transducing principles, materials, and structures: general
43.38.Kb Microphones and their calibration
43.30.Yj Transducers and transducer arrays for underwater sound; transducer calibration

Electromechanical properties of (Pb, Ln) (Ti, Mn) O3 ceramics (Ln = rare earths)

Hiroshi Takeuchi, Shigeru Jyomura, Etsuji Yamamoto, and Yukio Ito

J. Acoust. Soc. Am. Volume 72, Issue 4, pp. 1114-1120 (1982); (7 pages) | Cited 4 times

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Electromechanical properties of PbTiO3 ceramics modified by the partial substitution of rare earths for Pb, particularly, (Pb, Ln) (Ti, Mn) O3 (Ln = La, Pr, Nd, Sm, or Gd) ceramics, are examined. It is found that the Sm substitution for Pb dramatically increases the ratio of electromechanical coupling factor of the thickness dilatational mode to that of the planar extensional mode. Extensive studies of the resonant properties of rectangular strip resonators make it clear that the Sm‐substituted PbTiO3 ceramics are very useful for high‐frequency array transducer applications. It is also shown that the pulse responses of array transducers can be improved using Sm substituted PbTiO3 ceramics instead of the other PbTiO3 ceramics studied here.
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43.38.Fx Piezoelectric and ferroelectric transducers
43.38.Hz Transducer arrays, acoustic interaction effects in arrays
77.65.-j Piezoelectricity and electromechanical effects

An ultrasound power meter

Helge Engan

J. Acoust. Soc. Am. Volume 72, Issue 4, pp. 1121-1123 (1982); (3 pages)

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An ultrasound power measuring method based on measurement of the radiation force is described. The method requires no target to measure this force since the force is measured at the holder of the ultrasonic transducer that is transmitting. The actual power meter reported is based on modulated acoustic transmission to facilitate electronic detection and measurement.
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43.58.Dj Sound velocity
43.58.Vb Calibration of acoustical devices and systems
43.30.Sf Acoustical detection of marine life; passive and active
43.35.Yb Ultrasonic instrumentation and measurement techniques

Consonant‐feature transmission as a function of presentation level in hearing‐impaired listeners

Howard N. Gutnick

J. Acoust. Soc. Am. Volume 72, Issue 4, pp. 1124-1130 (1982); (7 pages) | Cited 1 time

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Normal‐hearing listeners and listeners with a high‐frequency sensorineural hearing loss identified 17 consonants as part of a consonant‐vowel syllable with /a/ or /i/ as the vowel. The syllables were set at presentation levels of 10 to 65 dB re thresholds at 1000 Hz. The performance for the consonants comprising each of 11 a priori acoustic‐phonetic features improved directly with increases in presentation level for both subject groups, but was better in the /a/ than in the /i/ context. The performance of the hearing‐impaired listeners was significantly poorer than the performance of the normal‐hearing listeners only for the higher‐frequency features of frication and sibilance. The lower‐frequency features of voicing and sonorance were reflected in the confusion matrices of hearing‐impaired listeners at presentation levels of 10 and 20 dB; only at 35 to 65 dB were higher‐frequency features transmitted in the confusion matrices of this group.
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43.70.Dn Disordered speech
43.66.Sr Deafness, audiometry, aging effects
43.71.Gv Measures of speech perception (intelligibility and quality)
43.70.Fq Acoustical correlates of phonetic segments and suprasegmental properties: stress, timing, and intonation

Tactile communication of speech: II. Comparison of two spectral displays in a vowel discrimination task

M. A. Clements, L. D. Braida, and N. I. Durlach

J. Acoust. Soc. Am. Volume 72, Issue 4, pp. 1131-1135 (1982); (5 pages) | Cited 1 time

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Vowel discrimination experiments were performed comparing two tactile, Optacon‐based, spectral displays: a frequency‐amplitude (FA) display and a time‐swept (TS) display, The set of vowel pairs tested consisted of all pairs from the set of ten American nondipthongized vowels. One set of materials consisted of natural /b/‐V‐/t/’s (with each vowel represented by 12 utterances generated by four speakers producing each vowel three times). A second set consisted of synthetic vowels (with each vowel represented by a single waveform). On the average, the score obtained with the second set of materials was substantially better than with the first (92% vs 79%); the score obtained with the TS display was slightly better than with the FA display (87% vs 83%); the feature best differentiated was tenseness, followed by the features high and low, then by round and back, and finally by retroflexion; and the correlation between discrimination performance and the physical parameters duration, amplitude, F1, and F2/F1 (taken singly) was relatively weak. In general, the results of this study, together with those of other studies previously reported, suggest that the two displays studied are far from optimum.
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43.70.Dn Disordered speech
43.66.Ts Auditory prostheses, hearing aids
43.66.Wv Vibration and tactile senses
43.80.Vj Acoustical medical instrumentation and measurement techniques

Subjective speech‐to‐noise ratio as a measure of speech quality for digital waveform coders

Mamoru Nakatsui and Paul Mermelstein

J. Acoust. Soc. Am. Volume 72, Issue 4, pp. 1136-1144 (1982); (9 pages)

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The ultimate performance measure for evaluating voice communication systems is the subjective quality of the received speech. Modern digital speech‐coding techniques achieve high intelligibility and significant transmission economies. The high level of speech intelligibility is a necessary but insufficient condition for user acceptance of the systems. Quality, as well, must meet acceptability criteria. However, no adequate single measure of overall speech quality has yet been developed. This work takes a utilitarian approach in attempting to satisfy the urgent requirement for a practical measurement method. The subjective speech‐to‐noise‐ratio (SNR), derived from the forced‐choice pair‐comparison test using the psychometric analysis procedure commonly used in the method of constants, is evaluated. A speech signal degraded by varying amounts of multiplicative white noise is selected as the reference system in the test. Seven types of digital speech coders are simulated and evaluated in this study, including log‐PCM, ADM, ADPCM coders with variable or fixed predictor, APC, residual‐excited and pitch‐excited LP coders (RELP and LPC). Thirteen configurations of these coders covering the transmission bit rates of 2.4 to 64 kb/s are included. Pair‐comparison tests were conducted in two separate sessions 14 months apart using different groups of speakers and listeners. The subjective SNR estimated from 13 coder configurations ranges from 7 to 40 dB and well represents overall speech quality in a single dimension. No significant speaker and listener variation is found for a wide range of waveform coders. The subjective SNR estimate is found to be highly reproducible with different speakers and listeners. Arbitrary selection of as few as five listeners yields a stable subjective SNR estimate for the waveform coders. On the other hand, highly significant listener variation is found for the narrow‐band digital vocoders (RELP and LPC). This listener variability reflects a limitation of the measure that may prevent its extension to vocoded speech whose distortions differ significantly from those of the reference speech.
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43.71.Gv Measures of speech perception (intelligibility and quality)
43.72.-p Speech processing and communication systems
43.72.Ar Speech analysis and analysis techniques; parametric representation of speech

Acoustic cues to final stop voicing for impaired‐ and normal‐hearing listeners

S. Revoile, J. M. Pickett, Lisa D. Holden, and David Talkin

J. Acoust. Soc. Am. Volume 72, Issue 4, pp. 1145-1154 (1982); (10 pages) | Cited 2 times

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Voicing perception for final stops was studied for impaired‐ and for normal‐hearing listeners when cues in naturally spoken syllables were progressively neutralized. The syllables were ten different utterances of /dæp, dæk, dæt, dæb, dæg, dæd/ spoken in random order by a male. The cue modifications consisted progressively of neutralized vowel duration, equalized occlusion duration, burst deletion, murmur deletion, vowel‐transition interchange, and transition deletion. The impaired subjects had moderate‐to‐severe lossses and showed at least 70% correct voicing for the unmodified syllables. For the voiced stops, vowel‐duration adjustment and murmur deletion each resulted in significant reductions in voicing perception for more than one‐third of the impaired listeners; all normals showed good performance following neutralization of these cues. For the voiceless stops, large percentages of both listener groups showed decreased voicing perception due to the burst deletion, though a majority of both groups performed well above chance even after the vowel‐duration adjustment and the burst deletion. When the vowel off‐going transitions were exchanged between cognate syllables in given pairs, the effect on voicing perception exhibited by many impaired‐ and all normal‐hearing listeners implicated the vowel transitions as an important additional source of cues to final‐stop voicing perception.
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43.71.Gv Measures of speech perception (intelligibility and quality)
43.70.Fq Acoustical correlates of phonetic segments and suprasegmental properties: stress, timing, and intonation
43.66.Sr Deafness, audiometry, aging effects
43.70.Dn Disordered speech

From text to speech with SRS

Susan R. Hertz

J. Acoust. Soc. Am. Volume 72, Issue 4, pp. 1155-1170 (1982); (16 pages)

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SRS (Speech Research System) is a highly flexible computer system for the development of text‐to‐speech rules for any language. Its powerful interactive facilities and special rule language have been designed to facilitate rule development by programmers and nonprogrammers alike. The system has been used for instruction in acoustic phonetics, for the generation of stimuli for perceptual experiments, and for the development of synthesis rules for a variety of languages. This paper focuses on the SRS rule framework, which allows users to express four kinds of rules that apply in succession to convert text to sound. The paper also illustrates the user‐oriented nature of the SRS interactive facilities, and describes the system’s implementation and use.
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43.70.Jt Instrumentation and methodology for speech production research
43.72.Gy Narrow, medium, and wideband speech coding
43.70.Fq Acoustical correlates of phonetic segments and suprasegmental properties: stress, timing, and intonation

Forward masking of diotic and dichotic clicks by noise

Thomas E. Hanna, Donald E. Robinson, Richard M. Shiffrin, and Robert H. Gilkey

J. Acoust. Soc. Am. Volume 72, Issue 4, pp. 1171-1177 (1982); (7 pages) | Cited 2 times

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The first experiment reported here measured thresholds for clicks in forward masking as a function of the masker level and as a function of the temporal relation of a 6‐kHz low‐pass noise masker to the click (300‐msec duration with a 20‐msec temporal gap or 10‐msec duration with a 5‐msec gap). Also varied were the spectral content of the click (low‐pass filtered at 1 or 5 kHz) and the interaural phase of the click (0 or π). The difference in frequency content had no effect on the amount of masking for the 300‐msec masker, while with the 10‐msec masker greater masking was found for the 1–kHz click. This combination (1 kHz, 10 msec) was also the only one to produce Masking Level Differences (MLDs) when the click was presented dichotically. A second experiment investigated the effects of combining the maskers used in the first experiment. Additional masking (above that predicted by an energy sum) was found, as has been reported elsewhere [Penner and Shiffrin, J. Acoust. Soc. Am. 67, 617–627 (1980)]. However, the magnitude of this additional masking was decreased for certain conditions. These data conflict with the predictions of additivity of masking obtained from a model proposed by Penner and Shiffrin and suggest that modifications to that model are needed. The results of both experiments can be explained by assuming that two processes are acting in forward masking [Duifhuis, J. Acoust. Soc. Am. 54, 1471–1488 (1973)].
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43.66.Ba Models and theories of auditory processes
43.66.Dc Masking
43.66.Mk Temporal and sequential aspects of hearing; auditory grouping in relation to music
43.66.Pn Binaural hearing
43.66.Rq Dichotic listening

Detectability of time‐varying interaural correlation in narrow‐band noise stimuli

D. Wesley Grantham

J. Acoust. Soc. Am. Volume 72, Issue 4, pp. 1178-1184 (1982); (7 pages) | Cited 14 times

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In a two‐interval, forced‐choice task, observers discriminated a binaural noise whose interaural correlation r varied according to the function r(t) = m cos 2π fmt from an interaurally uncorrelated noise [NU; r(t) = 0.0]. The former stimulus produces a perceptual binaural ’’flutter,’’ where the flutter rate is equal to the modulation frequency fm, and the amount of flutter corresponds to m. The stimuli were 0.4‐octave‐wide Gaussian noises with center frequencies of 500, 1000, 2000, or 4000 Hz. Presentation levels were 70–75 dB SPL; duration was 1.0 s. For a given modulation frequency, the peak interaural correlation m was varied in a blocked procedure, and thresholds were estimated as that value of m required for 75% discriminability. Plotting thresholds as a function of fm yields a modulation function, which can be interpreted as an ’’attenuation characteristic’’ of the binaural system. For the 500‐Hz stimulus, thresholds increased from m = 0.28 at fm = 1 Hz to m = 0.80 at fm = 50 Hz. For higher frequency stimuli, discrimination was generally poorer and the modulation functions were flatter: thus, for 2000 Hz, m = 0.54 at fm = 1 Hz and m = 0.71 at fm = 20 Hz; for 4000 Hz, m = 0.71 at fm = 1 Hz and m = 0.81 at fm = 10 Hz. The modulation function from an ’’ideal observer’’ (at 500 Hz) differed in both form and absolute level from those of real observers. The data are discussed in relation to previous work on dynamic binaural processing.
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43.66.Pn Binaural hearing
43.66.Mk Temporal and sequential aspects of hearing; auditory grouping in relation to music

Statistical properties of responses to dichotic listening with CV nonsense syllables

Charles Speaks, Nancy Niccum, and Edward Carney

J. Acoust. Soc. Am. Volume 72, Issue 4, pp. 1185-1194 (1982); (10 pages)

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Twenty‐four listeners received 20 dichotic listening runs of 30 pairs of natural CV nonsense syllables per run. Left‐ and right‐ear responses are represented by two partially overlapping normal distributions with equal variance. Observed ear advantages across listening runs are also distributed normally. The means of the distributions of ear advantage are listener specific, but the standard deviations are 10.8%±2.5. The origin of reversals in direction of ear advantage among listening runs is statistical—a small mean/sigma ratio—and approximately six listening runs (180 listening trials) are required to achieve a split‐half reliability coefficient of +0.90.
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43.66.Rq Dichotic listening
43.70.Dn Disordered speech

Formulation of the maximum signal‐to‐noise ratio array processor in beam space

D. A. Gray

J. Acoust. Soc. Am. Volume 72, Issue 4, pp. 1195-1201 (1982); (7 pages) | Cited 3 times

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The maximum signal‐to‐noise ratio (SNR) processor as formulated by Edelblute et al. [J. Acoust. Soc. Am. 41, 199–206 (1967)] has proved extremely useful in the analysis and interpretation of sonar data. In a known noise field this processor uses an optimum set of weights (or shading coefficients) derived from the crosspower spectral matrix of receiver noise outputs. In this paper an alternative maximum SNR processor is derived. This processor transforms the outputs of a conventional frequency domain beamformer in such a way that the SNR in the transformed beam is maximized. Expressions for the transformation (i.e., the complex beam weights) and the resulting array gain are derived. Some general properties of the beam space formulation are discussed and conditions for its equivalence to the element space formulation of Edelblute et al. are determined. Examples using both simulated and sonar data are given to compare the beam and element space formulations.
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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
43.30.Vh Active sonar systems

Regularization of Marchenko’s integral equation by total least squares

Manuel T. Silvia and Edgar C. Tacker

J. Acoust. Soc. Am. Volume 72, Issue 4, pp. 1202-1207 (1982); (6 pages) | Cited 3 times

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Succinctly, the inverse scattering problem is to infer the shape, size, and constitutive properties of an object from scattering measurements which result from either seismic, acoustic, or electromagnetic probes. Under ideal conditions, theoretical solutions exist. However, when the scattering measurements are noisy, as is the case in practical scattering experiments, direct application of the classical inverse scattering solutions results in numerically unstable algorithms. In this paper, we discuss an optimization technique called total least squares, which provides a regularization to the one‐dimensional inverse scattering problem. Specifically, we show how to use multiple data sets in a Marchenko‐type inversion scheme and how the theory of total least squares introduces an adaptive spectral balancing parameter which explicitly depends on the scattering data. This is in strong contradistinction to ordinary least squares techniques which utilize nonexplicit and nonadaptive spectral balancing parameters, generally derived by ad hoc considerations.
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43.60.Gk Space-time signal processing, other than matched field processing
43.40.Ph Seismology and geophysical prospecting; seismographs
43.20.Bi Mathematical theory of wave propagation
02.60.Nm Integral and integrodifferential equations

Effect of inlet/outlet locations on higher order modes in silencers

L. J. Eriksson

J. Acoust. Soc. Am. Volume 72, Issue 4, pp. 1208-1211 (1982); (4 pages) | Cited 2 times

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A series of insertion loss measurements was made using an impedance tube with a broadband noise generator and anechoic termination as well as a small, four‐stroke, single cylinder gasoline engine on a variety of expansion chambers to determine the effect of inlet/outlet locations on higher order mode propagation. Higher order mode excitation was evaluated for a variety of chamber diameters, outlet offsets, combined inlet and outlet offsets, and inlet and outlet angular positions. For both sources the (0,1) first symmetric mode and (0,2) second symmetric mode appeared to be excited in chambers with inline inlet/outlet locations and an expansion ratio greater than about nine. The (0,1) mode could be eliminated when the outlet was positioned on the pressure nodal circle of the (0,1) mode. Offset of the inlet and outlet appeared to excite the (1,0) first asymmetric mode. This mode could be eliminated by rotating the inlet and outlet to an angular separation of 90°. This configuration appeared to excite the (2,0) second asymmetric mode.
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43.50.Gf Noise control at source: redesign, application of absorptive materials and reactive elements, mufflers, noise silencers, noise barriers, and attenuators, etc.
43.20.Mv Waveguides, wave propagation in tubes and ducts
43.20.Ks Standing waves, resonance, normal modes

Reliability of social survey data on noise effects

Fred L. Hall and S. Martin Taylor

J. Acoust. Soc. Am. Volume 72, Issue 4, pp. 1212-1221 (1982); (10 pages) | Cited 5 times

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The results of household interviews provide essential data for the formulation of noise control policies. The few previous studies which have investigated the reliability of such data have yielded low test–retest correlations for measures of annoyance at road traffic noise. This paper complements those previous studies by investigating four related topics: the equivalence of three commonly used annoyance scales; the test–retest reliability of two such scales, for aircraft and overall noise as well as for road traffic noise; the repeatability of measures of average response, such as percent highly annoyed; and the effect on reliability estimates of the range of noise levels included in a survey. The data are from a sample of 212 persons in the vicinity of Toronto International Airport, who were interviewed one year apart, in 1978 and 1979. The sample was stratified by both aircraft and road traffic noise levels. The results show that three commonly used annoyance scales are acceptably equivalent (a composite index comprised of the three has reliability of α = 0.85), and that the effect on the reliability of the range of noise levels included appears to be minimal. The test–retest results are similar to previous findings, suggesting that instability of attitudes toward noise, as well as other sources of measurement error, affect such estimates, and reduce retest estimate of reliability. Much better retest reliability (r≳0.90) is found for measures of average group response such as the percent highly annoyed than for individual level response measures.
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43.50.Qp Effects of noise on man and society
43.50.Sr Community noise, noise zoning, by-laws, and legislation
43.50.Lj Transportation noise sources: air, road, rail, and marine vehicles

Community annoyance from aircraft and ground vehicle noise

Karl D. Kryter

J. Acoust. Soc. Am. Volume 72, Issue 4, pp. 1222-1242 (1982); (21 pages) | Cited 10 times

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Data from published noise‐annoyance surveys are related to a common measure of noise exposure Ldn. The results provide means for predicting the annoyance (experienced by percentages of people of normal and of supersensitivity) attributable to noise from aircraft and from street and road traffic. Correlations of 0.90 to 0.95 are found between Ldn and percentages of people annoyed by aircraft noise when low, moderate, and higher levels of annoyance are measured for both a broad range (35 dB) and a restricted range (20 dB) of Ldn. Noise from urban street and road traffic is shown to cause less annoyance than the noise from aircrafts when both have the same Ldn as typically measured or estimated for outdoors. The difference, equivalent to a difference of about 10 dB in Ldn, is attributed to acoustical factors that diminish in‐and‐around‐the‐home noise dosages from ground vehicular traffic compared to dosages from aircraft operations. Generalized functions showing degrees of annoyance and percentages of U.S. urban population exposed to effective levels of Ldn for aircraft noise and for street and road traffic noise are presented. It is shown that an earlier analysis by Schultz [’’Synthesis of social surveys on noise annoyance,’’ J. Acoust. Soc. Am. 64, 377–405 (1978)] significantly underestimates the annoyance associated with aircraft noise and significantly overestimates the percentages of the U.S. population to be exposed to effective levels of noise from vehicles of transportation.
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43.50.Qp Effects of noise on man and society
43.50.Ba Noisiness: rating methods and criteria
43.50.Lj Transportation noise sources: air, road, rail, and marine vehicles

Comments on K. D. Kryter’s paper, ’’Community annoyance from aircraft and ground vehicle noise’’

Theodore J. Schultz

J. Acoust. Soc. Am. Volume 72, Issue 4, pp. 1243-1252 (1982); (10 pages) | Cited 1 time

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This paper presents a critique of K. D. Kryter’s paper, ’’Community Annoyance from Aircraft and Ground Vehicle Noise’’ [J. Acoust. Soc. Am. 72, xxx–xxx (1982)] in which he purports to show that an earlier paper of Schultz, ’’Synthesis of social surveys on noise annoyance’’ [J. Acoust. Soc. Am. 64, 377–405 (1978)], significantly underestimates the annoyance associated with aircraft noise, and underestimates that due to surface traffic noise. While the earlier Schultz paper may not be entirely correct, a careful study of Kryter’s new analysis suggests that his conclusions are considerably more dubious than he regards those of Schultz.
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43.50.Qp Effects of noise on man and society
43.50.Ba Noisiness: rating methods and criteria
43.50.Lj Transportation noise sources: air, road, rail, and marine vehicles

Rebuttal by Karl D. Kryter to comments by T. J. Schultz

Karl D. Kryter

J. Acoust. Soc. Am. Volume 72, Issue 4, pp. 1253-1257 (1982); (5 pages) | Cited 2 times

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This paper contains further evaluation of Leq measures obtained in the French and German aircraft noise studies, and a rebuttal to comments made by T. J. Schultz [J. Acoust. Soc. Am. 72, xxx–xxx (1982)].[AIP]
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43.50.Qp Effects of noise on man and society
43.50.Ba Noisiness: rating methods and criteria
43.50.Lj Transportation noise sources: air, road, rail, and marine vehicles

Torsional impact response of a flat annular crack in a finite elastic cylinder

Y. Shindo

J. Acoust. Soc. Am. Volume 72, Issue 4, pp. 1258-1263 (1982); (6 pages)

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The torsional impact response of a flat annular crack in an elastic cylinder of finite radius is investigated in this study. Laplace and Hankel transforms are used to reduce the problem to the solution of a set of triple integral equations. These equations are solved by using an integral transform technique and the result is expressed in terms of a singular integral equation of the first kind. The singular stress field near the crack tip and the dynamic stress‐intensity factor are determined. Numerical results on the dynamic stress‐intensity factor are obtained to show the influence of inertia, geometry, and their interactions on the load transmission to the crack tip.
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43.40.Jc Shock and shock reduction and absorption
46.50.+a Fracture mechanics, fatigue and cracks
46.40.Cd Mechanical wave propagation (including diffraction, scattering, and dispersion)
46.40.Jj Aeroelasticity and hydroelasticity
43.40.At Experimental and theoretical studies of vibrating systems

Attenuation and dispersion effects of nonequilibrium molecular processes on acoustic waves in cylindrical tube

William W. Peng

J. Acoust. Soc. Am. Volume 72, Issue 4, pp. 1264-1268 (1982); (5 pages)

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Attenuation and dispersion effects of nonequilibrium molecular processes on acoustic waves in a cylindrical tube are studied. Both internal energy transfer and molecular transport processes are included in the linearized gasdynamic equations and the rate equations for two vibrational modes of energy. A finite Hankel transform technique is employed to solve the system of partial differential equations. General expressions for attenuation factor and wavenumber are given in closed form for the case of high Reynolds number. The limiting cases of molecular equilibrium and infinite Reynolds number are also obtained and compared with results from previous investigations. Applications of the theory to CO‐N2 mixtures at both room and high temperatures are given and compared with the simplified formulas.
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43.35.Ae Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in gases
43.20.Mv Waveguides, wave propagation in tubes and ducts
43.35.Fj Ultrasonic relaxation processes in gases, liquids, and solids

Intensity corrections in a random medium in the neighborhood of a caustic

R. Mazar and M. J. Beran

J. Acoust. Soc. Am. Volume 72, Issue 4, pp. 1269-1275 (1982); (7 pages)

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We apply the two‐scale expansion developed previously to solve the equation governing the propagation of the coherence function in a random medium with a mean speed‐of‐sound profile. We obtain a formula for the vertical intensity distribution, resulting from an acoustic beam propagating in a statistically homogeneous, isotropic random medium with channel velocity profile. We use this formula to calculate the intensity distribution in the vicinity of a caustic in two limiting cases: weak scattering and strong scattering. We present a numerical example.
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43.30.Bp Normal mode propagation of sound in water
43.20.Bi Mathematical theory of wave propagation

Optimization techniques and inverse problems: Probing of acoustic impedance profiles in time domain

D. Lesselier

J. Acoust. Soc. Am. Volume 72, Issue 4, pp. 1276-1284 (1982); (9 pages)

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A method of acoustic probing of an inhomogeneous plane stratified medium is discussed. The impedance profile is reconstructed from a time‐domain analysis of the pressure reflected when this medium is illuminated by a known pulse. This analysis is made from an exact integral formulation in an iterative manner by means of the optimization theory. At each step, the direct problem (scattered pressure computation) and its related adjoint problem are solved for a given impedance profile. The behavior of this probing procedure is examined particularly in comparison with known approximated techniques based on a deconvolution process.
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43.20.Fn Scattering of acoustic waves
43.20.Bi Mathematical theory of wave propagation
43.20.Px Transient radiation and scattering
43.58.Bh Acoustic impedance measurement

Coupling loss factors at a beam L‐joint revisited

M. J. Sablik

J. Acoust. Soc. Am. Volume 72, Issue 4, pp. 1285-1288 (1982); (4 pages) | Cited 2 times

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Transmission coefficients and coupling loss factors are obtained for an L‐joint between two beams when incident flexural waves are vibrating out of the plane of the L‐joint. In the analysis, it is found that torsional waves develop at the L‐joint and that flexural‐to‐torsional transmission can be more efficient than flexural‐to‐flexural transmission. Also treated are the cases of an incident torsional wave at the L‐joint and an incident torsional wave at a butt joint. The expressions developed in this paper may be utilized in a statistical energy analysis of a beam network.
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43.20.Fn Scattering of acoustic waves
43.20.Bi Mathematical theory of wave propagation
43.40.Cw Vibrations of strings, rods, and beams

The field of a focusing source

Bernard G. Lucas and Thomas G. Muir

J. Acoust. Soc. Am. Volume 72, Issue 4, pp. 1289-1296 (1982); (8 pages) | Cited 4 times

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An analytical description for the field of a focusing source is derived. It is valid for spherically concave sources with small aperture angle and large ka (radius a, wavenumber k.) The solution furnishes easy access to the sound distribution along the axis and in the focal plane, as well as to parameters such as focusing gain, width of the focal spot, and phase shifting in the focal region. Experiments conducted with an f/2 lens coupled to a planar array are discussed. The results support the utility of the analytical model for describing the distribution of sound along the acoustic axis and across the focal plane.
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43.20.Fn Scattering of acoustic waves
43.25.Jh Reflection, refraction, interference, scattering, and diffraction of intense sound waves
43.20.Rz Steady-state radiation from sources, impedance, radiation patterns, boundary element methods
43.20.Bi Mathematical theory of wave propagation

Investigation of interaural attenuation factors for frequencies above 8000 Hz

B. Z. Rappaport, S. A. Fausti, M. A. Schechter, and R. H. Frey

J. Acoust. Soc. Am. Volume 72, Issue 4, pp. 1297-1298 (1982); (2 pages)

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Interaural attenuation values for frequencies from 8000 to 20 000 Hz were obtained from subjects with profound unilateral hearing loss. The values presented are specific to the Koss HV/1A earphone and cushion which is used as a transducer in our high‐frequency testing system. Data are provided regarding the influence of nontest ears at frequencies above 8000 Hz in cases where ear asymmetry exists.
Show PACS
43.38.Si Telephones, earphones, sound power telephones, and intercommunication systems
43.66.Yw Instruments and methods related to hearing and its measurement
43.66.Rq Dichotic listening
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