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Journal of the Acoustical Society of America

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Dec 1973

Volume 54, Issue 6, pp. 1433-1768

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A rapid method for studying acoustic behaviour

M. E. Nute and K. Slater

J. Acoust. Soc. Am. Volume 54, Issue 6, pp. 1747-1749 (1973); (3 pages)

Online Publication Date: 12 Aug 2005

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A new swept‐frequency technique for studying acoustic behaviour is presented and has certain advantages over established methods where a rapid inexpensive assessment of the approximate acoustic performance of a material in the laboratory or in a field situation is required. The general behaviour may be envisaged by inspection, or a detailed analysis of the performance in selected frequency bands may be carried out by simple measurement and calculation in a few minutes.

Susceptibility to damage from impulse noise: chinchilla versus man or monkey

George A. Luz and David M. Lipscomb

J. Acoust. Soc. Am. Volume 54, Issue 6, pp. 1750-1754 (1973); (5 pages)

Online Publication Date: 12 Aug 2005

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Behavioral audiograms were taken on five surgically monaural chinchillas at 0.75, 1.5, 4.0, 6.0, 7.9, 11.0, 14.5, and 16.5 kHz. After exposure to 1 to 4 impulses of 168‐dB peak SPL and 60‐μsec A‐wave duration, temporary threshold shift was monitored at 1.5, 6.0, and 14.5 kHz for 32 days and complete audiograms taken at 64 days post‐exposure. Shifts were similar to those found by other researchers who have exposed the chinchilla to similar impulses, but were larger than those seen in monkeys and men exposed to the same impulse noise source. Cochlear hair cell losses for the five subjects exposed to one to four impulses were small and not significantly different from those of five others exposed to 10 to 40 impulses (but not tested behaviorally). The conclusions paralleled those of Hunter‐Duvar and Elliott [J. Acoust. Soc. Am. 52, 1181–1192 (1972)] in that stimulation “sufficient to produce permanent threshold shifts of 10–20 dB may not produce anatomical injuries to the organ of Corti that are detectable by phase microscopy.” Caution was urged in generalizing the results of impulse noise studies in chinchilla to human damage risk criteria. The use of pre‐exposure impedance measures to rull out middle ear conductive losses was also suggested for future studies.

Reverberation in a city street

Donald Aylor, Jean‐Yves Parlange, and Courtland Chapman

J. Acoust. Soc. Am. Volume 54, Issue 6, pp. 1754-1757 (1973); (4 pages) | Cited 2 times

Online Publication Date: 12 Aug 2005

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The decay of 1/3‐octave pink noise in a street was compared before and after the ivy on one building leafed out in the spring. The effect of the ivy on reverberation in the street was negligible except around 4000 Hz, where the decay of sound was increased by about 30 dB/sec. Since absorption of sound by the ivy is slight, the reduction of reverberation must be mainly by scattering of sound by the foliage.

Numerical method for computing multipath interference in a time‐varying medium

Harry A. DeFerrari

J. Acoust. Soc. Am. Volume 54, Issue 6, pp. 1757-1759 (1973); (3 pages)

Online Publication Date: 12 Aug 2005

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Ray‐model simulations of multipath interference of CW signals require precise computation of travel times along the paths between source and receiver. The travel times for each ray path must be known with sufficient precision to resolve the phase of the arrival. The effects of time‐varying sound‐speed profiles can then be simulated by allowing the state of the medium to change slightly for each multipath summation. This letter is concerned with a numerical method for making such computations.

Fundamental‐frequency component of a finite‐amplitude plane wave

Harold M. Merklinger

J. Acoust. Soc. Am. Volume 54, Issue 6, pp. 1760-1761 (1973); (2 pages)

Online Publication Date: 12 Aug 2005

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A method due to Westervelt [Proceedings of the Third International Congress on Acoustics, Stuttgart 1959 (Elsevier, Amsterdam, 1961), Vol. 1, pp. 316–321] is used to describe the fundamental frequency component of an initially sinusoidal finite‐amplitude plane wave. The result, expressed in terms of the extra loss (in decibels) introduced by nonlinearity, is given as 10 log10[1 + Γ2(1 − e−2σ/Γ)2/16] where Γ is the acoustic Reynold′s number and σ is range normalized to the shock formation distance. This relation is shown to lie within 1 dB of Blackstock′s results obtained from Burgers′ equation [D. T. Blackstock, J. Acoust. Soc. Am. 36, 534–542 (1964)].

Erratum: “High‐speed method for computing the exact solution for the pressure variations in the nearfield of a baffled piston” [J. C. Lockwood and J. G. Willette, J. Acoust. Soc. Am. 53, 735–74 (973)]

J. C. Lockwood and J. G. Willette

J. Acoust. Soc. Am. Volume 54, Issue 6, pp. 1762-1762 (1973); (1 page)

Online Publication Date: 12 Aug 2005

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A corrected version of Fig. 6 of the subject article [J. C. Lockwood and J. G. Willette, J. Acoust. Soc. Am. 53, 735–741 (1973)] is presented.
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