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Journal of the Acoustical Society of America

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Aug 1972

Volume 52, Issue 2A, pp. 465-500


Studies in a Reverberation Room with a Highly Absorbing Sample

B. Yegnanarayana and C. G. Balachandran

J. Acoust. Soc. Am. Volume 52, Issue 2A, pp. 465-470 (1972); (6 pages)

Online Publication Date: 12 Aug 2005

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This paper relates to a series of measurements undertaken in the reverberation room (25×20×14 ft) at the Indian Institute of Science, Bangalore. It is a common practice with all laboratories install diffusing panels in reverberation rooms for absorption measurements from decay rates. However, it has been observed that diffusers are not entirely satisfactory under all circumstances and hence the need for a method for the proper identification of the initial slope related to the material properties and subjective experience. With this aim in view, measurements have been performed on a large area of a highly absorbing polyurethane foam sample, and the following important features have been observed: (1) Choice of proper writing speed of the high‐speed level recorder is necessary to delineate the first part of the decay curve. (2) The loudspeaker location and directional characteristics will determine the proper excitation of the room modes giving rise to a correct initial slope. (3) The microphone should as far as possible be located close to the sample. From a study of the above factors it has been possible to establish an initial slope related to the sound‐absorption property of the material.

Detection of Amplitude Distortion in Flute and Clarinet Spectra

Alf Gabrielsson and Håkan Sjögren

J. Acoust. Soc. Am. Volume 52, Issue 2A, pp. 471-483 (1972); (13 pages)

Online Publication Date: 12 Aug 2005

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Two experiments about detection threshold values for quadratic and cubic amplitude distortion using flute and clarinet spectra are described. Distortion products were generated in an analog computer. Independent variables were spectrum, sound‐pressure level, tone onset, and fundamental frequency. A total of 174 subjects were tested. Data were subjected to analysis of variance and interpretations of main effects and interactions are given.

Maximum Available Sound‐Pressure Levels from Stereo Components

William S. Wood, III and David M. Lipscomb

J. Acoust. Soc. Am. Volume 52, Issue 2A, pp. 484-487 (1972); (4 pages) | Cited 1 time

Online Publication Date: 12 Aug 2005

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A commercially available tape recording of “rock” music was played through ten popular stereo receivers to drive, in turn, four stereo earphone sets. The sound generated by each system combination was analyzed into ten 5‐dB bands. Results of the acoustic analysis indicated that all combinations of receiver earphones set for maximum output consistently exceeded established damage‐risk criteria. It was concluded that popular stereo components can be potentially dangerous to the hearing mechanism if operated at or near maximum power output.

Community Noise Survey of Greater Vancouver

A. J. Price

J. Acoust. Soc. Am. Volume 52, Issue 2A, pp. 488-492 (1972); (5 pages)

Online Publication Date: 12 Aug 2005

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This paper describes a community noise survey of the Greater Vancouver Regional District, B.C., Canada, which extends over a land area of some 560 square miles. The survey incorporated approximately 100 000 individual noise measurements recorded over a four‐month period. The results are compared with published data from previous surveys and indicate that the statistical noise climate found in residentially zoned areas is almost identical in level distribution to that observed by Donley [Sound and Vibration (Feb. 1969)] for the mid‐Atlantic states some years earlier. The distribution of noise sources is discussed and compared to some previously published data. Some suggestions for the selection of community noise legislative levels are also made.
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Reverberation Time Formulae Reconsidered

Timothy Y. Yen

J. Acoust. Soc. Am. Volume 52, Issue 2A, pp. 493-494 (1972); (2 pages)

Online Publication Date: 12 Aug 2005

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The widely used reverberation time formula due to Eyring was derived on the assumption of step‐wise drops in the energy level of a diffuse sound field. The argument, besides being difficult to follow, was not justified from the statistical notion of a diffuse field. It is found that Eyring's formula can be extracted from a difference equation based on an energy principle which preserves the continuous nature of the decay process. Interpretations of the average absorption coefficient are also given.
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MATHEMATICAL DETERMINATION OF DECIBEL‐LOUDNESS INDEX, TABLES FOR VARIOUS FREQUENCIES

Calvin J. Kirchen

J. Acoust. Soc. Am. Volume 52, Issue 2A, pp. 495-497 (1972); (3 pages)

Online Publication Date: 12 Aug 2005

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An analytic procedure is developed to automate the calculation of loudness according to S. S. Stevens' Procedure for Calculating Loudness: Mark VI. Algebraic polynomials are determined that permit the calculation of loudness indices as a function of decibels at a specific frequency. A procedure is given to permit construction of a decibel‐loudness index table for any frequency from 25 Hz to 9 kHz.

HIGH‐FREQUENCY PHONONS: A NEW RESEARCH TOOL

J. Acoust. Soc. Am. Volume 52, Issue 2A, pp. 498-498 (1972); (1 page)

Online Publication Date: 12 Aug 2005

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HEARING LEVELS OF CHILDREN

J. Acoust. Soc. Am. Volume 52, Issue 2A, pp. 498-499 (1972); (2 pages)

Online Publication Date: 12 Aug 2005

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Airports and the Community

J. Acoust. Soc. Am. Volume 52, Issue 2A, pp. 499-499 (1972); (1 page)

Online Publication Date: 12 Aug 2005

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Noise from Gas Turbine Aircraft Engines

J. Acoust. Soc. Am. Volume 52, Issue 2A, pp. 499-499 (1972); (1 page)

Online Publication Date: 12 Aug 2005

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Surface Wave Phenomena

R. F. Wallis

J. Acoust. Soc. Am. Volume 52, Issue 2A, pp. 499-499 (1972); (1 page)

Online Publication Date: 12 Aug 2005

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Bistatic Acoustic Scattering from the Ocean Bottom

B. G. Hurdle, K. D. Flowers, and K. P. Thompson

J. Acoust. Soc. Am. Volume 52, Issue 2A, pp. 499-499 (1972); (1 page)

Online Publication Date: 12 Aug 2005

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GIANT SOUND WAVES ON THE SUN?

J. Acoust. Soc. Am. Volume 52, Issue 2A, pp. 499-499 (1972); (1 page)

Online Publication Date: 12 Aug 2005

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THE ULTRASONIC PIED PIPER

J. Acoust. Soc. Am. Volume 52, Issue 2A, pp. 499-500 (1972); (2 pages)

Online Publication Date: 12 Aug 2005

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UNDERWATER “CONE OF SILENCE”

J. Acoust. Soc. Am. Volume 52, Issue 2A, pp. 500-500 (1972); (1 page)

Online Publication Date: 12 Aug 2005

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UNDERWATER ACOUSTIC SIGNALS DETONATE EXPLOSIVES

J. Acoust. Soc. Am. Volume 52, Issue 2A, pp. 500-500 (1972); (1 page)

Online Publication Date: 12 Aug 2005

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