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Noise

Published online by Cambridge University Press:  28 July 2016

A. H. Davis
A. H. Davis*
Affiliation:
Physics Department, National Physical Laboratory
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Extract

Noise is becoming of increasing importance and interest in modern life, and we appear to be approaching the time when much that we endure now will be regarded as intolerable. Public protests arise spasmodically on every hand and noise has been the subject of a certain amount of attention in the medical and popular press. With many persons the chief deterrent to air travel is understood to be the discomfort caused by the noise experienced. Whilst we may not wish to investigate the physiological reason for such discomfort, it is of interest to notice that in a recent paper, Laird (Acous. Soc. Am. J., I, p. 256, 1930), has summarised experimental data on the effect of sound on living beings.

No fully representative commission of medical, legal, acoustical and engineering interests has yet been set up in England, but in 1929 the Aeronautical Research Committee appointed a Sub–Committee in connection with the reduction of aircraft noise, and traffic noises have been considered in conferences by the Ministry of Transport.

Type
Proceedings
Information
The Aeronautical Journal , Volume 35 , Issue 248 , August 1931 , pp. 675 - 710
Copyright
Copyright © Royal Aeronautical Society 1931

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References

Note on page 678 * In a progressive sound wave in air an oscillatory pressure of about 20 dynes per cm.2 is associated with an energy flux of 1 microwatt per sq. cm.

Note on page 681 * Wegel&Lane. Phys. Rev. 23, p. 266, 1924.

Note on page 685 † Nature 125, p. 48, 1930.

Note on page 685 * J. Acoustical Society of America, 2, p. 18, 1930.

Note on page 688 * The following note, supplied by Mr. R. S. Capon, relates to the conditions of the static tests.

“The noise of the airscrews tested was compared on the following basis: An examination of the results of tests of the family of airscrews, suggested that if the airscrews were to operate at the same point on the efficiency curve (for example at maximum efficiency), at the same power and forward speed, then the tip speed u and the diameter D must be so related that was constant, where f is the solidity. The tip speeds of the several airscrews were related accordingly in the tests on the spinning tower. The pitches were so set that the same power was absorbed at the appropriate tip speeds. In applying the results to flight the assumptions are evidently that an airscrew will emit the same noise in flight and at zero advance when (a) the tip speeds are the same, and (b) the torque coefficients are the same under the two conditions.”

Note on page 691 * Phil. Mag. 7, p. 1,050, 1929.

Note on page 693 * Bur. Stands. Sci., Paper 552.

Note on page 693 † Aeronautics Bulletin No. 25, U.S. Dept. of Commerce, 1930.

Note on page 696 * Roy. Aero. Soc. J., Vol. 32, p. 185, 1928. Google Scholar

Note on page 697 * This formula, due originally to Sabine, and obtained by him in connection with reverberation in buildings, refers only to uniformly diffused sound. It has distinct limitations in application to noise in aircraft cabins, but it is instructive to notice the tendency of this reverberation effect.

Note on page 697 † The “absorbing power” of the surfaces includes all losses on reflection, and is actually equal to (l–r)x(Area of surface).

Note on page 697 ‡ If t=l–r we have I=4W/v, and the intensity of sound in the empty cabin is thus independent of the transmission and reflection coefficients of the enclosing surfaces.