Acoustic calibration device

Details Acoustic calibration device Acoustic calibration device

1986-07-28

1987-12-29

Noland, Tom

Measuring and testing

Instrument proving or calibrating

Volume of flow, speed of flow, volume rate of flow, or mass...

367 13, 73 1R, G01H 1700, G01M 1900, G01D 2100

Patent

active

047152192

ABSTRACT:
An acoustic calibration device for intensity measuring systems comprising at least two pressure microphones to be calibrated without using an anechoic chamber. The calibration device comprises at least two cavities interconnected by means of one or several acoustic resistance elements. One of the pressure microphones is to be inserted into one of the cavities and the second pressure microphones is to be inserted into the second cavities. A sound source is connected to one of the cavities. In connection with the subsequent cavity the acoustic resistance thus forms an acoustic RC-link providing a phase shift proportional to the frequency corresponding to the conditions in the free field. By a suitable dimensioning of the RC-link a phase shift corresponds to the phase shift over a distance of e.g. 50 mm in the free field. The sound source is able to generate either white noise or pink noise depending on whether measurements are performed over fixed frequency intervals or relative frequency intervals.

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Acoustical Engineering; pp. 424-427; by Harry F. Olson; pub. 1957 by D. Van Nostrand Co., Inc., of Princeton, N. J.
"The Measurement of Sound Intensity"; Report No. 28, The Acoustics Laboratory, Technical University of Denmark; 1980, 89 pages, Finn Jacobsen.
"Electroacoustic Measuring Equipment and Techniques"; Proceedings of the IRE, vol. 50, No. 5, May 1962, pp. 762-768; Leo L. Beranek.
"Calibration and Free-Field Evaluation of a Pressure-Gradient Microphone"; The Journal of the Acoustical Society of America; vol. 34, No. 11, pp. 1779-1786; Nov. 1962; G. B. Thurston et al.

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