Description

The revision of ASHRAE Standard 36 required improvement of the method of measurement of sound power at discrete frequencies. One of the means by which the accuracy of the sound power measurement can be increased involves the rotating vane; therefore research concentrated on its applications. In order to study the vanes, their statistical properties, which determine the accuracy of measurement, must be studied first. Although theoretical relations for statistical properties of the sound fields at single frequencies were recently developed, their applicability had to be experimentally verified. Deviations from the diffuse sound field even at high modal densities were found. Major effort was concentrated on explanation of the modulation principles of sound field by rotating vanes, since it had been found that the vane provides the frequency and amplitude modulation of the sound field. Simple theory of the frequency modulation was worked out and experimentally verified. The effect of combined modulation was studied in terms of spectra generated by the vane action.

Citation: ASHRAE Transactions, Volume 80, Part 2, Montreal, QC

Product Details

Published:

1974

Number of Pages:

17

File Size:

1 file , 1 MB

Product Code(s):

D-MO-2305