Automatic Reverberation Time Recorder

Abstract

The method of measurement of reverberation time by tracing decay curves is tedious though accurate. Occasions frequently arise when the need for a quick determination of reverberation time vs. frequency curve is felt. An equipment constructed in the Research Department, All India Radio, which can plot the reverberation time vs. frequency curve of an enclosure under test, in a relatively short time, is described. The time taken for 40 db decay is measured and is taken as two-thirds the value of reverberation time, assuming an exponential decay of sound energy. The value of reverberation time thus obtained is indicated on a calibrated meter and also plotted on waxed paper as a straight line whose length is proportional to the value of reverberation time. A number of such lines is obtained automatically at close intervals, each line representing the value of reverberation time a frequency slightly higher than the frequency corresponding to the previous line. Since all these lines have the same zero axis, the curve joining the other ends of these lines gives the reverberation time vs. frequency curve. In this paper, the advantages and limitations of such an equipment are also mentioned taking a typical studio measurement as an example.