Absorption of Sound in Air below 1000 cps

Abstract

For many acoustic problems, it is of importance to have accurate data of absorption of sound in air as a function of humidity. Such information has not been available below 2000 cps. This paper presents data at lower frequencies in the range from about 125 to 1000 cps. The intensity attenuation coefficient m is given as a function of relative humidity at 20°, 0°, and −20°C for normal atmospheric pressure. Similar data are given at pressures of 400 and 200 mm Hg for a temperature of 20°C. The experimental results are compared with the theoretical values predicted by Kneser.