Absorption of Sound in Humid Air at Low Frequencies

The reverberation technique of Knudsen has been applied to the measurement of the absorption of sound over the frequencies 300 to 3000 cps in air with mole ratio concentrations of water vapor ranging from 0 to 0.02. Pressures from 5 cm Hg to atmospheric and temperatures from 0°C to 65°C were employed in the study. With the use of a 66‐in. spherical resonator and dry nitrogen gas as reference, following the method of Delsasso and Leonard, it has been possible to observe the anomalous absorption of humid air down to 300 cps. Pertinent graphs for the gases studied and detailed description of the experimental apparatus will be presented. [Support of this work by subcontract with the University of Michigan Signal Corps Contract No. DA‐36‐039‐SC‐52654 is acknowledged.]