Abstract
A theory of sound absorption in porous materials has been given by C. Zwikker and C. W. Kosten [Sound Absorbing Materials, Elsevier Publishing Company, Inc., New York, 1949] in terms of a mean pore radius, the kinematic coefficient of viscosity, and the ratio of specific heats. In order to investigate the theory, an experimental investigation has been carried out in which the kinematic coefficient of viscosity and the ratio of specific heats have been varied by using various gases. The normal specific acoustic impedance and the complex propagation constant of various samples of steel wool have been measured. The results are presented in terms of the complex compressibility and the complex density. These quantities are compared with the theoretical values predicted by the theory, and a frequency range from approximately 100 cps to 5000 cps has been covered in this investigation.
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