Acoustical properties of a porous plate

The acoustical properties of a porous metal plate are modeled and expressions are obtained for through‐transmission impedance and fractions of power reflected, transmitted, and absorbed. The plate is modeled as a rigid boundary of thickness much smaller than the acoustic wavelength. A fraction of the surface is assumed to consist of holes of a given diameter. An expression applicable to incompressible, oscillating flow in a tube is used to predict the velocity distribution in the holes as a function of the acoustic pressure drop across the plate. The acoustic velocity immediately on either side of the plate is taken to be the average velocity on the surface taken over both the rigid area and the area occupied by holes. The acoustic properties are expressed in terms of the operational impedance defined as the ratio of the pressure drop to the average velocity. Calculated results for specimen impedance and fractions of power reflected, transmitted, and absorbed agree well with a set of in‐water acoustical m...