Sound field of a baffled piston source covered by a porous medium layer

Abstract

Two models for the prediction of sound transmission through a thick layer of material which lies on a horizontal baffle are presented. These models are a preliminary investigation of a method for the acoustical and physical characterizations of porous materials. The acoustic source is assumed to be a circular, baffled piston source mounted under a layer of porous material. The sound is transmitted through the porous layer to the semi-infinite half-space above the layer. The models are used to calculate the transfer function between the volume velocity of the source and the sound pressure above the porous material. The first model is based on the integral method in which appropriate Green’s functions are used to describe the sound field, and on a collocation procedure. The second model uses a method of decomposition of the sound field into cylindrical waves. The numerical results of the two models are in good agreement. A significant sensitivity of the transmitted sound field to the material’s physical characteristics is observed. The models’ predictions are in good agreement with those from the literature on the limiting case of a circular piston radiating in a semi-infinite medium. The cylindrical wave decomposition method is found to be much faster in terms of computation time, and more general than the integral method model.