Application of a generalized acoustic propagation theory to fibrous absorbents

Abstract The propagation of sound through fibrous materials is analysed by using a generalized theory of acoustic propagation in a porous medium. The necessary “constants” are derived from an idealized model of stacked cylinders. It is found that the size and orientation of the fibres are the main factors involved. The “frame” itself plays only a small part in the propagation of sound in the medium. Bulk anisotropy may be included if certain conditions are satisfied. The work of previous authors is substantiated and for a large range of densities good agreement is found between computed results and measurements on “Rocksil” materials.