Analytical approach for sound attenuation in perforated dissipative silencers

A two-dimensional analytical solution is developed to determine the acoustic performance of a perforated single-pass, concentric cylindrical silencer filled with fibrous material. To account for the wave propagation through absorbing fiber and perforations, the complex characteristic impedance, wave number, and perforation impedance are employed. With expressions for the eigenvalues and eigenfunctions of sound propagation in the perforated dissipative chamber, the transmission loss is obtained by applying a pressure and velocity matching technique. The results from the analytical method are then compared with both experiments and numerical predictions based on the boundary element method ~BEM!, showing a reasonable agreement. The effects of geometry, fiber properties, and perforation porosity on the acoustic attenuation performance are discussed in detail. © 2004 Acoustical Society of America. @DOI: 10.1121/1.1694994#