Transmission loss prediction of silencers by using combined boundary element method and modal expansion approach

A technique combining the boundary element method (BEM) and analytical approach is proposed to calculate the transmission loss of silencers. The silencer is divided into several substructures, the BEM and the analytical approach are employed to evaluate the impedance matrices of substructures with irregular and regular shapes, respectively, and then the impedance matrices for all substructures are related. In order to reduce the computational time, a technique based on modal meshing approach is adopted. The transmission loss predictions of single expansion chamber, double expansion chamber and perforated tube absorptive silencer from the present approach agree well with three-dimensional numerical predictions and analytical solutions. The computational efficiency is analyzed and compared with the traditional substructure approach. The combined approach may save computational time efficiently.