Transmission loss estimation of three-dimensional silencers by system graph approach using multi-domain BEM

Transmission loss (TL) estimation of three-dimensional silencers with complicated internal structures such as inlet/outlet tubes, thin baffles, perforated tubes, and sound absorbing materials is a demanding job even by powerful numerical approach such as FEM (finite element method) or BEM (boundary element method).The transfer matrix method using the multi-domain BEM data may be an efficient tool to deal with multi-branched acoustic systems but the method has limitation in application since it is based on the assumption of plane wave propagation at the interface of sub-domains. Assembling the whole system equation directly using the multi-domain BEM data is a considerable means to deal with three-dimensional acoustic components, but the intermediate pseudo-unknown variables in the equation assembling process may be too large.An efficient practical method by system graph approach and multi-domain BEM is proposed to formulate the condensed overall acoustic system equation for the whole acoustic system, only with unknown sound pressures on the sub-domain boundaries. The solutions of the overall equation are used to compute the TL of silencers.An air suction silencer for air compressors is tested numerically and experimentally and both results are compared to back up the suggested method.