An Application of Fast Multipole Method in Analyzing Acoustic Filters

The purpose of this study is to investigate the acoustic performance of mufflers. As a numerical scheme for analyzing an acoustic filter, the boundary element method is more suitable than are domain methods, such as the finite element method, which has to mesh the domain. However, the coefficient matrices established by the boundary element method are full and often non-symmetrical. In order to decrease the computational time required, the fast multipole method has been applied. The fast multipole method, when compared with the boundary element method, reduces CPU time from an order of N 2 to Nlogγ N, where N is the number of unknowns and γ is a constant. This study focused on the different geometries of plates within simple expansion acoustic filters. Numerical analysis demonstrates that the transmission loss at a particular frequency performance is better when employing a simple expansion acoustic filter with plates.