The purpose of this study is to examine the acoustic performance of parallel simple expansion mufflers by a new approach for an acceleration of computational time required. The fast multipole method separated the field points and source points into two terms by means of addition theorem. When the boundary is divided into uniform meshes, the integration of source element can be calculated fast. Therefore, the fast multipole method, when compared with the boundary element method, reduces CPU time from an order of N2 to NlogγN, where N is the number of unknowns and γ is a constant. The numerical results have been compared with experiments and analytical approaches based on pressure and velocity continuity, as well as the modal meshing approach; the results clearly show that the agreements are good.
