Transmission Loss Investigation of Two-Dimensional Thin Mufflers by the Modal Expansion Method Using a New Line Source Model

Abstract

The transmission losses (TLs) of different types of two-dimensional thin mufflers have been investigated by solving the pressure response function using the modal expansion method. These thin mufflers are commonly employed in domestic refrigeration compressors because of the limited space in such compressors. The point source model has convergence problems at points close to the source, whereas the surface source model may generate a non-uniform pressure distribution on the source surface. A new square line source model was implemented in this study. Using this new model, a generic formulation of four-pole parameters by the modal expansion method was developed in two different curvilinear coordinates, enabling TL to be calculated. To verify the proposed line source model, the TL results for a cylindrical thin muffler were compared with those obtained by the three-dimensional finite element method (FEM). The TLs of rectangular and cylindrical mufflers with various inlet/outlet positions and dimensions were investigated. The results demonstrate that the proposed model can determine the effects of higher-order modes on TLs. In addition, comparison with the circular line source model revealed that the proposed square line source model is computationally efficient and can determine TLs with a sufficiently high accuracy.