Shape Optimization of Reactive Mufflers Using Threshold Acceptance and FEM Methods

The Shape optimization of reactive muffler under space constraint has become of great importance in the design of quieter environments. In this paper the acoustic performance of three different expansion-chamber mufflers with extended tube under space constraint is presented. A shape optimization analysis is performed using a scheme called Threshold Acceptance (TA), the best design obtained by the shape optimization method are analyzed by Finite Element Method (FEM). This numerical approach is based on the maximization of the sound transmission loss (STL) using the Transfer Matrix Method (TMM), a modelling method based on the plane wave propagation model. The FEM solution is based on the Acoustic Power method, a standard computational code COMSOL Multiphysics is used to analyze in 3D the sound attenuation of the mufflers by the FE method. The acoustical ability of the mufflers obtained is than assessed by comparing the FEM solution with the analytical method.  Results show that the maximal STL is precisely located at the desired targeted tone. In addition, the acoustical performance of muffler with outlet extended tube is found to be superiors to the other one. Consequently, this approach provides a quick scheme for the shape optimization of reactive mufflers.