Abstract

Based on the existence of higher order mode waves (HOMW) in expansion mufflers is proved theoretically, a 3-D FEM is used to obtain the four-pole parameters of a muffler which are in turn used to calculate the transmission loss. With this method, the distribution of sound pressure in a muffler is calculated, the effects of HOMW on the muffler performance are investigated and a technique to improve the muffler performance is put forward. It is shown that, because of HOMW, the sound wave in expansion chamber is not in plane form; HOMW can descent capability of muffler, and the position of inlet and outlet is important to the performance of mufflers.

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