Analysis of non-uniformly perforated muffler in concentric resonator type

In the muffler industry, the main purpose of the research works is to determine a way to increase the TL (Transmission Loss) properties of the muffler, without deteriorating the back pressure influence. In order to obtain better results, several works have been done by changing the geometrical characteristics of the muffler or the type of the muffler. This work will focus on the perforated muffler components with concentric chamber, to investigate the effect of a non-uniform porosity along the inner perforated tube of the muffler on the TL. It is noted that varying the perforation ratio affects the peaks frequencies of the TL, especially fer $2\pi < kL < 4\pi$ (in the case of L : 200mm for the concentric resonator). The magnitudes of the TL, for this range of frequencies, vary noticeably by changing the porosity distribution.