Attenuating Axial Pipe Resonances in Exhaust Systems using Micro-Perforated Patches

Micro-perforated panels are well known to be applied on acoustic barriers, absorbers, and mufflers etc. However, other types of acoustical applications are much less observed. In this paper, the use of several small patches with micro-perforations welded along the exhaust pipe at optimal positions to reduce axial pipe resonances is described. The patch performance is evaluated by comparing the acoustic levels at the tailpipe outlet with and without the micro-perforated patches. The performance of the patches is firstly modeled and assessed using acoustic finite element tool. Simulation results indicate that the effect of the axial pipe modes on tailpipe noise levels is significantly reduced. And then, the patch performance is evaluated on a demonstrator vehicle and compared with the conventional exhaust system. The results from the vehicle test validate both the capabilities of the micro-perforated patches to reduce pipe resonances and the potential for its use in designing light weight, resonance free exhaust systems. Finally, the practical concerns for applying the micro-perforated patches are discussed.