Modeling, Analysis and Optimization of Design Parameter in Periodic Micro-perforated Chamber Mufflers

Micro-perforated chamber mufflers are effective sound absorbers that reduce sound levels by offering high acoustic resistance and low mass reactance due to their micro-perforations. When arranged periodically, these mufflers exhibit enhanced efficiency in sound absorption. The transmission loss of sound waves in both mufflers and periodic acoustic devices are closely related. Specific frequency bands can generate the Bragg and local resonance effects, producing stop bands where waves cannot propagate. Dispersion curves can be calculated to identify these bands using the Floquet-Bloch theorem. This study utilized the Transfer Matrix method to analyze a periodic micro-perforated chamber muffler with three unit cells. Porosity variations are analyzed, and sound pressure level and transmission loss are calculated and presented. Additionally, a parametric optimization is conducted using differential evolution method, leading to a significant improvement in the efficiency of the originally proposed micro-perforated chamber muffler. The results indicate that transmission loss is not directly proportional to the number of micro-holes, emphasizing the importance of studying porosity in muffler design. The diameter ratio directly influences transmission loss, with the best value observed at a 0.8 mm micro-hole diameter.