Optimization of rectangular mufflers inserted with baffles at high-order-modes using differential evolution method

Although rectangular mufflers have been widely used in industry, there has been scant research on both rectangular mufflers equipped with baffles under space-constrained conditions. Moreover, much muffler assessments have been restricted to lower frequencies using the plane wave theory. This has led to an underestimation of acoustical performances at higher frequencies. Beside, an analysis of three-dimensional waves propagating for mufflers using the finite element and boundary element methods is time-consuming in calculating the noise level. Also, the optimization of space-constrained mufflers is complicated. Therefore, to enhance the acoustical performance of mufflers, rectangular mufflers internally inserted with three kinds of baffles are presented. To illuminate the acoustical effect in high-order-modes and develop an optimally shaped muffler within a space-constrained situation, an eigen function in conjunction with a differential evolution is adopted. In this paper, a four-pole system matrix for evaluating the transmission loss of a muffler is derived using an eigen function.