Abstract: A new method is presented for predicting the insertion loss of an exhaust mufflerby combination of the boundary element method with the four-load method,and a boundaryelement scheme is proposed to calculate four-pole parameters of a muffler with low Mach numberflow,and the four-load method is extended to evaluate the acoustical source impedance of theexhaust system.The insertion loss of two mufflers was studied,and the predicted results were ingood agreement with the measured ones.