In this paper, a design procedure to modify an acoustic system according to target acoustic characteristics is proposed and is applied to a design problem of a muffler for an automobile. The transmission loss values of a muffler mounted on an exhaust system should be changed considering the results of the sound quality evaluation test. The inlet and outlet of the muffler do not coincide with each other, and it has three holey baffles and three holey tubes. The effects of each part on the transmission loss curve are investigated in the frequency range of interest, and the dominant parts are selected for design. Two size optimization problems are formulated and are sequentially solved using a commercial finite element analysis program. The transmission loss curve of the obtained optimal muffler is compared with a target transmission loss curve, and an acoustical experiment on a manufactured muffler is carried out.
