Shape optimization of one‐chamber perforated plug/non‐plug mufflers by simulated annealing method

To economically and efficiently lower the venting noise, the development of a high‐quality muffler with compact volume has become crucial in the modern industrial field. The research work of shape optimization of straight silencers in conjunction with plug/non‐plug perforated ducts which may noticeably increase the acoustical performance is rarely addressed; therefore, the main purpose of this paper is not only to analyze the sound transmission loss (STL) of a one‐chamber plug/non‐plug perforated muffler but also to optimize the best design shape under a limited space. In this paper, on the basis of plane wave theory, the four‐pole system matrix in evaluating the acoustic performance is derived by using the decoupled numerical method. Moreover, a simulated annealing (SA) algorithm searching for the global optimum by imitating the softening process of metal has been adopted during the muffler's optimization. To assure SA's correctness, the STL's maximization of one‐chamber perforated plug mufflers at a targeted frequency of 500 Hz is exemplified first. Furthermore, a numerical case in dealing with a broadband noise emitted from a fan by using one‐chamber plug/non‐plug mufflers has been introduced and fully discussed. To achieve a better optimization in SA, various SA parameter sets of cooling rate and iteration parameter values were used. Before the SA operation can be carried out, the accuracy check of the mathematical models with respect to plug/non‐plug perforated mufflers has to be supported by experimental data. The optimal result in eliminating broadband noise reveals that the muffler with a plug acoustical mechanism has a better noise reduction than that of a non‐plug muffler. Consequently, the approach used for the optimal design of the noise elimination proposed in this study is certainly easy, economical, and quite effective. Copyright © 2007 John Wiley & Sons, Ltd.