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Abstract

Recently, research on new techniques of single-chamber plug silencers has been addressed. However, the assessment of a multi-chamber plug muffler’s optimal shape design within a constrained space as well as a pressure-drop limit which are mostly concerned with the necessity of operation and system venting in practical engineering work was rarely tackled. Therefore, this paper will not only analyze the sound transmission loss (STL) of a space-constrained multi-chamber plug muffler but also optimize the best design shape under a specified pressure drop. In this paper, the generalized decoupling technique and plane wave theory used to solve the coupled acoustical problem of plug mufflers with perforated tubes are presented. The four-pole system matrix used to evaluate acoustic performance is also introduced in conjunction with a genetic algorithm (GA). Before the GA operation can be carried out, the accuracy of the mathematical model for a one-chamber plug muffler is checked using Munjal’s experimental data. To appreciate the sensitivity of a muffler’s geometric parameters, the influence of sound transmission loss and related pressure drop with respect to design parameters is investigated. Furthermore, the noise reductions with respect to broadband exhaust noise emitted from a blower’s inlet is also introduced and assessed. The optimal result in eliminating broadband noise reveals that the overall noise reductions with respect to various mufflers under a maximal allowable pressure drop of 800 (Pa) can achieve 40, 83 and 124 dB. Consequently, the approach used for the optimal design of the multi-chamber plug mufflers under space and back pressure constrained conditions is indeed easy and quite effective.

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