Abstract: A combined muffler consists of collateral pipe and expansion-chamber muffler is designed. The modal and acoustic analysis are carried out by making use of the module of dynamics and acoustics in ANSYS，and then the natural frequency and the insert loss curve are obtained. The natural frequency and the insert loss curve of the collateral pipe muffler and the expansion-chamber muffler are also obtained in the same way. The result of numerical simulation shows that the combined muffler does well in the engine fundamental exhaust noise as well as its low frequency harmonic wave. What’s more，comparing with the single part of collateral pipe muffler and the expansion-chamber muffler，the noise elimination effect of combined muffler improves a lot，which achieves the design requirements. The result of numerical simulation is available to predict the muffler property and then judge whether the structure designs meet the demand or not.

Key words: modal analysis, acoustic analysis, insert loss

摘要： 设计了一种由旁支管和扩张式消声器组合而成的消声器，利用ANSYS 的动力学及声学模块，对其进行模态分析和声学分析，得到该组合消声器的固有频率和消声插入损失曲线。对旁支管和扩张式消声器分别进行声学分析，得到它们的消声插入损失曲线。仿真分析发现: 组合消声器在发动机基频排气噪声及低频谐次波处有很好的消声效果，与单独的旁支管和抗性消声器相比，其消声效果有明显提高，达到了设计要求。该仿真结果可用于预测消声器的性能，并判断其结构设计是否符合要求。

关键词: 模态分析, 声学分析, 插入损失