Structure Design And Optimization Of A Multi-layer Micro-perforated Tube Muffler Based On The Sound Transfer Matrix Method

In recent years,the micro-perforated plate structure has been made into a pipe structure because of its good sound-suppression performance and no limitation of material,and has been widely used in muffler.Compared with other kinds of muffler,micro-perforated tube muffler is a new kind of sound absorption structure with low sound quality and high acoustic resistance.In order to obtain the high absorption at some special frequencies or meet the needs of some special environments,scholars at home and abroad have carried out a series of research on modeling and structural design of micro-perforated tube mufflers.At present,the research of micro-perforated tube muffler is mainly focused on the single-layer structure,and the theoretical study of double-layer or even multi-layer structure is seldom introduced in literature.The research methods also focus on the traditional transfer matrix method or finite element method.Generally speaking,although the modeling of multilayer micro-perforated tube is more complicated,the sound absorption performance of multilayer micro-perforated tube is better than that of single layer,so it is of great significance to model theoretically and design optimally.Therefore,the acoustic performance of multi-layer micro-perforated tube muffler is studied.Firstly,based on one-dimensional plane wave hypothesis and micro-perforated plate sound absorption theory,a new transfer matrix method is proposed by combining the traditional transfer matrix method with fine integration method,and applied to analyze the acoustic characteristics of single-layer micro-perforated tube silencers.Compared with the results of acoustic finite element analysis,it is shown that the new transfer matrix method can accurately calculate the acoustic characteristics of single-layer micro-perforated tube silencers and has high efficiency.Furthermore,the new transfer matrix method is applied to analyze the influence of cavity length,perforated wall thickness,aperture and perforation rate on acoustic characteristics of micro-perforated tube mufflers.The results show that the cavity length has a great influence on the acoustic characteristics of the muffler.The thickness of the perforated tube wall,the aperture and the perforation rate have no obvious influence on the low frequency of the micro-perforated tube muffler,but have obvious influence on the middle and high frequency of the muffler.After that,due to the limited acoustic performance of single-layer micro-perforated tube muffler,the new transfer matrix method is extended to analyze the acoustic performance of double-layer micro-perforated tube muffler.Compared with the results of acoustic finite element analysis,it is shown that the new transfer matrix method can effectively calculate the acoustic characteristics of the double micro perforated tube muffler,and has high accuracy.Based on the new transfer matrix method,the effects of single and double layer micro-perforated tube silencers are compared and analyzed,and the effects of different expansion chamber thickness on the acoustic performance of double-layer micro-perforated tube silencers are studied.The results show that the sound suppression effect of double layer is better than that of single layer,and the acoustic performance of double layer micro-perforated tube muffler can be improved by increasing the thickness of expansion chamber.Finally,in order to obtain a better muffler,the new transfer matrix method is extended to analyze the acoustic characteristics of a three-layer micro-perforated tube muffler.Compared with the results of acoustic finite element analysis,it shows that the new transfer matrix method has higher accuracy.In addition,based on the new transfer matrix method,the influence of the structural parameters of the three layer micro-perforated tube muffler on the acoustic performance is analyzed.The results of Parameter discussion show that the cavity length,aperture,inner perforated tube diameter,interlayer perforated tube diameter and cavity diameter have obvious influence on the acoustical performance of muffler.Based on this,these parameters are selected as optimal design variables,and the average sound transfer loss is chosen as the optimization objective.The response surface method is used to optimize the structure of the three-layer micro-perforated tube muffler.The optimization results show that the average sound transfer loss of the three-layer micro-perforated tube muffler is obviously increased,and the noise attenuation effect of the three-layer micro-perforated tube muffler is improved.