Car Composite Muffler Acoustic Properties Of Research

With the rapid development of our economy and our national income rising, as akind of quick and convenient traffic tools, cars enters the life of people. Cars bring ourdaily life convenient and some harm. Traffic noise produced by automobile affectspeople’s life and work, and people begin to pay close attention to noise hazards of thevehicles. The exhaust noise is one of the main noise sources of vehicle, exhaust muffleris the main noise reduction device that controls the car exhaust noise, and it is also themost effective method of redacting the noise. Therefore, the exhaust muffler attenuationcharacteristics directly affect the quality of automobile noise. By3-d sound-vibrationsoftware, the acoustic characteristics of muffler system are analyzed and calculated.Firstly, the current research situation of domestic and foreign are introducedmuffler that provides a direction for later research. Secondly, this paper introduces andanalyzes of relating theory knowledge of acoustic properties muffler, that can providestheoretical basis for the future research of the muffler noise characteristic.Acoustic properties of the muffler are calculated by finite element method. Usingthe CATIA to create models of the single expendable muffler and compound structuremuffler, using finite element software HYPERMESH to mesh the geometry model ofmuffle, and then the muffler finite element mesh models are imported into the soundradiation software SYSNOISE to simulate and analysis.The muffler transmission loss,the acoustic field distribution and velocity distribution are studied.Through calculation and analysis of transmission loss of the single expendablemuffler and composite muffler, the results show that a plane wave theory is notapplicable to analyze the high frequency noise, expansion ratio affects amplitude oftransmission loss and has no influence to attenuation frequency bandwidth of themuffler, expansion chamber length can change the muffler attenuation frequencybandwidth and has no influence to the amplitude of muffler transmission loss, theacoustical noise performance of composite muffler in the most frequency range is thesuperposition of simple attenuation component acoustics performance, the trend of transmission loss the muffler with liquid flow is consistent with that of muffler withoutflows and passing frequency is improved greatly, and composite muffler have betternoise performance in the low and medium frequency.The researches provide the reference to the muffler noise performance analysis andoptimization design.