Research On The Noise Control Of JS125 Motorcycle

Noise from motorcycle is a major public nuisance, and with noise statute being more strict, the noise is necessary to be controlled and reduced. Aiming at the heavy noise of a type 125 of motorcycle and acceleration noise doesn't meet national standard, the noise source of motorcycle is identified by the pass-by noise experiment, near-field acoustic pressure test and sound intensity test, exhaust noise being the major noise source is confirmed; by doing the computer simulation, the acoustic performance of muffler is analyzed and improved , the result of pass-by noise experiment indicates the noise of motorcycle is reduced, and meets the request of the national standard.Accelerating noise of motorcycle doesn't reach the request of the national standard through the experiment, and the noise of right side is more heavier than left. The analysis of noise spectrum shows a range of 0-1000Hz low frequency is a major ingredient of motorcycle noise for their sound power contributing mostly to the noise, and the frequencies of sound pressure peaks level are the multiple of 60Hz fundamental frequency, a preliminary inference that peaks caused by induction noise and gas pulsation from engine is ascertained.The experiments of noise identification using the near-field acoustic pressure and near-field sound intensity are done. The result with the first method indicates that the intake noise is the heaviest, the noise of transmission is the least one, and the noise of the exhaust is bigger than the head of engine. The result of the test with second experiment shows that the main source of the noise is the exhaust noise, while the motorcycle is accelerating, the main component of frequency is the low frequency and the sound power of right side is bigger than the left side of the motorcycle. Owing the vent-pipe is in the right side, we can get a conclusion that the effect of the muffler is not good.So the 3-D geometry model of the muffler is built, the transmission loss calculation simulation is done using the method of boundary element method. The frequency analysis, the transmission loss analysis and the insertion loss analysis of the original muffler is done using the testing method as well. The result reveals that the model is reasonable, it can be using for structural optimizing and designingThree methods of the muffler being improved are proposed basing on the SYSNOISE analysis. The transmission loss and the insertion loss experiments of the improved muffler are done. The result of the simulation and test all indicate that the effect of the muffler improved by the three methods are better than the original. Doing the experiment of acceleration noise with improved muffler, its result indicates the noise of motorcycle with three improved muffler meet the request of the national standard, in which the limit of the pass-by noise is 77dB , and the purpose reducing noise is achieved.