The Test And Improvement Of The Motorcycle Noise

The pass-by noise level is an important performance to evaluate the quality of vehicles. The noise control of motorcycle became obliged to conform to more stringent statutory pass-by noise requirements. The design method based on numerical simulation is widely used for its reduction on cost and short development period. In this paper, the acoustic simulation was applied to improve the noise performance of muffler to control the exhaust noise which was contributed much to pass-by noise. The new improved muffler did contribute to the reduction of pass-by noise of motorcycle from the result of experiment.The characteristic of pass-by noise was studied according to the results of measurement. The test conditions of sound intensity and near-field sound pressure were confirmed. Different methods including near field sound pressure test, sound intensity measurement, and order analysis etc were applied to analyze the noise distribution of the motorcycle, then the main noise sources was identified. The exhaust noise of engine was one of the main noise sources, and it has more thing to do with the pass-by noise. The transmission loss characteristic experiment of muffler was carried on got at semi-anechoic room, and the analysis results of the experiment and acoustic simulation show the acoustic performance of muffler below 1000 Hz is deficient.The CAD model and the finite element model were built. The mechanical performance, air dynamic performance and acoustic performance were calculated and analyzed based on the FEM, what keystone being improved is ascertained combining with the experiments. Due to the basic principle of noise reduction that impedance mutation of muffler cause the noise diminished, and using the acoustic simulation method, three projects of the modified muffler were optimized. Compared with the original muffler on performance, the improved projects which are better acoustic performance, and the invariant pressure loss and mechanical performance basically are adapted to be the product sample piece.The product sample pieces of improved projects are made to be used to experiment that are the test of noise emitted by stationary, the test of insertion loss and the test of power loss, compared with the original, the acoustic performance of the improved projects was enhanced and the pass-by noise of the motorcycle reduced by 1dB(A). Insertion loss also increased by 2-3 dB(A) than original muffler, the power loss still keeps invariant and meets the requirement of the nation standard, and the result of the calculation simulation had a high coherence with the result of experiment...