Research On The Control Of Motorcycle Pass-by Noise And The Acoustic Simulation Of Air Cleaner

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 expend and short development period. In this paper, the acoustic simulation was applied to improve the noise performance of air-in filter to control the induction noise which was contributed much to pass-by noise. The new designed air cleaner did contributed to the reduction of pass-by noise of motorcycle 125-C from the result of experiment.The characteristic of pass-by noise was studied by the results of measurement. Different methods including near field sound pressure, sound intensity measurement technique, and order analysis etc., were applied to analyze the noise distribution of the motorcycle, then the main noise sources was identified. The induction noise was one of the main noise sources, and it did an important contribution to the pass-by noise. The transmission loss of air-in filter was got both on the engine test rig and at stationary state. Compared the transmission loss and the spectrum of pass-by noise, the conclusion can be got that the improvement of acoustic performance of air-in filter below 1000 Hz is very important to reduce the induction noise.The CAD model and the boundary element model were founded. The transmission loss was calculated based on the boundary element method, the agreement of the calculation result with the experiment one showed the reliability of BEM method in anticipating the noise performance of filters with complex structure. The numerical model was simplified rationally, which were validated through the method of experiment and calculation. According the principles of acoustics, many different design scheme of air cleaner was proposed, and the transmission loss was anticipated by BEM. Two kinds of design show more noise reduced below 1000 Hz, one is the air-in filter with only one expand chamber, and the other is with the Helmholtz resonator. According the result of numerical simulation the CAD model was founded, then the physical model.The new air-in filters showed good acoustic performance in the pass by noise tests. Compared with the original air cleaner, the one with Helmholtz resonator got 1.8dB reduced of the pass-by noise, and the other one with expand chamber got 1.6dB reduced of the pass-by noise. The pass-by noise of motorcycle 125-C got 3 dB reduced using the new air cleaner and the new designed muffler together. Another experiments show that, new air-in filters do not harm to the power and the induction efficiency of the engine.