Study On Pass-by Acceleration Noise Analysis And Control Of New Car

With the development of automotive industry and increase in car's possession, the pollution of vehicle noise become more and more severe, which has a bad influence on people's life quality, especially on the people in cities. To reduce pollution of vehicle noise, controlling pass-by acceleration noise is very fruitful method, which is the main reason why international automobile profession make the measurement standard of vehicle acceleration noise strict step by step. The cause of pass-by acceleration noise is so complex that noise control is difficult. To control the noise effectively, the major noise must be identified first, and then taking various economical measures to reduce the major noise. Firstly,this paper summarize the importance of the vehicle pass-by acceleration noise identification and control research and the status of noise control at home and abroad. This thesis research content and purpose was proposed, the vehicle noise source identification and control was researched,which combined specific project; Secondly, the composition and the noise mechanism of the vehicle pass-by acceleration noise was summarized,including engine noise, transmission noise, car body noise and other noise; Thirdly, the main sound source identification techniques of the vehicle pass-by acceleration noise were described, including the noise source separation technology, strong lead-covering method and sound measurement techniques;Fourthly, after doing pass-by acceleration noise experiment we found that noise value exceed national standard's requirement, so noise source identification and noise reduction of the new car were necessary. First of all, making plan of the noise source separation program.The separate-running method was applied to identify the noise source, and separated and ranked the contribution of the main assemblies of the new car to the whole of accelerating noise ,we concluded that the engines and gearbox was the largest proportion of radiated noise, exhaust system was a certain percentage of radiated noise; Secondly,sound density method was applied to identify the noise source of engine and define the positions of major radiating noise,we concluded that left surface's noise was oil sump and right surface's noise was belt pulley and top surface's noise was camshaft; spectrum analysis method was applied to analyze the spectrum characteristics of noise source to exhaust system and engine, and find out the maximal frequency value of the major noise contribution of main assemblies. Based on the identification of the major noise source, some economical controlling methods are made.One was based on numerical simulation,using one-dimensional fluid simulation software GT-POWER to analyse the muffler the acoustic properties and to optimize design plan, and finally through the test, the performance muffler made a good improvement;Second,sound absorption and insulation are taken to reduce the noise of engine surface emissivity. Through improving muffler and sound absorption and insulation for the engine, we made the car meet the requirement of the second stage of GB1495一2002 regular.Through the research on this paper, a suit of applied technology and method of pass-by acceleration noise control of vehicle is built up, which also can be extended to noise control engineering in different cars.