Study On Pass-by Accelerating Noise Identification And Control Of Automobiles

When vehicles bring great convenience to us nowadays, the noise of the automobile also deeply disturbs the life, the work, and health of physical and mental of people in the same time. published in 1996, and of GB 1495-2002 are all for the purpose of controlling noise including that of vehicles on roads.The measurement and analysis of sound density is an effective way to identify the original source of noise. The thesis discusses a new sound density arithmetic, which can exclude the environment noise and just account for the sound density of radiation wave when the direction of the wave is known. The method is based on the theory of the equality of eradiated sound wave density level and sound pressure level. The validity of the arithmetic is experimental proved, and it was successfully applied to identify the noise source of the F368Q3 engine. Based on the feature of engine noise's periodicity, the thesis studied the affection of rotation fluctuation on calculation results when applying integral-period truncation to improve precision of sound density spectrum, and discussed the shortest length and least segment of the truncation under certain measuring allowance,so greatly speed up the sound density measurement at discrete points.In the work of SC7080A mini-car noise reduction project, at first time the separate-running method was applied to identify the noise source, and successfully separated and ranked the contribution of the main assemblies of SC7080A to the whole of accelerating noise, and recognized the greatest one is the noise of fuel combustion in engine. Through Sound density theory, the burning noise's radiation progress approach was successfully identified. We found that burning noise first passes through intake cover,along the intake pipes to the air-intake filter,and through air filter and intake throat, then eradiate out-side, which is one of the major way for the burning noise radiation. On the precondition of not reducing the function and capability, and fully considering economical factor, and at the same time consulting noise status of all mostly noise production parts at home and abroad, the total noise reduction was distributed to some parts which have the potential of noise reduction. To some assemblies,measures for noise reduction were brought forward and the feasibility was demonstrated, such as three-parallel-connected resonant silencer (Patent No.: ZL00264613.7) and cylinder head cover with sound absorption (Patent No.: ZL00264614.5) et al. Thus the SC7080A exterior accelerating noise was successfully reduced from 80.8dBA to 72.4dBA. The experimental study on the capability of three-parallel-connected resonant silencer was also conducted. The noise reduction of SC7080A experienced a process of evaluating of road test, sound source separate-running experiment and test results analysis, sound source identification bench test, studying on control scheme optimization and experiment improvement, engineering production improvement,and so on, thus formed a measuring and technique system to analyze and control of the exterior noise of vehicles.The product of the project passed the scientific evaluation organized by ChongQing Scientific Committee.