Research On Noise Source Identification Of Pass-by Accelerating On Motorcycle

Accelerating pass-by noise is regarded as one of the targets for vehicle noise levels, So China has successively constituted series of new regulations on motorcycle pass-by noise. With the increasing awareness of environmental protection and the enhancement of the environmental requirements, these regulations will be more rigorous; Because of the new regulations, many vehicles'noise can't achieve the requirements and must be controlled ;The precondition for noise control is to identify the main sources of the noise accurately ,then reduce them to meet the requirements.At first, this paper determines the condition corresponds with the noise peak level by studying on the accelerating pass-by noise experiment, and divides the noise frequency of the moment into three sections, namely Low frequency for 20-500 Hz, middle frequency for 500-1500Hz,and high frequency for 1500-6000 Hz, the energy of High-frequency band account for about half of the whole energy, middle about 1/3,low about 15%;Latter, do the surface acoustic intensity experiment on engine pedestal, as the sound intensity contour lines of front, top, left and right surfaces show, low frequency noise is mainly from the intake and exhaust, the left and right of crankcase and drive shaft shell radiating noise is a major contributor to middle frequency band noise, high-frequency noise mainly comes from the cylinder head radiation. The radiation of exhaust pipe is much more high in whole frequency band; Generally speaking, the radiating noise of intake, exhaust, cylinder head and driveshaft are the major sources of noise.According to requirements of the motorcycle road experimental measurement, establish the acoustic model of the moving point sound source about decay and reflecting, simulate the effect of Doppler at different speed and frequency, the speed more fast and frequency more high, the doppler effect more obvious; And imitate the actual measuring noise of one motorcycle with satisfactory results,which saving much time and money expend at identification of noise source. through the frequency spectrum analysis,power spectrum array analysis,time and frequency domain analysis, found the cause of noise produce.