Development of a novel instrument based on DSP for measuring vehicle noise combined with engine rotating speed

In order to measure vehicle´s noise and the engine speed, a novel instrument is developed based on digital signal processor DSP-TMS320VC33 and monolithic processor AT89C51. The DSP is mainly used to process the data and the monolithic processor is used for human-machine interface and management. The new idea applies non-contact measurement of vehicle noise by the microphone to extract the vehicle engine speed. By using noise reduction method based on Wavelet Transform, vehicle engine speed information is picked up from the noise at the outlet of vehicle exhaust pipe. The developed instrument can meet the practical measurement requirements with measuring speed scope within 30~8000 rpm and the error within 10 rpm, the measured noise rang is 30~130 dB and the resolution ratio is 0.1 dB.