Noise source identification and noise abatement of truck under idle speed condition

In order to eliminate the obviously abnormal noise of truck under idle speed condition, the noise source was identified based on sound intensity method and source separation method. The results showed that intake orifice and shell surface of air cleaner were dominant radiation sources whose frequency range from 288 Hz to 344 Hz, and root of noise source was the air compressor. The modification that expansion muffler was added into air compressor intake system was put forward. The analysis results of transmission loss of air compressor intake system based on finite elements method showed that the muffler could fulfill the requirement. Furthermore, experiment results of modified vehicle showed that the noise range from 25 Hz to 1 600 Hz at the typical measurement point had been reduced from 77.48 dBA to 73.21 dBA. The abnormal noise is eliminated and the sound quality is improved obviously.