Noise source of automobile exhaust system

Automobile is a comprehensive noise source including all kinds of noise. Because none of the automobile noise sources are completely sealed (some are only partially sealed), the noise radiated by the whole vehicle depends on the sound level, characteristics and interaction of each sound source.

Automobile noise sources can be roughly divided into engine noise and chassis noise, which are mainly related to engine speed and automobile speed. Engine noise is the main noise source of automobiles. Engine noise can be divided into aerodynamic noise, mechanical noise and combustion noise.

Aerodynamic noise mainly includes intake, exhaust and fan noise. This is the noise generated by air vibration caused by intake, exhaust and fan rotation, which directly radiates into the surrounding air. When there is no intake and exhaust muffler, exhaust noise is the biggest noise source of the engine, followed by intake noise. Fan noise is usually one of the main noise sources, especially in air-cooled internal combustion engines. Including transmission noise (gearbox, transmission shaft, etc.). ), tire noise, braking noise, aerodynamic noise generated by the car body, etc.

Noise source identification is to analyze all kinds of sound sources existing on the machine, understand the mechanism of vibration and noise, determine the position of vibration source and sound source, and analyze the characteristics of sound source (including the type of sound source, the size of sound level, frequency characteristics, sound change and propagation law, etc.). ), and then arrange the order according to the size of the noise, so as to determine the main noise source.