As environmental protection regulations are quite strict on vehicle emission standards, no matter idling, accelerating, low-speed driving, high-speed driving or decelerating, all vehicles must meet the emission standards. In the face of such strict restrictions, in addition to achieving balance between performance and emission, the only thing is catalytic converter. The catalytic converter is usually made of precious metals, including oxidation catalyst, reduction catalyst and three-way catalytic converter used in most vehicles. After the exhaust manifold, the catalytic converter is connected to convert the incompletely burned pollutants into harmless substances to protect the environment.

It is connected to the muffler from the catalytic converter. The cross section of the muffler is a round or oval object, which is welded with thin steel plates and installed in the middle or rear of the exhaust system. There are a series of baffles, chambers, orifices and pipes inside the muffler. The phenomenon of acoustic reflection interference and cancellation is used to gradually weaken the sound energy, so as to isolate and attenuate the pulsating pressure generated each time the exhaust valve is opened.