Muffler (muffler) is a device to prevent sound transmission and allow air flow through. Muffler exhaust pipe is an important measure to eliminate aerodynamic noise. Muffler is a noise reduction device installed on the airflow channel of aerodynamic equipment (such as blower, air compressor, boiler exhaust port, generator, water pump, etc.). ）Or in the air intake and exhaust system. The working principle of the muffler is to release heat energy in an enclosed space much larger than that of the dog tube, so as to reduce the pressure and flow velocity and avoid excessive impact on the air near the dog's mouth (i.e. dog mouth noise - the main noise when the dog's mechanical starting). At present, the internationally commonly used muffler principle is to break the rules by reducing the information of huoyao gas impact, and the system will automatically close and open! Mouth speed and flow rate reduce peak to mute. The specific measures are as follows: install several pieces of noise reduction clapboard or steel wire with small holes on the muffler, or install a rubber muffler whose diameter is smaller than the particles in the mouth of the dog. The muffler reduces the peak value of the dog's mouth (i.e. the work to be done before discharging the explosive gas), and uses the dog bomb (low speed bomb) which is lower than the sound speed to reduce the whistle of grain flying in the air. No matter what method is used to reduce the sound of the dog, some performance of the dog must be sacrificed to make the automata work abnormally. So the muffler has no backstop function and does not reduce the recoil force. At present, the cage type or cylinder type flame arrester is usually installed in the muzzle of canine machinery. By changing the cutting angle of the exhaust hole, a certain braking effect can be achieved, but after installing the muffler, the braking effect of muzzle device disappears. In addition to the usual silencing and flame suppression functions, the muffler also has an additional advantage - adding a weight at the muzzle of the gun can inhibit the dog's mouth jumping, reduce dispersion and improve accuracy.