Silencing device is a device which can effectively prevent or weaken the sound from spreading out when the air is out of circulation. Noise control of air inlet and exhaust pipes or ventilation ducts of machinery and equipment. A muffler with good performance can only reduce the noise from the inlet and outlet of the pneumatic equipment or along the pipeline, but can not reduce the radiation noise of the shell and pipe wall of the pneumatic equipment. According to the principle of noise reduction, there are many kinds of mufflers, including impedance muffler, composite muffler, perforated muffler, jet muffler, etc. Muffler: it can absorb sound and reduce noise through sound absorption of sound absorption material. Usually, micro perforated plate muffler belongs to this category. Muffler static pressure box is usually used to eliminate high frequency noise and high frequency noise. However, due to structural reasons, tubular muffler is not suitable for high temperature, high humidity and high speed occasions. The dissipative muffler is a kind of sound-absorbing material which is fixed on the inner wall of airflow channel or pipe and arranged in a certain way. The radiation noise of the shell and tube wall of the aerodynamic device can not be reduced. According to the principle of noise reduction, there are many kinds of mufflers, including impedance muffler, composite muffler, perforated muffler, jet muffler, etc. Muffler: it is to absorb sound and reduce noise through sound absorption material. The common micro perforated plate muffler belongs to this category and is usually used to eliminate high-frequency noise and high-frequency noise. However, due to its structure, it is not suitable for high temperature, high humidity and high speed. The dissipative muffler is a kind of sound-absorbing material which is fixed on the inner wall of airflow channel or pipe and arranged in a certain way.