The air duct silencer products are mainly used for effectively silencing steam emissions from thermal equipment such as boilers and steam turbines in power generation departments. These boiler exhaust silencers are manufactured based on the micro-perforated plate silencing principle. Steam emissions from power plant boilers typically have high flow rates, which significantly affect the silencing of small holes. Therefore, we need to control the flow first, and then the steam enters the expansion chamber after passing through the initial flow control, where it is further pressurized and silenced. After the steam is subjected to a large-volume pressure drop, it forms low-pressure steam emissions. During this process, the gas flow is ejected through small holes. After ejection, the sound power in various frequency bands is reduced, and the sound pressure level frequency is pushed above 20,000Hz, greatly diminishing the noise. However, secondary noise at certain frequencies still requires further silencing. We install a resistive absorbent cotton structure outside the expansion chamber, which is designed based on the frequency spectrum characteristics of the residual noise emitted by the pressure reduction body, to effectively absorb the remaining noise. After the user installs it according to specifications, the total silencing level should reach 30-60 decibels, meeting the required standards.