Muffler outlet plenum chamber is an essential accessory air-terminal, the main air duct or directly through a hose connected to the plenum chamber diameter portion has a valve here, you can control the air flow into the plenum, increase static, stable gas flow system, the airflow tends to be more rational organization, to achieve the desired air conditioning effect. Glass wool or other sound-absorbing material, the plenum sound-absorbing material affixed to the surface, can eliminate the aerodynamic noise outlet while preventing crosstalk adjacent room.