Abstract: After the fresh air conditioner is installed, when the air conditioner is shut down, when the outdoor wind speed is higher than 6 m/s, there may be a loud noise in the indoor air conditioner, which affects the normal rest of the user. In order to improve the comfort of the air conditioner and enhance user satisfaction, through the analysis of the sealing structure and noise excitation source of the whole fresh air system, it is found that when there is a strong wind outside, the wind will pour into the fresh air pipe, and the wind will impact the inner wall of the fresh air pipe in the process of high velocity to produce noise, and the sound will be transported through the fresh air pipe into the cavity inside the fresh air module of the air conditioner. Thus producing backflow noise on the indoor side. In order to optimize the noise scheme of fresh air backfilling, it is proposed to design a circular muffler hole on the fresh air pipe, and the noise reduction effect is obvious.

Key words: Backflow noise, Fresh air duct, Muffler round hole