In the design of HVAC system, reducing the noise form fan is one of the most critical factors. Although axial fan which is widely used in ship HVAC system has many advantages in operability and durability, the low frequency noise called blade passing frequency (BPF) noise has always been an issue. The conventional type of silencer can effectively reduce the noise of mid-high frequency band, but it has limitations on removing noise of low frequency band such as BPF noise. This paper suggests the application of side branch resonators to reduce the BPF noise. Along with sound absorbing material installed on silencer inner wall and resonators outer wall, we can control the noise from all frequency bands.