Abstract： The behaviors of noise through the heat exchanger of indoor unit at a low-speed free stream were studied by aeroacoustic performance measurements in a semi-anechoic chamber with different velocities and angles. The experimental results indicate that the noise can be generated at particular velocity and angles which are considered as the most important factor that influences the aerodynamic performance of the heat exchanger. With the increasing in the flow velocity, the frequency of noise increases linearly, and there exists a fixed Strouhal number for the given heat exchanger.