Noise: Because the blades are periodically subjected to the pulsating force of the uneven airflow at the outlet, noise is generated. On the other hand, due to the uneven distribution of pressure on the blade itself and the blade, the disturbance to the surrounding gas and parts during rotation will also constitute rotational noise. In addition, when the gas flows through the blade, the outer layer and the vortex are separated, which causes the pulsation of the pressure on the blade and generates vortex noise.

Abnormal sound: The abnormal sound is different. When the fan is running, if there are other sounds (with more than two kinds of sounds) in addition to the wind sound, it can be judged that the fan has abnormal sound. The cooling fan may collide due to foreign matter or deformation in the bearing, improper assembly, or uneven winding of the motor winding, resulting in loosening, which may produce abnormal noise.