As a kind of electrical equipment, AC fans often produce noise in use, which affects our living and working environments. This noise mainly includes gas-driven noise, mechanical equipment noise, electromagnetic induction noise and structural vibration noise, etc., in which gas-driven noise dominates. In this paper, we will discuss the causes of AC fan noise and propose some noise reduction methods.

The main reasons for AC fan noise are as follows:

1. speed: the speed of the AC fan is an important factor affecting the noise. The higher the speed, the higher the noise.

2. Friction: The friction between the AC fan's bearings and the fan's impeller can also produce noise.

3. Vibration: The vibration of an AC fan can also create noise.

4. Alternating current (AC): AC fans work on the principle that the energised coil in the AC motor rotates under the force of a magnetic field, converting electrical energy into mechanical energy, and at the same time, due to the resistance of the coil, a part of the electrical energy is converted into heat, which also generates noise.

For the above reasons, we can take the following noise reduction methods:

1. Adjusting the speed: Noise can be reduced by adjusting the speed of the AC fan. For example, using a larger size fan and adjusting the fan speed of the AC fan can reduce the noise.

2. Improvement of bearings and fan impellers: Choosing good quality AC fan bearings and fan impellers can reduce friction and vibration, thus reducing noise.

3. Installation of silencers: Installation of silencers at the air inlet and outlet of the AC fan can effectively reduce noise.

4. Modify the sound enclosure: installing the sound enclosure around the AC fan can cut off the noise transmission path and reduce the noise.

5. Modification of isolators: Installing isolators inside the AC fan can reduce vibration and thus reduce noise.

6. Handling the environment of the AC fan room: Handling the environment of the AC fan room to reduce the reverberation in the room and the A-class sound pressure outside the room can effectively reduce the noise.

In conclusion, the causes of AC fan noise are manifold, we can reduce the noise by adjusting the speed, improving the bearings and fan impellers, installing silencers, modifying the acoustic enclosure, modifying the isolator, and dealing with the environment of the air-conditioning cooling fan room.