Noise is any sound that is perceived as loud and annoying, and its intensity can sometimes vary with one's mood. However, continuous noise can also pollute the surrounding environment. The general reasons for noise produced by fans can be described as follows:

Noise generated due to blade rotation

Blades generate friction or impact with the air as they rotate. The faster the rotation speed, the higher the frequency of air contact, resulting in a sharper noise. This phenomenon becomes more pronounced with an increase in blade width or thickness. The frequency of the noise is composed of multiple frequencies, all of which are related to the fan's rotation speed.

Axial fans with both moving and stationary blades should have different numbers of blades to prevent greater noise resonance. Regardless of whether they are axial or centrifugal fans, those with higher wind speeds and pressures will produce more noise.

2. Noise is also generated when vortices are formed on the leaves.

During the operation of the wind turbine, vortices are generated on the back of the moving blades. These vortices not only reduce the efficiency of the turbine but also produce noise. To minimize this phenomenon, the installation angle of the blades must not be too large, and the curvature of the blades should be smooth, avoiding sudden drastic changes.

3. Noise Caused by Turbulence

When air flows and encounters a sharp obstacle, it tends to cause turbulence. Although this turbulence is different from that of vortices, it still generates noise or high-frequency hissing sounds, which can also result in efficiency losses for fans.

4. Resonance with duct casing causing noise

The interior seams of the duct and fan housing must be smooth to avoid roughness that could cause tearing sounds. Due to the resonance caused by consecutive pipe sections, even subtle sounds can amplify, resulting in increased noise. During design, it is sometimes possible to cover the duct with soundproof material to reduce noise levels.

Noise Caused by Wind Turbines Other Than the Turbine Itself

In addition to the inherent fixed noise of the fan itself, there are numerous sources of noise. These include: abnormal noise caused by insufficient precision in bearings, improper assembly, or poor maintenance. Noise can also be generated from the motor section, some due to poor design or substandard manufacturing quality, but sometimes it is caused by the internal and external cooling fans of the motor.

Noise can also be generated from the motor part, some due to poor design or inadequate manufacturing quality control, but sometimes it's caused by the internal and external cooling fans of the motor. Gear and belt noise is also a result of friction. The resonance from other structural components should not be overlooked either; sometimes, this is due to an imbalance in the body.