The causes of air blower noise and the relevant formula


1. Counting the best range, so as not to cause more noise. Axial flow fan if a fixed wing and static wing configuration, both the number of blades is best unequal, so as not to cause more noise. But both axial and centrifugal fan, wind speed is fast, high wind pressure, the produce of the noise is big. 
2.Because of the vane of eddy current also can produce noise
During Blower operation, Will produce eddy current on the back of the fixed wing, the eddy current will not only reduce the efficiency of the fan, and will produce noise. To reduce the phenomenon, the blade installation Angle may not be too big, and the blade bending to be smooth, do not suddenly change is too big.
3.The noise due to turbulence
When air is moving ,If encounter sharp obstacles, Easily happened turbulence. This turbulence while with eddy current is different, Also can produce noise, or a high frequency of the noise, Also can lead to efficiency loss for fan. 
4.With the duct casing produce resonance and noise 
Duct with blower shell inside juncture place should level off, avoid rough, cause tearing sound. Due to the duct line of succession will resonate, Make small sound bigger, Cause more big noise. When design, Sometimes can be covered on the outside of the duct in case material, can reduce noise.
5. Outside the blower noise
In addition to the fixed noise fan itself, There are a lot of noise, such as, Bearing due to insufficient precision, Poor improper assembly or maintenance can cause abnormal noise. Motor parts also can produce noise, Some of them are poorly designed or manufactured goods caused by poor control, But sometimes it is the inside and outside of the motor cooling fan. Gear and belt also can produce noise due to friction. Other works produced by the resonance of a noise also cannot be ignored, This is sometimes due to the imbalance body.

The calculating formula of noise
Air supply equipment'noise to db (decibel) as the unit of measurement noise, the noise in the db value of air supply equipment (decibel) as the unit of measurement, the value of the db = 10 ㏒ 10 (I), I0 for the estimation of noise intensity, while "the noise intensity of db is equal to zero. According to the American standard, the db value is 1 x10-16 w/cm2.According to the American standard, the db value is 1 x10-16 w/cm2.