The gearbox is an important part widely used in mechanical transmission. When a pair of gears meshing, due to errors such as tooth spacing and tooth shape, there will be meshing impact and noise corresponding to gear meshing frequency in the process of operation, and friction noise will also occur between teeth due to relative sliding. 

As the gear is the basic part of gearbox transmission, reducing the noise of the gear is very necessary to control the noise of the gearbox. Generally speaking, the causes of gear system noise mainly include the following aspects:

1. Gear design. Improper selection of parameters, too small overlap, improper or no modification of tooth profile, unreasonable gearbox structure, etc. In gear processing, the errors of base and tooth shape are too large, the clearance of the tooth side is too large, and the surface roughness is too large.

2. Gear system and gearbox. Eccentric assembly, low contact accuracy, poor parallelism of the shaft, insufficient stiffness of the shaft, bearing and bearing, low rotary precision of the bearing and improper clearance, etc.

3. Input torque in other aspects. The fluctuation of load torque, torsional vibration of shafting, the balance of motor and other transmission pair, etc.