(1) bearing radial clearance size. (2) the end cover and frame stiffness. Motor stator and rotor and the end cover is composed of a vibration system, poor axial rigidity of bearing and an end cover will be with the vibration of the motor system occurred "tuning", causing large amplitude axial vibration is through a bearing reached the end cover and the motor and resonance noise, also electromagnetic noise of motor will through a bearing reached the end cap and the motor. (3) axial movement. Due to the effects of electromagnetic force between the stator and rotor, chute more axial electromagnetic force components as well as the axial dimension is processing, assembly of the accumulating error, when the motor runs total some axial movement. Such measures properly, there will be a "buzz" sound, low frequency and big and small. In the axial spring element (such as waveform spring), can reduce the "buzz" sound, the sound level of stability. It can obviously reduce the vibration. But it is necessary to point out that only in the bearing, the other assembly condition is correct and the elastic element elastic stability can achieve the desired effect. (4) bearing assembly. Bearing assembling quality of the motor noise impact is very big, the difference of assembly 5-10dB. to select the appropriate size of the grease; pay attention to assembly the purity of the can not be mixed with iron powder, fine sand, dust and other debris; the filling amount of grease to the right; bearing into the bearing chamber to hand push, avoid hammer hit. In addition, to ensure motor coaxial degree of the mouth of the accuracy and installation must be correct, otherwise a skewed rotor will affect the bearing clearance.