Motor noise generated in different ways, can be broadly divided into electromagnetic noise, mechanical noise and aerodynamic noise.

    Determine the various categories of noise of an electric motor, usually requires a combination of several methods to achieve. Analysis of the mechanical noise of the motor used to cut off the power supply method, the noise generated by the motor by the inertia continue to operate after power outage for the main part of the mechanical noise; electromagnetic noise characteristics change with the current size by changing the voltage method to determine the voltage rapidly to a certain limit, as the voltage is decreased, significantly reduce the noise of electromagnetic noise; aerodynamic noise generated in the factory production, the most simple identification method is to remove the fan contrast before and after the change in the noise, or replace the type the diameter and type of the fan motor with two mutually drag method, at different speeds to distinguish the difference of the noise, this method can more accurately identify the aerodynamic noise.