The ventilation noise of the motor is mainly the following three kinds of components:(1) when the blades rotate, the blades of the vortex fan make the vortex flow, which is caused by the viscous force, and they break down into a series of small vortices, which cause the air to be disturbed. In addition, in the corner of the airflow movement, if there is a large cavity, it will produce a vortex sound. Vortex sound is a random steady noise of broadband. (2) the monotonous sound (Qi Disheng) is generated by the fan rotation to make the cooling gas periodic pulsation and the air flow collision, the fastening bolts and other outstanding obstacles. (3) the noise caused by the resonance of a thin wall part such as the wind shield, etc.. The ventilation system of the motor is very complex, which can be used in different wind structure, such as axial ventilation, radial ventilation and mixed ventilation. And can be used by different fans, such as centrifugal fan, axial flow fan, etc.. With the same wind path structure and the fan, the layout and structure of the ventilation element can also be different. Therefore, it is impossible to solve the problem of ventilation and noise calculation of all motors with one method, and the influence of many factors can be concluded by a lot of experiments.