The radiation noise of motor shell vibration during operation is studied by finite element method. Firstly the finite element model is established to calculate the vibration frequency response characteristic. And on this basis the frequency response characteristic of the sound pressure under the work condition is calculated. The result shows that the vibration of the lateral wall and upper wall of the shell produces the radiation noise. And the radiation noise from the lateral wall makes a more significant contribution by comparison. While the method of adding the surrounded structure and stiffener to the shell can effectively reduce the vibration of the lateral wall and upper wall, which can finally reduce the vibration noise by 10dB.

Linear finite element analysis model of the typical rotor system is established by the finite element method. Considering the gyroscopic effect of the rotor, critical speed in the rotor system is solved. Then the effect of the rotor system by the unbalanced force on dynamic characteristic is analyzed by frequency response curve. The result shows that support damping coefficient has a great effect on critical speed in the rotor system. With the support from rigid support to elastic support, the critical speed greatly reduces. Because of the unbalance exciting force, maximum resonance amplitude of the disk is near the critical speed of the rotor.