Based on the theory of elasticity

the elastic model of gear body is established

and the analysis of elastic dynamics is conducted. The natural characteristic and vibration response of the gear device are obtained. The quantitative relation between vibration modal parameter and acoustics modal parameter of vibration device is determined

so that the sound radiation characteristic parameter and the sound power are obtained for the gear structure vibration. And those are verified by the experimental data. The conclusions in this paper can be used for the calculation of ringing noise of the gears.