<p>Compared with traditional vibration detection, acoustic emission detection method can collect weak fault signals well and is more suitable for early fault monitoring to avoid further deterioration of faults. However, the current acoustic simulation analysis, which comprehensively considers the coupled model of multi-stage gears, shafts, and boxes based on vibration response, is lacking in-depth research. This paper presents a calculation method for predicting gearbox noise from dynamic response to sound radiation. Firstly, a dynamic model of multistage gear-shaft-housing system is established, and the vibration acceleration response of the system is calculated by using this model. Then, the system acoustic model is built with the box vibration response as the boundary condition to predict the noise distribution of the gearbox. The distribution pattern of SPL (sound pressure level) between the surface of the gearbox and the external sound field was explored. The acoustic characteristics of gear transmission system under different vibrational frequency and input speed are revealed. It is found that the gear meshing frequency has great influence on vibration and noise. The SPL is positively correlated with the input speed. Finally, an experimental bench was built to measure the vibration and noise of the gear box at different rotational speeds, which verified the accuracy of the simulation results. This paper provides a new way to evaluate and reduce the impact of gear noise and optimize the design of multistage gearboxes by using acoustic theoretical simulation analysis.</p>