Research On Coupled Acoustic-Vibration Of Mini-Car Transmission House

Automobile noise is the pollution problem that urgently needs to be solved in our country. Reducing the noise of automobile not only is beneficial to environment, but also avails to people health and improving the living standard. Many data shows, noise of transmission house is one of the main sources of the automobiles noise. Controlling the noise of transmission house has become an important research topic in many automobile enterprises. Therefore, with the support of Chongqing science technology & commission (project number: CSTC, 2005AC6035), the automobile's transmission house has been taken for investigation object; vibration-noise of the transmission house is researched by combining FEM analysis, BEM method and experimental analysis method in this paper. It provides theory basis for the prediction and control of the vibration and noise.Firstly, theory of decaying wave and acoustics modal finite element is researched in the view of acoustics theory. It's pointed that self-singing noise is the main noise source of transmission house by analysis of transmission mechanism of gear-box noise.Secondly, the mini-car transmission house is taken for investigation object and assembly relationship is simulated using the Multi-Point Constraints (MPC) technique. The intrinsic property is investigated building the finite element model of the transmission house. The problem that how to deal with the connection or assembly relationship in order to research truly dynamics characteristic is overcome. Validity and reliability of the finite element model is validated through modal experiment. It provides effective approach to optimize the dynamics characteristic of the transmission house. It's very helpful to the research on the intrinsic property of the complex structures with the assembly relationship.Acoustic finite element model of transmission house cavity sound field and the structure-acoustic coupled finite element model of transmission house structure-cavity sound field are established. And then acoustic characteristics of transmission house cavity sound field and the dynamic characteristics of transmission house structure-cavity sound field structure-acoustic coupling system have been investigated by means of dynamic analytical technology for structure and sound field. The noise mechanism is pointed; the highest sound pressure appears at the top and bottom parts of transmission house. The frequency of structure, which is close to acoustics resonance vibration positions, can be forecasted and avoided. The results provide theoretical basis for the noise prediction of transmission house.