Research On Reduction Bus Interior Structure Noise At Low Frequency Base On Acoustic-Structure Coupling Analysis

The bus interior acoustic-space is a sealed cavity enveloped by different panelsand glasses. The structure will be motivated by the ground, the powertrain, the intakeand exhaust system and the aerodynamic in the process of driving. The panels vibrateunder external excitation then radiate sound wave inward, will ultimately affecting theacoustic environment of the bus. The generation of bus interior noise may affect theidentification of the driver for emergency, easy to cause traffic hidden trouble. Thenoise may also affect the communication between the passengers who will have a badride comfort. Therefore，to reduce vibration and noise is significant for improving busacoustic performance．The thesis has a combination of finite element analysis and acoustic-structurecoupling analysis theory. Using Hyperworks and Nastran to predict the bus interiornoise caused by structure vibration and amylases the characteristics of structure noiseat low-frequency.Firstly, on the basis of current research on acoustic-structure coupling at homeand abroad, the mechanism of interior noise and the common means of control areintroduced The vibration and noise test data of the prototype is got through the roadtest. Through the preliminary analysis the noise source location and noise passingthrough are found.Then, establish the finite element model of bus skeleton base on modelsinformation and studies key point. In order to build a closed interior space, the finiteelement model of skeleton with interior panels is build. Base on this closed structuremodel the acoustic finite element model is build. Finally, the skeleton model withinterior and the acoustic model are combined to construct the acoustic-structurecoupling model. Four kinds of models are carried out for modal analysis. The modalparameters of each order are obtained which is helpful to analysis the relationship ofthe tune, the structure, and the coupling model. Lay the foundation for the analysis ofvehicle vibration and noiseFinally, by comparing the curve peak between NTF result and IPI result, the weakness of structure design is found. Through improving the vertical dynamicstiffness of left rear suspension of engine, the vibration isolation performance oftransmission path is optimized. By paving damping materials in places which haslarge vibration, changing the size of correspond panels and some other measures tosuppress vibration to realize noise reduction and achieved good results.