Research On Noise Reduction Of Special Vehicle's Cab

The special vehicle is developing towards high-speed and light-weight now.While their driving safety and reliability are steadily increasing,the vibration and noise problems of cabs are quite serious.The causes of these problems are complex and the factors are changeable.Therefore,it is of crucial importance to propose fast and efficient measures to control cab noise,so as not to damage the performance of other subsystems and the whole vehicle.Based on the above background,this paper takes a new special vehicle cab as the research object,and studies the low frequency noise by combining the test with the finite element simulation analysis.The cab's structural-acoustic coupling FE model(finite element model)is established and the sound field is rebuilt by extracting sound pressure load from the noise test.The acoustic response in the cab is analyzed,and effective measures of noise control in low frequency are proposed basing on the result of contribution analysis.First of all,the FE model of the cab's body-in-white structure is established and the cab free modal is tested.Through the correlation analysis and sensitivity analysis,the optimization parameters are determined and the FE model is modified so that the simulation model's accuracy and credibility can be guaranteed,furtherly the whole cab's FE model is completed.The acoustic FE model without seats and dashboard is established using the cab interior boundary.Based on the modified whole cab's FE model,the structural-acoustic coupling FE model is built by defining the mapping relationship between the structural FE model and the acoustic FE model,and the structural modal characteristics are analyzed before and after models coupled.Then,the frequency responses functions are obtained between the export of acceleration response or sound pressure response and the import of exciting force in cab's installation position by the hammer test,which can represent the vibration and noise performance of interior cab.The structural modal damping and the acoustic modal damping are corrected to make sure the simulation analysis results and test results remain basically same.The sound field load near the cab is obtained by the test of sound field reconstruction and the low frequency noise response in the cab is predicted.Compared with the experimental results,the coupling model is proved to be effective and the goal of predicting the noise is achieved,also the credibility of control measures is guaranteed.Finally,the optimized targets are confirmed to improve panels in the middle side,the right side of the roof and the front side of the glass through the structural modal contributionanalysis and panel contribution analysis,and it is proposed to change the material of the front glass and increase the strengthening beams in the roof.Contrasted the total sound pressure value around the right ear of the driver and the passenger before and after the control measures,the noise reduction effect is more obvious by increasing the strengthening beams and the total sound pressure value around the driver's right ear is reduced by nearly 3 dB.This paper achieves the purpose of noise control in the special vehicle's cab.