Analysis And Reduction Design Of The Interior Low Frequency Noise Based On Acoustic-Structure Coupling

Interior noise level is one important indicator that reflects the vehicle ride comfort.For armored vehicle,interior noise environment will directly affect the soldier's operational efficiency and ability.So it is greatly significant to take research on vehicle interior noise.This paper takes domestic wheeled armored vehicles as the research object.Firstly established the body structure model,cavity model,and acoustic structure coupling model,analyzed the dynamic characteristics using finite element analysis software.Then conduct the real vehicle test and compared the real measured vibration data,internal pressure data with the simulation results.Results verify the effectiveness of the vehicle body structure and the acoustic structure coupling model.And also take the acoustic contribution analysis of the car panels that influence the noise level,finding the panel that contributes the biggest sound pressure.Finally,through pasting damping materials on the most contributed panel to reduce the vibration and noise,this provides reference for the optimization of the vehicle interior noise.Now the research work of this thesis mainly carries out is listed as follows:1.Established the finite element model of the vehicle body structure,cavity of the vehicle and the acoustic structure coupling model.Carried out the modal analysis and obtained the panel that most prone to vibration.Through analyzing the intrinsic and coupling modal of the cavity,comparing results shows that the body structure vibration will have a certain impact on the vehicle interior sound pressure.2.Take the vehicle rode test.To acquire the vibration signal,place vibration acceleration sensor on the longitudinal side of the engine mounting points,door,floor,roof and other location.To collect interior pressure signal,place microphones on the main driver's ear,deputy driver's ear,the rear seat occupant in the middle.Set four kinds of test conditions and measure according to the GB/T 18697-2002?Acoustics-Measurement of noise inside motor vehicles))standard.3.Apply the incentive that collected from the engine mounting points on the corresponding finite element structure model and acoustic structure coupling model as boundary conditions,take the frequency response analysis.By comparing the vibration frequency response curve of the door,floor,roof with the simulation results,verify the validity of the finite element model of the car body structure.At the same time,by comparing the sound pressure frequency response curve at specific sites of the car with the test values,found the change trend in frequency is basically consistent.From the whole frequency range,the simulation results and the experimental value of error in the total sound pressure level is controlled within 6%,which indicates that the simulation model can effectively predict the noise in the vehicle,and can be used for further analysis.4.Panel contribution analysis was carried out on the in-car noise sites.Through analyzing the peak frequency at different sound pressure sites in a variety of conditions respectively,finally found the main panels that contribute most to the interior noise big are the cowl panel,front plate,front windshield glass and the instrument panel.5.It is selected to use the damping to optimize the interior noise after analyzing several different interior noise optimization methods.To determine the paste position of the damping materials,first of all conduct the modal strain energy analysis of the panels that contribute the most to the interior noise,finding the panel area with the largest strain energy.Then paste the damping materials to the region,and also increase the thickness of the front windshield to improve its stiffness.Results show that the sound pressure peak of in-car sites and total sound pressure level are lower than before by comparing the sound pressure frequency curve before and after optimization.So the damping optimization effect is obvious.