Analysis Of Reducing Bus Interior Structure Noise In Low Frequency Based On Structure-acoustic Coupling Model

Vehicle noise level is one of the important factors for modern automobile design and manufacturing quality evaluation.The vehicle noise is not only the noise environmental pollution,but also seriously affect the ride comfort of the car.Therefore,it is of great engineering significance and practical significance to reduce the vibration,improve the acoustic environment in the vehicle,reduce the noise inside the vehicle and improve the ride comfort.In this paper,the finite element method and the structure-acoustic coupling analysis theory are combined to research the bus.The finite element analysis software HyperWorks,Virtual.Lab Acoustics and MSC Nastran are used to analyze the low-frequency structural noise and put forward the measures to reduce noise.Firstly,the vehicle was tested to measure the vibration isolation rate of the engine suspension cushion,the acceleration spectrum of the engine excitation,the sound pressure of the measured point in the vehicle and the vibration acceleration spectrum of the floor.Through the test,it is found that the riding experience of the vehicle is not good,there will be "roar" sound,causing physical discomfort,so this problem is analyzed.Secondly,according to the design drawings of the bus,the finite element model of the bus skeleton,the finite element model of the bus with interior parts and the acoustic finite element model and the coupling model are established by using HyperMesh software.Then,calculate modals of skeleton finite element model(using HyperWorks),the finite element of the bus with interior parts(using MSC Nastran)).And the acoustic finite element model,the coupled model(using Virtual.Lab),and these modal were compared.Then,the experimental results are applied to the bus structure model for frequency response analysis.The floor vibration acceleration data are compared with the tested values to verify the accuracy of the model.The calculated vibration displacement of bus is applied as a boundary condition to the acoustic cavity,and the acoustic response analysis is calculated.And the acoustic response of the vehicle interior point is compared with the test values.According the compared,it is showed that the simulation results can reflect the actual acoustic response.Then,the acoustic sensitivity analysis of the coupled model is carried out,and it is found that there may be some problems in the dynamic stiffness.Finally,the IPI(Input Point Inertance)analysis is carried out for the front suspension joints.It is found that the main reason for the peak of the acoustic response is the problem of the transmission path.MPF(modal participation factor)and PPF(panel participation factor)analysis are carried out for the transmission path,and the main problems of the roof and the floor are found.The skeleton of the roof and the floor skeleton were improved,and the acoustic response of the optimized model was analyzed.The results of the comparison show that the improved interior noise has been reduced obviously.