Car Passenger Compartment Structural Noise And Vibration Simulation And Its Control

In this thesis, a finite element model for analyzing automobile passenger compartment cavity acoustics and sound-structure-interaction system by exterior structured loads is established. The prediction, analysis and control of low frequency noise are systematically studied.Firstly, the producing principle, radiation approach and control procedures of noise in passenger compartment are introduced. An example for a rectangular sectional cavity and submerged spherical shell are simulated with the finite element method. The calculated results compare well with analytical ones, and the characteristic of the sound-structure-interaction frequency is illuminated.Secondly, making use FEM software ANASYS and LMS Virtual.lab, the structural and cavity acoustic modal analyses are conducted. Through comparing the direct and modal superposition method for predicting vehicle noise, it is found that identical results can be obtained from both two techniques, provided that sufficient modes are included in the latter case. Different damping and absorbing coefficients are also considered, and the results also show that the damping and absorbing can control the sound pressure peaks well.Thirdly, the application of BEM (Boundary Element Method) and ATV(Acoustic Transfer Vector) to the noise analysis of passenger are introduced. Interior noise response of vehicle passenger compartment is calculated by using direct BEM with LMS Virtual.lab software. Then, using the concept of the acoustic contribution, the element and panel acoustic contribution analysis are done to determine the vehicle body region of the vehicle passenger compartment contributing most to the noise levels at the driver's right ear. Base on analysis, the structure can be modified. Structure-borne noise is reduced in the interior of the compartment by updating the structure model.Finally, using the ANSYS software and APDL language, the sensitivity analysis model is established. In the model, the objective function is the noise levels at the drivers' right ear, the state variables is acoustic potential energy of passenger compartment, the design variables is panel thickness. According to this model, the sensitivity analysis for coupled system interior noise response is carried out. This work provides a fundamental procedure for the optimization of coupled system at low frequency acoustic field.The research presents a systematic means to the automobile interior acoustic analysis and noise control for low noise vehicle design.