Analysis And Optimization Of Min-car Interior Low-frequency Noise

In this paper, taking a mini-car as the research object to research the acousticcharacteristics of the mini-car under the force of the engine excitations and takethe optimization method for reducing vehicle interior low-frequency noise. Firstly,using FEM (finite element method) method to analyze the dynamic response of bodystructure and the acoustic performance of the acoustic cavity. And taking the methodsof damping treatment to reduce the vehicle interior low-frequency noise. Thenthe topology optimization analysis is carried out to optimize thecomposite damping structure, getting the optimal layout of free damping layer. Theride comfort is improved by using the topology optimization analysis, and theweight and fuel economy are also under control. In this paper, the researchabout field of the vehicle interior low-frequency noise mainly focuses on thefollowing aspects:The finite element model and acoustic finite element model is established basedon the geometric model of a mini-car body, and the structure modal and the acousticmodal analyzed, then getting the natural frequency and vibration type.A mini-car acoustic-structure coupling model is established, and calculatedthe acoustic-structure coupling modal based on the acoustic modal and thestructure mode, and then analysis of the interaction between acoustic cavity andstructure, to prepare for the prediction and analysis of the low frequency noise.Dynamic response analysis for the body and frequency response of the vehiclespeed is analyzed by using the finite method with the influenced of the engineexcitation. The body surface normal velocity is set as the boundary conditions so as tocalculate the sound pressure frequency response. The sound pressurelevel frequency response curve of acoustic-structure coupling model of thetarget point is analyzed with the influence of engine excitation and getting the peakpressures and peak frequency.The acoustic panel contribution of body is calculated, getting the result of the contribution coefficient corresponding to each peak frequency of the fieldpoints. And derive a conclusion that the acoustic press is mainly contributed to thefront floor, after floor, roof and firewall etc, because they have larger contributioncoefficient. After a comprehensive analysis and comparison, the roof makes the mostimportant contribution to the low-frequency noise contribution of the field points.Drives the conclusion that the roof is the most important plate to thelow-frequency noise contribution of the field points, to establish a compositedamping structures by adding surface free damping in automobile roof, The dampingcomposite structure topology optimization analysis is carried out, getting thereasonable layout of damping. The sound pressure frequency response ofthe optimized structure is calculated, and the vehicle interior low frequencynoise has been effectively improved. And the local peak pressure is reduced about2dB, improving the acoustic quality and the ride comfort of passengers effectively.