Research On Prediction And Analysis Methods Of Automotive Interior Mid-Frequency Noise

The problem of noise pollution has gradually become an important issue affecting people’s normal life.Nowadays,the increase of productivity makes the use of cars more and more popular in family life,and the using of vehicles brings about the noise problems.In addition,the academia and engineering community have also been working on the issue of car noise.Many noise prediction analysis methods have been developed,and a series of application measures for sound absorption and reduction have also been proposed.However,the problem of Mid-Frequency Noise prediction in the car has always been a problem in this field.This is because most of the complex structural systems in actual engineering exhibit both the behavior of long-wave deformation generated by subsystems with lower modal density and the behavior of short-wave deformation generated by subsystems with higher modal density in the midfrequency.Therefore,the research on the method of predicting the mid-frequency noise in the car has important theoretical significance and practical value of engineering.Firstly,the theory of WBM has been researched.Aiming at the problem of uncoupled flat structure and uncoupled internal acoustic cavity system,the theoretical model of flat wave function and the acoustic cavity wave function based on WBM are established respectively.In order to verify the correctness of the theoretical models,taking a rectangular thin plate and a rectangular acoustic cavity as examples,and building mathematical models and calculated by using MATLAB.Compare the results with the FEM simulation results,and the superiority of WBM in model establishment and convergence speed can be verified.Secondly,the theory of Hybrid FE-WBM has been researched.The theoretical models of structural FE-acoustic WBM method and acoustic FE-acoustic WBM method are established respectively.The coupling formulas of the two theoretical models are derived respectively by indirect coupling method,and the system response differential equation have been obtained.In order to verify the correctness of the theoretical models,taking a simple structure-acoustic system and a simplified 2D interior acoustic cavity of a car as examples,and building mathematical models and calculated by using MATLAB.Compare the results with the FEM simulation results,and conclusions can be got that hybrid FE-WBM method provides less DOF of modeling,higher computational efficiency,and faster convergence speed.Therefore,this method can be applied to analyze the noise problems in higher frequency.Then,the theory of Hybrid WB-SEA has been researched.The theoretical model of the acoustic WB-SEA method is established,and the system response differential equation is derived in detail.In order to verify the correctness of the theoretical model,taking a structure-acoustic coupling system as an example,and building mathematical model.Simultaneously,the example is solved by FEM and hybrid FE-SEA.The modeling information and the calculation results of the three methods are compared and analyzed.It is verified that the hybrid WB-SEA method has faster convergence speed when analyzing the mid-frequency noise.Finally,Based on the theory of Hybrid FE-WBM and Hybrid WB-SEA,the application of Hybrid FE-WB-SEA in vehicle interior noise analysis is studied.Taking a simple car cab as the research object.A simplified car cab model based on hybrid FEWB-SEA method was established,and the numerical calculation was realized by MATLAB.In order to make a comparative analysis,a simplified car cab model based on the traditional hybrid FE-SEA method was established and simulated.Comparing the calculation results of the two methods with the simulation results of pure FEM,some meaningful conclusions are obtained.