Research On Inner Sound Field Simulation And Structure Optimization For Acoustic Impedance Tube

Acoustic package is widely used in vehicle noise reduction,and the main constituent parts of which are acoustic materials.The performance measurement of acoustic materials has showed its specific significance in noise control engineering.At present,the acoustic impedance tube method can be used to effectively and accurately measure the sound absorption property of materials.Howerer,large error would be observed at specific frequence in the sound insulation property test.In this thesis,experiments and simulations are conducted for specific factor analysis and verification of the error.The Genetic Algorithm(GA)is performed to optimize the structure parameters of the acoustic impedance tube and improve the measurement accuracy to reduce the error.Firstly,absorption coefficient and transmission loss(TL)testing experiments are respectively carried out based on the basic theory.Comparing the experimental results with the theoretical ones,larger error occours in the TL test.Factor analysis for the error is carried out,and acoustic resonance is which causes the error while structure parameters of the acoustic impedance tube are defined to be the main factors.Secondly,the finite element method(FEM)is employed to carry out the internal sound field simulation,modal analysis and vibaration analysis.The method is verified through the comparison of simulation and experiment results.The influence of structural parameters on the error is obtained through single factor analysis of structural parameters.Finally,the optimization objective function is established based on the results of the error analysis and simulation,and Genetic Algorithm is used to optimize the objective function.Based on the optimized structural parameters,a new finite element model is built and simulated.The results show that the resonant frequency is nearly beyond the test range,which exercises little influence on the measurement of TL.Thus the error is reduced.The purpose of this thesis is to analyze the reason and influence factors of error occours in TL test of acoustic impedance tube.Experiments and FEM are used to optimize the structural parameters of acoustic impedance tube to reduce the error.The result of this work can be used as a reference for the measurement of acoustic material.The proposed method can also be used for other engineering test equipment optimization research.