Study On Acoustic Properties Of Multi-cavity Structures Combined With Porous Materials And Microperforated Plates

The traditional sound absorbing materials have some defects such as large volume,easy damage and single sound absorbing frequency band.However,the noise generated by high-speed train operation is mainly medium and low frequency noise and also has high frequency noise.The traditional sound absorbing materials are difficult to deal with the complex noise environment.Therefore,this thesis will porous materials and structure combination of microperforated panel and by theory analysis,impedance tube experiment and numerical simulation method to study the multi-cell series-parallel structure sound absorption performance of microperforated panel,using hybrid particle swarm algorithm to the optimization,polyurethane porous materials,introduced the structure of the optimized,get a predominantly in the low frequency sound absorption balance between the combination of high frequency acoustic absorption structure.Firstly,by comparing the research mechanism of acoustic and electric analogy method and transfer matrix method,the acoustic impedance of micro-holes and cavities was analyzed to obtain the main reasons for the errors of acoustic and electric analogy method.The acoustic absorption coefficient of micro-perforated plate structure was measured by finite element simulation and impedance tube experiment,and the reliability of the theoretical method was verified.Secondly,the study of micro perforation plate in parallel structure,analysis of absorption unit structure parameters effect on the sound absorption performance of the parallel structure,the introduction of hybrid particle swarm algorithm to optimize the structural parameters of the parallel structure,and comparing the optimized double units,4 units,eight units in parallel structure,determines the structure of each unit of the coupling effect of sound absorption performance.Thirdly,the double-layer micro-perforated plate parallel structure is studied,and the influence of the structural parameters of each layer on the sound absorption performance of the double-layer structure is analyzed.The hybrid particle swarm optimization algorithm is used to optimize the double-layer parallel structure,and the influence of the double-layer element structure on the coupled sound absorption performance is determined.Based on the characteristics of double-layer sound absorption unit,the design requirements of smooth sound absorption are discussed.Finally,porous materials were introduced into the optimized doublelayer micro-perforated plate parallel structure,and the sound absorption performance of the combined structure was analyzed.Through acoustic impedance analysis,the reason for the improvement of the sound absorption performance of the composite structure is determined,and it is proved that the composite structure can significantly improve the sound absorption performance under the premise of ensuring the rigid support.