Study On Functional Optimization Design Of Double-layer Acoustic Absorber

At present,the effective and easy-to-implement noise control method is to adopt the sound absorber structure to reduce the noise in the way of propagation.The commonly used structure of sound absorber is porous material and micro-perforated panel structure proposed by professor Dayou Ma.In this paper,the acoustic properties of the series structures of porous materials,micro-perforated panel,double-layer micro-perforated panel and porous composite micro-perforated panel have been studied,and the structure optimization has been carried out.The research contents of this thesis mainly include the following four aspects.Firstly,the sound absorption characteristics of micro-perforated panel and porous material are summarized.The characteristic parameters such as diameter,panel thickness,perforation rate and cavity thickness of micro-perforated panel sound absorber are studied by MATLAB numerical simulation.The effects of structural parameters on the sound absorption characteristics of micro-perforated panel are obtained.At the same time,the effects of flow resistance,porosity,thickness and curvature on the sound absorption properties of porous materials are also studied.Secondly,a multi-population genetic algorithm is proposed to solve the premature convergence of the standard genetic algorithm,and the optimal design based on multi-population genetic algorithm is carried out for single-layer micro-perforated panel and porous materials at low frequency,intermediate frequency,high frequency and fixed frequency points respectively.It is found that the sound absorption effect of micro-perforated panel is better at low frequency,and the band of medium-high frequency optimized micro-perforated panel sound absorber is too narrow to be used as a general sound absorbing material in practical engineering,and the optimization of fixed frequency point is carried out.The sound absorption coefficient of the micro-perforated panel can reach the peak value at the fixed frequency point.For porous materials,the average absorption coefficient of porous materials can reach 0.6 in the medium frequency range and 0.8 or more in the high frequency range by optimizing the design.The porous material has better sound absorption effect than that in the micro-perforated panel,and the sound absorption coefficient of the porous material is better than that of the micro-perforated panel in the medium frequency range.The frequency band is broadened,but the low-frequency sound absorption effect is slightly less than that of the micro-perforated panel.Thirdly,the obvious disadvantage of ordinary single-layer porous materials and micro-perforated planel absorber is that the sound absorption band is narrow and the sound absorption coefficient is relatively low.In order to improve its sound absorption performance,broaden the frequency band of sound absorption.In this paper,the sound absorption performance of the double-layer micro-perforated panel and the porous material composite micro-perforated panel in series structure is studied,and the structure optimization of the double-layer sound absorber is carried out by using the multi-population genetic algorithm.In order to meet the practical requirements and reduce the blindness of noise control,the limited conditions are set up to find the optimal combination of structural parameters under the conditions of machining technology and practical installation conditions.At the same time,compared with the standard genetic algorithm,the advantages of the algorithm are highlighted.The experimental results show that the sound absorption performance and sound absorption bandwidth of multi-population genetic algorithm is obviously better than that of standard genetic algorithm,and the multi-population genetic algorithm can be used as an effective algorithm,and the performance of multi-population genetic algorithm is better than that of standard genetic algorithm.A fast optimization tool is used to optimize the structure of the double-layer absorber.In the low frequency environment,the sound absorption performance of the double-layer micro-perforated panel is slightly higher than that of the porous material composite micro-perforated plate series structure,and in the medium-high frequency environment,the sound absorption performance of the porous material composite micro-perforated panel series structure is much higher than that of the double-layer micro-perforated panel.Porous material composite micro-perforated plate series structure can be used as a good sound absorber in real life.