Research On The Composite Sound Absorption Structure Of A Vehicle-mounted Power Cabi

The mobile power vehicle is a special emergency vehicle,which is widely used in all aspects of social production and life such as command and communication,medical rescue,and engineering rescue.The mobile power vehicle will produce a large noise when generating electricity.Because their diesel generator sets are generally custom-made,it is difficult to deal with it from the noise source.The cabin of the mobile power vehicle needs to be equipped with a sound-absorbing structure for reducing noise.This paper takes the sound-absorbing structure of micro-perforated plate as the research object.By analyzing the sound absorption characteristics of the singer-layer / double-layer micro-perforated plate sound-absorbing structure and micro-perforated sound-absorbing material composite structure,the design scheme of sound absorption structure is put forward.Firstly,based on the classical theoretical model of micro-perforated plate sound-absorbing structure,the theoretical model of Single-layer / double-layer micro perforated plate sound absorption structure is established by using the transfer matrix method.The correctness of the theoretical model is verified by the experiment of measuring the sound absorption coefficient of singer-layer / double-layer micro-perforated plate by impedance tube.Secondly,based on the established theoretical model,the influence of geometric parameters on the acoustic performance of single-layer / double-layer micro perforated plate sound-absorbing structure is analyzed.According to the space provided by the cabin of the mobile power vehicle,the sound absorption performance of the single-layer / double-layer micro perforated plate sound absorption structure is optimized based on particle swarm optimization algorithm.The results show that the acoustic performance of the optimized single/ double-layer micro perforated plate sound-absorbing structure is improved.The acoustic performance of the double-layer micro perforated plate sound-absorbing structure is better than that of the single-layer,but its performance in the high frequency band is poor.Next,to solve the problem of poor high-frequency acoustic performance of the doublelayer micro-perforated plate,a micro perforated plate sound-absorbing material composite structure is proposed.Based on COMSOL,the finite element simulation models of melamine sound-absorbing sponge and glass wool sound-absorbing materials are established.The correctness of the simulation model is verified by acoustic experiments.The acoustic properties of the two materials are compared and analyzed,and it is concluded that the acoustic performance of glass wool is better;The acoustic performance of different ways of glass wool filling the back cavity of micro-perforated plate are analyzed.The acoustic performance of micro-perforated plate-glass wool-cavity composite structure and micro-perforated plate-glass wool composite structure are similar,but the former can reduce the glass wool material.The correctness of the simulation calculation of the two composite structures is verified by acoustic experiments;Based on the orthogonal test,the effects of geometric parameters and their interaction on the acoustic performance of micro-perforated plate-glass wool composite structure are analyzed.The results show that the interaction of glass wool material thickness and perforation rate has the greatest influence on the peak sound absorption coefficient and average sound absorption coefficient,and the material thickness has a decisive influence on the peak resonance frequency.Then,the elliptic basis neural network agent model of micro-perforated plate-glass wool composite structure is constructed,and the acoustic performance of the structure is optimized by multi island genetic algorithm;Based on the optimized micro-perforated plate parameters,the influence of air layer thickness on the acoustic performance of micro-perforated plate-glass wool-cavity composite structure is analyzed,and the optimization scheme of micro-perforated plate-glass wool-cavity composite structure is determined.Compared with micro-perforated plate-glass wool structure,the material can be reduced by 25%,its average sound absorption coefficient is 0.76 and the acoustic performance is only reduced by 2.45%.Finally,based on the acoustic indirect boundary element method,the changes of the sound field inside and outside the cabin before and after the installation of the micro-perforated plateglass wool-cavity composite sound absorption structure are simulated and analyzed in LMS Virtual Lab software.The results show that after the installation of the structure,the noise reduction of the measuring points inside the cabin is about 10 d B,and the average noise reduction effect of the four measuring points outside the cabin is about 10 d B.It is proved that the optimized micro-perforated plate-glass wool-cavity composite structure scheme is feasible.