Research On Noise Reduction Of Vehicle Based On The Plant Fiber And Acoustic Metamaterial

Compared with the traditional synthetic fibers,plant fibers have the advantages of a wide range of sources and environmental protection.Their naturally formed,interpenetrating porous structure makes it easier for energy dissipation of sound waves to occur,thus giving them better sound absorption properties.Acoustic metamaterials have the properties of negative mass density and negative bulk modulus,which can break the law of mass density and make them have better low-frequency sound insulation performance while satisfying lightweight design.Therefore,in response to the broadband noise transmitted from the engine compartment into the passenger compartment via the front panel,this paper conducts an in-vehicle noise reduction study based on plant fibers and acoustic metamaterials in three aspects: sound absorption,sound insulation and vibration damping.The research content and conclusions are as follows:(1)Research on the sound absorption model of plant fiber.Firstly,the sound absorption performance index of fiber materials and existing sound models are discussed,thus the JCA(Johnson Champoux Allard)model is selected to predict the sound acoustic coefficient of fiber materials in combination with the acoustic mechanism of plant fibers.Secondly,a non-acoustic parameter identification model is established,and a modified particle swarm optimization algorithm for identifying non-acoustic parameters is proposed.Then,the feasibility of the proposed identification algorithm for non-acoustic parameter identification is also verified by the data in the existing literature.Finally,based on the impedance tube test values of the sound acoustic coefficient of jute fiber felt,the non-acoustic parameters of jute fiber felt are identified by the proposed identification algorithm,and the sound absorption model of jute fiber felt is completed.The research in this paper shows that the modified particle swarm optimization algorithm can identify the non-acoustic parameters more efficiently and accurately.Compared with the traditional particle swarm optimization algorithm,the modified particle swarm optimization algorithm makes the predicted curve of the sound absorption coefficient of jute fiber felt agrees better with the experimental curve.(2)Simulation research on the sound absorption performance of jute fiber felt.Firstly,using finite element simulation software,the finite element analysis model of jute fiber felt is constructed based on the identified non-acoustic parameters.Then,the reliability of the constructed finite element analysis model model is verified by comparing with the impedance tube test results of jute fiber felt.Finally,based on the established finite element model,the effects of seven parameters on the sound absorption performance of jute fiber felt are simulated and analyzed.The research results show that the established finite element analysis model for the sound absorption performance of jute fiber felt is reliable and can be used for the simulation study of the sound absorption performance of plant fiber materials.The flow resistivity,tortuosity,thickness of the jute fiber felt and the thickness of the cavity behind it have more obvious effects on its sound absorption performance.(3)Simulation research on the sound insulation performance of membrane-type acoustic metamaterial.First of all,a multi-mass membrane-type acoustic metamaterial with metric-like swing arm is designed.The sound insulation finite element analysis model of this acoustic metamaterial is constructed,and its sound insulation performance is simulated.Next,the influencing factors analysis and orthogonal optimization design of the acoustic metamaterial’s sound insulation performance are carried out.Finally,the application of the optimized membranetype acoustic metamaterial with jute fiber felt in the front panel acoustic package of automobile is discussed.The research results show that the designed membrane-type acoustic metamaterial has good low-frequency sound insulation performance in a wide frequency band of 90-1000 Hz.The optimized membrane-type acoustic metamaterial can achieve an average sound transmission loss of 30.1 d B for a unit cell.The combined acoustic package of membrane-type acoustic metamaterial and jute fiber felt can significantly improve the broadband sound insulation performance of the front surround panel.(4)Research on vibration and noise reduction of flexible acoustic metamaterial plate.Firstly,the reliability of the band gap finite element method is verified by calculation example.Secondly,in view of the vibration and noise of structural parts in the engine compartment,a flexible acoustic metamaterial plate is designed.The influencing factors of the band gap characteristics are analyzed by the band gap finite element method.Finally,through the analysis of the band gap characteristics of the parameter combination,a set of parameters that meet the requirements of the band gap width are selected.The vibration transmission loss of the flexible acoustic metamaterial plate under this parameter combination is analyzed.The research results show that the designed flexible acoustic metamaterial plate can form a complete bending wave band gap in the low frequency range.The acoustic metamaterial plate with the optimized parameters can make the band gap in the low frequency range of 299-357 Hz.The vibration transmission loss curve of the flexible acoustic metamaterial plate also indicates that the structure has excellent low-frequency vibration and noise reduction performance.This study lays the theoretical foundation for the application research of jute fiber material,membrane-type acoustic metamaterials and acoustic metamaterial panels in the field of vehicle noise reduction,and provides a design reference for the combined design of automotive acoustic packages.