A Research On Sound Insulation Characteristics Of Honeycomb Membrane-type Acoustic Metamaterial

With the development of society,noise pollution is becoming more and more serious.Therefore,the importance of noise reduction is increasingly reflected.In the field of automotive and other fields where noise reduction is required,dealing with low-frequency noise has always been a challenging problem.Its long wavelength and strong penetration ability cannot be effectively controlled by traditional acoustic materials.The advent of acoustic metamaterials has opened a new path for low-frequency noise control.Acoustic metamaterial is a kind of period arrangement new material or structure which is specially designed and has extraordinary physical properties.Based on the principle of local resonance,they can achieve good sound insulation effect in low frequency bands.And the membrane acoustic metamaterial has a simple structure,which is easy to realize lightweight and low-frequency sound insulation,and has a wide application prospect.This paper designed a honeycomb membrane acoustic metamaterial structure,and its low and wide frequency sound insulation characteristics are studied.The main work is as follows:Firstly,according to the current requirements of low-frequency noise reducing,a kind of honeycomb membrane acoustic metamaterial structure is designed,which is composed of regular hexagonal unit periodic array.The basic unit includes the upper and lower frame,the elastic film between the frames and the central mass block.Secondly,the sound insulation test method of the honeycomb metamaterial is introduced.By making the test samples of single cell and multi cell,then conducting impedance tube sound insulation tests.The excellent sound insulation characteristics of the honeycomb membrane metamaterial structure at low frequency are preliminarily verified.In addition,the comparative experiments between the honeycomb metamaterial and the traditional acoustic material are carried out to further illustrate the advantages of low-frequency sound insulation of the honeycomb metamaterial and the feasibility of its application.Thirdly,the spring mass model of membrane metamaterials is introduced,then derived the expression of its negative equivalent mass.The simulation models of single cell and multi cell of honeycomb metamaterials are established through the finite element software COMSOL multiphysics,and solved to get its sound transmission loss curve.Compared with the test results,the correctness of the simulation model is verified.By comparing the modal parameters with the vibration morphology at the corresponding frequency,and the single cell sound insulation mechanism is analyzed.Then studied the influence of lattice size,mass weight,contact area between mass and film and lattice shape on sound insulation characteristics of honeycomb metamaterials.Finally,the broadband sound insulation design of the honeycomb membrane metamaterial was carried out.By introducing the concept of acoustic metamaterial defect state,and analyzing the acoustic characteristics of metamaterials with defective units,it is found that it can generate two new sound insulation peaks,which widens the sound insulation bandwidth.Several doublelayer structures with defects are designed,which can effectively combine the sound insulation advantages of the upper and lower metamaterial structures,greatly improve the overall sound insulation performance,and realize the functions of broadband sound insulation and acoustic waveguide.Combining the honeycomb metamaterial and the traditional sound insulation material EVA to form a sandwich structure can not only obviously improve the sound insulation performance at the low-frequency section,but also make up for the disadvantage of the sound insulation at the medium and high-frequency section,which lays the foundation for the engineering application of the honeycomb membrane metamaterial.