A Research On Low-frequency Sound Insulation Performance Of Membrane-type Acoustic Metamaterial

For a long time,the low-frequency noise problem in the automotive field has troubled people.Traditional sound insulation materials are limited by the law of mass sound insulation,and it is difficult to achieve good sound insulation in the low frequency range.At this time,the emergence of acoustic metamaterials provided a new direction for low-frequency sound insulation.Studies have shown that membrane-type acoustic metamaterials have better sound insulation in light and low frequency bands,which is the main research trend of acoustic metamaterials at present.This paper takes acoustic metamaterials as research objects,establishes a sound insulation calculation model,studies its sound insulation performance in the low frequency range,and designs single-mass and multi-mass metamaterials to achieve lightweight and low-frequency broadband sound insulation.The main work is as follows:First,the current acoustic metamaterials are divided into four categories according to their structural characteristics,namely Helmholtz type,thin plate type,membrane-type,and other types.Based on domestic and foreign research paper,the research status of these four structures are described and summarized respectively,and determine the membrane-type acoustic metamaterial as the final research object.Second,based on the multiphysics analysis software Comsol,the acoustic-solid coupling model of the typical structure of the membrane-type acoustic metamaterial is established.From the perspective of negative effective mass,modal analysis,and energy distribution,the sound insulation mechanism of membrane-type acoustic metamaterial is studied in depth.The analysis shows that the negative effective mass will appear at the peak of sound insulation of metamaterials.The first and fourth modes of the structure are related to the frequency of the peak and valley of the sound insulation curve,and the peak of strain energy appears at the frequency of the valley of sound insulation.And membrane-type acoustic metamaterial is mainly based on reflected energy.Third,taking the typical structure of the membrane-type acoustic metamaterial as a prototype,the selected material is designed to design a single mass membrane-type acoustic metamaterial.Based on the sound insulation calculation model,the influence of the structuralparameters of metamaterials on its sound insulation was studied,including the thickness and area of the elastic film,the material of the rigid frame,the bisected form of the mass,and the pitch angle of the sound wave.A single-mass metamaterial sample was produced by 3D printing,and an impedance tube test was performed to verify the correctness of the sound insulation calculation model.Finally,a multi-mass membrane-type acoustic metamaterial is designed.The calculation results show that the sound insulation of multi-mass meta-material is higher than that of single-mass meta-material.A multi-mass metamaterial sample was prepared for impedance tube test to verify the correctness of the multi-mass metamaterial sound insulation calculation model.Based on the sound insulation calculation model,the sound insulation characteristics of multi-mass metamaterials under the same mass distribution and different mass distribution are analyzed.Then,based on the actual engineering,the membrane-type acoustic metamaterial was compared with homogeneous EVA of the same weight for sound insulation test,and the composite flat structure was made with acoustic blanket materials such as cotton felt and EVA,and the sound insulation test was performed on the test samples.The results show that the sound insulation effect of metamaterials is better than that of equal weight materials.After compounding with other acoustic package materials,the sound insulation volume is still higher than that of traditional sound insulation materials.