Study Of Low Frequency Sound Insulation Performance Of Membrane-type Acoustic Metamaterials

With the development of all aspects of society,noise pollution is becoming more and more serious,and the demand for sound insulation technology materials is increasing,not only to improve the effect of sound insulation,but also to take into account the requirements of lowfrequency,broadband and light weight of material structures.Due to the sound insulation mass law,traditional sound insulation materials are difficult to achieve good low-frequency sound insulation,and the emergence of acoustic metamaterials provides a new way to solve the problem of low-frequency noise reduction.Acoustic metamaterials are composite materials consisting of a periodic arrangement of artificially designed structural units with extraordinary physical properties,which can achieve specific low-frequency frequency band sound insulation with a small surface density.Membrane-type acoustic metamaterials have attracted much attention from researchers and engineers because of their simple structure and easy fabrication and good sound insulation effect.In this paper,we study the sound insulation performance of membrane-type acoustic metamaterials and its influencing factors through a combination of simulation analysis,numerical analysis and experimental verification,and propose the corresponding structural optimization design based on the conclusion.The main work of the paper is as follows.(1)The problem of membrane stress relaxation during the preparation of metamaterials was solved,and metamaterial samples with stable membrane tension were obtained.The impedance tube was used to test the sound insulation ability of the metamaterial samples,and the results were compared with the calculated values of the sound insulation mass law to initially reflect the advantages of the sound insulation frequency band of the metamaterial.Then,the finite element model of the metamaterial was established by simulating the test conditions of the impedance tube,and the transmission loss curve was calculated,the finite element model was modified by using the test results as a benchmark to obtain more accurate calculation results.(2)The vibration characteristics of the membrane are studied by using modal analysis and theoretical analysis,and the mechanism of producing the low-frequency sound insulation effect that breaks the sound insulation mass law is analyzed by combining the transmission loss curve of the membrane.Then,the effect of attaching a mass block to the membrane on the vibration characteristics is studied,and how the additional mass block adjusts the peak frequency of sound insulation of the metamaterial is analyzed.Finally,a spring-mass model of the metamaterial is established,and a method to calculate the sound insulation peak frequency of the metamaterial is proposed.corresponding simulations and tests are designed to verify the accuracy of the method,the results show that the error of the method with simulation and test results are below 6%.(3)An in-depth analysis of the regulation law of each parameter on the sound insulation performance of metamaterials,the results are analyzed and summarized,and several structural design solutions for metamaterials are proposed,so that the metamaterials can achieve the purpose of broadening the sound insulation band while maintaining the adjustable frequency of sound insulation peaks.The effect is verified by simulation or testing and the results show that the band width of the transmission loss greater than 20 d B is increased from 580 Hz to 2150 Hz.The methods of multiple sound insulation peaks and reduction of the structural mass of the metamaterial are studied.