Sound Insulation Performance Of Asymmetric Couple-membrane Local Resonance Acoustic Metamaterials

With the development of modern science and technology,the resulting noise has seriously affected people’s quality of life and physical and mental health,especially the lowfrequency noise with strong penetrability and long propagation distance did.Limited by the acoustic quality law,it is difficult for traditional sound absorbing materials to attenuate low frequency noise.The newly proposed local resonance acoustic metamaterials which are lightthin and win the attentions of the researchers have broken the law of acoustic quality,with blocking the spread of sound waves below 1000 Hz,showed significant acoustic noise reduction effect.How to effectively expand narrow bandwidth and make this kind of sound insulation material better applied to strict requirements on size and weight in aviation,aerospace and other fields has become a problem to be solved today.In this paper,the theoretical model of local resonance membrane acoustic metamaterials is established based on the theory of membrane vibration,and the effective factors affecting the bandwidth of the structure are analyzed.In addition,the effective methods for broadening bandwidth are proposed.The main research contents and results are as follows:Firstly,the intrinsic characteristics of the membrane-mass system are analyzed based on the single-cell monolayer membrane phonon crystal.On this basis the low-frequency sound insulation characteristics of the single-membrane local resonant system are analyzed considering the interaction between sound waves and the membrane-mass system,and the key factors affecting the sound insulation characteristics of the system are discussed.The results show that the material parameters and the geometric parameters of the membrane and mass have significant influences on the sound insulation characteristics of the system.Secondly,on the basis of the model of local resonant phonon crystal of monocyte monolayer membrane,the local resonant structure of couple membrane filled with air is studied.Because of the addition of air layer,the vibration equation is established considering interaction of two membranes and mutual coupling of air and membrane.The key factors of acoustic characteristics in the previous chapter analyzes are discussed,and the influences of couple symmetric structure and asymmetric structure in sound insulation properties of local resonant phonon crystal.Results show that compared with single layer membrane structure,couple membrane local resonance structure presents the characteristics of more transmission loss peaks show that it can effective attenuation low-frequency and multiple frequencies sound waves,and asymmetric structure compared with symmetrical structure displayed multiple peaks and light features below 1000 Hz,shows that broadband sound insulation at the low-frequency,providing theoretical basis for designs of the membrane type phononic crystal.In practical engineering applications,monocyte structure arrays are usually arranged to form panels.For this reason,we arrange the monocyte of asymmetric double membrane locally resonant phonon crystal in 1x2 and 2x1 array,taking into account the coupling interactions between the monocyte and the monocyte,and study the overall sound insulation characteristics of this type of structural panel.The results show that the array structures can realize the sound insulation properties of low frequency,multi-frequency and wide bandwidth,and the sound insulation properties of array structures can be achieved by selecting the appropriate membrane size,increasing the membrane tension and reducing the mass radius.