Influence Of Micro Structure Characteristics On Sound Insulation Performance Of Membrane-Type Acoustic Metamaterials

With the development of science and technology,The acceleration of the industrialization process noise problems in people’s life and production is becoming more and more serious.Due to the limitation of the law of mass action,the technique of noise barrier in the low frequency range has been unable to meet the requirements.membrane-type acoustic metamaterials emerge as the times require.In this paper,the sound insulation properties of membrane-type acoustic metamaterials composed of thin membranes and added mass blocks are studied.First,the vibration characteristics of thin membranes are analyzed and predicted based on the discrete model of vibration.Then,the simulation of transmission loss based on the the vibration characteristics of thin membranes is carried out to further study the acoustic insulation performance of the structure.Finally,a hybrid FE-SEA method is used to optimize the first two sound insulation troughs,which are controled by the modal of the metamaterial.Firstly,based on the local resonance mechanism,the vibration model of the cell spring mass block of the membrane acoustic metamaterials is presented.The numerical results are in good agreement with the finite element simulation of the thin membranes mass system and the results of the literature.The characteristics of the discrete vibration model established in this paper can directly reflect the influence of the structure parameters on the vibration and sound insulation.Secondly,the modal analysis of the acoustic metamaterial is the vibration characteristics of the structure.It is a very important research.Based on the modal analysis of the single cell structure of the thin membranes,the modal results,especially the modal shapes which corresponds to discrete model are analyzed.The influence of microstructure characteristics on the modal frequencies and mode shapes of thin membranes was studied by discrete model.The method to confirm the discrete model is feasible.Then,through the acoustic wave transmission principle,to understand principle of the sound transmission loss.Based on the modal analysis of the thin membranes acoustic metamaterials,the transmission loss is simulated and analyzed,and the influence of the membranes thickness,the prestress and the mass of the additional mass on the transmission loss is discussed.Then further explore on the relationship between he corresponding frequency where thin membranes acoustic metamaterial transmission loss valley accured and natural frequency is studied.Analysis of vibration mode of frequencies,corresponded to transmission loss valley and peak frequencies.Finally,on the basis of the modal contribution,the critical region of the formation under the natural frequency of the transmission loss trough isidentified.Adding additional mass blocks in critical areas,after the simulation and comparison,it is found that the arrangement of the additional mass block has obvious improvement on the transmission loss of the first two troughs.