The Sound Insulation Performance Of Composite Structure Of Membrane Metamaterial And Micro-perforated Plate

Sound is everywhere in earth.Sometimes it plays a role to make communications and deliver happiness.But in many occasions,sound can interrupt our daily life and work,where we call it noise.Even in some fields,noise can be deadly,such as underwater diving.Nowadays more demanding needs in sound insulation materials are asked in aerospace,civil architecture and traffic et all.They all ask the deadening to own the properties like light-weight,high performance in suond insulation,especially in low frequency.But,traditional deadening such as solid wall performs bad in low frequency.In addition that,according to mass-controlled law,the sound transmission loss plus 20 d B when the solids wall's thickness multiplies 10 times.So it is not realistic to increase the thickness to enhance sound insulation performance.Thanks to the arising of acoustic metamaterials.It can break the restrictions of mass-controlled law to fullfill a extraordinary sound transmission loss at frequency which we call anti-resonant frequency.At that frequency,the material shows a unusual negative effective-mass value,so we call it metamaterials.Though the acoustic metamaterials performs well in low frequency,it performs bad in medium to high frequency.Microperforated plate shows well medium to high frequency sound absorption and insulation performance.So it is naturally to combine these two materials to generate a new structure to fullfill a wide-ranged sound insulation performance.The article combined these two materials and found it can realize a wide-ranged good sound insulation performance in 100-5000 Hz.Firstly,according to Langfeldt's theory,we used point-match method to analyse the single-cell's sound insulation performance,including the parameter analyses,such as mass,membrane surface density,offcent of the mass,prestress,and radio of length and width,and we calculated the value of TL,the effective-mass density and effective-impedence.Secondly,we combined the acoustic metamaterial membrane(MMM)with microperforated plate(MPP),generating a new MPP-MMM-MPP composited structure.Then we adopted equivalent-circuit method to analyse the composite structure's sound insulation performance and found that this structure can fullfill a wide-ranged sound insulation.Finally we analysed multi-cell MPP-MMM-MPP structure's sound insulation performance.Giving a through method to design and analyse the MPP-MMM-MPP structure from single-cell with vertical incidence of plane wave to multi-cell oblique incidence of plane wave.