Structural Design And Sound Insulation Performance Of Membrane Acoustic Metamaterials

Thin film acoustic metamaterials have the advantages of light weight,low-frequency and high-efficiency sound insulation.They provide new ideas for low-frequency noise reduction and become one of the hotspots of metamaterials research.In this thesis,the thin-film acoustic metamaterials are taken as the research object,and the composite structures composed of single-layer thin-film structure,double-layer thin-film structure,laminated thin-film structure,sandwich plate and thin-film acoustic metamaterials are designed.The sound insulation characteristics of each structure in the range of medium and low frequency(50 ～ 1000Hz)are deeply studied.Based on the sound insulation principle of membrane system and combined with the natural mode of the structure,the sound insulation characteristics and sound insulation mechanism of single-layer membrane structure are analyzed.The equivalent mass and equivalent stiffness of the structure are analyzed.The research shows that the equivalent parameters of the structure are negative in some frequency ranges.The experimental sample of single-layer film structure is made.Based on the four microphone acoustic impedance tube test system,the sound transmission loss of the structure is measured,and the correctness of the simulation results is verified.The influence of different structural parameters on its sound insulation characteristics is discussed,and the regulation law of structural sound insulation characteristics is obtained.A double-layer film structure is designed and its sound insulation characteristics are studied.According to the asymmetric acoustic characteristics of the structure,the back transmission characteristics,equivalent mass density and equivalent bulk modulus on both sides of the structure are analyzed.Aiming at broadband sound insulation,a laminated film structure is designed,and its sound insulation and back transmission characteristics are studied.Make the experimental samples of double-layer film structure and laminated film structure,measure the sound transmission loss of each structure,further analyze the sound insulation characteristics of the structure from the perspective of experiment,and verify the correctness of the simulation results.A composite structure composed of pyramid lattice sandwich plate and thin film acoustic metamaterial is designed to make the thin film structure in a protected state and transform to engineering application.Using the method of finite element calculation and experiment,the sound transmission loss of pyramid lattice sandwich panel is compared,and the sound insulation characteristics of composite structure are analyzed.The sound insulation characteristics of infinite composite structure are studied,and the effects of different structural parameters on its sound insulation characteristics are discussed,and the regulation law of structural sound insulation characteristics is obtained.