Study On The Acoustic Characteristics Of Composite Structure With Anti-reflection Layer

Low-frequency broadband noise reduction is a research hotspot in the field of noise control currently.Acoustic anti-reflection layer has the characteristics of suppressing sound scattering and reducing echo intensity.In view of that,the anti-reflection layer is introduced into the field of sound absorption and noise reduction for the first time in this paper.A novel type of composite structure with anti-reflection characteristics is constructed to reduce the echo intensity.A new coupling mechanism for energy dissipation is formed to realize the dissipation of sound energy.It provides a new idea for breaking through the bottleneck of low-frequency broadband sound absorption.First,based on the anti-reflection theory and the homogenization method,a basic theoretical model of the anti-reflection layer composed of scatters is established.The suppression effect of anti-reflection layer on acoustic scattering in the broadband frequency range is studied through simulation and experimental test.The influence of key parameters on anti-reflection performance is discussed,which provides a theoretical basis for the development and application of the anti-reflection layer.Secondly,a new composite structure consisting of metal foam anti-reflection layer,perforated panel and porous material is proposed to suppress acoustic scattering in the air acoustic environment.The anti-reflection layer in the structure can make the sound waves interfere with each other.The metal foam,perforated plates and porous materials are tuned to dissipate energy to achieve broadband acoustic absorption.Based on the homogenization theory and equivalent method for porous materials,the equivalent parameters of the antireflection layer are solved.Combined with the transfer matrix method,a complete theoretical model of sound wave propagation is established.The accuracy and effectiveness are verified by the finite element method.At the same time,the key parameters of the composite structure are analyzed to reveal the internal sound absorption mode and energy dissipation mechanism.Then,considering the excellent performance of anti-reflection layer in air acoustics,combined with the bottleneck problem of low-frequency broadband absorption in underwater acoustics,the anti-reflection layer is introduced into underwater acoustics.A composite structure composed of rubber anti-reflection layer and eccentric resonance layer is proposed.Based on the finite element method,a complete theoretical model is established and numerical simulation is carried out.The results show that the anti-reflection layer can promote the acoustic coupling,and the eccentric resonance layer can significantly improve the broadband absorption capacity through the core resonance and overall resonance modes.The combination of the two modes can effectively suppress the underwater acoustic scattering in broadband frequency range.It is proved that the structure has wide application potential in underwater acoustic stealth.In this paper,the anti-reflection layer is deeply studied by theoretical research,simulation analysis and experimental verification.The internal energy consumption mode and sound absorption mechanism are discussed.The results show that the anti-reflection layer can make sound waves interfere with each other and eliminate them,realizing the regulation of sound waves and the dissipation of sound energy.This paper provides a basis for the precise development of anti-reflection layer and the application of anti-reflection layer in the field of sound absorption and noise reduction,which has a certain academic value.