Research On The Band Gap And Sound Absorption Performance Of Acoustic Metamaterials

Being different from natural material,metamaterial is a kind of composite material which not only has artificial designed structures,but possess unusal physical properties.The propagation of sound wave in metamaterials is determined by the "order" of the arrangement of artificial microstructures and microstructure units.Thus metamaterials have some special physical phenomena and functions,such as acoustic superlens,negative refraction,acoustic cloaking,low frequency sound absorption,etc.In recent years,materials associated with the sound insulation and noise reduction have been studied widely in the high frequency range,in this regard,the researches on the corresponding materials in the low frequency range have become a hot topic.And the demand for these low-frequency sound absorbing metamaterials is grradually increasing in our daily life.In this paper,an acoustic metamaterial model of two-dimensional internal mass triangular lattice periodic structure is designed.The propagation of elastic wave is simulated by matlab in this structure,and band gaps are regulated by setting appropriate parameters.The results show that changing mass and elastic coefficient of the internal mass periodic structure,the band gaps can be artificially controlled.The external mass has a great effect on the band gaps.As the external mass decreases,both the 3rd and 2nd band gaps are widened,and the 1st band gap is narrowed,while the internal mass has an opposite effect on the band gaps.Stiffness change also has influences on the band gaps,some of which to be compressed and some to be broadened.As a result,the low frequency wide band gap can be realized by adjusting parameters of this kind of structural model.Aluminum foam and rubber powder composite metamaterial with different porosity,particle size and thickness were prepared by experimental method.The sound absorption coefficient of the composites was measured by standing wave tube.The results indict that the prepared metamaterial has a good sound absorption property.With the thickness of the material increasing,the sound absorption frequency slowly shifts to the low frequency,and the sound absorption coefficients remain basically unchanged.Increasing the porosity of aluminum foam is more beneficial to the sound absorption of materials.As the particle size of the rubber powder material increases,the sound absorption coefficient gradually increases,and the frequency slowly shifts to the high frequency.The viscoelasticity of the rubber in the rubber powder materials can be released by the proper ratio of the solvent and the rubber component.The sound absorption coefficient is the best as a ratio of 1:2.The prepared composite metamaterial has a good stability over time.All in all,the composite metamaterial prepared by this way has a well sound absorption property with adjustable parameters,which sets the stage for people to explore the preparation and application of composite materials.