Design And Acoustic Properties Of Composite Thin Film Acoustic Metamaterials With Laminates

Because the influence of mass density law on low frequency noise is limited,traditional sound insulation materials are difficult to play an effective role in the environment of low frequency noise,so the suppression of low frequency noise has become a difficult problem for scholars and engineers.Since the introduction of phononic crystals and acoustic metamaterials in the 1990s,it has provided effective methods and new ideas to solve the problem of low frequency noise.It is found that the traditional locally resonant phononic crystals have congenital shortcomings in suppressing low-frequency elastic waves,but the acoustic properties of thin-film acoustic metamaterials have obvious advantages in the low frequency domain.The structural and acoustic characteristics of this type of metamaterials are not conducive to direct application.Therefore,this paper considers the composite design with other excellent structures to improve its sound insulation effect at low frequency.This paper focuses on the difficulty of suppressing the propagation of low-frequency industrial noise.The specific contents are as follows:Firstly,the basic law of sound insulation is analyzed based on the plane wave equation.Through modal analysis,the theoretical model of thin film acoustic metamaterial is established,the calculation formula of sound insulation is derived,and the correct calculation method is determined,which provides support for the following calculation.Secondly,the sound insulation mechanism and regulation law of thin film acoustic metamaterials are analyzed through the mode shapes and the transmission loss of thin film acoustic metamaterials.Based on the method of cooperative behavior,the sound insulation performance of thin film acoustic metamaterials in low frequency domain is improved.Based on the composite design of thin film acoustic metamaterial and classical Helmholtz structure,a new metamaterial model of membrane sandwich plate is proposed.Based on the equivalent model,the effects of Helmholtz structure parameters and new sandwich plate structure parameters on sound insulation performance are analyzed,and the sound insulation mechanism is analyzed in detail based on the concept of double negative equivalent parameters.According to the acoustic-solid coupling environment,the problem of structural bulk vibration caused by acoustic-structural coincidence effect is solved by the introduction of thin film metamaterials,and the vibration characteristics of new structures are lightweight.The thin film metamaterial structure based on cooperative behavior proposed in this paper can improve the sound insulation performance in the low frequency range.The experimental results show that the membrane sandwich plate structure can effectively reduce energy consumption and design cost according to its acoustic and vibration characteristics,and has a large sound insulation loss,which provides a new idea for the practical engineering application of thin film acoustic metamaterials.