Research On Low Frequency Sound Absorption Characteristics Of Membrane Structure Based On Resonance Sound Absorption Principle

Aiming at the problem of sound absorption control of low frequency noise which is difficult to attenuate and with strong penetration power below 500 Hz,the traditional sound absorbing materials can not achieve good absorption effect.The two-dimensional acoustic metamaterials with negative mass density have the potential of low-frequency sound absorption during local resonance.Membrane acoustic metamaterials(MAM)which are light-weight,designable and low-cost have become a research hotspot in the field of low-frequency sound absorption control.In this paper,the resonance sound absorption characteristics of MAM with the additional mass are studied systematically.The experimental result verifies that the two-layer composite structure of MAM with multi-mass proposed by the research has high-efficiency and low-frequency broadband sound absorption performance which promotes the process of engineering application.Firstly,the theoretical model of the sound absorption coefficient of MAM with a circular mass is established which is based on the modal superposition and the relative acoustic resistance and impedance methods.The characteristics of the sound absorption coefficient,the relative acoustic resistance and impedance and eigenmodes of MAM with or without additional mass are compared and analyzed.The regulation characteristics of sound absorption performance of MAM with two resonance sound absorption peaks in low-frequency band are studied.Then,thicknesses of the membrane and the mass in the subsequent study are determined.According to the eigenmodes' correspondence analysis of MAM with the additional circular mass,MAM with a semi-circular mass which has three asymmetric modes in low-frequency band is proposed.The finite element simulation analysis of the acousticstructure coupling is carried out.According to the resonance characteristics in the sound absorption valley,multi-frequency sound absorption design and simulation of MAM is carried out.The multi-mass design realizes that the three resonances in low-frequency band contribute to three peaks of the sound absorption coefficient which improves the multi-peak sound absorption characteristics in low-frequency band.Then,broadening the sound absorption band of the two-layer MAM coupled air cavity is studied.The theoretical model of the sound absorption coefficient of the twolayer MAM with center-added circular mass is established which is based on the transfer matrix method.Based on the theoretical analysis of its bandwidth characteristics,the parameters of membrane tension and coupled air cavity depth in the subsequent study are determined.Combined with the single-layer MAM with multi-mass which radius is 10 mm,the multi-mass design of the two-layer MAM coupled air cavity and its sound absorption simulation.Then its low-frequency sound absorption performance is evaluated.Finally,the sound absorption coefficient test of MAM is carried out based on the standing wave tube method.The experimental result of the absorption coefficient is consistent with the simulation result in general trend,indicating that the simulation analysis method and the theoretical analysis method are feasible.The experimental results of the low-frequency average sound absorption coefficient and the noise reduction index show that the two-layer MAM with multi-mass has high-efficiency of low-frequency broadband sound absorption performance which promotes the practical process of membrane acoustic metamaterials.