| Because of its unique penetrating effect,low-frequency noise affects the equipment's performance of stealth and stealth,which challenges the traditional noise reduction materials and structures.The emergence of acoustic metamaterials provides a new solution to the problem of low-frequency noise control in acoustic engineering.In this paper,based on the analysis of the working principle and acoustic performance of acoustic metamaterials,for the drawbacks of the traditional acoustic metamaterials that have a single working principle and the band gap cannot be adjusted,this paper designs a combination of Helmholtz resonance effect and spring mass resonance effect.The acoustic metamaterial structure with double local resonance effect,when the noise frequency is the same as the resonance frequency of the Helmholtz cavity and the resonance frequency of the spring mass system,local resonance occurs separately,converting acoustic energy into kinetic energy to achieve low-frequency noise control.Firstly,a piezoelectric acoustic metamaterial structure coupled with a flexible thin film with dual local resonance effect and its control method are studied.Using theoretical research and simulation analysis methods,the acoustic metamaterial structure is designed,and the equivalent mathematical model of the dual local resonance acoustic metamaterial is established.The simulation results show that the transmission loss of the acoustic metamaterials has resonance peaks at 50 Hz and 390 Hz,respectively,and shows a significant dual local resonance effect.When the noise frequency is the same as the dual local resonance frequency of the metamaterial,localization occurs separately.Resonance converts sound energy into kinetic energy,thereby reducing the noise of these two frequency components.The research reveals the resonance coupling law of the spring mass system and the Helmholtz resonance system,so that the acoustic metamaterial can adjust its structural parameters adaptively according to the change of the noise frequency,enhance the handling ability of the low-frequency sound wave transmission process,and widen the low-frequency noise The purpose of suppressing the frequency band.Secondly,an inflatable acoustic metamaterial structure combining Helmholtz resonator and flexible film is designed.Simulation analysis shows that in the frequency range of 0 ~ 1000 Hz,the metamaterial has two band gaps,forming a double local Resonance effect.In order to control the metamaterial anechoic band,the Helmholtz cavity is filled with compressed gas.The test results show that: the frequency of the first transmission loss peak of the dual local resonance unit remains stable;the second transmission loss peak As the pressure of the injected gas increases(0~2kPa),it shifts from 540 Hz to 720 Hz and 180 Hz towards the high frequency.The resonance frequency of the bilocal metamaterial can be adjusted as the inflation pressure increases.Finally,build an acoustic experiment platform to test the acoustic performance of the designed acoustic metamaterials.For piezoelectric acoustic metamaterials,when the driving voltage is increased from 0V to 350 V,the first transmission loss frequency peak frequency shifts from 30 Hz to 110 Hz,the offset is 80 Hz,and the second transmission loss frequency peak value shifts from 410 Hz To 420 Hz,the offset is 10 Hz.For inflatable acoustic metamaterials,when the pressure of the charged gas increases(0 ~ 2kPa),the first transmission loss peak frequency of the dual local resonance unit remains basically unchanged;the second transmission loss peak frequency increases from 550 Hz to 720 Hz,Offset by 170 Hz.Tests have shown that the designed acoustic metamaterials are consistent with the simulation results.Piezoelectric acoustic metamaterials and inflatable acoustic metamaterials have good noise control effects in the low frequency range,generating two transmission loss peaks and forming a double local resonance effect.,You can control the noise in two frequency ranges at the same time. |
PDF Full Text Request