Study On Broadband Sound Absorption Performance Of Fabry-Pérot Resonant Acoustic Metamaterials

With the improvement of people’s living standards,the noise problem has attracted more and more people’s attention.In addition to the common traffic noise,construction noise,elevator noise,and air-conditioning noise,noise problems in the power industry and national defense have also attracted more and more attention.In recent years,the emergence of acoustic metamaterials has provided new ideas for solving noise problems in all walks of life.Aiming at the increasingly concerning noise reduction problem,this paper takes Fabry-Pérot(F-P)tube as the research object.The main work assists with theoretical analysis,simulation analysis,and experiments to solve the specific problems in the design process.The main research work of this paper is as follows:Aiming at the problem of the need for trial-and-error in the design of the section size of the FP tube,an innovative method to obtain its optimal section size based on the loss equation is proposed.This equation is obtained by linking the critical loss with the transmission loss of the tube.Using this method,single-frequency perfect sound-absorbing metasurfaces with circular and rectangular cross-sections were designed.The designed metasurfaces were verified by the simulation and experiment.The results show that both metasurfaces achieve perfect sound absorption at the designed target frequency.This verifies the feasibility and accuracy of the design method.Additionally,according to the complex-frequency plane and the normalized surface acoustic impedance ratio,the essence of the loss equation is further explored.Aiming at the problem that the right-angle bend in the coiled F-P tube will cause the peak frequency shift,a length correction theoretical model is proposed.The length correction model equates the effect of the right-angle bend to the effective length.Additionally,a polynomial regression fitting model based on data is also proposed.The two models can be used to predict the peak frequency of the F-P tube with a right-angle bend.Moreover,it can guide the length design of the F-P tube.According to the two models,the peak frequencies of the F-P tubes with a right-angle bend for the given geometric parameters are accurately predicted.And the predicted results are in good agreement with the simulation and experimental results.Through the analysis of the two models,it is found that the relative error of the peak frequency is reduced from the highest 6% to within 0.4% and 0.15%,respectively.Additionally,according to the sound velocity,sound pressure,the power dissipation density,and the dissipated energies,it is determined that the distribution change of the power dissipation density in the tube is the root cause of the frequency shift.Aiming at the broadband noise reduction problem,a broadband sound-absorbing metamaterial with 30 F-P tubes is constructed.In the design,the cross-section parameter design method and the study of frequency offset in the previous section are applied.A broadband sound absorption with an average sound absorption coefficient of 0.89 in the range of 300Hz-3000 Hz is achieved.And,the material thickness is only 112 mm.To optimize the sound-absorbing properties of metamaterial,a composite structure is constructed by coupling the broadband sound-absorbing metamaterial with the porous material.By analyzing the influence of porous material parameters on the sound absorption performance of the composite structure,a composite structure with better sound absorption performance was found.This composite structure achieves broadband sound absorption with an average sound absorption coefficient of 0.91 in the range of 250Hz-3000 Hz.The thickness is only 131 mm.In general,this paper takes the F-P tube as the research object.The problem of cross-section parameter design and corner effect frequency offset in the application process is solved.A composite structure of porous material and F-P resonance metamaterial is designed.The research in this paper has guiding significance for the parameters design of F-P type metamaterials,and also provides a useful reference for the design of broadband soundabsorbing metamaterials.