Research On The Properties Of The Plate-type Double Negative Acoustic Metamaterial

Acoustic metamaterials are artificially designed periodic subwavelength materials which can achieve singular properties that natural structures do not have.These properties include cloaking,super-lens,extraordinary transmission and so on.Considering the similarity between the electromagnetic metamaterials and acoustic metamaterials,acoustic metamaterials with negative elastic modulus and negative mass density have been widely concerned and developed rapidly in the field of acoustics.At present,most double negative acoustic metamaterials are realized by introducing a variety of resonance forms into different structural elements,using the coupling of dipole resonance and monopole resonance.The main disadvantage is that the composite structure is complex,the resonant frequency band is narrow and the achieved band with double negative is always single.Therefore,this paper proposes an plate-type metamaterial with effective parameters.This structure couples multiple different resonant units on the same plate,which can realize and control the negative effective parameters.The work of the paper mainly involves the following aspects:(1)Two types of plate structures with Open End-Open End(OE-OE)and Open End-Close End(OE-CE)hollow rectangular tube(HRT)that can achieve negative effective mass density are designed.Meanwhile,the structural parameters of the resonant cavities and the arrangement of different plates are changed to analyze the influence on the acoustic performance of the plate.The results show that as the number of resonant cavities increases,the plate structure will exhibit stronger negative effective mass characteristics,and the band of negative mass density will be wider;the greater the length of the resonant cavity is,the lower the resonance frequency is.By designing a plate with the combination of different length OE-CE cavities can achieve negative equivalent mass density in dual-band,triple-band or even multi-band.(2)A plate structure with nine periodically arranged split hollow cuboids(SHC)resonators is designed,which can realize negative equivalent elastic modulus.The effect of aperture radius,side length and aperture thickness is studied and analyzed.On this basis,the hole radius of different resonators are changed to research acoustic performance after multi-structure coupling.Using the method of equivalent acoustic-electric analogy to analyze its influence,the results show that with the increase of the radius,the equivalent acoustic inductance become smaller,and the resonance frequency get higher.With the thickness of the opening increases,the equivalent inductance increases,and the resonance frequency become lower.With the volume of the cavity increases,the equivalent sound capacity increases and the resonance frequency become lower.The combination of different types of SHC can realize the negative modulus in triple frequency bands.(3)A plate structure with periodically arranged SHC and HRT is designed.The intermediate cavity is set as a OE-OE cavity or OE-CE cavity,both can provide negative effective mass density for the plate structure.Furthermore,the cavity is coupled with SHC which can provide negative effective elastic modulus to prepare a coupled plate type double negative acoustic metamaterial.By designing OE-CE HRT and SHC with two kinds of parameters,the plate achieve double-negative from 1325-1520Hz and 1940-1955Hz.Furthermore,the plate structure with different geometric parameters are arranged and combined to achieve double negative parameters in triple and multi frequency bands.(4)On the basis of HRT,the perforated plate structure is designed by drilling holes in the wall of HER,which can realize the double negative in single frequency band or double frequency bands.The results show that as the hole radius r and the hole position w increases,the double negative frequency band will be blue shifted.