Investigation on the Band Gap and Negative Properties of Concentric Ring Acoustic Metamaterial

Heng Jiang,Yuren Wang,Meng Chen,Dan Meng

doi:10.1155/2018/1369858

Abstract

The acoustic characteristics of 2D single-oscillator, dual-oscillator, and triple-oscillator acoustic metamaterials were investigated based on concentric ring structures using the finite element method. For the single-oscillator, dual-oscillator, and triple-oscillator models investigated here, the dipolar resonances of the scatterer always induce negative effective mass density, preventing waves from propagating in the structure, thus forming the band gap. As the number of oscillators increases, relative movements between the oscillators generate coupling effect; this increases the number of dipolar resonance modes, causes negative effective mass density in more frequency ranges, and increases the number of band gaps. It can be seen that the number of oscillators in the cell is closely related to the number of band gaps due to the coupling effect, when the filling rate is of a certain value.

Highlights

IntroductionAcoustic metamaterials possess certain peculiar acoustic characteristics that natural materials do not have (e.g., negative effective mass density, negative effective modulus) and as such have garnered considerable attention for their promise in applications such as acoustic/elastic filters, acoustic mirrors, and sound insulators/absorbers [1, 2]
Acoustic metamaterials possess certain peculiar acoustic characteristics that natural materials do not have and as such have garnered considerable attention for their promise in applications such as acoustic/elastic filters, acoustic mirrors, and sound insulators/absorbers [1, 2]
A negative effective mass density is generated by dipolar resonance at low frequencies [4,5,6], while a negative effective bulk modulus is caused by monopolar resonance at low frequencies [7,8,9]

Summary

Introduction

Acoustic metamaterials possess certain peculiar acoustic characteristics that natural materials do not have (e.g., negative effective mass density, negative effective modulus) and as such have garnered considerable attention for their promise in applications such as acoustic/elastic filters, acoustic mirrors, and sound insulators/absorbers [1, 2]. The multioscillator system here investigated was created by introducing multiple resonators into a unit cell and generating new forms of resonance through mutual coupling between each oscillator in order to control acoustic properties [13, 14]. The concentric ring structure is a typical multioscillator system, the acoustic properties of which are enhanced by larger quantities of oscillators Studies on this subject have focused primarily on the transmission characteristics or band gaps while neglecting the effective medium parameters. The concentric ring structures were designed to build 2D single-oscillator, dual-oscillator, and triple-oscillator acoustic metamaterial systems and the properties of each were thoroughly analyzed by numerically analyzing and comparing their respective band structures, transmission characteristics, effective medium parameters, and other necessary factors. According to the effective medium theory, the waves at these frequencies were not able to propagate; the number of acoustic/elastic wave bands increased significantly

Models and Calculation Methods

Results and Discussion

Conclusion