Membrane-based acoustic metamaterial with near-zero refractive index
Li Yi-Feng1, 2, †, Lan Jun1, Yu Hui-Yang1, Liu Xiao-Zhou3, Zhang Jia-Shu4
       

(color online) FEM simulation results of acoustic pressure field in the composite system at the frequency (a) below, (b) equal to, and (c) above f 1 (465 Hz).