Giant band gaps in a phononic crystal with touching solid inclusions

Abstract

We present a two-dimensional phononic crystal structure that exhibits exceptionally large complete band gaps, akin to those typically associated with bubble crystals. Our analysis begins with numerical simulations of a phononic crystal characterized by material parameters that are continuous functions of spatial coordinates, arriving at a sawtooth material parameter function, whose band structure can be replicated by a surprisingly simple configuration with inclusions touching at a single point, effectively functioning as a broadband filter. This allows us to perform acoustic frequency response measurements on a real system that confirm the sound isolation capabilities of our design, thereby underscoring its practical potential.