A recipe for making materials with negative refraction in acoustics

TL;DR

This paper provides a detailed method for creating acoustic materials with negative refraction by embedding numerous small particles with specific boundary impedances into a known medium, enabling control over wave propagation.

Contribution

It introduces a practical recipe for fabricating negative refraction acoustic materials through particle embedding, detailing particle distribution and impedance design.

Findings

Method for embedding particles to achieve negative refraction

Calculation of particle density for desired refraction properties

Design guidelines for boundary impedances of particles

Abstract

A recipe is given for making materials with negative refraction in acoustics, i.e., materials in which the group velocity is directed opposite to the phase velocity. The recipe consists of injecting many small particles into a bounded domain, filled with a material whose refraction coefficient is known. The number of small particles to be injected per unit volume around any point $x$ is calculated as well as the boundary impedances of the embedded particles.