Acoustic metamaterial exhibiting four different sign combinations of density and modulus

TL;DR

This paper reports the fabrication and experimental analysis of an acoustic metamaterial that exhibits four different sign combinations of density and modulus, enabling advanced acoustic manipulation.

Contribution

The study introduces a double negative acoustic metamaterial with experimentally demonstrated sign transitions and a wide negative refractive index range, advancing acoustic metamaterial design.

Findings

Demonstrated three frequency points with sign transitions in density and modulus.

Achieved a wide negative refractive index from -0.06 to -3.7.

Provided experimental data on transmission and dispersion relations.

Abstract

We fabricated a double negative acoustic metamaterial which consisted of Helmholtz resonators and membranes. Experimental data on the transmission and dispersion relation are presented. The system exhibits three frequencies where the acoustic state makes sharp transitions from density negative ({\rho} -NG) to double negative (DNG), modulus negative (B-NG), and double positive (DPS) in sequence with the frequency. We observed a wide range of negative refractive index from -0.06 to -3.7 relative to air, which will allow for new acoustic transformation techniques.