Negative Effective Density in An Acoustic Metamaterial

TL;DR

This paper introduces a new acoustic metamaterial with negative effective mass density, demonstrated through theoretical modeling and experimental validation, showing negative density below 735 Hz in a membrane-structured tube.

Contribution

It presents the first experimental realization of a one-dimensional acoustic metamaterial with negative effective density, aligning with a new theoretical model.

Findings

Negative effective density observed below 735 Hz

Experimental results match theoretical predictions

Analogous behavior to electromagnetic plasma oscillation

Abstract

We report theoretical and experimental results for a new type of homogenized acoustic metamaterials with negative effective mass density. We constructed one-dimensional metamaterial, which is a tube with an array of very thin elastic membranes placed inside. This structure exhibited negative effective density in the frequency range from 0 to 735 Hz. The experimental result is in excellent agreement with our theoretical model that predicts negative effective density below a cut-off frequency. The frequency characteristics of this effective density is analogous to that of the permittivity of the electromagnetic plasma oscillation.