Airborne Minnaert-Like Resonance of an Air-Filled Elasto-Bubble

TL;DR

This paper introduces air-filled elastomer shells called elasto-bubbles that mimic bubble-like Minnaert resonances in air, enabling new applications in airborne acoustic metamaterials and filters.

Contribution

It demonstrates that soft elastomer shells can achieve deep-subwavelength monopolar resonances in air, modeled accurately without adjustable parameters.

Findings

Elasto-bubbles sustain strong monopolar resonances despite being subwavelength.

Resonance frequency, transmission dip, and absorption are quantitatively captured by the model.

Shell radius and thickness can be independently tuned during fabrication.

Abstract

Deep-subwavelength acoustic resonators are key building blocks of acoustic metamaterials, yet achieving bubble-like resonances in air remains challenging because the Minnaert mechanism relies on the inertia of a surrounding liquid. Here we demonstrate that air-filled soft elastomer shells, termed elasto-bubbles, realize an airborne analogue of the Minnaert resonator. Using impedance-tube measurements together with the theory of layered-bubble scattering, we show that these soft hollow capsules sustain strong monopolar resonances despite being deeply subwavelength. Their resonance frequency, transmission dip, and absorption are quantitatively captured, without adjustable parameters, by a model accounting for shell elasticity and viscoelasticity. Because shell radius and thickness can be tuned independently during fabrication, elasto-bubbles provide a simple and versatile platform for airborne acoustic metamaterials, resonant absorbers, and acoustic filters.