Ultra-broadband Noise-Insulating Periodic Structures Made of Coupled Helmholtz Resonators

TL;DR

This paper demonstrates methods to significantly broaden the operational frequency range of acoustic metamaterials using coupled Helmholtz resonators, through tuning local coupling and structural modifications, verified by experiments.

Contribution

It introduces novel techniques for ultra-broadband noise insulation in periodic structures by controlling local coupling and structural parameters, supported by optimization and experimental validation.

Findings

Tuning local coupling creates ultra-broad stop-bands.

Chirped structures and lossy resonators enhance bandwidth.

Experimental results confirm numerical predictions.

Abstract

Acoustic metamaterials and phononic crystals represent a promising platform for the development of noise-insulating systems characterized by a low weight and small thickness. Nevertheless, the operational spectral range of these structures is usually quite narrow, limiting their application as substitutions of conventional noise-insulating systems. In this work, the problem is tackled by demonstration of several ways for the improvement of noise-insulating properties of the periodic structures based on coupled Helmholtz resonators. It is shown that tuning of local coupling between the resonators leads to the formation of ultra-broad stop-bands in the transmission spectra. This property is linked to band structures of the equivalent infinitely periodic systems and is discussed in terms of band-gap engineering. The local coupling strength is varied via several means, including introduction of the so-called chirped structures and lossy resonators with porous inserts. The stop-band engineering procedure is supported by genetic algorithm optimization and the numerical calculations are verified by experimental measurements.