An active acoustic metamaterial for the control of sound transmission

Abstract

Metamaterials have received significant interest in recent years due to their potential ability to exhibit behaviour not found in naturally occurring materials. This includes the generation of band gaps, which are frequency ranges with high levels of wave attenuation. In the context of acoustics, these band gaps can be tuned to occur at low frequencies where the acoustic wavelength is large compared to the material, and where the performance of traditional passive noise control treatments is limited. Therefore, such acoustic metamaterials have been shown to offer a significant performance advantage, however, due to their resonant behaviour, the band gaps tend to occur over a relatively narrow frequency range. Previous work has demonstrated that a significant increase in performance can be achieved by incorporating active control elements into acoustic metamaterials. This paper demonstrates how the performance of an acoustic metamaterial, consisting of an array of Helmholtz resonators, can be significantly enhanced through active control. Loudspeakers are embedded into the resonators and these are driven via a fixed broadband feedforward control scheme to minimise the transmitted pressure. It is demonstrated that by incorporating the active mechanism into the acoustic metamaterial a significant enhancement in the transmission loss is achieved.

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ORCID for Jordan Cheer: orcid.org/0000-0002-0552-5506

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