Case study: Sub-metamaterials for Broadband Aircraft Noise Reduction Across Low and High Frequencies

Controlling broadband noise across the entire frequency spectrum, from low to high frequencies, poses a significant challenge for the aerospace, transportation, and construction industries. Recent research has primarily focused on low-frequency noise control solutions using acoustic metamaterials, but these materials are often limited by their narrow-band resonances. This paper addresses this limitation by presenting a novel sub-metamaterial system that broadens the resonance frequency band from low to high frequencies through a parallel assembly of sub-metamaterials. The proposed system comprises an arrangement of structured metamaterials and Helmholtz Resonators embedded in a layer of glass fiber. By meticulously grouping individual resonant frequencies, this assembly effectively attenuates noise across the desired frequency range. Our research demonstrates promising potential for significant noise reduction within practical constraints, contributing to the development of durable solutions for aircraft noise mitigation over a broad frequency spectrum.