Optimised thermoformed metamaterial panel design with a foam core for improved noise insulation performance

Resonant metamaterials are a lightweight noise insulation solution due to their tunable stop band effect. In previous works, the authors have shown how resonant metamaterials can be manufactured and fully integrated into a thermoformed twin sheet panel. This work shows an design optimisation procedure for the resonant structure of the metamaterial panel, based on its modal effective mass. Additionally, foam is added in the core of the panel, to achieve high noise insulation performance at the high-frequency range, which is deteriorated by the slits introduced to create the resonant structures. Two panels are designed, targeting single and double stop bands. Their insertion loss is experimentally evaluated, showing a pronounced noise insulation performance at the stop band targeted frequency, and no loss of noise insulation in the high-frequency range thanks to the foam addition. Therefore, this work shows that resonant metamaterials can be designed through optimisation and work in synergy with classical solutions while keeping a lightweight design.status: accepte