Métasurfaces acoustiques absorbantes large bande en régime basses fréquences

Achieving broadband sound absorption below 500 Hz remains challenging, even with metamaterials and metasurfaces, especially when the absorber must be thin (thickness << λ) due to size or structural restrictions. Solving this challenge with passive metamaterial super-cells relies on coupled resonant unit-cells and controlled impedance matching. This dissertation conceptualises, designs, numerically analyses, and characterises metasurfaces aimed at absorbing acoustic noise experienced by passengers in aeroplanes during flight. The goal is to achieve acoustic absorption between 100 and 500 Hz with a metasurface absorber no thicker than 50 mm (∼ λ/68). The designs target two frequency ranges: 300-500 Hz and 100- 200 Hz. A new hybrid metasurface is introduced, incorporating a simple design element to the conventional coiled Helmholtz resonator (HR) super-cell metasurface, which significantly increases the absorption bandwidth. It demonstrates a bandwidth of 307 to 571 Hz, improving it by around 100 Hz at 50% absorption. An optimised variant reaches over 79% absorption from 300 to 508 Hz. At 100-200 Hz, the hybrid metasurface doubles the absorption bandwidth compared to the conventional design. In-depth analysis provides strong indication for the presence of both local and nonlocal coupling between the unitcells and the ability to manipulate pole-zero pairs in novel ways, not previously reported in the literature. A lumped electric equivalent model for the hybrid metasurface is also introduced and analysed.