Ultra Thin Acoustic Metamaterial Panels Based on Resonant Bricks for Perfect Absorption
Résumé
Perfect absorption by an ultra thin acoustic metamaterial panel working in reflec- tion is theoretically and experimentally reported in this work. The system is made by a rigid panel with a periodic distribution of thin closed slits, the upper wall of which are loaded by Helmholtz Resonators (HRs). The propagation in the slit is highly dispersive due to the presence of the resonators, producing a slow sound propagation before the HRs resonance, and down shifting the resonance frequency to low values. By controlling the geometry of the HRs, the visco-thermal losses can be tuned in order to compensate the leakage of the system and ful- fill the critical coupling condition so activating the perfect absorption of sound. Theoretical predictions and experimental results show the possibility to design simple structures with deep sub-wavelengths dimensions (λ/88).