Fig. 7: Meta-cages based on Helmholtz resonance.
From: Resonance-based acoustic ventilated metamaterials for sound insulation
a The meta-cage comprises an axisymmetric array of cylindrical columns which are constructed from Helmholtz resonators, with corresponding transmission loss spectra for both internal and external acoustic source configurations. Reproduced with permission from ref. 125. b The meta-cage constructed with the metamaterial, which is composed of periodically arranged resonant cavities in series, with a star-shaped opening. Reproduced with permission from ref. 126.
