Fig. 6: Directional sound propagation with acoustic metamaterials.
From: Directional sound propagation in acoustic artificial structures
a-d Directional emission in a zero refractive index metamaterial: a Three-dimensional dispersion surfaces near Dirac-like cone. Measured pressure fields radiated by acoustic point source embedded (b) in the zero refractive index metamaterial and (c) in the empty waveguide. d Directivity of collimated plane wave. The blue circles and red curves represent pressure field radiations from (b) and (c), respectively. Adapted with permission from ref. 69., Copyright © 2017, Marc Dubois et al. e-h Bioinspired conformal transformation acoustics for acoustic collimation: e Sound-speed distribution in the artificial forehead. f Schematic illustration of the bioinspired artificial model assembly. g Normalized sound intensity distribution of the artificial model at 30 kHz. h Directional pattern of the artificial model. Adapted with permission from ref. 70., Copyright © 2020, American Physical Society.
