Figure 4: Acoustic measurements of metamaterial response.
(a) Schematic of photonic–acoustic metamaterial hybrid sensing system. The inset shows the configuration and dimension of the fibre optic probe. Scale bar, 40 mm. The metamaterial device was constructed with an array of stainless plates spaced by air gaps. The distance between the air gaps is 1.4 mm and the array periodicity is 3.4 mm. The height and thickness of plates are 40 and 2 mm, respectively. The width of each plate increases from 0.5 to 50 mm with a step of 0.5 mm. (b) Experimental characterization of wave propagation and compression in the metamaterial structure at 7 kHz. (c) Pressure-gain spectra measured at different gap positions Z1, Z2 and Z3, which correspond to gaps 30, 45 and 66 shown in a, respectively. In b,c, the diamond dots represent the experimental data and solid lines represent the simulation results. Different colours of the simulation results correspond to different frequency bands.
