Fig. 2. Probing acoustic satellite Dirac cones.

a Photograph of the PC. The upper inset shows a zoomed-in view of the structure, while the lower inset illustrates the first longitudinal cavity mode. b Schematic of the PC design to achieve strong TNN couplings. The labeled parameters are $h_0=35\mathrm{mm}$, $r_0=6\mathrm{mm}$, $r_1=r_3=1.55\mathrm{mm}$ and $d=3.46\mathrm{mm}$. The dashed hexagon labels a unit cell. c Acoustic dispersions obtained from experiments (colormaps), simulations (orange curves) and the tight-binding model (white dashed lines), respectively. The inset denotes the schematic for BZ. d, e Measured acoustic dispersions (colormaps) along $K{\Gamma }_1$ and $K{\Gamma }_2$, respectively.