Acoustic Beam Splitting and Cloaking Based on a Compressibility-Near-Zero Medium

We report an artificial acoustic compressibility-near-zero medium made of a phononic crystal composed epoxy blocks arranged in square lattice. Its anisotropic effective density leads to linear cross its isofrequency contour the vicinity Brillouin zone center, as compressibility approaches zero. When Gaussian beam is normally incident on crystal, splitting effect achieved at frequency crossing point. Based such beam-splitting effect, cloaking irregular-shaped object embedded demonstrated both theoretically and experimentally. Such zero-index material offers potential method control waves.