  A reconfigurable phononic crystal (PnC) is proposed where elastic properties
can be modulated by rotation of asymmetric solid scatterers immersed in water.
The scatterers are metallic rods with cross-section of 120{\deg} circular
sector. Orientation of each rod is independently controlled by an external
electric motor that allows continuous variation of the local scattering
parameters and dispersion of sound in the entire crystal. Due to asymmetry of
the scatterers, the crystal band structure possesses highly anisotropic
bandgaps. Synchronous rotation of all the scatterers by a definite angle
changes regime of reflection to regime of transmission and vice versa. The same
mechanically tunable structure functions as a gradient index medium by
incremental, angular reorientation of rods along both row and column, and,
subsequently, can serve as a tunable acoustic lens, an acoustic beam splitter,
and finally an acoustic beam steerer.
