  The artificial crystals for classical waves provide a good platform to
explore the topological physics proposed originally in condensed matter
systems. In this paper, acoustic Dirac degeneracy is realized by simply
rotating the scatterers in sonic crystals, where the degeneracy is induced
accidentally by modulating the scattering strength among the scatterers during
the rotation process. This gives a flexible way to create topological phase
transition in acoustic systems. Edge states are further observed along the
interface separating two topologically distinct gapped sonic crystals.
