  The extremal transmission of acoustic wave near the Dirac point in
two-dimensional (2D) sonic crystal (SC), being inversely proportional to the
thickness of sample, has been demonstrated experimentally for the first time.
Some unusual beating effects have been observed experimentally when the
acoustic pulse transport through the 2D SC slabs. Such phenomena are completely
different from the oscillations of the wave in a slab or cavity originating
from the interface reflection or Fabry-Perot effect. They can be regarded as
acoustic analogue to Zitterbewegung of relativistic electron. The physical
origination for the phenomenon has been analyzed.
