Characteristics of multi-point defect modes in 2D phononic crystals

The characteristics of multi-point defect modes in 2D phononic crystals composed of aluminium circular cylinders/air square lattices were studied based on the plane-wave and supercell methods. The result indicates that two point defects separated the defect modes and the width between the frequencies of the two defect modes decreases as the distance between two point defects increases. The defect modes of multi-point defects can be decoupled in some directions where the defect mode decays rapidly, even if the distance between the point defects is close. These characteristics of multi-point defect modes will be useful in the implementations of directional sonic filters and narrow band sonic waveguides.