Experimental realization of lower-frequency complete band gaps in 2D phononic crystals

The lattice configurations are used to produce the different effects of band gap. Based on the well-known ultrasonic immersion transmission technique, the experimental investigation of acoustic wave propagation in two-dimensional phononic crystals for square, honeycomb and (4.8
²
) lattices of steel rods in water is reported at the same normalized radius. Using the plane-wave expansion method we calculate the band structures of phononic crystal. The configurations of square, honeycomb and (4.8
²
) lattices have an atom-rods, two atoms-rods and four atoms-rods per unit cell respectively. We found the structure of (4.8
²
) lattice can have the advantage over other lattice structures and open the very lower-frequency complete band gap. Also, a good agreement between experimental results of complete band gaps for three lattices phononic crystals and theoretical predictions is obtained. Thus, the (4.8
²
) phononic crystal may help to design the new controlling materials in lower-frequency ranges as noise barriers.