Experimental determination of acoustic bands in two‐dimensional sonic band gap crystals

The dispersion relation of acoustic bands in sonic band gap crystals built up with periodic arrays of rigid cylinders in air have been characterized both experimentally and theoretically. A technique based on the analysis of the phase‐shift experienced by the sound is used to construct the experimental acoustic dispersion relation. Measurements have been performed in square, triangular, and honeycomb lattices for different filling fractions. The experimental setup also allows to detect the so‐called ‘‘deaf bands’’ [J. V. Sanchez‐Perez et al., Phys. Rev. Lett. 80, 3080–3083 (1998)]. A variational method is employed to calculate the corresponding acoustic bands. The good agreement between theory and experiment supports the experimental technique here described as an important characterization tool for these systems. [Work supported by CyCIT of Spain and Generalitat of Valencia.]