Sonic-crystal wave-guides by acrylic cylinders in air - experimental observations based on numerical analyses

This work reports numerical analyses and experimental observations of full band-gaps of a sonic crystal made up of a periodic array of acrylic cylinders in air and also guided sound waves highly confined in a sharp 90/spl deg/ bending wave-guide made of sonic crystals. We have clarified the correspondence relationship between sonic crystals and photonic crystals, which are both artificial crystals made of a periodic array of scatterers with a lattice constant of approximately a half wavelength, and obtained the dependence of the full band-gaps on the filling ratio of the scatterers through numerical investigations with the FDTD method. Based on the theoretical results, we have performed experiments and observed the existence of a full bandgap of -30 dB between 7.0 kHz and 9.5 kHz for a sonic crystal of 10/spl times/10 acrylic cylinders in air with a lattice constant of 24.0 mm and a scatterer's diameter of 10.2 mm. Further we have observed well-confined sound waves in a straight wave guide, and also in an sharp bending wave guide with a relative leakage of -30 dB to the guided sound waves, both wave guides being fabricated in the sonic crystal. Other reports of sonic wave guides made of the sonic crystal have not been seen.