Guiding and filtering acoustic waves in a two-dimensional phononic crystal

An experimental and theoretical study of the guiding, bending and filtering of acoustic waves in an ultrasonic crystal is reported. The crystal consists of a 2D periodical array of steel rods immersed in water, for which a complete acoustic band gap is found experimentally. Waveguides for acoustic waves are created by removing one row of rods and the possibility of including sharp bends, owing to the strong spatial confinement within the full band gap, is demonstrated. Stubs can be further added by removing rods from the side-walls of the waveguide. Depending on the stub geometry, definite wavelengths are reflected from the stubs creating a 1D bandgap within the waveguide transmission spectrum, the bandwidth of which can be controlled by arranging a proper sequence of stubs.