Transmission of acoustic waves through waveguide structures in two-dimensional phononic crystals

Transmission of acoustic waves through waveguide structures in a two-dimensional phononic crystal made of PVC cylinders arranged on a square array in air is studied. We investigate particularly the transmission through a perfect rectilinear waveguide and waveguides coupled with a side branch resonator. A rectilinear wave guide obtained by removing one row of cylinders in the perfect phononic crystal can support one or several modes falling in the complete band gap of the phononic crystal. The effect of a side branch resonator is to induce zeros of transmission in the spectrum of the perfect guide that appear as narrow dips with frequencies depending upon the shape of the resonator. Most of these theoretical predictions obtained by using the plane wave expansion (PWE) and the finite difference time domain (FDTD) methods are compared to experimental measurements made in the audible frequency range. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)