Wave guiding and wave modulation using phononic crystal defects

In this article, we address the effect of regular and irregular distribution of phononic lattices on acoustic wave and investigate wave bending and refraction phenomena for some specific patterns of phononic crystals consisting of a square array of polyvinylchloride cylindrical rods in air matrix using finite element model. Bucay et al. have demonstrated that for a given configuration, the striking acoustic beam angle varying between 20° and 40° at 14.1 kHz central frequency shows positive, negative, and zero angle refraction inside phononic crystal and exhibits beam splitting after exiting the phononic crystal. These results are used as the benchmark in this article to validate the proposed model. Transmission spectrum in the phononic crystal has been studied for complete acoustic band gap as well as for positive and negative dispersion bands at frequencies ranging from 1 to 18 kHz. Using this established theory, in this article, the acoustic beam propagation through irregular phononic crystal structures and waveguides are investigated. It can be seen that small irregularity produces significant change in the acoustic field. It is shown that with a localized defect, resonating cavity waveguide is formed in the proposed acoustic metamaterials.