Band gap and defect state engineering in a multi-stub phononic crystal plate

Abstract

In this paper, we investigated the characteristics of band gaps and defect states in a locally resonant phononic crystal structure consisting of multiple square stubs deposited on both sides of a thin homogeneous plate. Using the finite element method and supercell technique, we calculated the dispersion relationships and power transmission spectra of this structure, which agree well with each other. This structure offers wide band gaps at extremely low frequencies. Moreover, we investigated how the band gaps are affected by the distance between two adjacent square stubs, finding that acoustic band gaps are very sensitive to the distance between two adjacent square stubs, a property important for practical applications. Based on this finding, we proposed a novel method to form phononic crystal structure defect: Defect bands can be induced by creating defects inside the original complete band gaps. The frequency can then be tuned by changing the distance between two adjacent square stubs of the defect scatterer. These results will help in fabricating devices, such as acoustic filters and waveguides whose band frequency can be modulated.