Low-frequency band gap and defect state characteristics in a multi-stub phononic crystal plate with slit structure

Abstract

In this paper, we investigated the low-frequency characteristics of band gaps and defect state in a two-dimensional phononic crystal structure consisting of multiple square stubs deposited on both sides of a thin slotted plate. Using the finite element method, we calculated the dispersion relationships and power transmission spectra of this structure, which agree well with each other. In contrast to a system of homogeneous plate, system of slotted plate show wide band gaps and an increased quantity of band gaps at lower frequencies. In addition, based on the finding that acoustic band gaps are very sensitive to the distance between the two adjacent square stubs in our earlier works, we investigated the point defect state in the multi-stub phononic crystal plate with slit structure. Through changing the distribution of stubs in specific scatterers, the defect phononic crystals are formed. We designed and fabricated the defect phononic crystal experimental platform to verify the existence of defect bands in the phononic crystal structure. Results show that defect bands can be induced by creating defects inside the original complete band gaps. These results will help in fabricating devices, such as acoustic filters whose band frequency can be modulated.