Defect Mode Properties in a 1D Acoustic System Based on Closed Serial Resonators

This study investigates the complex dynamics of waveguides by analyzing periodic structures incorporating closed resonators. We have examined a specific configuration composed of N single resonators, with and without geometrical defects in the main waveguide. The approach adopted is based on the transfer matrix method, enabling detailed analysis of the defect impact and complete characterization of low-frequency resonance phenomena. Under optimal conditions, the structural periodicity of the system leads to the creation of an acoustic band gap where the wave cannot propagate in the structure. Moreover, the presence of a defect has a significant effect on the appearance of localized modes in the acoustic band gap. Increasing the defect guide leads to the generation of multiple resonant modes with high acoustic transmittance. The position of these modes was well controlled by varying the length of the defect. These results are very useful in the field of acoustics, and pave the way for innovative applications such as acoustic filters and high-resolution sensors. This study thus offers an innovative framework for exploiting the effects of defects in waveguide systems, contributing to the evolution of modern acoustic technologies.