Vibroacoustic properties of plates with tuned Acoustic Black Holes

The Acoustic Black Hole (ABH) is a novel effective passive vibration control method for attenuating bending wave speeds by asymptotically diminishing the beam or plate structural thickness. The wave speed reduction also affects the structural-acoustic radiation and response. It has been shown that embedded ABH cells have a negligible effect on vibration and radiated sound below the first local ABH mode, “cut-on frequency,” which is a critical parameter for improving the low frequency performance of the ABH structural system. In this paper, an investigation was conducted to evaluate, and tailor, the vibration response and resulting structural-acoustic radiation by attaching discrete tuning masses at the center position of each ABH cell. The first local ABH modes were tuned to lower frequencies in order to improve the low frequency vibroacoustic performance of the plate structures. Finite element models were used to evaluate the vibration response, modal loss factors and radiation efficiency performance for several plate configurations. Uniform plates were also modeled as a baseline for comparing to the ABH plates with and without tuning masses. Varying the tuning of adjacent ABH cells exhibited extended effective bandwidth in the reduction of the plate radiation coupling.