Loss factor estimates for plates with periodic grids of embedded Acoustic Black Holes

Embedded Acoustic Black Holes (ABH) have significant potential as a passive treatment for attenuating structural vibration. The ABH effect is produced using a power taper in the plate structure thickness profile, resulting in a local asymptotic reduction of wave speed within the ABH. Theoretically the local wave speed approaches zero at the ABH center, thus the waves are "trapped" in the black hole. This work focused on plates with periodic grids of ABHs for structural vibration and radiated sound reduction. Plates with embedded ABH grids were modeled with finite element models, with the active and reactive air loading modeled with coupled boundary element models. The results show the ABHs reduce the radiated sound power by up to 20 dB. The reduction of radiated sound is due to both an increase in the mechanical damping and also a reduction in the plate structural-acoustic coupling. Detailed results for several ABH plates are compared with uniform plates, giving insight into key ABH design performance parameters.