Resonant pillar-type acoustic black hole for ultralow frequency vibration reduction

This paper proposes a resonant-type acoustic black hole (ABH). The ABH is achieved with gradient refractive index varies from the center of the lens to its outer surface. The performance of wave focusing and vibration reduction via the ABH is explored theoretically and numerically. Results show that the designed ABH can achieve wave focusing inside the lens and provide good vibration reduction at low frequency.