Acoustic Black Holes for Flexural Waves: A Smart Approach to Vibration Damping

The present paper provides a brief review of the theoretical and experimental investigations of 'acoustic black holes' for flexural waves in plate-like structures. Such acoustic black holes are relatively new physical objects that can absorb almost 100% of the incident wave energy. This makes them attractive for vibration damping in plate-like structures. The main principle of the acoustic black holes is based on a linear or higher order decrease in velocity of the incident flexural wave with propagation distance to almost zero. The decrease in velocity should be accompanied by efficient energy absorption in the area of very low velocity via insertion of small pieces of absorbing materials. This principle can be applied to achieve efficient damping of flexural waves and vibrations in plate-like structures using both one-dimensional acoustic black holes (power-law-profiled wedges) and two-dimensional acoustic black holes (power-law-profiled cylindrical indentations). The key advantage of using acoustic black holes for damping structural vibrations is that it requires very small amounts of added damping materials, in comparison with traditional methods, which is especially important for vibration damping in light-weight structures.