Analysis of the physical mechanisms responsible for the Acoustic Black Hole effect

An acoustic black hole (ABH) inserted into a mechanical structure provides effective vibration damping without making the structure heavier. This property is particularly interesting in contexts where mass reduction is important. In practice, the ABH effect embedded in a beam or in a plate results from the combination of a local reduction in thickness and the addition of a thin viscoelastic damping layer. Consequently, an ABH is a weak point in the structure, which leads to the existence of local modes. An ABH can be seen as a penetrable resonant scatterer, with a high density of modes, all critically coupled. These properties intrinsically define the conditions required to obtain a true ABH effect. This definition will be presented and illustrated on examples of increasing complexity.