Acoustic Black Holes – Modelling, Shaping, Placement and Application

Acoustic Black Holes (ABHs) are passive acoustic measures that allow the efficient damping of structure-borne sound in plate-like structures. They represent a continuous impedance reduction in a local area of the structure, usually achieved by a material thickness reduction. This leads to high deflections in the ABH, which can be efficiently reduced in combination with a damping patch (including constrained layer damping). This paper summarises essential results on modelling, shaping and placement of ABHs as well as their application to realistic structures. In particular, the challenges of modelling the layer structure in the area of the damping patch in the ABH but also the ABH itself are addressed. The studies are based on numerical simulation results – using the finite element method – which are always compared with experiments. Generic beam and plate structures are used to investigate the basic phenomena. A major focus is on the design parameters (e.g. geometrical parameters of the shape function and outer shape) of the ABH. Furthermore, the challenges and potentials of the ABH integration into other material systems (e.g. wood, additively manufactured structures) are discussed and demonstrated by experiments. In the end, the findings are used to demonstrate the application of ABHs to a real component (oil pan). The results show the great potential of ABHs but also sensitive parameters that need to be considered when designing the measure, to achieve a high level of effectiveness.