Acoustic Black Hole

The term "black hole" is associated with the cosmological phenomenon by the gravitational field of a very massive object. The force of attraction is so great that even light can't get out of this trap. The General Theory of Relativity shows that this capture is associated with slowing down the speed of light, or, more generally, with slowing down the flow of time, from the viewpoint of an external observer. In classical wave physics, there are well known examples of slow propagation of waves. The speed of sound in gas decreases as the temperature decreases in proportion to the square root of the temperature. The speed of bending waves in the rod is proportional to the square root of its thickness. The speed of shear waves in ocean sedimentary rocks depends on how much precipitation has been deposited. The question that, as a result, gave rise to the branch of Black Holes in acoustics is as follows. Is it possible to slow down the propagation of a wave on a way of finite length, so that the propagation time would be infinite? However, the change must not be too sharp, so that there would be no reflections from the intermediate sections. The answer is - Yes. Based on aforementioned discussion, this lecture start from the birth and growth of acoustic black hole (ABH) research with a historical review. Then, a couple of studies done by the authors are explained in theoretical, numerical and experimental aspects. This lecture ends with the efforts and trials for practical application of ABH to real-world problems with a short concluding remark on perspectives and opportunities of ABH for the researchers in structural vibrations, vibro-acoustics, and wave physics.