  The analogy between sound wave propagation and light waves led to the study
of acoustic holes, the acoustic analogues of black holes. Many black hole
features have their counterparts in acoustic holes. The Kerr metric, the
rotating metric for black holes in general relativity, has as analogue the
draining bathtub metric, a metric for a rotating acoustic hole. Here we report
on the progress that has been made in the understanding of features, such as
quasinormal modes and tails, superresonance, and instabilities when the hole is
surrounded by a reflected mirror, in the draining bathtub metric. Given then
the right settings one can build up from these instabilities an apparatus that
stores energy in the form of amplified sound waves. This can be put to wicked
purposes as in a bomb, or to good profit as in a sonic plant.
