Acoustic black holes
  We discuss some general aspects of acoustic black holes. We begin by describing the associated formalism with which acoustic black holes are established, then we show how to model arbitrary geometries by using a de Laval nozzle. It is argued that even though the Hawking temperature of these black holes is too low to be detected, acoustic black holes have interesting classical properties, some of which are outlined here, that should be explored. 
Vitor Cardoso