http://io9.com/5294348/sonic-black-hole-swallows-every-so...

Israeli scientists have recently devised a “sonic black hole;” any sound that passes its edge can never come out again. This is achieved by two clouds of atoms (called a Bose-Einstein condensate) cooled to almost absolute zero, with a pool of very low density between them. Atoms can flow very rapidly, pretty much unhindered, into this area of low density at speeds over four times the speed of sound.

Gustavo Araoz Community Contributor posted about 2 years ago