ScienceDaily (Sep. 17, 2012)
Black holes that get deformed, because of other black holes or stars crashing into them, are known to emit a new sort of radiation, called gravitational waves, which Einstein predicted nearly a hundred years ago.
Gravitational waves are ripples in the fabric of spacetime that travel at the speed of light but they are extremely difficult to detect.
Kilometer-sized laser interferometers are being built in the US, Europe, Japan and India, to detect these waves from colliding black holes and other cosmic events. They are sensitive to gravitational waves in roughly the same frequency range as audible sound waves, and can be thought of as a microphone to gravitational waves.
Two black holes orbiting around each other emit gravitational waves and lose energy; eventually they come together and collide to produce a black hole that is initially highly deformed. Gravitational waves from a deformed black hole come out not in one tone but in a mixture of a number of different tones,