Astrophysics Lecture Series ( Black Holes Sing) Prof. Janna Levin of Barnard College Columbia University.

Black Holes may be heard but not seen. As the death state of a

star, black holes emit no light.They are dark against the dark sky. But like

mallets on a drum, black holes can ring out a song on space

itself. Monumental Earth and spaced-based missions aim to record the

songs from space for the first time thereby turning up the volume on the

soundtrack to the Universe.