“Astronomers have detected the deepest note ever generated in the cosmos, a B-flat flying through space like a ripple on an invisible pond,” trumpets an article on the website Science.com. The discovery was made in 2003 by NASA’s Chandra X-ray Observatory, which attributes the sound to a black hole in the Perseus cluster, the on-ramps of which spin off gas in waves strong enough to warm interstellar space. The tone thus generated stands 57 octaves below the middle-C note on a piano, and is therefore inaudible to the human ear. It has been sounding across the universe for 2.5 billion years.

George Michelsen Foy, Zero Decibels, loc. 278