Interesting - Voyager 1 captures the Sounds of Interstellar Space:

Voyager 1 just left the Earth's Solar System and sent back the "sound of interstellar space". NASA's Voyager 1 spacecraft captured these sounds of interstellar space. Voyager 1's plasma wave instrument detected the vibrations of dense interstellar plasma, or ionized gas, from October to November 2012 and April to May 2013.
The graphic shows the frequency of the waves, which indicate the density of the plasma. Colors indicate the intensity of the waves, or how "loud" they are. Red indicates the loudest waves and blue indicates the weakest.

Voyager Captures Sounds of Interstellar Space