https://turbofuture.com/industrial/The-Worlds-Most-Mysterious-Noises-Broadcasts-and-Transmissions
http://www.smashinglists.com/10-unexplained-sounds/
http://www.sciencealert.com/apollo-10-astronauts-heard-eerie-music-on-the-far-side-of-the-moon-declassified-nasa-audio-reveals
http://hubpages.com/education/Strange-sounds-in-the-sky-from-around-the-world
http://www.wired.co.uk/article/bloop-mystery-not-solved-sort-of
http://www.pmel.noaa.gov/acoustics/sounds/noise97139.wav
https://en.wikipedia.org/wiki/List_of_unexplained_sounds