Web Urbanist has an interesting list (with video) of 8 Mysterious Unsolved Sounds. I didn’t know about these before and they’re pretty cool and interesting.
- The Bloop
- The Hum
- Bizarre Booms
- The ‘Slow Down’ Sound
- Quacker
- The Spooky Sounds From Saturn’s Rings
- The UVB-76 Buzzer
- The ‘Wow’ Signal