Unidentified Sounds

From the National Oceanic and Atmospheric Administration, here is something to blow your mind (meaning, mine). The division that is Acoustics Monitoring. They have been recording and listening to oceanic noises since 1991 using the U.S. Navy Sound Surveillance System network and autonomous underwater hydrophones.

The site is overwhelming and full of frightening whimsy. You can listen to all of these specific sounds here, in small ten second to one minute segment audio files: here

I found this because of the unidentified sounds category, particularly the Slow Down (the link above allows you to listen to the Slow Down as it was recorded). According to their website,

This sound was recorded May 19, 1997 on the Equatorial Pacific Ocean autonomous hydrophone array. The sound slowly descends in frequency over about 7 minutes and was of sufficient amplitude to be heard on three sensors at 95W, and 8S, 0, and 8N, at a range of nearly 2,000 km. This type of signal has not been heard before or since. It yields a general location near 15^oS; 115^oW. The origin of the sound is unknown.

These are the spectrograms from the sounds listed.

Volcanic Seismicity

Marine Mammals

Man-Made Sounds

Unidentified Sounds