"Well, that sounded like a concert in a cosmic stalactite cave and leads us back to the bottom of our earthly seas. This and the next three posts are about very special sounds from the depths of the oceans!"
2010 April 27
The Bloop: A Mysterious
Sound from the Deep Ocean
* Credit: NOAA, SOSUS
https://www.pmel.noaa.gov/eoi/
https://irp.fas.org/program/collect/sosus.htm
Explanation: What created this strange sound in Earth's Pacific Ocean? Pictured above is a visual representation of a loud and unusual sound, dubbed a Bloop, captured by deep sea microphones in 1997. In the above graph, time is shown on the horizontal axis, deep pitch is shown on the vertical axis, and brightness designates loudness. Although Bloops are some of the loudest sounds of any type ever recorded in Earth's oceans, their origin remains unknown. The Bloop sound was placed as occurring several times off the southern coast of South America and was audible 5,000 kilometers away. Although the sound has similarities to those vocalized by living organisms, not even a blue whale is large enough to croon this loud. The sounds point to the intriguing hypothesis that even larger life forms lurk in the unexplored darkness of Earth's deep oceans. A less imagination-inspiring possibility, however, is that the sounds resulted from some sort of iceberg calving. No further Bloops have been heard since 1997, although other loud and unexplained sounds have been recorded.
https://apod.nasa.gov/apod/ap100427.html
Original icequake (bloop) sound:
The broad spectrum sounds recorded in the summer of 1997 are consistent with icequakes generated by large icebergs as they crack and fracture. NOAA hydrophones deployed in the Scotia Sea detected numerous icequakes with spectrograms very similar to “Bloop”. Recorded signal sped up 16 times.
[...]
https://www.pmel.noaa.gov/acoustics/specs_cryogenic.html
CREDIT
DOC / NOAA/ OAR / PMEL / Acoustics Program