Unexplained sounds OCT 15 2012
Every once in awhile, something somewhere will make a sound and no one really knows where it came from. Among the unexplained sounds listed on Wikipedia are mistpouffers, The Bloop, The Hum, and Julia.
The NOAA's Dr. Christopher Fox does not believe its origin is man-made, such as a submarine or bomb, or familiar geological events such as volcanoes or earthquakes. While the audio profile of the Bloop does resemble that of a living creature, the source is a mystery both because it is different from known sounds and because it was several times louder than the loudest recorded animal, the blue whale.