In 1997, the National Oceanic and Atmospheric Administration recorded "the bloop," a one-minute sound emanating 1,500 miles west of Chile's southern coast. The unexplained sound was never recorded again.
The ultra low-frequency sound was so loud that sensors nearly 2,000 miles apart both recorded it. They took it to Navy intelligence in case it was some classified sound, but they said it was not theirs. It was many times louder than a blue whale. After listening to Cara Cusumano's moody piece for The Atlantic above, check out Coventry Paranormal's analysis, including the bloop played at 16 times normal speed.
They spin through the theories of massive life forms, then conclude it was a cyroseism, or an icequake caused by calving icebergs in Antarctica. They include some other weird sounds of unknown or unconfirmed origin.