Decades Ago a Huge Noise Roared in The Ocean. For Years It Was a Mystery. : ScienceAlert

In 1997, a deep belch echoed through the belly of Earth’s oceans. The super low-frequency sound came out like a sliding ‘bloooop’.

For years, it remained the loudest unidentified noise ever recorded underwater.

Scientists called it the Bloop.

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Theories on where the eerie sound came from have since abounded. Perhaps it was the noisy product of underwater military exercises or ship engines. Some even…