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The original was posted on /r/todayilearned by /u/PabloTheUnicorn on 2023-06-21 23:16:51+00:00.

Original Title: TIL that when the submarine ARA San Juan disappeared in 2017, initial search crews picked up a banging noise at the search site, like tools hitting metal. After analyzing the audio, it was determined the sound was not from the submarine and was probably from a biological source.