A newly-released audio recording of the Titan submersible’s final moments sheds new light on the timeline of the ill-fated 2023 underwater expedition.

The sound of the implosion was captured on June 18, 2023 by a moored passive acoustic recorder roughly 900 miles away from the deadly event. The brief clip begins with a few moments of relative silence before a deep, sustained rumbling that nears 400 Hz, according to an accompanying frequency graph.

The recording, released by a defense website, comes from a National Oceanic and Atmospheric Administration recorder that was monitoring the area at the time.