Previously unheard audio from the Titan submersible that imploded last summer has been released as part of a new documentary.
Five people lost their lives after OceanGate's submersible descended into the Atlantic Ocean, where it was set to travel to around 12,5000 feet below sea level to view the wreckage of the Titanic.
Approximately one hour and 45 minutes into the trip, the mother ship on the surface lost contact with the Titan, meaning its location was completely unknown.
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The situation prompted a search mission to try and save those on board before they ran out of oxygen, but when pieces of the submersible were discovered in the ocean, it was revealed Titan had suffered a 'catastrophic implosion'.
Now, a new documentary offers further insight to the final moments of the Titan and the five people on board: OceanGate CEO Stockton Rush, French Titanic expert Paul-Henri Nargeolet, UK billionaire Hamish Harding, businessman Shahzada Dawood, and his son Sulaiman Dawood.
The documentary draws attention to banging noises which had been detected by the Canadian Air Force during the search, taking place at 30-minute intervals deep in the ocean.
Reports of the banging led to chilling theories that it could be those on board who were making the noises, perhaps in an attempt to draw attention to themselves and aid in the rescue.
The audio of the banging is featured in the documentary The Titan Sub Disaster: Minute by Minute, which is set to air across two nights on 6 and 7 March.
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In the doc, former Navy Submarine Captain Ryan Ramsey comments: "It could be somebody knocking, the symmetry between those knockings is very unusual.
"It's rhythmic, it's like somebody is making that sound, and the fact that it is repeated is really unusual."
The sound was first recorded at around 11.30pm at night, with the US Navy confirming reports of the noises the next morning.
However, in spite of the theories emerging about the banging, Coast Guard Captain Jamie Frederick said at the time: "With respect to the noises, specifically, we don't know what they are, to be frank with you."
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Speculation that the banging noises were coming from the Titan's crew was dashed when it was determined that the sub had imploded on the day it had gone missing.
Carl Hartsfield, an expert with the Wood Hole Oceanographic Institution, told CBS News there were a number of possible explanations for the sounds, saying: “The ocean is a very complex place, obviously — human sounds, nature sounds, and it’s very difficult to discern what the sources of those noises are at times."