The Titan submersible. Photo: Handout / OceanGate Expeditions / AFP
By Georgie Hewson, ABC News
A new clip from a documentary about the Titan Submersible disaster shows never before released audio of banging noises heard by rescuers during their search for the vessel last year.
In June 2023 five passengers were killed when the submersible vessel they were in imploded during a trip to explore the wreckage of the Titanic.
For several days rescue crews from all over the world searched for the vessel after it lost contact with its mother ship just under two hours into the dive, with many initially hopeful they were still alive.
But after several days of searching in a remote area of the North Atlantic, debris was discovered 500 metres from the bow of the Titanic on 22 June.
On 20 June, two days into the search, the Canadian Navy's sonar picked up noises.
They reported "banging noises" at 30 minute intervals.
"That changed everything," American journalist Ryan Cooke said in the documentary clip.
The noises sound like a rhythmic and repeated knock on a door.
"It's like somebody is making that sound and the fact that it is repeated, is really unusual," former navy submarine captain Ryan Ramsey said in the clip.
The audio, which has never before been released to the public, was given to the documentary by the Canadian Air Force team which led the search-and-rescue effort.
The sounds in the Titan search were picked up using devices called sonobuoys, which can be tossed out of aeroplanes to detect noises, to avoid interference with ship sounds.
At the time, US Coast Guard Captain Jamie Frederick said that analysis of the noises had been inconclusive.
"When you're in the middle of a search-and-rescue case, you always have hope," he said.
"With respect to the noises specifically, we don't know what they are, to be frank with you."
But the clip describes how the development gave many hope the five passengers could have been alive.
There is still no confirmed explanation of the noises.
An investigation by US and Canadian authorities into the disaster is still underway.
The US Coast Guard said it had transferred the remaining debris from the North Atlantic Ocean Floor in October last year.
The last update from the United States Coast Guard on the investigation was on 15 November.
It said the US Coast Guard, National Transportation Safety Board (NTSB), Transportation Safety Board of Canada (TSB) and the French Marine Casualty Investigation Authority (BEAmer) conducted an evidence review of recovered Titan submersible debris.
"The Marine Board of Investigation will continue its evidence analysis and witness interviews as part of the ongoing investigation, leading up to a public hearing addressing the tragedy."
The documentary, The Titan Sub Disaster: Minute by Minute, will air in the UK in March.
This story was originally published by the ABC.