The mysterious knocking sounds heard for the first time beneath the Atlantic Ocean gave hope of life to the families of those trapped inside the doomed Titan submersible.

The Titan was destroyed a few hours into a dive to the Titanic shipwreck on June 18, which took the lives of OceanGate Expeditions CEO Stockton Rush, father and son Shahzada and Suleman Dawood, Hamish Harding, and Paul-Henri Nargeolet.

Mystery Banging Sounds Heard in Titanic Submarine

US Coast Guard officials revealed that sonar devices had detected tapping sounds from the extensive search area in the North Atlantic Ocean during a frantic and ultimately futile multi-day search for survivors.

The search and rescue operation was led by the Royal Canadian Air Force, which recently released the audio of the repetitive knocking sounds to the creators of a new documentary, 'Minute by Minute: The Titan Sub Disaster.'

According to The Independent, the documentary, which will air on Channel 5 in the UK on March 6 and 7, will feature rescuers who heard the banging sounds ringing in regular 30-minute intervals.

Former Navy submarine Captain Ryan Ramsey said in the documentary that the symmetry between those knockings is very unusual. Ramsey described the sound as rhythmic and said it was like somebody was making that sound.

The taps were initially detected at around 11:30 pm on June 20. The US Navy confirmed it had also heard the sound the next morning.

International search and rescue teams speculated that the sounds might be survivors knocking on the walls to signal their location when they landed on the Titanic wreck.

Furthermore, the US Coast Guard officials described the noises as "inconclusive" and tried to lower hopes that they were a sign of life.

The hope of the US Coast Guarded ended as they announced on June 28 that they had retrieved "presumed human remains" from the sea floor near the debris about 1,600 feet.

It was later discovered that the sub's carbon fiber hull had collapsed less than two hours after the departure of the support ship, the Polar Prince. The extreme water pressure had killed everyone on board in a matter of milliseconds.

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(Photo: IBRAHIM CHALHOUB/AFP via Getty Images)
A picture taken on September 2, 2018, off the shore of the Lebanese town of Khaldeh, about 10 kilometers south of the capital Beirut, at a depth of 38 meters underwater, shows divers near the wreckage of the WWII-era French submarine Souffleur. Souffleur, a Vichy government vessel, was sunk on June 25, 1941, after being torpedoed by the British submarine HMS Parthian during the combined British-Free French campaign in the Levant, leaving 51 crewmembers to drown with only four survivors.

Ex-former OceanGate Director Voiced Safety Concerns

Weeks after the disaster, David Lochridge, a former director of marine operations at OceanGate, revealed that he warned in 2018 that taking shortcuts in the company's design would have deadly consequences.

Rush, who also died on the Titan, was later discovered to have disregarded safety warnings from passengers, industry experts, and former co-workers.

In a wrongful termination complaint, Lochridge claimed that he was met with hostility and denial of access to important papers after discovering multiple problems during a quality inspection process.

Related Article: OceanGate Titan Sub Update: US Coast Guard Claims to Recover More Human Remains-Another Public Hearing to Happen