The Journal, citing unnamed U.S. defense officials, said the sound was picked up by a top-secret system designed to detect enemy submarines.
In an interview with Reuters on Thursday, filmmaker James Cameron, who directed the Oscar-winning movie "Titanic" and has ventured to the wreck in submersibles himself, said he learned of the acoustic findings within a day, and knew what it meant.
"I sent emails to everybody I know and said we've lost some friends. The sub had imploded. It's on the bottom in pieces right now. I sent that out Monday morning," he recounted.
Sonar buoys dropped by aircraft had picked up some sounds on Tuesday and Wednesday that temporarily offered hope that the Titan was still intact and that its occupants were alive and trying to communicate by banging on the hull.
But officials said analysis of the sound was inconclusive and that the noises probably emanated from something else.
"There doesn't appear to be any connection between the noises and the location on the sea floor," Mauger said on Thursday.
REMOTE-CONTROLLED VEHICLES
Robotic craft on the seabed will continue to gather evidence, Mauger said, but it was not clear whether recovering the victims' remains will be possible given the nature of the accident and extreme conditions at those depths.
"We will begin to demobilize personnel and vessels from the scene over the course of the next 24 hours," the admiral said.
The search had grown increasingly desperate on Thursday, when the submersible's estimated 96-hour air supply had been expected to run out if the Titan were still intact, a countdown that proved irrelevant.
The RMS Titanic, which struck an iceberg and sank during its maiden voyage in 1912, killing more than 1,500 people aboard, lies about 900 miles (1,450 km) east of Cape Cod, Massachusetts, and 400 miles (640 km) south of St. John's, Newfoundland.
The undersea expedition to the wreck, which OceanGate has been operating since 2021, cost $250,000 per person, according to the company's website.
Questions about Titan's safety were raised in 2018 during a symposium of submersible industry experts and in a lawsuit by OceanGate's former head of marine operations, which was settled later that year.
The sweeping search covered more than 10,000 square miles of ocean. On Thursday, the deployment of two specialized deep-sea robot vehicles expanded the search farther into the ocean's depths, where immense pressure and pitch-black darkness complicated the mission.
The fate of the tourist submersible captured global attention in part due to the mythology surrounding the Titanic. The "unsinkable" British passenger liner has inspired both nonfiction and fiction accounts for a century, including the blockbuster 1997 "Titanic" movie, which rekindled popular interest in the story.