Sonar technology may have been key in locating doomed Titan submersible, N.S. expert says

Underwater acoustic sensing may have been the key to locating the wreckage of the Titan submersible, according to a Nova Scotia-based sonar expert.

The Titanic-bound submersible lost communication with its surface vessel on Sunday, leading to a massive international search.

The wreckage of the submersible was found by a remotely operated vehicle on the seafloor about 500 metres from the Titanic's bow on Thursday. All five passengers and crew of the Titan are presumed dead.

The same day, the United States Navy said it had detected an acoustic "anomaly consistent with an implosion" in the area hours before the vessel was reported missing. 

It said it shared the information with the Canadian Coast Guard and officials from OceanGate Expeditions, the company operating the Titan.

Canada's Department of National Defence confirmed Friday that the data was shared with them but the "information assessment was not definitive" that the submersible was the source of the sound. 

Joe Hood, the vice-president of sonar processing for GeoSpectrum Technologies in Dartmouth, N.S., said to detect the sound, the U.S. Navy must have had a ship, a submarine or possibly an aircraft with sonar equipment within a few kilometres of the area.

Hood said an underwater sound like an implosion happens quickly, but sound travels relatively slowly in water at about 1,500 metres a second.

Hyperbolic fixing

With multiple sensors on sonar equipment, Hood said the arrival time of the sound at each sensor could be used to estimate a position for the sound — a process called hyperbolic fixing.

But Hood said even if the sound of an implosion was detected it would require analysis to determine its source.

"There's lots of things that can make those short duration sounds in the water," Hood said.

 "It could have been somebody banging on the hull to get attention, it could have been cracking of the hull, it could have been the hull failing, or it could have been fish in the area making grunts and pop noises."

Hood said it's unlikely that any of the sounds could have come from the Titanic itself as there wouldn't have been enough of a current at that depth and the wreck would have settled by now.

Once the search and rescue operation was underway, Hood said there were other possible ways to gather sound.

Underwater microphones

He said, based on reports he saw, there was a CP-140 aircraft on site which would have sonobuoys, a type of buoy with a radio transmitter and an underwater microphone on board.

Hood said sonobuoys are dropped in the water and deploy the underwater microphone to a specified depth. Sounds detected by the microphone are relayed by the transmitter.

He said four or more sonobuoys would have been needed to estimate the position of the submersible based on any sound coming from it. 

Hood said the situation of the submersible was "certainly odd."

He said aircraft and military submarines have an underwater locator beacon — called a pinger — to alert people to their location if they go missing at sea.

"We've had similar situations in the past where people have tried to find these underwater pingers," Hood said

"In this case, I don't know if there was a pinger on board the submersible."

The Transportation Safety Board of Canada said Friday it is launching an investigation into the operation of the Titan submersible by the Polar Prince Support vessel. The Polar Prince is a Canadian registered vessel.