A recording of a mysterious sound picked up during the search for the ill-fated submersible was released. It is heard for the first time in a new documentary, “The Titan Sub Disaster: Minute by Minute.” The world held its breath last summer after the Titan was lost with five men on board, including the vessel's designer, Stockton Rush. The discovery of the banging sounds soon after the search began raised hopes they were still alive. The Titan later imploded, killing all on board instantly.