The SOSUS network was declassified in 1992, and has been (most likely) partially decommissioned in recent years. But much of the hardware still remains operational, hence my suggestion that the US Navy may have detected the sound of the submersible’s demise, especially only several hundred miles off the Canadian coast.
They had the sound of the USS Scorpion imploding in 1968 off the coast of the Azores.............
SOSUS perhaps. It’s replacement probably not so much.