Wow, what a boomer! /sarcasm
I bet this joke is incredibly noisy and we can 'hear it' from miles away.
Its going to be diesel/electric so no when its stopped its going to be as quiet as any western nations nuclear submarine. If not quieter.
Only when it moves will it be noisy.
Depends. If it's running on batteries, it's probably fairly quite. It won't be going all the fast, so flow noise won't be much of a factor, and electric motors are pretty quiet. However, if it's running on the surface, or snorting its diesels while at periscope depth, it's toast. If we are deaf and can't hear it, the radar in the P-3 and various helicopters will see it. Then they'll kill it.