You still don't get it, do you? A submarine moving through water displaces water. Move it fast enough, and the bow of the boat will create cavitation, no different from cavitation caused by the screw. That's why even nuclear submarines can't move fast if they are to remain undetected.
Further, that "kettle" in the nuclear reactor, that's a pretty noisy apparatus, much more so than a modern diesel engine.
The diesel engine on a conventional submarine is even louder than a nuclear reactor. For one, the diesel engine vibrates a lot when running, and even though the installations are often rafted, they still transmit vibrations to the hull. Also, when they snorkel, the snorkel transmits vibrations through the water as well. A conventional submarine has to come up to snorkel to recharge the batteries, and if they are pushing the boat fast (say in excess of 5 knots), they are coming up to snorkel at least once a day. And with that noise coming from the engine and snorkel, it renders the sub effectively blind and deaf from using their passive sonars.
In addition, the depth at which the boat operates for snorkelling is usually well above the thermocline, further diminishing the boat's ability to acoustically detect submarine (or surface) threats… including incoming torpedoes.
Also, the snorkel produces a wake on the surface, and if the sub is moving in excess of 5 knots, it produces a fairly large wake that's easily observable from the air.
Nuke subs generally never have any reason to break the surface unless there's a specific need to. That's a big advantage, especially if you have ASW helicopters and aircraft combing the seas with their radars and IR sensors.
The real differentiator would be the quality of the crew; if a particular sub's crew was extremely professional and sound discipline was top notch, it doesn't matter if they are in what should be a noisier boat; they will be a hole in the water.
VSMUT wrote:Yeah, no. The Soviet coastline is nowhere near as congested as the seas around China. Not in any way comparable.
The Soviets had more assets to search their coastlines, period during the Cold War. They had lots more satellites, and more recon aircraft can cover more ground quicker. And the Soviets were pretty good at their craft.