Reply to post:

I think that you have to consider more than just the quietness of a conventional verses nuclear submarine.

Whilst you have a point, it needs to be noted that nuclear submarines are larger, and so can bury the cooling system deeper in the hull, can dive deeper so can put more distance between them and the surface ships, and can travel much faster underwater than a conventional boat can. All of these things make just the noise of the boat at rest less important.

It has long been the case that the best way of sinking a nuclear submarine is by attacking it with another nuclear submarine. Even at it's quietest, a conventional submarine is relatively easy to locate (because it has to come very close to the surface regularly), and would not be effective against nuclear submarines because of their limited speed, endurance and depth of dive characteristics.

When it actually comes to noise, there is a huge difference between different country's submarine fleets. Russian submarines were always regarded as being noisy (although I've read that the more modern boats are a lot better), whereas UK designed boats have long been regarded as being very quiet, so much so that the US commercially licensed the pump-jet propulsion system used in the Swiftsure and Trafalgar classes (but not Trafalgar herself), and obtained a number of other technologies as part of the Trident II technology deal.