The USN has long maintained that modern diesel-electric subs are inherently quieter than nukes (which have to keep pumps going to cool the reactor.) Underscoring this long held view, a recent two week training exercise between a new Australian Collins class diesel-electric sub (HMAS Sheean) and a U.S. Los Angeles class attack sub (USS Olympia), saw the Australian sub constantly holding it's own. Whether playing the hunter or the prey, the Australian sub scored the same number of hits as the American SSN. The only solace the Americans could take from this was that the Sheean crew was well trained and were in a modern boat. Most of the hostile nations U.S. subs are likely to face have older boats and poorly trained crews.