@Hoss @whiteline makes sense, nuclear produce steam energy generator noises and electric engine noises, diesel-electrics only the latter when running with the diesel turned off.
On the other hand they can't be this stealthy 100% of the time so they have an advantage at sneaking up on targets they know are around but disadvantage on sneaking around overall. Unless the diesel is somehow quieter than the nuclear generators? I know the big ones can be pretty quiet.