The level of noise made by the torpedo depends on its speed. Torpedoes are not made to be silent, they are made to move fast and kill their target.
A passive homing torpedo will be quieter then an active homing torpedo. High speed makes the acoustics useless, they must run slower and therefor quieter. Active homing torpedoes are going to make noise once they start pinging, so you might as well run them as fast as possible.
I think that for a torpedo to run fast yet silent it would have to be rather large. I am not expert, but I doubt that any torpedoes have acoustic padding and other sound lessening items incorporated. That sort of thing is used on the subs. Heh.
Am I rambling? Must be the vodka.
Извините. До свидания.
