Carl, I can't say I've heard any unusual noises from the Type XXI or any other automatic in my collection. Is this an intermittent sound that can only be heard occasionally? Or, is it a routine noise that's intrusive all the time? Either way, bring your watch to your local dealer and have them diagnose it. You wouldn't want the noise to manifest itself into a mechanical problem that interferes with the proper function of your watch. My guess is that something is probably broken and you'll have to deal with it sooner than later anyway. You could also compare your watch to another Type XXI at your local dealer.
Good luck, and let us know how it turns out.