It's not hard and fast. In Dianetics, Hubbard says that people should try not to say anything or make noise around a woman in childbirth (also a pregnant woman who's been injured, too) because the sounds and words may become part of something vaguely analagous to her subconscious mind (called "reactive mind" in Dianetics/Scientology). The idea is the same for someone undergoing surgery. It's considered something to aim for. There is no HCOB (Hubbard Communications Office Bulletin) or HCOPL (...policy letter) out and out requiring it. It's sort of an ideal situation type thing. I never made any doctor or nurse be silent around me in any operating room. I wasn't worried about it, and, yes, I am a Scientologist, because Scientologists believe you can "audit it out" later. It's just ideal if you don't have to. Personally, I'd be yelling and begging for mercy- and that's just during conception. Heh.