Just because it's loud, isn't a good excuse not to open. I know what you mean about repeating yourself. You need to practice projecting your voice. A great way to practice is get a voice recorder, stand 10 feet away and run your opener without yelling, and projecting your voice. Secondly, if you have to repeat anything, make them repeat something to keep you on an even playing field.

Besides around A3 you are going to go for a move to a quieter area of the venue. It only takes about 15 min or so to hit that stage, so you won't have to put up with that stuff long.
How do you make yourself feel more comfortable? A.} Go there more often so that it becomes like a second home to you. That's why Mystery's newbie mission works so well. You get comfortable in those 4 venues you constantly go to. Also you are opening a lot as well.