Dont know if this has been mentioned yet.
I was lining the bottom of my bird cage this evening using this mornings chronic. I noticed a Q & A session with David Carr.
One of the Questions and Davids answer:
Q: Why does it seem like every time you call an audible, it is to a run?
A: That's a lot of our offense. We don't audible a lot, but when we do, sometimes it's in a situation when we go run to run. Sometimes we go pass to pass, but that's rare. Most of the time, it's just based on the look. If we call a play where they're going to give us the run, that's usually the most demonstrative I get. When you notice that I'm audibling is when I have to yell out to the guys. Pass audibles can be done with a simple hand signal, so you rarely have to say anything
Bet the opposition hasn't caught on to this yet.