It depends on when my last bowel movement was (smell-wise), how long I've been holding it in, whether or not I force it out or let it out slowly, and whether or not I'm alone or between other people. Next thread is probably how do you sweat :lol: (Maybe I should make that thread...hmm)
I announce when I fart because 1. It's silent, 2. Nothing's worse than being blamed for one you didn't do; no one believes you.