I say silent but deadly. I did this a couple of times. I got on an elevator in a high rise building. where I was working. I knew I had some bad gas. I held it until my floor comes up. This is a lot better with some people on the elevator. Anyways, get close to my floor, let out the silent, but violent as I was exiting and hit all the remaining floors on the way out. In other words, if I got out on the 12th flr and another person was getting out on the 20th flr, I tried my best to hit all the buttons so the elevator would stop at every flr. In this case, she was not too happy...