When I'm checking acoustics I just randomly shout "AH", very short and loud, without any warning to anyone else, without any real thought on my part..
It scares the shit out of my girlfriend, who runs the studio with me, cos she never knows when I'm going to do it; and neither do I.
Maybe it's a mild form of Tourettes Syndrome?
I do also do the handclaps (which also scares the crap out of my girlfriend), but I find that I can shout louder than I can clap.
It's something I started doing when we were treating one of our live rooms, and I wanted to see what difference our work was making to the sound of the room, but now it's a bit of a habit..