Quoted from pezpunk:nope, the game turns the volume all the way up just for that scream, no matter what volume setting you have the game at!
I discovered this the hard way. i was playing in the basement at about 1 am and "the scream" happened. My wife got out of bed and ran downstairs to see who was being murdered. I apologized and turned the game volume down to "3". Two hours later, I got the scream again. full blast, loud as hell!
I love this feature, by the way. It adds a real scare and makes everyone in the room turn and look and go "holy crap", even in a crowded bar.
i am not sure what triggers it, but it seems to only happen during the "We Got One" mode start animation.
Wow. I would imagine that is going to get a lot of complaints! Especially the emergency-scare kind, like in a busy arcade. At least it can be turned off. Shocked it is on by default. I love it, but I'm surprised they would include it!