I teach 4th & 5th grade science/social studies. This year I have started using power teaching. This means lots of student talking. I have mine set at the highest decibel. It's hard to make it go to red. I challenge my kids to teach so hard with gestures and talking that they can make the light go to red. The only limit is that they shouldn't be shouting or screaming. I tell them to use their teacher voices. They haven't been able to get it to red yet, but they sure are trying which means that they are teaching each other away like mad!!!
Before I tried that, they were super quiet while teaching each other. My principal came in the other day and was very impressed with the way the students were responding as they taught each other the steps of the scientific method.
He even groaned with them, when they got a frownie for not teaching with gestures.
So I guess I've got a bit of reverse psychology going on. BTW -- mine has the siren option as well and I keep it turned off.