Miss Kindergarten is hosting a classroom management linky party and at our school we also have something similar to the volume control she mentions, except ours go from levels 0-4. Our Kindergarten team got together to take pictures of ourselves modeling the voice level (kind of hard to do!) and made a little poster out of it. We hang it in our rooms and use a clothespin to clip it to the level we want the students to be using during that time/activity. The kids responded really well to it and they got used to the language really quickly ("Show me a voice level zero!")
The hardest one to model was voice level 1 whisper. A lot of students come to Kindergarten not really knowing what a whisper is so we do a simple experiment. They touch their throats while talking in a regular voice to feel the vibrations. Then I tell them to whisper while touching their throats. They'll know they are whispering correctly if they don't feel any vibrations at all. So in the Voice Level 1 picture we have a teacher "checking her throat" to make sure she is whispering.
Another classroom management tool I use is having pictures on popsicle sticks. All I have to do is hold up a picture and students need to follow exactly what it says. It's handy because I can pull it out and not even have to interrupt my lesson!