My teacher uses a Noise Meter similar to this one. The Noise Meter is a cool way to remind students the correct noise level that they should be using! You just use the paper clip and move it to the appropriate noise level the students should be using.
It gives students the opportunity to move up the chart with good behavior instead of merely punishing the negative. I use this in my room except I have mine on a yard stick to make it portable. Really good classroom management tool :)