Get students to self-regulate their volume level!

Take advantage of your classroom overhead LCD projector with one of these browser based noise level meters. During quite reading time, or group work time if you want the students to be active participants in controlling the volume in your classroom try Bouncy Balls:

Bouncy Balls shows students the volume of the noise in your classroom by displaying a set of colorful bouncing balls. The higher the decibel level goes in the room; the higher and more frequently the balls on the screen bounce. To use Bouncy Balls simply go to the website, click "Begin Bouncing", and then click the microphone icon to allow the site to access your computers microphone. 

Calmness Counter is similar to Bouncy Balls. The difference is that Calmness Counter displays a dial meter to indicate the decibel level in your classroom. You can adjust the microphone input sensitivity directly on the Calmness Counter screen.