The TooLoud! app is ideal for the teacher who needs to limit noise in the classroom environment. It records decibels, displaying the volume levels in numbers. Use it to let the class know when they cross the auditory line. Hook your iPad up to the projector and manage the working noise level in class by letting the students see the feedback for themselves.
This App "Noise Control" magically ask your students & kids to keep quiet on your behalf..... It's so magical that teachers found that students are more willing to corporate in classroom activities.... http://theteachingpalette.com/2010/01/29/shhh-noise-control-2/
I have used this is my classroom for three years. It works like a charm. The students love to see how many gum balls they can earn during the given time. I have either set the timer for the full amount of work time or set it for smaller increments of time. As a reward, if they reach the goal, I sometimes give a piece of bubble gum, or something toward a classroom goal for some other reward...For example I might give them a letter toward building the word Compliments.