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.
If the clip is on Table Voice, then only the members of their table should be able to hear their voices. Teacher Voice is their louder speaking voice. This is generally the voice they use when they are reading or sharing with the class.
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.