I have a lovely system in my classroom for maintaining a suitable noise level.
It's a Noisometer. Or Noise Monitor.
Permitted noise levels vary from silence to group discussion.
Unfortunately, it doesn't work. The noise is usually off the scale.
Boys don't 'do' whispering or talking quietly.
It doesn't matter too much, but I just wish I could find the volume button sometimes.
Or even turn them off.