Jon
As Amy said it can be anyone who shouts out. To be honest I don't like just sitting there shouting like a teacher (no offence ) but also most people within a fairly short while should and do know this (VCs do say). I think it's just a bit of concentration slip from time to time.
Get 'em all on fixed that will stop the freewheeling . If you want to freewheel you may as well just sit in a chair.