There has been discussion on various thread about sound levels at the regionals and the Championship event.
We have taken data at Atlanta and you can view some of it here:
http://www.kellrobotics.org/files/Sound_2008.pdf
In the future we will be logging as much data as possible at the Championship and at least two or three regionals.
Roughly speaking, the events runs in the mid 80 dbA. Large crowd clapping and excitement pushes the number to 100 dbA (which doesn't have a volume control)
There has been some instances of music levels approaching 90 dbA but generally below.
Anecdotal evidence on the regionals is sketchy but indicates inconsistent results across the system with some regionals in good shape and others clearly exceeding the limit so much so you don't need a meter to make that determination.