It is interesting that you chose a picture of Joe Bonamassa. On his podcast a week or two back he was talking about a gig when he was a teenager at an outdoor venue (I believe in Atlanta) that was very close the governor's mansion or mayor's house and had a very strict decibel restriction. The restriction was enforced by decibel meters on stage, and even with his amp turned to like 1 he was still too loud. He said the decibel meter was right in front of his amp. He eventually kept everyone happy by placing his guitar case between the amp and the meter. He said it didn't really change the volume but kept the guy checking the meter happy.