Just for completeness, The microphone used to decide on sound levels in venues is calibrated very precisely. (and bleeding expensive to boot!)
Also, the parameters are incredibly variable.
Imagine a band in a village hall, playing at level "A" (doesn't matter what DBa that is)
Now put the same band, at exactly the same volume (all amps set the same for instance) in the RAH, and then in the marquee at Cambridge on a hot day with all the sides removed...You'll get wildly different readings of "perceived" sound levels.
Official sound readings are normally taken at the FOH mixing desk.
So, there is a lot of subjectivity going on here.
An interesting aside. Years ago, when at the BBC, I used to work on Radio 1's Sound City...7 days of "Rawk" music, over two venues,
One year (think it was Manchester, we all had to wear Sound recorders on our bodies to note Sound Level dosage during the week. (Elf 'n Safety, doncha know!)
All fine and dandy...slight problem, the microphone was attached to my T shirt..I was cocooned inside a set of BOSE noise cancelling headphones! (for comms purposes) When the readings were analysed at the end of the week. the management were horrified by the levels recorded. Me, meanwhile in my safe little headphone world, felt no pain at all...In fact it was quite quiet!
My point being that as Don T says. If you don't like it, leave....!
What I really hate, whilst rigging drum mics, is for the drummer to hit the snare as loud as he can, just as I'm 4 inches from the skin...Now that really hurts!