Cletus
Since you and I both hit on the point
that the surroundings and location of you club set the standard as to what is 'too loud',
(by either good manners or legislative action)...
AND your referral to AMA being in no position to set the standard...

... we could say that 'too loud' is not up to the AMA at all.

What is 'too loud' for one place and set of folks
could very well be acceptable in other places and peoples

Such as flying in the CA desert BLM land,
if the planes seem loud start shooting shotguns at the club
to place the engine/prop noise in scale as to what is allowed out there
(havent seen an AMA rule against shooting guns on chartered club property as a non-aeromodeling activity)

I still recall the old folks in Fla that complained about the noise from a flying club
.... a SOARING flying club [:@]
Subjective terms at their best: Granny says them gliders are too loud