ORIGINAL: Red Scholefield
I don't think that there are many clubs that have any sound level restrictions unless imposed by local conditions or ordinances. If such are in existence they usually specify how it is to be measured.
Some if not many do, and AMA's IAC is one site where such restrictions apply (maybe, it depends.......): The limit is 98 dBA measured at 9 ft.
OP asked "IS there a uniform test?" Obviously not as far as AMA is concerned. I presume Scale Aerobatics is flown at the IAC, and the rules for that event allow 107 dBA @ 9 ft. I don't even want to know what sound levels are allowed for Pylon racers.
Abel