wolfpenny-

Maybe the reason you can't agree is because you're looking to the wrong authority for guidance. AMA's latest position is in a nutshell, comply with the standards of the community you are operating in. AMA is not the controlling authority for matters of noise abatement, your local community government is. In the US, the allowable levels are usually set by ordinance at the city or county level. You need to look into those local ordinances as a first step. The allowed levels are normally specified at the receptor's location, usually at the property line. As the received noise level diminishes predictably with distance between source and receptor, there is no one-size-fits-all number for allowable source level, which is what we measure and and have some control over.
AMA, while the sound committee chairman was Howard Crispin, recommended a limit on source level of 90 dBA measured at a distance of 9 feet from the source. This was copied from BMFA and DoE standards in the UK, and is based on a nominal distance of about 1/4 mile separating the source from the neighbor, which is in line with with a reasonable separation for safety reasons. It is important to bear in mind that nominal distance that was presumed, though it was rarely stated, to make sensible decisions as to whether it is applicable to you flying site. If your closest neighbor is 1/2 mile away for example, it would be overly conservative. The doubling of separation distance would allow operation at 96 dB source level while keeping the received level the same as for a 90 dB source at 1/4 mile. You don't want to be overly conservative, as that puts a limit on on the size of powerplants your models can use. The limiting factor will be the power absorbed by the prop (assuming effective mufflers are used), and that is directly proportionate to the sound level generated. To meet the 90 dB at 9 feet rule, you will be limited to IC power in the range of .40-.50 cubic inch displacement for 2-strokes, a little larger for 4-strokes. If that's what you have to do to comply with local ordinances, then of course do it or risk losing yor field. If the separation distance from the nearest potential complainant is significantly greater, then the 90 dB limit would be overly restrictive and unnecessarily ban larger engines - in which case the complaints will come from within your club.

Abel