[Matchless]

I've been a member of my club for 22 years. During that time, we've lost 2 fields due to new construction moving closer. Before we lost the first one, we began imposing new rules regarding noise and using a DB meter to enforce them. Doing so helped us keep the field another 2 years IMO, however we eventually lost it anyway.

Some things to consider in rules about noise....
Different tones affect people in different ways.
Different tones also appear to 'carry' for further distances.
Different surfaces allow the sound to carry in different ways.... (thick woods kills the sound compared to an open desert surface)
Its not always the 'loudness' of noise that bothers people, but also the structure of the sound.

Props make as much or more noise than the engine in many cases.
You mentioned IMAC and pattern, they have great rules. Much research has also been done by the AMA on the subject. Call them and I'm sure they'll hook you up.