Most of the traditional model engines are difficult to hear past a 1/2 mile under most conditions. However, the Community College I have taken many courses at is almost a mile from our previous field. One day as I was getting into my car at the front parking lot, the farthest from the field, I noticed a faint engine sound. Someone was flying a Zenoah powered plane with what was claimed to be a stock muffler. I didn't bother going to the back lot where I might have been able to see the plane.
Some days later, several of us were discussing the noise of the engine with the plane owner. The engine in question was tied down and running at idle. He wasn't too happy when I pointed out we couldn't hear the ST 60 being run up at full throttle right next to it.
Our club has a sound level meter which I occasionally check against my company's lab standard. One day I brought it out to see what a Quadra powered plane with a Byron muffler mount measure. It was almost 105 dba on the ground, and at a distance of about 100' and 40' altitude, about 125 dba. That's loud. I was very happy to hear that IMAC has started enforcing sound level limits, even if they seem to be higher than the AMA recommendations. It's a start. It's hard enough someimes to keep a field, but even harder when people don't want to accept facts.
Noise can be a problem. And in our part of the country, flying fields are becoming scarce.