Yup. Waterford Hills is situated right next to a subdivision that has been competing for the same groud for the past 55 years. Our rules read that the cars must meet the 75db sound requirement at the property line and must run a muffler that is readily available to the public. There are ways to get creative to quiet a car down.
There were some races that I'd have to pedal the car past the sound tower and other days I'd ding sound from across the track. Some cars exhaust might not be the problem, it maybe the whine of the gears or the intake sucking air. Some days the car will make sound if it is clear skies and some overcast "low ceiling" days the car won't pass.