At the 24 Hours of Electricross event I got to interview a guy with the Blue Ribbon Coalition. He was there to measure sound levels because there is some thinking about the potential of electric vehicles to mitigate noise complaints related to offroad activities like motorcycle races.
Using the dB meter he found the race noise level was 65 dB or so. This is equivalent to normal conversational speech. On the other hand normal motorcycle races have sound levels above 100dB hence the noise complaints.
That's the essence of the interview except I rambled on with some other ideas ...
Here in the eastern US, the noise is certainly obnoxious, but the biggest impact of ORV use is the impact on the woodlands from their ad-hoc trails and erosion, and the littering from the redneck element that seem to particularly enjoy this activity.