Oh, absolutely. The noise you hear are both a combination of prop speed as well as exhaust noise. But, for a given throttle setting, your RPM may be higher than it was with a higher pitch because the engine is working less, and will turn at a higher RPM.

Prop tip speed is a real problem in some areas. We have neighbors, well, one in particular, that complains about everything. It seems that he is unhappy in the fact that the Forestry folks drive by his home on the way to the field to fly their air tanker. We live in the middle of the "Pine Barrens" where there is a large forest area with a lot of, well, pine trees and scrub pines. So, they keep a pair of air-tankers at the field during peak months of potential forest fires. So, the noise generated from the full scale aircraft as well as the cars and trucks (fuel and water tankers) drive past his house, bothers him.

I've been at his house when we were flying and could not hear a darned thing. I brougt a sound meter to measure the background noise when we were flying.. and there was nothing to detect. But, he knows when we are there and seems to want to complain about us, even though we don't drive by his house (we have a separate entrance about a mile east of his house) and don't fly over that portion of our field.

But, we've instituted noise limits in the "just in case" mode, to prevent problems from coming up.

Anyway, this is drifting away from the point of this post and I don't want to hijack it any further.

Thanks for the input, though. Any of this sort of information is helpful for those that are thinking of experimenting. There is more than aircraft performance to think about when changing props. And, as I said, I envy those that fly at fields that are well away from populated areas.

CGr.