Anyway, in all this searching, I have managed to create a map that joined the airport overlay district information for both Loudoun and Fairfax counties (something I could not find online). The line is the LDN 60 line (which stands for loudness day and night measured in dB). It's supposed to represent the average noise generated by the planes in and out of Dulles airport. Loudoun county also has a 1 mile boundary that you can find on their website. However, even outside of this boundary, there are definitely places where the planes are quite low/loud and have scared our son quite a bit.
So, still no house. Maybe someday... I'll keep you updated.
"There is a time for everything, and a season for every activity under the heavens... a time to search and a time to give up" - Ecclesiastes 3