I live near the Airport in Alta Sierra and if you are thinking of this "Air Park" then give me a call (530)477.2277 as I have friends who live on the tarmac. I would be happy to introduce you to them and you can ask them questions. First hand knowledge is always better than speculation.
My suggestion would be to go hang out around the area, especially on the weekend. It is surprising where I have been able to hear the Airport, the sound travels, it is not bad to me, but I have had clients that were affected by what most of us would feel is very little noise. Same goes for the trains & freeway.
I live on Banner and in the flight route. If there is a fire and the spotter and fighter planes are working we hear them but are gratefull to see them working to put fires out. At the time of the air show in July for maybe 2 to 3 days there is more air activity but we like seeing all the old planes flying overhead. Other than that it, I don't notice hardly any planes. If you need any help looking for something I would love helping you out. I am very familar with all of Nevada County and I work for ERA Cornerstone. I am always ready to go look when you are and I have lots of patience. Please give me a call. Thanks much. Barbara 530-205-6665