I believe that the noise complaints are because people can moan about it knowing nothing too much can be done to reduce it (regardless of exactly what noise is actually made), so they gain the 'importance' of being a complainer.
I used to work in a one man operated, very small country airport in Australia (1990-1996). We had a total of 3 flights a day on Shorts 330 and 360 aircraft and I regularly received telephone complaints from the local residents. My response was always the same question...."When did you purchase the your home?" The answer was always within 5 to 8 years ago. My reply was a simple..."the airport has been here since the early 60s, goodbye" and I'd hang up on them.
In my opinion, the crux of the matter is people building/buying properties near to any airport and then complain that the area is too noisy. Sorry, but I have no time for people like that.