The answer is quite subjective and involves a plethora of factors:
1) How loud is the airplane, jet, etc.
2) What time of day (or night) is it flying overhead
3) What direction is the airplane flying in
4) Are there any natural sound absorbers (mountains, trees, shrubbery, freeways)
5) It the property on a raised foundation or a slab
6) Is the property attached or detached
7) Is there attic insulation, dual-paned windows, etc.
8) How acute is the hearing of the person affected by the sound
9) Are there other sounds masking the jet noise (radio, lawn mower, car engine, train, etc.)
10) Check your local airport and the FAA to obtain more info on this subject.
There are seniors living in Leisure Village, Camarillo who are directly below a flight path, and a large percentage of them never notice the air traffic activity sounds.