Thank you for asking the question.
As you mentioned at the beginning, it's a very complex topic. There are numerous factors that should be considered, and they're very location-specific, so it is critical that studies be executed in the locations where you seek to propose certain mitigation measures. Factors can vary between demographics—the types of housing, the type of area, the type of neighbourhood, the levels of ambient noise that you have present in the neighbourhood.
Mr. Isaac brought up the point in his opening remarks that in certain neighbourhoods, you have relatively low ambient noise, so any type of overflight would cause a significant disturbance, whereas a more dense urban environment, where ambient noise is in excess of 40 decibels, an overflight might not be perceived as a disturbance.
Any study should be location-specific. It should look at any personal or attitudinal or cultural factors that relate to that specific location. Data have shown that there is significant variance between surveys that are done in different regions.
I hope I've answered your question.