From long and bitter experience with people like this it can be very hard to appease them if they look up and see a helicopter then to them it's right over their house !? Recently two such complainers near me were asked what was louder the helicopter flying circuits or the cars driving past their house , needless to say it was the cars after which they shut up for awhile .
Eight flights in a day does not seem that much maybe take the guy flying and show him the efforts being made to minimise the noise impact and if that doesn't work maybe have him sectioned ?
CBS