We had a chap turn up in the middle of the night in the old control tower in pyjamas and dressing gown to complain about an engine run. No security in those days. He was very polite.
Whilst the Airport Duty Officer was called to speak to him he was sat down and given a cup of tea. He stayed over and hour then said he ought to go, still very polite.
For my sins, in the 90s, I was in charge of the person that looked after the Noise & Track and dealt with noise complaints. Unfortunately, I had to let him go on leave occasionally and then I had to deal with the complaints.
Rather than write letters I would telephone people. By and large, they were all reasonable, they had been annoyed by a particular event and felt they wanted to complain as they had every right to do. I would even invite them in to see the Noise & Track monitoring although not everyone would 'you are trying to brain wash me'. For that, you need a brain (no, I didn't say that) :-)