20 events per day....at a minute per event....equals a rate of .01388888 of the day L and L is being bothered. Assume he is away at work for one third of the day and the flights stop after 11PM...that leaves him suffering about 0.0046266 of the day. That is ahh....errr....about 6.66 minutes a day.
For crapsakes....the Missus barks more than that?
Now where in the world does he live that there is an air corridor that has that kind of traffic to begin with? Under the London Heli-lanes.....or under the traffic pattern of a training field I wonder?
As to living there old bean....been there and done that and flew helicopters...some very noisy ones too....and never had a complaint about the noise. Lots of compliments however as it was a very special sound one of the old girls put out. You could hear it for miles....and miles and that was if I was "flying neighborly" as we try to do.
Tell us which little hamlet you live in and lets compare our knowledge of the area and see if there is an explantion for all the air traffic you report. Maybe one of us can help you find a solution to your problem.
That is your goal I assume....finding a way (if there is one) to cut down on the number of flights directly overhead your garden?