Tony SLF
Just reread your post, please state the facts. The definition of a noise nuisance is from when you can't hold a conversation to when you can. For a National Park planning permission case I had to land a Hughes 500 ( a very noisy helicopter )
The NP took its noise reading ( I was landing within 25 m of them ) The result was 12 seconds. So where does 30 to 60 seconds come from please ? Bear in mind the helicopters you are seeing / hearing will be 500 ft plus away from you not 25 m.
Most of us try very hard not to cause a nuisance however i understand you are upset but it does seem that you are perhaps exaggerating somewhat, hence some of the reply.