Regarding helicopter noise, there is at least one that is very noisy and the sound can rattle buildings and people too, particularly affecting those with hearing or balance problems. Based on 30 years experience flying in various helicopters, I was always under the impression that such “rotor crack” can usually be avoided by altering slightly the helicopters angle of approach, descent, etc. relative to the wind. If the “whap whap” noise continues,maybe there should be a petition for regulating this noise that disturbs everyone else in our valley.
Mike Curran, Nelson