I'm away from my books, but I recall a noise abatement procedure for the 206 which, amongst other points covered here, recommends reducing Nr to 97% (IIRC) on approach. I have used this on occassion when being checked by EPA for helipad approval, and it helped keep the Db down to acceptable limits. Keeping the weight to minimum is another trick for EPA checks
My pad at home is steadily being encroached by developments, but I've got a 20 year history to help me continue. Plus warning/advisory signs along every fence to counter the possibility of complaints from new neighbours
