On the subject of the 365C and it's fenestron, try living next to a hangar full of them
The first 365N for the Vic PAW is now test flying, and sounds more like a lawn mower on steroids, but it's a delight after the deafening shriek of the C model.
On the original question, there is an ICAO noise compliance that has to be met for C of R, and this is now being used to limit movements for some helicopter types in Helipad planning and approval. Before it was canned by the current State Gummint, the proposed (and approved by the previous political incumbents) Sydney Heliport at Darling Harbour was limited in movements based on noise factors, with an Agusta A109 landing having a factor equivalent to nearly three JetRanger landings. And charged accordingly!!