As a professional engineer (quite sad really) i have always been suprised by the fact that most tail rotor designs use square tipped rotor blades. Most of the noise that the complainant can hear will be tail rotor generated, since main rotor is sub audible. I accept that fenestrons are not suited to all applications.
Have a listen to a Grob Demona light plank some time. The use of elliptically tapered blades makes a serious difference to the noise signature of the machine. Perhaps future legislation is required to make manufacturers consider consider this aspect at the design stage. In the auto/truck industry, we are quite use to being constrained by both noise and exhaust emissions. It makes for a better product in my view - especially if you have to live in Los Angeles or London...
Mart