Hi Steve,

...in my observation, they are the quietest by far, almost eerily so... Every owner I've talked to loved theirs...

However, they are quite large and heavy, and among the most expensive out there today...

http://www.transmarinestore.com/D400_Wind_Generator_p/d4001.htm

For a boat like mine, one of these would be overkill, and I don't particularly care for their appearance... If I were buying a generator to be permanently installed, I'd probably go with the SilentWind that John P mentions, I've heard good things about them, as well... the blue carbon fiber blades definitely make a big difference, although I recently delivered a boat with a SilentWind, and must say I was a bit disappointed how noisy it still was, at times... As John suggested, I think much of the sound was from the internals rather than the blades, and in this case I think a less than ideal mounting arrangement might have also contributed a bit...

I'm still pretty pleased with mine from Hamilton Ferris that can be converted from a water generator to wind, and suspended in the rigging... You probably want something permanently mounted, however, and I will confess having to hoist mine every time I want to use it does get a bit old at times, and of course I don't have the use of it when under sail... Still, it's a good system that works well on a small boat like mine, whenever I'm staying put for awhile...

http://www.hamiltonferris.com/products/Wind_Power/WindPower_200_Generator_Systems/50

best regards,

Jon