I'm tinkering with building a backyard wind turbine "as we speak."  So far a 10ft. diameter "prop" on a 10ft. tall by 2in. diameter PVC plastic waterpipe pole. Needs taller pole.  Blade can whip by 5ft. above ground.  Am putting up a 20ft. pole, 3in. and 4in. dia. PVC.  Way less than strong enough, but safer for now.
 
The blades are 5ft. long pieces of thinwall electrical conduit metal pipe.  A 4ft. long >>cloth<<< sail is attached to the pipe.
 
As to sound; so far, the blades have turned at a maximum of 1rev./sec.. Thats 60rpm and absolutely no sound (as I remember),  except that at that speed part of the sail fllutters in the wind.