My noisy windmill used a different design. I simply built a vertical axis "skeleton of a turbine" with 3 or 4 arms.
I stretched a piece of (metal or plastic) wire mesh over each blade. I then hang down a flap from the top of each blade with small hinges. When all the blades had flap,
the wind pushed them against the wire mesh on one side, and on the opposite side the wind lifted them away from the wire mesh. The lift up rotation had to be less than 90 degrees in order for them to come down. Next to a waterfall, no noise !

I like it.
Ten years ago, I worked on the same principle. Your solution (prototype) looks better than mine, and could even be quieter.