In Europe where noise is a bigger issue you often see four blade props on small single engine planes. That, combined with mufflers make a huge difference in overall noise. It costs on the order of 3% of performance.
I think the noise is also an important issue for CPU cooling fans or electric fans for homes.
Would love to see such propeller made into everyday small fans.
If you're going to spend the space, simply use a bigger fan at lower RPMs.
Electric fans for homes are a more interesting question. I was going to suggest that a Vorando or Dyson already has a lot of elements of this, and gives more bang for the buck, but I think the two could be combined. A Vornado-style fan really reduces vortex shedding, but probably has some turbulence internally. A modified prop design could reduce that a lot.