Here are some photos of electric fans with variety of blade designs.
fans tend to have a boat-propeller styled blades; fat and small with deep attack angle. The brand Vornado has always been making fans of this style. Its name makes one think of vortex and tornado. Its ads make-believe that the design can generate current that cycles the whole room without changing blow direction. Spins clockwise.
In general, i think that metal blades generate the most noise, and traditionally shaped fans that has wide area generate the most current (most efficient). Traditional shaped fans with their plastic blades tend to be the lightest and cheapest as well. I think all the fancily shaped blades are only for the looks.
Can any aerodynamics student or engineer summarize the blade design situation? That is, number of blades, attack angle, shape of blades (warped, flat), edge shape of blades (concave/straight/convex), surface area… what makes whiling blades noisy?