I'm Brazilian, and until a few years ago most commercial electric fans sold in the country looked like this: But then one company started making them with 6 blades, claiming it had better wind output and made less noise than the 3-bladed fans (they didn't directly made this claim; it was implied by the choice of words). Apparently this marketing worked, because the company above followed suit and now sells their fans like this: Is there any validity to their claim that 6-bladed fans are more silent, efficient or effective? I would assume not, because engineers are not dumb and such a simple idea would have been implemented decades ago already if it had any scientific ground. But I hope to be surprised! Any articles I can read on the topic?