A bit of a weird hack mod, but if you get some of the chunky foam they come packaged in, cut a square out about 2cm wider than the fan, then cut the middle out the exact fan size (so basically it's like a picture frame) then mount it on the fan so it sits out about 1cm, it alters the pitch and stops a lot of the whine.

I think the term used is 'velocity stack', and whatever flow dynamics logic that goes along with it.

P.S. Anyone wanna throw me an S7 voucher?