So far from th 970GTX's I've seen. I wouldn't recommend the Gigabyte, I found it too loud compared to others. Not the worst but definitely not the best one.
Zotac 2 fan smaller models: too loud, too hot, medium coil whine
Zotac Omega core: cool, pretty silent, coil whine only noticeable in benchmarks.
EVGA too hot, annoying fans okayish coil whine.
Gigabyte: fans too loud, coil whine was annoying even with game sound on.
Galax/G2A: piece of crap, returned to store because the coil whine was painful, gave me a headache. The fans aren't just loud it's like standing next to a vacuum cleaner. The good thing is people with less sensible hearing won't hear the coil whine at all as the fans are just so damn loud. Also not recommended for pet owners, may involve animals going crazy.
Asus strix OC: damn that thing is silent and cool.. Coil whine only appears at 200+FPS in benchmarks. I can hear it, boyfriend couldn't.
Even then the coil whine can be devastating and hits at random. order two identical cards one has it, the other not.