yeah, it's coil whine, I have it on my 1070s as well, only when running x17. But it mostly comes out of the speakers, if I turn off the speakers it can still be heard but it's much more silent. There's some sort of interference with the on board sound card. You can try turning off the speakers/amp and see if it's better that way if it bothers you.
X17 algorithm does a very wierd oscillation of the card's power limit, and you can even hear the sound change as you go through different power limits (slower to faster as you increase it)
So that oscillation in power limit might cause the chokes on the card to vibrate so you get coil whine. I was also thinking that x17 algorithm might be further optimized in the future, and then the sound might stop.