Well thats just a coil whine nothing can do about it, just learn to live with it.
I mean, every single PSUs, video cards, motherboards have coil whine, just some very inaudible, and others very loud.
This is not affecting the hardware in anyway, not performance, not lifespan, anything, just can be anoying , thats it.
My RM750 v2 has to coil whine on loads...also my VRM from my motherboard...but thats ok,
its just part of the desing, the condensadors are vibrating, and thats what produce the noise, thats it.