Yes - Coils. Happens on Nvidias usually.
Its usually with coins/miner software where there is large fluctuation of electricity up and down. when I look at my UPS stats - exmaple - goes from 450W to 650 for second, etc. Sometimes drops to 300+, sometimes for 700. Don't know whether its the algo or the miner software that is so not efficient.
I get this on zcoin and used to have it on signatum with some of the crappy miners back in Aug. Never tried X17 but I can bet its the same thing.
If you get very near to the GPU, like almost touch it with your ear you can get the noise clearly. The funny part is the PSU could also eventually get this if its abused and not of solid quality.
To avoid all that, switch algo
Whether its harmful for extended periods - I don't know. Never tried more than few days.