2014 iMac Buzzing

[Evergreen2]

My 2014 refurb has started an intermittent buzzing three months out of warranty, it's worse during graphics intensive activities like scrolling. The noise can be heard most clearly from the lower vents, I can't tell on which side it is louder. I'm guessing this is a power supply issue, I'd like advice on the options: ignore it, ask Apple to fix it, or fix it myself. Thanks in advance!