High pitch humming / chirping / buzzing sound when guitar connected to PC

I've tried two different guitars, two different USB Audio interfaces, different cables... and it's there on any amp sim I use, so def not software related.

It's definitely to do with either the room, or the PC. Now, on my PC one side of the casing is glass and I've heard glass let electromagnetic interference occur, while metal might not. Do you think it's wise to try buying a new metal panel and swapping with the current glass panel of the case ?