If it’s not happening with your Switch, the buzzing could be interference coming from other electrical components in your PC.

I don’t have the Salnotes Zero but they might be extremely sensitive IEMs and are picking up on when your pc is and isn’t outputting sound.

A cheap USB audio dongle can fix it, like the apple USB-C to 3.5mm if your PC has a USB-C port. Lots of USB products if not.