This problem seems to be somewhat common out there and mostly the solution is unique to your particular setup. Recently I was struck with a bad case of audio feedback from my computer whenever anything was happening on the screen. It was so bad I couldn’t even play computer games any more as the noise was too distracting. After trying a ton of different combinations I finally figured it out.
I had recently purchased a new computer desk and in anticipation of it I’d tidied up the room, hoovering behind it and sorting out my cables.
However at the same time I had been trying out some old hard drives in my computer and also randomly my PC power button had stopped working. Plenty of variables to work with then.
I’ll cut to the chase. I have two active speakers, a six socket extension cable and another 4 socket extension. It turned out that actual issue was that during my tidying up I had put one speaker on the left hand extension cable and another on the right hand extension cable.
Having two different wall sockets involved with the speakers and the PC was creating a feedback loop.
If you’re having audio problems double check that your PC and your speakers / amp are on the same plug.