It could be both.
If the volume is set too high it can cause your speakers to distort the sound.
Un-plug and re-plug the cables between your speakers and your PC.
The power plug on your PC should have 3 prongs that go into the outlet on your surge protector, make sure all 3 are used -- no 3prong -> 2prong adaptors.
Same for the plug from your surge protector into the wall
Same for the power plug on your speakers -- but that one may not have 3 prongs.
If you dont have a surge protector -- get one.