Poor audio or scratchy sound
Electric Magnetic Interference
Are there any other devices around the speakers or wires for the speakers? Electric Magnetic Interference (EMI) can cause poor audio. Try moving your speakers and wires around and away from other devices.
If you have recently added any new expansion cards into the computer and your sound card is an expansion card move the card to another available slot. Cards within the computer can also cause Electric Magnetic Interference.
Verify that you are not encountering a hardware issue with the speakers by trying another pair of computer speakers.