What version of Windows -- 7, 8, 10? Any other issues with audio? Have you tried a different cable (could be defective, though unlikely)? AMD or Nvidia GPU / what model? Have you tried over HDMI if that's an option? Latest drivers for your GPU installed? If your GPU has mini and full size DP available on it, have you tried switching which end of the cable is used for the GPU and the monitor? Just trying to narrow it down.