Hi i have a really annoying problem when im playing games or watching films my brightness switches darker and the sound stops for a split second, then comes back tiny sounding. I replaced my graphics card as i thought it was that but now it does it still just for a shorter time before it goes back to normal.
I suspected it was to do with the on board sound drivers but its the same with the drivers uninstalled with onboard audio switched off.
My system 
cpu fx 6100
motherboard 970a-ds3  rev 1.1
ram 8gb 1866mhz
graphics gigabyte r9 280x windforce oc 
antec tp 650 psu
I really would appretiate any help
 thanks ben.