For people who having problems with their sound in BF3, for example the sounds cut or it disappears:
Go to ''Documents -> Battlefield 3 -> settings -> "PROV_SAVE_profile'' and open it with editor. I took notepad++ (best imo). Change AudioQuality from 0 to 4. (You can only do 0 = Standard 1, 2, 3, 4). Hope it helps you.