I've done everything you said before already, but you gave me a hint.
I have found out it might be releated to a pre-HDMI config. I have began to use my HDMI audio output just recently and it could be releated to a config file in "My documents" directory. I deleted the entire folder "Battlefield 4" and I let the game decide what new settings should be. I assume it could he been due to an old line in config file I am using motherboard's sound card instead of my monitor's one. I am testing it now. So far I am in-game for 40 minutes and sound works flawlessly. I am using LG IPS 225. I will let you know if it has fixed my issue ( I hope it did, because it's very annoying being forced to restart the game in order to get the sound back.
