Some games make this, it happened to me once before. I restart the computer, then no problem. Then, when I reenter the game, it crackles again. Not all games, just some. I don't want to make false predictions, but I do hope you do something about it. Restarting steam has no effect. Restarting computer solves it for a bit, but not for long. Thank you for your help in advance, I don't know what is causing this. I'm using Ubuntu 14.04.4