My Ps3 (120gig) sometimes makes "Crackling" noises, not sound from TV or games, but the system itself =[?

Yeah, I have the same problem. I bought the same system that you have and I keep it in my room so I do hear it. Now I don't have a perfect response to this but I'm pretty sure its universal, your PS3 is not broken and it has nothing to do with Call of Duty or your t.v. or anything. Hope this helped