Is your char a Mage? Or your follower? I experience the same thing at times, especially when I use Thunderbolts or Fire. I generally shut down the XBox and sound system my XBox goes through (Sony Surround), and that usually works.
The crackling sound I figured was coming from my casting hand, I use my right to Conjure a Lord, my left to cast Destruction, and at times I'll hear crackling on my left speaker's. Or if my Follower has a Staff that use Lighting or Sparks. Or Fire, I'll hear it crackling until I have her sheath it or I take it.
For me on the origination of the crackling I believe comes from what castings you might do, or the staff your follower might be using.