Cracking and distortion is most likely due to too much bass trying to be reproduced out of a tiny laptop speaker.
Concider investing in external speakers. I am a bit of an audiophile and have 150$ speakers, but it is worth it IMO, music sounds so much more crisp and clean.
Glad to hear you are getting that fixed though, crackling like that would drive me beyond insane.
UPDATE:
Took it in to the Apple Store today... They told me that while the 5,1 MBPs are known to have some buzz, this was likely a severe case since it was so noticeable and it's the first time they've had someone bring in a MBP for this reason. They're replacing my speakers, we'll see if that solves the problem.
Other than this issue, I really love this computer.
Concider investing in external speakers. I am a bit of an audiophile and have 150$ speakers, but it is worth it IMO, music sounds so much more crisp and clean.
Glad to hear you are getting that fixed though, crackling like that would drive me beyond insane.