Android :: Pandora App Crackles Badly In Car

I can't figure it out. At first I thought I had a blown speaker (specifically the front left speaker) because it makes popping/cracking noises VERY bad when playing music. After some experimentation, however, I found that it's only when using Pandora. If I play music from my phone off last.fm or internal memory, or non-phone sources like my other MP3 player or FM radio, there is no crackling no matter how loud I go (and for reference it happens more noticeably at low volumes, I can crank it up and drown out the popping mostly).

What gives? If I listen to pandora with headphones there is almost no problem, although on some songs I can kinda-sorta hear the popping.

I'm using the motorola droid if it's relevant (although I don't think that has anything to do with the problem).