@johnnybravo: I saw that thread yesterday and it inspired me to post my n810 question, but it's not the same This only affects audio when charging, and only with the car charger (as far as I can tell). It sounds like a pulsing and a low buzz. I use a standard 3.5mm audio cable. This doesn't affect the speakers either.

@gowen: Thanks for confirming. That's exactly it. A pulsing sound that is easy to ignore with music playing close to max. My guess is that it's because the power and audio jacks are right next to each other.

In fact, they're so close together that the first audio cable I had was too big to even plug the power in at the same time.

Anyway, I'm glad that it's not a problem specifically with my n810 (or car outlet). I'm far from an audiophile, but I guess I might try to find a more expensive audio cable that claims "low interference" soon.