I've experienced auditory hallucinations too. It's like 2 people having a conversation on the radio, and sometimes it's as if there are people having a chat in my drive. Sometimes I can hear music, and it's so real that I feel I could almost tap my fingers to the beat. When I told my psychiatrist about the hallucinations she was a bit dismissive about them, and said that they were side effects of the medicine I was taking.
I'm aware that a great deal of medical advice given over the Internet is baloney, but nearly all of the literature claims that hallucinations are common to bi-polar sufferers. I can't help but feel that on occasion my psychiatrist makes it up as she goes along.