Just want add, I am BP-II (mild), and never heard voices neither has my brother who is Bipolar-I.
Hearing is not commonly associated with Bipolar, but comon with Schizophrenia.
I guess with all the various forms of Bipolar anything can be possible, especially if a person has more than one disorder. There has been cases where some meds can have that sort of side effect, so I'd say talk it over with your pdoc, ask him all the questions you have, jot them on a piece of paper so you do not forget them and then bring them when you go to your next appt. I write things down from time to time to ask my pdoc as well as my family practitioner.
Any good doc appreciates questions and will do their best to answer them.
Again, good luck to all

DE