I get this, too. I've had friends who are not bipolar tell me this is "normal." I know it is not an everyday occurrence for me, however, so I consider it a mild hypomanic thing. We're not "hearing voices" per se, but more of what I consider having "noisy thoughts." I do ONE of these things to handle it (or sometimes more than one I'm really anxious about it):

1. Take some extra medication (ask your pdoc if you can do this PRN (as needed) with one of your antipsychotics. I will take an extra Risperdal as needed at times that my thoughts are racing too much or I have too many "noisy thoughts.").
2. Take a Xanax. (My pdoc prescribes it PRN for me).
3. Take Bee Pollen with a glass of milk. Bee Pollen is a natural supplement that calms down my hypomania. It's inexpensive and worth trying, IMO. I doubt there are any interactions with it, but you can check with your pharmacist first to be on the safe side. I feel like milk is very calming.
4. Listen to guided meditations or relaxing music while falling asleep. That will keep the noisy thoughts from happening altogether.

Hope this helps! You're not psychotic, trust me. This happens to me and I've been pretty stable for quite some time. I would only be concerned if you think you are ACTUALLY hearing voices outside of yourself that make you think someone is in the room or if you are having other alarming symptoms. You will be just fine. Try the things I suggested. They work for me.