Shyboy, I have heard voices in my head also during panic attacks, and i attribute them to the attack itself, since it doesn't happen any other time. I suppose, tho, if the nature of the voices you hear is scary or weird, you should see your doctor. My own 'voices', i know, are just me trying to make sense of what i'm feeling during the attack. I hope this is helpful.
The mind is a complicated thing. I would say if one is hearing voices, a visit to a professional is in order. A professional can sort out whether is is anxiety or schizophrenia and treat appropriately.