(Psychological / emotional perspective)
A voice that speaks through, or to, us as in trance work (an altered state of consciousness) has two areas of significance.
Through us suggests information for others, whereas to us is more personal.
If we believe in the spirit realm, this is communication from a discarnate spirit. More psychologically, when we suppress certain parts of our personalities they may surface in dreams as disembodied voices.
This does not constitute a form of madness.