Sleep is a state in which the spirit is often much more active. Given the materialistic nature of our culture, we tend to be "all thumbs" when it comes to the phenomena described in this thread. Less materialistic cultures have more robust explanations, which often have to do with spiritual faculties. For example, it is possible that the auditory hypnagogic image you received was caused by your mother calling out for help in a dream, either physically or spiritually. It is remarkably difficult for the unexperienced to discern the difference between a physical locution and a spiritual locution. These experiences happen more often than we think. Usually when we receive a spiritual locution we hear it as a physical locution and react or respond accordingly. A misunderstanding will ensue where the person who "spoke" will profess that they said nothing at all, both parties will scratch their heads, and then they will go their separate ways. The event is immediately written off and forgotten.