Strange thing happened in sleep I remember clearly that last night I suddenly woke up when I was dreaming, because I listened a girl voice, but I am not sure if I have opened my eyes unconsciously before I listened a little bit of humming song of that girl voice. What I can make sure is that I couldnot hear that voice after I was aware that I have woke up and kept my eyes opening. However, after I thought of many things quickly as I waking up, and when I closed my eyes again, I heard some other voice at the same time.Once I opened my eyes or I wanted to listen to it more clear, it disappeared. I didn't feel any fear at first, only when I heard my smartphone dropped from the bed, I couldn't stop my fear and rapid hearbeat.