Yesterday I woke up during the night after a dream - when I was slipping out of the dream, I became lucid. Because I was aware of being awake, and I remember reading about DIELD, not moving when you wake up from a dream, I stayed still. For some reason I just knew that it was going to work, but I wasn't sure how long it was going to take. After only a few seconds, there was a white flash, and then, the best way to describe it, it felt like I had fallen into my head, and it was completely dark – not like dark like closing your eyes, like there was nothing there. I had no idea it would feel that way, but once it happened, then I remembered there was likely to be hypnagogic imagery, and not to be afraid.

It was then that I heard a strange, screeching noise, like really off radio frequency, and it was really, really loud, and crackled. It seemed so realistic, and really, really loud that it surprised me that nobody else in the house heard it, (even though I knew it wasn't real.) Then I suddenly saw a room, it was black, with white shakey outlines of furniture and the angles of the walls. Then I suddenly heard the exact same noise I first heard repeated again, and I suddenly panicked and woke up. I don't remember moving, but I think the sudden fear woke me.

Now I know that people hear strange noises and experience strange feelings during this stage, but are the things I experienced normal?
That, and how long does it usually last, and is there any way to get through it without panicking?