(Without reading all the other posts)
Sleep paraliysis.
What happens is your body wakes up before you exit REM sleep or if you enter REM sleep before your body shuts down.
The auditory sound and sensation you describe is not unusual. You can have visual halucinations as well and they do look very real.
I suffer SP from time to time. I've trained myself to not be afraid while they happen. Instead of having the sensation something evil is after me, I end up feeling aware of what is going on and that it is only SP. I feel more frustration than anything, because while that is happening, I'm not sleeping and lack of sleep means being groggy in the morning.
I still have little luck with sleeping because it will happen repeatedly almost several times a minute. For me it feels like several neetles poking my back creating a tingly feel and wakes me up with a sore back. I also get a sound. It sounds like yawning with my mouth closed.
I've found the best way around it if I can't sleep through it is to wake up fully and stay awake for an hour and then try sleeping.
SP is actually a rather common thing and is fairly normal as far as I've found out. Some people may be more prone to it than others, I guess.
If you need more info I can google it.
BTW I had googled it foir myself expecially during my senior year in high school. They were happening so often it seemed like I was having an experiance on a weekly basis, almost like 3 out of 7 days with at least one epsode. It got to the point I as afraid to sleep.
The first episode (that I know as SP) occured to me when I was around 10 years old and while I was a little bit sick with a flu. That *REALLY* freaked me out. I was seeing nothing but a tingly blue patch (like if you glanced at the sun or stared into a light bulb) drift from one side of the darness to the other and with it a chiming noise.
I think I had eposodes before that maybe since I was five years old, but I only remember the fear, not the paraylysis. Some of the dreams with those were quite vivid.
But since I researched it I've managed to remove the OMG I'm being attacked by an evil spirit fear for the most part. If you can train yourself to think about it being just a common problem right after you wake up, you may be able to think that when the episode occurs. It's quite comforting, really.
Lucid dreams are fun. I take those as an opertunity to fly. I've even had dreams where I'm dreaming and then waking up to talk about my "dream" but then wake up from even that to talk about the dream I had while I was dreaming.
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One of the oddest was when I had like a 3 part dream where at the end I wrote it all down, read it aloud and then vomited like crazy. I woke up later realizing it was all a dream. I've also "collected" things in my dreams, wishing I could keep them, but somehow aware I'd lose them. I can also remember things from previous dreams. Sometimes I'll even have a series with a very story-like plot. The series can be within a night, or be random dreams spread across several years. I can be just about anything in my dreams. I can be any age, any gender, any ethnicity, and I can even be any animal such as an eagle or pig. Sometimes it's a realistic animal, and sometimes a fantasy creature such as a dragon or a phenox like bird.
My dream world is quite interesting, really interesting.
You can PM me too if you want.