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I created this video back in 2008. This was a very scary time for me, and decided to do research into what it was. It turned out to be a combination of lucid dreams and sleep paralysis. I Embraced the fear which eventually turned my nightmares into lucid experiences which I could eventually control (to some extent). However, there times when I'd wake up from a lucid dream, and hear frightening, surreal sounds.
One day, after waking up, I recreated these sounds through an audio editor called GoldWave (https://www.goldwave.com/). I immediately posted it to Youtube. Through comments I was surprised by how many people shared near identical experiences.
You can hear the audio here. Be advised though. Many folks reported it to be disturbing.