I had a scary experience, I listened this during a long time yesterday and when I went to bed I could still hear it so I tried to focus on something else and eventually succeeded but then on the edge of reaching unconscious sleep this vibration came back but psychologically it was very loud and frightening it made me woke up in a sec, had me like "what the hell just happened?". I think it's most likely like a visual illusion but psychological, you don't really hear the sound it's just the brain that keeps activating the location where it was stimulated for a long time, though now I am not sure if it's a good thing or not.
It's intended for use one time, not on repeat. :)
Valentin Degenne