When I used to have constant out of body experiences (OOBEs), I would hear a buzz in my head, which sounds rather like the way a mobile phone vibrates when it receives a text message. I would then feel myself taking off. I haven't had any OOBEs for a while but I still hear the buzz when I'm asleep.
Just last night while I was asleep, I heard the buzz to my left which woke me up. When I opened my eyes everything seemed "normal" at least from what I could discern with my senses, but I felt a kind of presence.
Right, I'm buzzing off!
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