I think I have heard some people mention they have this experience sometimes... Sometimes when I wake up from a dream but I'm not quite awake, I get this LOUD piercing beeeeep right in my head. It feels as if I can control its intenseness and as It gets more intense I feel like I'm starting to drift off into another lucid dream, but it also feels like my head might explode so I back off LOL. I really wonder what the hell that is lol.