A few years back... It was around 3.30 am, and I woke up because of a horrendous noise outside my bedroom door (which leads straight to a patio, ie: more or less to the open). The noise could be described like this: Imagine the largest array of speakers you can think of. Now imagine some pretty deep synthesizer bass sound played through all of them. It was approximately like that, although that sound was freakier. Also, it was kind of oscillating at a very slow pace, approx 4 or 5 seconds. At first, when it woke me up, I was in a semi-dreamlike state, but when I realised that it was real, and one of the loudest things I had heard, I bolted up and sat upright in my bed, listening. It seemed to be on for ages. I was relieved that I couldnt see into the patio, as, if there would have been something present, I would have probably shit myself, and if there wouldn´t, I would still shit myself, totally baffled as to the whereabouts. However, I was still kinda scared without seeing anything. On top of that, a light starting shining into my room, through the covered window. As if someone had come up the driveway. Except there was no car and my house is isolated in that the only car that would come up that driveway would be that of our family and not just random cars riving by. I slapped myself to make sure I was not dreaming.
After about 10 minutes, I realised that it was slowly getting further away (as the sound pitch got higher), and after another 5 it was gone. (maybe it was less, I didnt count). It took me a while to get back to sleep. Thank god that I wasnt fully aware of what had happened, as I think I probably wouldnt have been able to fall asleep then.
I know it was real, as the first thing I did when waking up, was smack my alarm clock to (by help of the backlight) see what time it was, ie: approx 3.30 am.
What also freaked me out, was that the next morning while playing ping pong with my (younger) bro, he said that the door to the computer/living room was open, and I KNEW that I had closed it as the last person leaving it the night before.