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google the "Bloop"

answers

There are many things that could be making that noise, and they range from a hungry stomach to an earthquake. If you don't see the buildings shaking, however, then I wouldn't be too concerned.

Most likely Cthulhu.

It's called thunder.

HL3 confirmed

o ya? =D

Woke up this morning to the bed shaking violently, some ominous rumbling and stuff falling off shelves.

At first I thought it was just last night's Prawn Vindaloo, but we've been having some nice lively earthquakes here all day :)

You're not in New Zealand too, perchance?

Happened to me a few nights ago... I heard rumbling outside the door.

I got up slowly and the rumlbing resumed. The light outside was off, so it couldn't be a human.

I got closer to the door and suddendly... MEOW. My cat stepped out when I came back home and I forgot to let him back in again. ^^

Make sure you're not hungry, your sanity is adequate (if not, eat some flowers just in case), there is a light source on at all times, and you're near a herd of beefalo's (who are not in heat) in case that sound is a pack of wild dogs getting ever closer.

I remember one winter night last year I was sleeping alone (I rarely sleep alone). I woke up, it was pitch black. At first I didn't know why I had woken up but then I heard this weird screeching sound coming from somewhere. I got up and listened for awhile, I noticed it was coming from behind the closed bathroom door. I opened the door, turned the lights on and instantly the lamp burned out. However, in that short moment I saw a figure, a shape in there. Definitely didn't look human. It scared the crap out of me, I quickly turned on the hallway light to see better and then there was nothing.

Air Conditioning possibly.
Or a distant train. Where I live the diesel trains can be heard sometimes very late at night (sound travels further at night and there is less ambient noise) and it's a very low frequency rumbling sound.

Go see a doctor son