Was hanging out with a friend of mine while he was babysitting his nephew (Kenny) who's about 5 years at the time. We were like 16-17. And it's about 9:30 at night and it had been about 30 minutes since my friend put his nephew to bed. So we've been sitting on the couch playing Mario or Zelda or some wii game for about the last 30 minutes in the living room. Directly behind the living room is the nephew's room and we are sitting on the couch with our backs to his bedroom wall. All the lights are off at this point besides the tv and a small kitchen light. Out of nowhere it seems, we hear an extremely loud roar that can be described as an old demonic man or beast of some sort come from the wall behind us. the nephew's room. We stand up and look at the wall where a large painting hangs and it happens again. Right in front of our eyes. Holy fuck we think. Kenny's in there by himself. Is that him?? The roar frightened the hell out of us. It shook the fucking 3x5 foot painting. It filled the room. It was coming from in there. My friend and I then go to the door armed with kitchen knives and are about to bust in terrified of what we're about to encounter. A holy war is about to ensue between us and this demon we're about to encounter. The worst part is we're afraid the demon may be in Kenny and that we'll have to exorcise it out of him before his father comes home. I look at my friend and he begins to quietly whisper "Kenny! Kenny!". After no response he begins to open the door. Upon first sight there's nothing going on in the room. The bed is on the left and the tv is off and you can see Kenny quietly sleeping. My friend wakes him up and asks "Kenny, you ok?". Kenny, quite sleepy responds in an odd manner saying something about voices telling him to do things. "What things?" my friends says. "BAD THINGS" he says. We tell Kenny "hey buddy, you wanna come hang out with us in the living room until your dad gets here?" He says yeah and we just have him sit there on the couch while we go back to trying to play video games. We ask each other things like "Dude WTF was that?" but we don't want to traumatize Kenny who's just falling asleep again on the couch.
Kenny's dad soon arrives back home and we begin to tell him as best as we can. Obviously he was concerned but besides inspecting the room and making sure Kenny's alright there isn't much more that could be done. It didn't necessarily change my belief system but I could never be a full blown atheist after experiencing that. I'll never really know what that noise was.