Popping from engine after shutoff

Hey all;

I've noticed that for the past week or so, when I shutoff the engine after driving, there is a popping noise coming from the engine compartment. I opened the hood and it sounds like its coming from the block, kinda far down, in the middle or so. It's steady, like once every 4 seconds or so. Kinda loud, but then goes away after a little bit. Anyone know what this can be? I'm thinking it may have something to do with the oil filter or something, not sure why I think that, but it seems good. I haven't had a chance to get under the car in awhile, but there's no leaks or anything. Any ideas? Thanks.

its your car wanting a turbo... j/k... like is it likea knock or what i don't think i have heard a "pop" before

It kinda sounds like a knock. Like something is falling into place, or something popping. I don't get it though, bcause nothing is moving. It's hard to explain. It sounds muted out alittle. It's louder in the car then outside, unless the hood is open. It goes away though. I can't hear it if the car is on, so I don'tknow if it does it then or not.