I just started my car to let it warm up and it made a sound that it's made a few times now. I was just sitting here in the computer room and I hear my car make this really loud low-pitch moaning sound as it's just sitting the idling. It's also made the same sound a few times while I was down-shifting. It sounds like a damn bull horn or something and sounds like something might be rubbing together. It only does it for a couple of seconds. I have no clue what it could be, I've never heard a car make this sound. Anyone know?