The type of noise that distracts me more is definitely internal noise. If I am dying for food or am bored out of my mind, it can be quite hard to stay focused on what the speaker is trying to present. If I have something going on after school or am trying to work through a problem in my head, I may as well not be listening because I am more focused on my thoughts rather than the speakers words. I try my best to block said noises out, which can be tough. The harder I focus on listening, usually, the better I do with it.
I agree that things like hunger make it very hard to listen, especially during a lesson that doesn't interest you. I like your methods of trying to stay focused by locking in on what a speaker is saying.
I have noticed you get quite cranky when you get hungry. I completely agree that much of the noise that affects me is internal.