noise is whatever you're not interested in studying/analyzing at the moment.

it's more a property of a thinking agent than it is of the universe.

if you see it everywhere it's because we are the same type of observers, maybe other kinds of hypothetical agents can segments the universe in different ways.

Your retina does quite a lot of noise filtering at the beginning of visual processing.

Background radiation is also a noise property of the universe, as is the background microwave radiation from the start of the universe. Is this just noise because it's an artefact of the measurement aparatus?

I think it’s just the normal noise/lighting/etc that is always there. You just have no reason to actually notice it (it provides no benefit to e.g. a hunter gatherer) so the brain normally disregards it. It’s a fundamental property of the universe but then again so is everything else.

I was thinking of noise - or randomness. It crops up in many places. When I was studying visual perception a long time ago (back during the second wave of neural networks) it amazed me what a hostile mechanism light is for actually getting a coherent signal that looks well put together (like what our brain does)