I don't think anyone has. When it's that dark you get a free light show courtesy of your eyes. It was quite disconcerting the first time it happened to me.

Clearly you've never been in the (real) middle of nowhere at night when it's cloudy. Rural North Dakota, for example.

Stars put out quite a bit of light in remote areas, cloud cover may block ~75% of this, but it's still far from 'pitch black'. One of the stranger things about caving is it just keeps getting darker as you go deeper.

PS: As a kid I used to spend a lot of time walking around in starlight. I only ever really used a flashlight inside. I moved much closer to a city and light pollution is terrible to the point where there is little need to turn lights on in my apartment unless I want to read something.

I think he means the noise you see in the complete absence of light, or Eigengrau.