2. Photonic noise and electronic noise

It's a fact known to all of us: the human brain is not only sensitive to the "intelligible" signal it receives, it is also unable to disregard the "surrounding" noise, and more precisely, it is the relationship between these two quantities that matters to it. Defining what noise is is a complicated (and sometimes subjective...) task beyond the scope of this article, and we'll confine ourselves to general considerations. Any signal X = s + n perceived by the brain (an image, a sound...) is the sum of an "interpretable", meaningful, deterministic component, s, and a component that cannot be interpreted, which appears to be stochastic in nature and which we call noise, n.

We'll come back to these considerations in