  Linear functions of many independent random variables lead to classical
noises (white, Poisson, and their combinations) in the scaling limit. Some
singular stochastic flows and some models of oriented percolation involve very
nonlinear functions and lead to nonclassical noises. Two examples are examined,
Warren's `noise made by a Poisson snake' and the author's `Brownian web as a
black noise'. Classical noises are stable, nonclassical are not. A new
framework for the scaling limit is proposed. Old and new results are presented
about noises, stability, and spectral measures.
