A simple method for testing whether broadband noise comes from driven dynamical effects (rather than equilibrium fluctuations) is described. Asymmetrical higher-order time correlation functions can violate detailed balance, providing a key signature of dynamical effects. Simulations of a one-dimensional sandpile model are used for an initial illustration. Also, a hitherto unreported phenomenon—growth of the non-Gaussian nature of the statistics with system size—is found and attributed to the presence of correlations on the scale of the whole system.

• Received 29 June 1992

DOI:https://doi.org/10.1103/PhysRevA.46.R4475