A phenomenological description of excess noise in a nonequilibrium system is presented. The development involves two basic physical ideas. Firstly, the excess noise is ascribed to the fluctuation of the local reference level to which equilibrium and other white fluctuations are compared. Secondly, it is assumed that excess low‐frequency noise involves a nonlinear process. This implies the noise power in different frequency regions are coupled. A further simple assumption requires the integral of the power spectral density over specially chosen intervals to be a constant. This leads to a 1/fspectrum for the power spectral density. Possible generalizations that provide for other spectral laws are also mentioned.