  We show how the semiclassical Langevin method can be extended to calculations
of higher-than-second cumulants of noise. These cumulants are affected by
indirect correlations between the fluctuations, which may be considered as
"noise of noise." We formulate simple diagrammatic rules for calculating the
higher cumulants and apply them to mesoscopic diffusive contacts and chaotic
cavities. As one of the application of the method, we analyze the frequency
dependence of the third cumulant of current in these systems and show that it
contains additional peculiarities as compared to the second cumulant. The
effects of environmental feedback in measurements of the third cumulant are
also discussed in terms of this method.
