  Simple analytically solvable model of 1/f noise is proposed. The model
consists of one or few particles moving in the closed contour. The drift period
of the particle round the contour fluctuates about some average value, e.g. due
to the external random perturbations of the system's parameters. The model
contains only one relaxation rate, however, the power spectral density of the
current of particles reveals an exact 1/f spectrum in any desirable wide range
of frequency and can be expressed by the Hooge formula. It is likely that the
analysis and the generalizations of the model can strongly influence on the
understanding of the origin of 1/f noise.
