We propose a stochastic model of phonon-number fluctuations that allow
s to simulate 1/f-like behavior. The fluctuation process is described
as a random walk on the ladder of energy levels of a harmonic oscillat
or. Two characteristic time scales are involved in the process: the me
an life time of states tau(l) and the correlation time tau(c). When th
e ratio tau(c)/tau(l) is large, the 1/f-like spectrum is observed with
in the frequency range 1/tau(c)<f<1/tau(l). Conditions for large value
s of the ratio are discussed.