Pulses and 1/f Noise

Low-frequency fluctuations with a 1/f frequency spectrum were first noticed by Johnson [1] in thermionic-emission currents in vacuum tubes, and exist in a very wide range on phenomena. A feature common to most of these phenomena is that they involve a quasirandom sequence of pulses on the microscopic scale. The spectrum of energies associated with a short pulse of characteristic width Δt is roughly flat up to Emax = h̄/Δt. In general, the pulse process can be associated with quanta (such as phonons or photons) of energy h̄ω, so the number spectrum of these quanta varies as 1/ω up to ωmax = 1/Δt. When a phenomenon consists of a sequence of closely spaced pulses, such that the macroscopic behavior is quasistatic, the microscopic behavior involve fluctuations with the frequency spectrum of the assciated quanta, namely 1/ω, i.e., 1/f .