= Flicker noise
{title2=$S(f)\propto1/|f|$}
Low-frequency <noise> with an approximately inverse-<frequency> <power spectral density> over a specified range. It can dominate the flat spectrum of a weakly confined mechanical coordinate or an electronic readout at low <frequencies>. A $1/f$ law cannot hold with finite total <variance> over unlimited frequency range, so its measured bandwidth and low-frequency cutoff matter. An observed excess alone does not uniquely identify the microscopic source.
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