sentences:  The modified moving window method, or method of reassignment, changes (reassigns) the point of attribution of formula_22 to this point of maximum contribution formula_23, rather than to the point formula_16 at which it is computed.This point is sometimes called the "center of gravity" of the distribution, by way of analogy to a mass distribution.This analogy is a useful reminder that the attribution of spectral energy to the center of gravity of its distribution only makes sense when there is energy to attribute, so the method of reassignment has no meaning at points where the spectrogram is zero-valued.