sentences:  If this property is not met, then the desired multi-component decomposition cannot be achieved, because the parameters of individual components cannot be estimated from the short-time Fourier transform.In such cases, a different analysis window must be chosen so that the separability criterion is satisfied.If the components of a signal are separable in frequency with respect to a particular short-time spectral analysis window, then the output of each short-time Fourier transform filter is a filtered version of, at most, a single dominant (having significant energy) component, and so the derivative, with respect to time, of the phase of the formula_47 is equal to the derivative with respect to time, of the phase of the dominant component at formula_48 Therefore, if a component, formula_49 having instantaneous frequency formula_50 is the dominant component in the vicinity of formula_51 then the instantaneous frequency of that component can be computed from the phase of the short-time Fourier transform evaluated at formula_48 That is,
  
  Just as each bandpass filter in the short-time Fourier transform filterbank may pass at most a single complex exponential component, two temporal events must be sufficiently separated in time that they do not lie in the same windowed segment of the input signal.