These windows are obtained by the polynomial expression w(n)=(16(n/Ns-1))^4-8(n/8Ns-1))^2+1)^L
where w(n) is the nth value of the window (in the time domain) and Ns is the number of samples of the window itself. The equation is computed only for positive values of n because the relationship w(-n)=w(n) holds(the function is even). The parameter L is used to vary the frequency response behaviour: low values of L lead to narrow main lobes and moderately low slidelobes, whilw increasing L broadens the main lobe and reduces sidelobes.
[D'Amico M., Ferrigno G. (1992), Comparison between the more recent techniques for smoothing and derivative assessment in biomechanics, Med.& Biol. Eng.& Comput., 1992,30, 193-204]