Patent ID: 6629068
Filing Date: 2003-09-30
Classification: G10L

Abstract:
A method for calculating a postfilter frequency response for filtering digitally processed speech, the method comprising identifying at least one formant of a speech spectrum of the digitally processed speech; and normalising points of the speech spectrum with respect to the magnitude of an identified formant, wherein the points of the speech spectrum are normalised according to a function of the form Rpost&it;(k)=(R&it;(k)Rform&it;(k))Î²where R(k) is the amplitude of the spectrum at a frequency k and Rform(k) is the amplitude of the spectrum at a frequency k which corresponds to an identified formant frequency and &bgr; controls the degree of postfiltering, and Î²=k-kmaxkmin-kmax&it;o&it;â€ƒ&it;Î³&it;â€ƒ&it;Î²=kmin-kkmin-kmax&it;o&it;â€ƒ&it;Î³&it;â€ƒ&it;forâ€ƒ&it;kmax<k&leq;kmin&it;â€ƒ&it;and&it;â€ƒ&it;Î²=kmax-kkmax-kmin&it;o&it;â€ƒ&it;Î³&it;â€ƒ&it;forkmin<k&leq;kmax&it;â€ƒwhere k is a point in frequency, kmin is the frequency of a spectral valley, kmax is the frequency of a formant and &ggr; controls the degree of postfiltering.