METHOD CAPABLE OF EXTRACTING A VALUE OF A SPECTRAL ENVELOPE PARAMETER WITH A REDUCED AMOUNT OF OPERATIONS AND A DEVICE THEREFOR

A logarithmic frequency spectrum related to an input signal is converted by the use of an inverse Fourier transform into a cepstrum. The cepstrum has a first and a second frequency component which have a first peak and a second peak spaced apart from the first peak by a preselected period on an axis of frequency, respectively. The second frequency component is processed into a peak controlled frequency component having a controlled peak coincident with the first peak. The peak controlled frequency component and the first frequency component are summed up to produce an ultimate frequency component which corresponds to the value of the envelope parameter.