the present invention is a method and system to convert speech signal into a parametric representation in terms of timbre vectors , and to recover the speech signal thereof . the speech signal is first segmented into non - overlapping frames using the glottal closure instant information , each frame is converted into an amplitude spectrum using a fourier analyzer , and then using laguerre functions to generate a set of coefficients which constitute a timbre vector . a sequence of timbre vectors can be subject to a variety of manipulations . the new timbre vectors are converted back into voice signals by first transforming into amplitude spectra using laguerre functions , then generating phase spectra from the amplitude spectra using kramers - knonig relations . a fourier transformer converts the amplitude spectra and phase spectra into elementary waveforms , then superposed to become the output voice . the method and system can be used for voice transformation , speech synthesis , and automatic speech recognition .