A system for estimation of spectral envelopes and group delays for sound analysis and synthesis comprising: a fundamental frequency estimation section configured to estimate F0s from an audio signal at all points of sampling; an amplitude spectrum acquisition section configured to divide the audio signal into a plurality of frames, centering on each point of sampling, by using a window having a window length changing with F0 at each point of sampling, to perform Discrete Fourier Transform analysis on the plurality of frames of the audio signal, and thus to acquire amplitude spectra at the respective frames; a group delay extraction section configured to extract group delays as phase frequency differentials at the respective frames by performing a group delay extraction algorithm using DFT analysis on the plurality of frames of the audio signal; a spectral envelope integration section configured to obtain overlapped spectra at a predetermined time interval by overlapping the amplitude spectra corresponding to the frames included in a certain period determined based on a fundamental period of F0, and to average the overlapped spectra to sequentially obtain a spectral envelope for sound synthesis; and a group delay integration section configured to select a group delay corresponding to a maximum envelope for each frequency component of the spectral envelope from the group delays at a predetermined time interval, and to integrate the thus selected group delays to sequentially obtain a group delay for sound synthesis, characterized in that: the spectral envelope integration section is configured to obtain the spectral envelope for sound synthesis as a mean value of the maximum envelope and a minimum envelope of the overlapped spectra; and the group delay integration section is configured to store, by frequency, the group delays in the frames corresponding to the maximum envelopes for respective frequency components of the overlapped spectra, to compensate a time-shift of analysis and to normalize the stored group delays for use in sound synthesis. a fundamental frequency estimation section configured to estimate F0s from an audio signal at all points of sampling; an amplitude spectrum acquisition section configured to divide the audio signal into a plurality of frames, centering on each point of sampling, by using a window having a window length changing with F0 at each point of sampling, to perform Discrete Fourier Transform analysis on the plurality of frames of the audio signal, and thus to acquire amplitude spectra at the respective frames; a group delay extraction section configured to extract group delays as phase frequency differentials at the respective frames by performing a group delay extraction algorithm using DFT analysis on the plurality of frames of the audio signal; a spectral envelope integration section configured to obtain overlapped spectra at a predetermined time interval by overlapping the amplitude spectra corresponding to the frames included in a certain period determined based on a fundamental period of F0, and to average the overlapped spectra to sequentially obtain a spectral envelope for sound synthesis; and a group delay integration section configured to select a group delay corresponding to a maximum envelope for each frequency component of the spectral envelope from the group delays at a predetermined time interval, and to integrate the thus selected group delays to sequentially obtain a group delay for sound synthesis, the spectral envelope integration section is configured to obtain the spectral envelope for sound synthesis as a mean value of the maximum envelope and a minimum envelope of the overlapped spectra; and the group delay integration section is configured to store, by frequency, the group delays in the frames corresponding to the maximum envelopes for respective frequency components of the overlapped spectra, to compensate a time-shift of analysis and to normalize the stored group delays for use in sound synthesis.