Formant excitation before and after glottal closure

Some results are presented of the use of partial inverse filtering to produce waveforms representing single formants of voiced speech. These waveforms confirm the well known fact that the main formant excitation normally occurs at glottal closure. However, there is frequently evidence of additional excitation, not only at glottal opening and during the open phase, but also after closure. The latter effect might be accounted for by air displacement resulting from small movements of the surface of the vocal folds, as often seen on high speed motion pictures of the larynx. The implications for speech analysis and synthesis are discussed.