Variability in closed phase analysis of speech

Accurate characterization of the vocal tract filter relies on speech data obtained from the closed glottal interval. Use of the electroglottograph (EGG) as a noninvasive and reliable means of monitoring glottal vibratory characteristics has increased the popularity of the two channel approach to speech analysis. The cycle by cycle auxiliary glottal information provided by the EGG facilitates implementation of pitch synchronous closed phase procedures. This paper shows that the closed phase method can yield variable results if the EGG information, or an alternative closed phase indicator, is not used correctly for analysis frame positioning. Synchronized glottal area waveforms obtained from ultra high speed laryngeal films verify true closure for our analyses. Results presented for other known regions also confirm many previous observations.