The glottal waveform’s closing phase is abrupt and carries most excitatory energy.

Evidence

Glottal oscillation, the almost periodic opening and closing of the vocal folds, is the main excitation in voiced sounds. Glottal functioning has been modelled mathematically in several ways, for example as a simple mass–spring system as in Figure 5.9 (Flanagan, 1972), as a spatially distributed mass–spring system (surface-wave transmission line), or just as experimental functions of time for volume velocity (Fant et al., 1985). Figure 5.3 on page 81 plots the volume velocity at the glottis during static phonation of a vowel. The glottal waveform typically resembles a half-wave rectified sinusoidal signal with asymmetry, so that the opening phase is relatively slow and the closing phase is more abrupt, as seen in the figure. — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 610

Categorization

• XREF: Connects to source-filter speech synthesis theory — same glottal source model used in parametric synthesizers.
• corroborated: 2 independent passages support this claim — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 610