One of the types of objects in Praat. The Electroglottogram represents changes in vocal fold contact area during vocal fold vibration.

The Electroglottogram waveform

The following picture shows part of one cycle of a stereotypical (stylized) waveform, with landmarks.

The orientation of the signal is in the (now) conventional way where the positive y-direction signals larger vocal fold contact area (VFCA). The landmarks refer to:

• a – initial contact of the lower vocal fold margins;
• b – the upper vocal fold margins make initial (but not full) contact;
• c – maximum vocal fold contact reached;
• d – de-contacting phase initiated by separation of the lower vocal fold margins;
• e – upper margins start to separate;
• f – glottis is open, with minimal contact area.

How to get an Electroglottogram?

From standard electroglottography measurements generally a multi-channel sound file results. One channel of this file contains the recorded electroglottogram, the other the recorded sound. You can extract the electroglottogram with the Extract Electroglottogram... command that you will find under the Sound: Convert - menu.

Glottal opening and closure times

Getting exact timing of the glottal closure instants (GCI) and glottal opening instants (GOI) from the Electroglottogram is problematic because as Herbst (2019) notes: the vocal folds do not vibrate as a uniform mass. Rather, their vibration is characterized by phase differences along both the inferior–superior and anterior–posterior dimensions. These phase differences cause time-delayed contacting and de-contacting of the vocal folds along the respective axes. There is thus no specific instant of glottal closing and opening, but rather an interval during which the closing and opening, respectively, occur.

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