Electroglottogram: To TextGrid (closed glottis)...

Calculates the intervals where the glottis is closed from the selected Electroglottogram.

## Settings

Pitch floor (Hz)
  intervals with a lower pitch will not be considered.
Pitch ceiling (Hz)
  intervals with a higher pitch will not be considered.
Closing threshold
  the moment of closing of the vocal folds will be taken at a fixed point between a cycle's peak and valley amplitude level.

  The picture shows, for a closingThreshold value of 0.3, the Closed Glottis Interval that starts at time t1 and ends at time t2. These times were found by calculating the two level crossings at amplitude valley+closingThreshold(peak–valley).
Peak threshold
  cycles with peaks whose relative amplitudes with respect to the maximum peak are lower than this value are not considered.

## Algorithm

The algorithm first tries to find peaks and valleys, guided by the settings for the pitch floor and ceiling. From the level crossings before and after a peak the times of glottal closing and opening are determined.

## Warning

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.