FIG. 11.  Selected magnitude spectra of the output of the voicing source model of Klattalk as the duration of the open portion of the glottal cycle is varied from 1 ms (NOPEN=40) to 6 ms (NOPEN=240). Note the significant change in relative energy content at low frequencies; the amplitude of the first harmonic varies by about 24 dB from top to bottom panels. Short samples of the glottal waveform Ug(t) and its first derivative are shown to the left of each spectrum.