THE EFFECT OF SUSTAINED PHONATION AT HIGH AND LOW PITCH ON VOCAL JITTER AND SHIMMER

Looking for possible signs of vocal fatigue, acoustic waveform perturb ation was measured in normal female subjects during sustained phonatio n at various fundamental frequencies (F(o)). At none of the pitch leve ls a rise of the jitter or the shimmer was found after 25 min of vocal ization. On the other hand, an effect of F(o) was seen from the start: above the habitual speaking F(o) of our subjects' voices there was a tendency for the jitter to be higher and for the shimmer to be lower.