Directional perturbation factors for jitter and for shimmer.

Directional perturbation factors for jitter and shimmer were calculated from the sustained production of the vowels /i/, /a/, and /u/ by 20 adult male and 20 adult female speakers. Directional factors for jitter were less than directional factors for shimmer. Shimmer directional factors for females had greater values than for the male speakers. Speculations on the relationship of directional factors and magnitude factors are made with reference to the laryngeal reflexogenic system. The usefulness of directional factors to early diagnosis of laryngeal disease are discussed.