Differences in fundamental frequency, jitter, and shimmer among four types of infant vocalizations.

An inaudible voice variable, known to be influenced by stress-arousal in adults, was recently discovered to differ significantly among four situationally defined types of infant vocalizations. Other research suggests that jitter in adults also may be altered by stress-arousal. Further, there is a lack of normative data on jitter and shimmer in infant vocalizations. These findings prompted this study comparing F0, jitter, and shimmer among four situationally defined vocalizations ("pain," "hunger," "fussy," and "cooing") of 2-6-month-old infants. Data showed no significant difference in either jitter or shimmer among the four vocalizations; no significant difference in F0, jitter, or shimmer due to the sex or age of infant; a significant difference in F0 among "hunger," "cooing," and either "pain" or "fussy" vocalizations; and no significant difference in F0 between "pain" or "fussy" cries.