What are jitter and shimmer measures primarily used for?

Jitter and shimmer measures are specifically used to quantify the frequency and amplitude variability in a person's voice, which are key indicators of voice quality and stability. Jitter refers to the cycle-to-cycle variations in the fundamental frequency of the voice, while shimmer indicates the cycle-to-cycle variations in the amplitude. These measures are instrumental in identifying voice disorders because they provide objective data on the consistency and reliability of vocal production.

When there is an increase in jitter and shimmer, it often suggests issues with the vocal folds or other physiological factors affecting voice production. This is particularly relevant in clinical assessments where professionals evaluate the voice quality of individuals suspected to have voice disorders, such as dysphonia or other pathologies.

While the other options like assessing speech fluency, measuring vocal pitch, or determining speech rate may relate to voice or speech characteristics, they do not directly utilize jitter and shimmer as their primary measures.