What does the term "jitter" refer to in the context of speech?

The term "jitter" refers specifically to the variation in frequency of periodic signals, particularly in voice signals. It is a measurement related to the stability or consistency of vocal fold vibrations during phonation. When there is jitter, it indicates that there are small, rapid fluctuations in the fundamental frequency of the voice, which can affect the perceived quality of speech, making it sound less stable or more mechanical.

In the context of speech, jitter is crucial for understanding voice quality, particularly in the assessment of voice disorders. A higher level of jitter suggests irregularities in vocal fold function, which may be due to pathology or other factors affecting the voice.

The other terms mentioned in the options relate to different aspects of speech characteristics. Variation in loudness pertains to intensity levels, variation in pitch is generally associated with changes in perceived frequency rather than the stability of frequency, and variation in duration relates to the length of phonemes or speech sounds. Each of these aspects is distinct from the concept of jitter, which focuses on frequency fluctuations specifically.