Which of the following is a frequency measure of speech?

The correct answer is shimmer, as it pertains specifically to a quantitative measure related to frequency variations in voice quality. Shimmer refers to the small, rapid variations in amplitude of the voice signal, which can be linked to how consistently a person is able to phonate. It is often used in voice assessments to evaluate voice stability and can be particularly important in understanding the frequency characteristics of an individual's vocal quality.

Other options, while important in their own contexts, do not specifically measure frequency. Duration refers to the length of time a sound is held, which relates more to timing than to frequency. Voice onset time is a temporal measure that evaluates the time between the release of a consonant and the onset of the vocal fold vibrations for the following vowel, rather than measuring frequency. Speech rate quantifies the number of syllables or words spoken over a given time, focusing on how fast speech is produced instead of analyzing frequency properties. Therefore, shimmer is the only option that directly measures aspects of frequency related to speech.