In phonetics, voice onset time, commonly abbreviated VOT, is the length of time that passes between when a consonant is released and when voicing, the vibration of the vocal folds begins. Phonetics (from the Greek word φωνή, phone = sound/voice) is the study of sounds (voice). ... In articulatory phonetics, a consonant is a sound in spoken language that is characterized by a closure or stricture of the vocal tract sufficient to cause audible turbulence. ... A voiced consonant is a sound made as the vocal cords vibrate, as opposed to a voiceless consonant, where the vocal cords are relaxed. ... Laryngoscopic view of the vocal folds. ...

The three major phonation types of stops can be analyzed in terms of their voice onset time. In phonetics, phonation is the use of the laryngeal system to generate an audible source of acoustic energy, i. ...

• Simple unaspirated voiceless plosives, sometimes called tenuis plosives, have a voice onset time at or near zero, meaning that the voicing of a following sonorant (such as a vowel) begins at or near to when the stop is released. (An offset of 15 ms on [t] or 30 ms on [k] is inaudible, and counts as tenuis.)

• Aspirated plosives followed by a sonorant have a voice onset time greater than this amount, called a positive VOT. The length of the VOT in such cases is a practical measure of aspiration: The longer the VOT, the stronger the aspiration. In Navajo, for example, which is strongly aspirated, the aspiration (and therefore the VOT) lasts twice as long as it does in English: 160ms vs. 80ms for [kʰ], and 45ms for [k]. Some languages have weaker aspiration than English. For velar stops, tenuis [k] typically has a VOT of 20-30 ms, weakly aspirated [k] of some 50-60 ms, moderately aspirated [kʰ] averages 80-90 ms, and anything much over 100 ms would be considered strong aspiration. (Another phonation, breathy voice, is commonly called voiced aspiration; in order for the VOT measure to apply to it, VOT needs to be understood as the onset of modal voicing. Of course, an aspirated consonant will not always be followed by a voiced sound, in which case VOT cannot be used to measure it.)

• Voiced plosives have a voice onset time noticeably less than zero, a negative VOT, meaning the vocal cords start vibrating before the stop is released. With a fully voiced stop, the VOT coincides with the onset of the stop; with a partially voiced stop, such as English [b, d, g] in initial position, voicing begins sometime during the closure (occlusion) of the consonant.

Because neither aspiration nor voicing is absolute, with intermediate degrees of both, the relative terms fortis and lenis are often used to describe a binary opposition between a series of consonants with higher (more positive) VOT, defined as fortis, and a second series with lower (more negative) VOT, defined as lenis. Of course, being relative, what fortis and lenis mean in one language will not in general correspond to what they mean in another. Phoneticians define phonation as use of the laryngeal system to generate an audible source of acoustic energy, i. ... A stop or plosive or occlusive is a consonant sound produced by stopping the airflow in the vocal tract. ... A tenuis consonant is one which is unvoiced and unaspirated. ... In phonetics and phonology, a sonorant is a member of a class of speech sounds that are continuants produced without turbulent airflow in the vocal tract. ... In phonetics, aspiration is the strong burst of air that accompanies the release of some obstruents. ... Reading Adahooniigii — The Navajo Language Monthly Navajo or Navaho (native name: Diné bizaad) is an Athabaskan language (of Na-Dené stock) spoken in the southwest United States by the Navajo people (Diné). It is geographically and linguistically one of the Southern Athabaskan languages (the majority of Athabaskan languages are spoken... The English language is a West Germanic language that originates in England. ... Breathy voice or murmured voice is a phonation in which the vocal folds are vibrating as in normal voicing, but the glottal closure is incomplete, so that the voicing is somewhat inefficient and air continues to leak between the vocal folds throughout the vibration cycle with audible friction noise. ... Phoneticians define phonation as use of the laryngeal system to generate an audible source of acoustic energy, i. ... Fortis (from Latin fortis strong) and lenis (from Latin lenis weak) are linguistics terms. ...

Voicing contrast applies to all types of consonants, but aspiration is generally only a feature of stops and affricates.

Reference

• Taehong Cho and Peter Ladefoged, "Variations and universals in VOT". In Fieldwork Studies of Targeted Languages V: UCLA Working Papers in Phonetics vol. 95. 1997.