| Voice onset time |
|---|
| + Aspirated |
| 0 Tenuis |
| − Voiced |
In phonetics, voice onset time, commonly abbreviated VOT, is a feature of the production of stop consonants. It is defined as the length of time that passes between when a stop consonant is released and when voicing, the vibration of the vocal folds, begins. Some authors allow negative values to mark voicing that begins during the period of articulatory closure for the consonant and continues in the release, for those unaspirated voiced stops in which there is no voicing present at the instant of articulatory closure.
A graphical representation of the VOT of voiced, voiceless unaspirated and voiceless aspirated plosives
The concept of Voice Onset Time originated from the development in the early 1950s of a mechanical device for converting spectral information to an audio waveform, called the 'pattern-playback' machine.[1] Initially, the term was only applied to schemes for acoustically-based speech synthesis that used the pattern-playback device, in order to create a consistent perceptual differentiation between synthesized voiced and unvoiced stop consonant phonemes, primarily in English.[2] However, the concept was later brought into phonetics research to describe differentiations in stop consonants in actual languages[3]. Positive values of VOT generally measured what in previous articulatory and aerodynamic models of speech was referred to as the duration of the period of aspiration.[4][5][6]
However, a number of problems arose in defining VOT in some languages, and there is presently a call for reconsidering whether this speech synthesis parameter should be used to replace articulatory or aerodynamic model parameters which do not have these problems, and which have a stronger explanatory significance[7]. As in the discussion below, any explication of VOT variations will invariably lead back to such aerodynamic and articulatory concepts, and there is no reason presented why VOT adds to an analysis, other than that, as an acoustic parameter, it may sometimes be easier to measure than an aerodynamic parameter (pressure or airflow) or an articulatory parameter (closure interval or the duration, extent and timing of a vocal fold abductory gesture).
According to VOT analysis, the three major phonation types of stops can be analyzed in terms of their voice onset time.
Voice Onset Timing spectrograms for English "tie" and "die". The voiceless gap between release and voicing is highlighted in red. Here the phoneme /t/ has a VOT of 95 ms., and /d/ has one of 25 ms.
- 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 or less on [t] and 30 ms or less 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.
Voicing contrast applies to all types of consonants, but aspiration is generally only a feature of stops and affricates.
| Table. Relative VOT distinctions in various languages. | ||||||||
|---|---|---|---|---|---|---|---|---|
| Voice Onset Time | Examples | |||||||
| (fortis) | Strong aspiration | Tlingit | Navajo, Korean | |||||
| ↑ | Moderate aspiration | English | Cantonese | Thai, Armenian | ||||
| Mild aspiration | Navajo, Korean | |||||||
| Tenuis | Cantonese | Tlingit | Korean | Spanish, S. Japanese | Thai, Armenian | |||
| ↓ | Partially voiced | English | ||||||
| (lenis) | Fully voiced | Spanish, S. Japanese | N. Japanese | Thai, Armenian | ||||
References[]
- 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.
- ↑ LIBERMAN, A.M., DELATTRE, P.C. and COOPER, F.S., The role of selected stimulus variables in the perception of the unvoiced stop consonants, American J. of Psychology Vol. 65, 497-516, (1952).
- ↑ LIBERMAN, A.M., DELATTRE, P.C. and COOPER, F.S., Some cues for the distinction between voiced and voiceless stops in initial position, Language and Speech, Vol. 1, 153-167 (1958).
- ↑ LISKER, L. and ABRAMSON, A.S., A cross-language study of voicing in initial stops: acoustical measurements, Word Vol. 20, 384-422 (1964).
- ↑ STETSON, R.H.: Motor Phonetics, 2nd ed., North-Holland Publishing Company, Amsterdam (1951).
- ↑ SMALLEY, W.A., Manual of Articulatory Phonetics, University Press of America (1989).
- ↑ ROTHENBERG, M. The Breath-Stream Dynamics of Simple-Released Plosive Production, Vol. 6, Bibliotheca Phonetica, Karger, Basel, 1968.
- ↑ ROTHENBERG, M. "Voice Onset Time vs. Articulatory Modeling for Stop Consonants", The Jan Gauffin Memorial Symposium, October 16, 2008. Royal Institute of Technology, Stockholm. (To be published in the proceedings)
External links[]
- Buy a pie for the spy A description of the mechanism of voiced, voiceless unaspirated and voiceless aspirated plosives in relation to voice onset time
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