Voice onset time

In phonetics, voice onset time (VOT) is a feature of the production of stop consonants. It is defined as the length of time that passes between the release of a stop consonant and the onset of voicing, the vibration of the vocal folds, or, according to other authors, periodicity. 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.

History

The concept of voice onset time can be traced back as far as the 19th century, when Adjarian (1899: 119) studied the Armenian stops, and characterized them by "the relation that exists between two moments: the one when the consonant bursts when the air is released out of the mouth, or explosion, and the one when the larynx starts vibrating". However, the concept became widely known only in the 1960s, in a context described by Lin & Wang (2011: 514): "At that time, there was an ongoing debate about which phonetic attribute would allow voiced and voiceless stops to be effectively distinguished. For instance, voicing, aspiration, and articulatory force were some of the attributes being studied regularly. In English, "voicing" can successfully separate /b, d, ɡ/ from /p, t, k/ when stops are at word-medial positions, but this is not always true for word-initial stops. Strictly speaking, word-initial voiced stops /b, d, ɡ/ are only partially voiced, and sometimes are even voiceless." The concept of VOT finally acquired its name in the famous study of Leigh Lisker and Arthur Abramson (Word, 1964), done while working together at Haskins Laboratories.

Analytic problems

A number of problems arose in defining VOT in some languages, and there is 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. 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).