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Department of Linguistics

PHONETICS AND PHONOLOGY

Voice Onset Time (VOT)

Robert Mannell

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Voice Onset Time (VOT)

This diagram defines Voice Onset Time (usually referred to as VOT). VOT can be positive, zero or negative and the timing is always relative to the stop release burst. This definition is only valid for syllable-initial stops, including VCV stops. The following vowel in this diagram can be replaced by a following approximant in a syllable initial consonant cluster (a group of two or more consonants).

A pre-voiced stop (eg. [ɡ]) has negative VOT, a voiceless unaspirated stop (eg. [k]) has zero VOT and a voiceless aspirated stop (eg. [kʰ]) has positive VOT. In practice, a VOT in the range of -20 ms (milliseconds) to +20 ms sounds like a zero VOT.



VOT for English Word-Initial Stops

This diagram defines stop voicing for syllable-initial English stops. It can be seen from this diagram that a voiced oral stop phoneme, such as /ɡ/, can be realised by a stop with negative, zero or positive VOT, but these values are usually in the range of -20 to +20 ms and so are perceptually equivalent to zero VOT.

English voiceless aspirated stop phonemes, such as /k/, are only audibly aspirated if the VOT is significantly greater than +20 ms (this usually means in practice a VOT in excess of about 40 ms).