In phonetics, prevoicing means that voicing begins before the release of a stop consonant. This means that the voice onset time has a negative value. In the Extended IPA for speech pathology, this is transcribed with a voicing diacritic ( ̬, U+032C) placed in front of the consonant, as in [ ̬z].
Phonemically prevoiced consonants such as [dtʰ] and [dtsʼkxʼ] have been reported from some of the Khoisan languages of Southern Africa, such as Ju/’hoan and !Xóõ. [dtʰ] is often analyzed as a single segment, a voice contour. However, some linguists have analyzed it instead as a consonant cluster with mixed voicing.