Prevoicing, in phonetics, is voicing before the onset of a consonant or beginning with the onset of the consonant but ending before its release. In the extensions to the International Phonetic Alphabet for speech pathology, prevoicing is transcribed with a voicing diacritic (̬, U+032C) placed in front of the consonant, as in pronounced as /[̬d]/.
In several Khoisan languages of Southern Africa, such as Taa and !Kung, stops such as pronounced as //dzʰ// (pronounced as /[dsʰ]/ or pronounced as /[dtsʰ]/) and pronounced as //dzʼ// (pronounced as /[dsʼ]/ or pronounced as /[dtsʼ]/) are sometimes analyzed as being prevoiced pronounced as // ̬tsʰ// and pronounced as // ̬tsʼ//,[1] though the cessation of voicing has also been analyzed as phonetic detail in the transition of a phonemically voiced consonant to its voiceless aspiration or ejection. (See aspirated voiced consonant and voiced ejective.)
Kelabit has a similar set of aspirated voiced consonants. Not all speakers produce the aspiration, resulting in prevoiced (or mixed voiced) pronounced as /[b͡p, d͡t, ɡ͡k]/ (or equivalently pronounced as /[ ̬p, ̬t, ̬k]/, and neighboring Lun Dayeh has pronounced as /[b͡p, d͡tʃ, ɡ͡k]/ (= pronounced as /[ ̬p, ̬tʃ, ̬k]/.