Unvoiced

Unvoiced is a term used in phonetics to describe speech sounds produced without vibration of the vocal folds. In an unvoiced articulation, there is no periodic glottal vibration; the vocal cords are essentially not vibrating, so the sound lacks voicing. This contrasts with voiced sounds, where the vocal cords vibrate during production. The unvoiced versus voiced distinction is a primary feature distinguishing many consonants across languages.

Most unvoiced consonants are obstruents, including stops such as p, t, k; fricatives such as f, s, ʃ; the dental fricative θ; and glottal h. Some languages also have voiceless affricates. Voiceless stops may be aspirated or unaspirated depending on context and language. Vowels are typically voiced, though some languages exhibit rare cases of voiceless vowels or other unusual phonation patterns in specific environments.

In acoustic terms, unvoiced sounds lack the periodic low-frequency voicing that accompanies vocal fold vibration, and they often exhibit either a sharp transient or continuous aperiodic noise depending on the segment. In many languages, voicing contrasts are phonemic for obstruents; in other languages, final obstruent devoicing reduces such contrasts in word-final position. The term unvoiced is commonly synonymous with voiceless in linguistic references.