 Voicing

Voicing is the use of vocal fold vibration during speech production. Airflow and the mechanical state of the vocal folds can sustain repeated opening and closing, introducing a periodic component into the emitted sound. The fundamental frequency of this repetition contributes to perceived pitch.

A practical comparison is to sustain [s] and [z] while gently feeling the front of the throat: the added vibration during [z] makes the distinction tangible. Both involve a similar oral constriction, so the comparison separates voicing from place of articulation and manner of articulation. The physical state of the glottis is an additional dimension of the sound.^[ref]

A binary transcription is a useful classification rather than a complete time record. Voicing can begin, end or weaken during a sound, and an acoustic estimate depends on the interval examined. A pitch contour should therefore distinguish missing or unreliable periodicity from a measured low fundamental frequency.