vocaltract

The vocal tract is the air-filled cavity above the larynx that shapes the sounds produced by the vocal folds. It extends from the glottis to the lips, and in the case of nasal sounds, to the nostrils. It comprises the pharynx, oral cavity, and nasal cavity, with the velum acting as a valve at the velopharyngeal port to direct airflow into the oral or nasal passages.

Anatomy and movable parts: The pharynx lies behind the mouth and larynx; the oral cavity is bounded by the lips, teeth, palate, and tongue; the nasal cavity connects to the outside via the nostrils. Key articulators include the tongue (various parts), lips, jaw, velum, and the soft tissues of the palate and pharynx. The larynx provides the sound source, while the surrounding tract functions as a resonator that shapes the sound.

Function and acoustics: The vocal tract shapes the glottal sound by adjusting constrictions and resonances, yielding vowels with formants and consonants with characteristic places and manners of articulation. Formant frequencies (such as F1 and F2) reflect vowel height and frontness, while the overall tract shape influences timbre and intelligibility. Nasality is controlled by opening or closing the velopharyngeal port, coupling or isolating the nasal cavity from the oral cavity.

Dynamics and measurement: Articulators move rapidly to create vowels, diphthongs, and consonants, with coarticulation causing overlapping influences between sounds. In speech science, the vocal tract is often modeled as a resonant tube, and formants are estimated from spectra for acoustic analysis, synthesis, and clinical assessment.