In birds it consists of the trachea, the syrinx, the oral cavity, the upper part of the esophagus, and the beak. In mammals it consists of the laryngeal cavity, the pharynx, the oral cavity, and the nasal cavity.
The estimated average length of the vocal tract in adult male humans is 16.9 cm and 14.1 cm in adult females.
- Goldstein, Ursula Gisela (1980). An articulatory model for the vocal tracts of growing children (Ph.D.). Cambridge, MA: Massachusetts Institute of Technology.