Vocal tract
The vocal tract or speech apparatus is the cavity in mammals and in birds where the sound produced at the sound source is filtered.
In mammals, it consists of the laryngeal cavity, the pharynx, the oral cavity, and the nasal cavity. In birds, it consists of the trachea, the syrinx, the oral cavity, the upper part of the esophagus, and the beak.
The estimated average length of the vocal tract in men is 16.9 cm and 14.1 cm in women.