The Vocal Tract and Airstream Mechanisms

The vocal tract is the system of cavities above the larynx that shapes speech sounds, while airstream mechanisms are the means by which moving air is generated to produce them.

Definition

The respiratory, laryngeal, and supralaryngeal structures used in speech, together with the pulmonic, glottalic, and velaric mechanisms that set air in motion.

Scope

This topic describes the anatomy of the speech apparatus—the lungs and respiratory system, the larynx and vocal folds responsible for phonation, and the pharyngeal, oral, and nasal cavities that act as resonators and sites of constriction. It also covers the three airstream mechanisms used in human speech: pulmonic (lung-driven, the basis of most sounds), glottalic (used for ejectives and implosives), and velaric (used for clicks). The treatment is descriptive, surveying the physiological resources from which speech sounds are built.

Core questions

• What are the major components of the vocal tract and what roles do they play?
• How does the larynx produce voicing and other phonation types?
• What are the three airstream mechanisms and which sounds use each?
• How do non-pulmonic sounds such as clicks and ejectives differ from ordinary speech sounds?

Key theories

Classification of airstream mechanisms

Catford's analysis of speech sounds by the source of airflow—pulmonic, glottalic, and velaric, each egressive or ingressive—which provides a principled account of the full range of sound types including clicks, ejectives, and implosives.

History

Understanding of the vocal tract advanced with anatomical study and, later, instrumental techniques such as X-ray and imaging that revealed articulatory movement. Catford's systematic treatment of airstream mechanisms clarified how non-pulmonic sounds, common in languages of southern Africa and the Caucasus, are produced.

Debates

Typology and rarity of non-pulmonic sounds

Scholars discuss why some airstream types, such as velaric ingressive clicks, are confined to particular regions and language families, and how to characterize the articulatory and historical factors involved.

Key figures

• J. C. Catford
• Peter Ladefoged
• Ian Maddieson

Seminal works

• catford2001
• ladefoged1996

Frequently asked questions

What is a pulmonic airstream?

A pulmonic airstream is air pushed out of the lungs by the respiratory muscles. It is egressive and is the airstream used for the vast majority of speech sounds across all languages.

How is a click produced?

A click uses a velaric ingressive airstream: a pocket of air is trapped between two closures in the mouth and rarefied, so that releasing the front closure produces a sharp inward-rushing sound, independent of lung air.