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Department of Linguistics

PHONETICS AND PHONOLOGY

Introduction to Speech Production

Robert Mannell


An Introduction to Speech Production

Readings

Cox (2012) (pages 20-26)

Recommended

Clark, Yallop & Fletcher (2007) (pages 10-16)
Clark, Yallop & Fletcher (2007) (Chapter 6)

Overview of Speech Generation

Speech is achieved by compression of the lung volume causing air flow which may be made audible if set into vibration by the activity of the larynx. This sound can then be made into speech by various modifications of the supralaryngeal vocal tract.

  1. Lungs provide the energy source - Respiration
  2. Vocal folds convert the energy into audible sound - Phonation
  3. Articulators transform the sound into intelligible speech - Articulation

Click here to see a diagram of the vocal tract

Lung Structure and Function

Expanding the thoracic cavity by expanding the rib cage (raising the ribs) and by lowering the diaphragm increases lung volume, decreases air pressure in the lungs and so air is drawn in from the from the outside to equalise pressure. Contracting the thoracic cavity by contracting the rib cage (lowering the ribs) and by raising the diaphragm decreases lung volume, increases air pressure in the lungs and so air is expelled from the lungs to equalise pressure with the outside air. Click here to see a flow chart overview of the above processes.

Click here to see a simplified diagram of the lungs' function as the energy generator in speech production.

Larynx Structure and Function

The larynx is a continuation of the trachea but the cartilage structures of the larynx are highly specialised. The main cartilages are the thyroid, cricoid and arytenoid cartilages. These cartilages variously rotate and tilt to affect changes in the vocal folds. The vocal folds (also known as the vocal cords) stretch across the larynx and when closed they separate the pharynx from the trachea. When the vocal folds are open breathing is permitted. The opening between the vocal folds is known as the glottis. When air pressure below closed vocal folds (sub-glottal pressure) is high enough the vocal folds are forced open, the vocal folds then spring back closed under both elastic and aerodynamic forces, pressure builds up again, the vocal folds open again, ... and so on for as along as the vocal folds remain closed and a sufficient sub-glottal pressure can be maintained. This continuous periodic process is known as phonation and produces a "voiced" sound source.

Different laryngeal adjustments affect the way that the vocal folds vibrate and can result in different voice qualities, some of which are important linguistically in some languages.

Articulation

When sound is produced at the larynx, that sound can be modified by altering the shape of the vocal tract above the larynx (supralaryngeal or supraglottal). The shape can be changed by opening or closing the velum (which opens or closes the nasal cavity connection into the oropharynx), by moving the tongue or by moving the lips or the jaw.

Click here to see an overview diagram of the major articulators.