The Dynamics Of Normal Speech Production

Running head: THE DYNAMICS OF NORMAL SPEECH PRODUCTION 1

The Dynamics of Normal Speech Production

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THE DYNAMICS OF NORMAL SPEECH PRODUCTION

The biomechanics of normal speech production involve groups of muscles, body structures

and physiology, all of which are underpinned by major theoretical frameworks. Contrary to

popular rhetoric, speech production does not start in the lungs but rather in the brain, where a

message with all its lexico-grammatical structures is formulated. A sound sequence is then

established, which is communicated through commands to the speech organs that coordinate

rhythmically to produce the required utterance. This paper focuses on the physiology, structures

and muscles involved in speech production, besides exploring the theories that support the concept.

Speech Production Muscles

The muscle groups involved in speech production are either identified as inhalation of

exhalation muscles. The inhalation muscles enlarge a person’s thoracic cavity while the

exhalation muscles decrease this volume.

Inhalation Muscles

The diaphragm is the most essential of these muscles, which originates from the inner

surface of the rib cartilage and the sternum’s lower tip. According to Perrier and Fuchs (2015),

this muscle is responsible for the enlargement of the thoracic cavity through contraction, which

increases air pressure within the lungs to produce the energy required to facilitate the production

of sounds.

External intercostal muscles similarly play a critical role in speech production and they

typically run from the lip to the ribs’ upper border. With the help of their fibers, these muscles

raise the thoracic cage to facilitate inhalation and coordinate lung functions. Related to these

THE DYNAMICS OF NORMAL SPEECH PRODUCTION

muscles is the pectoralis major, which is an abductor of the arms (Perrier & Fuchs, 2015). It is a

supplemental inhalation muscle, which raises the sternum and rib cage.

Exhalation Muscles

Internal intercostal muscles top the list under this category, which run laterally and

inferiorly within the intercostal spaces. These are the major muscles involved in the exhalation

process and are vital to the process of phonation (Perrier & Fuchs, 2015). Internal intercostal

muscles work in coordination with abdominal muscles to lower the rib cage and therefore facilitate

exhalation

Internal and external obliques contribute considerably towards speech production by

compressing the abdomen to either raise or lower the diaphragm. They are highly functional in

cases of forced exhalation and this enables speech production under pressure. The transversus

thoracic equally plays a critical role and it is typically a muscle that runs from the sternum’s inner

surface. It depresses the ribs, besides tightening the intercostal spaces to facilitate exhalation.

Lip Muscles

Besides the inhalation and exhalation muscles, speech production is a consequent of lip

muscles, which either bring the lips altogether or raise the upper lip. Upon contraction, the

orbicularis Oris muscle pulls the lips together and may even round them through sphincter actions

to transform sound into intelligible speech (Mannel, 2009).

Levator labii superioris is another muscle of the upper lip, which raises it rhythmically to

produce labiodental fricatives. It works in coordination with the depressor labii inferioris, which

draws the lower lip laterally and downwards to produce bilabial consonants.

THE DYNAMICS OF NORMAL SPEECH PRODUCTION

Mandibular movement muscles

The masseter originates from the zygomatic arch and is responsible for raising the

mandibles. By drawing the mandible angle forward, the muscle closes the jaws to control

articulation.

Tongue Muscles

The tongue’s superior longitudinal muscle is an intrinsic muscle that transforms the

tongue’s shape. Upon contraction, it shortens the length of the tongue besides widening it to enable

retroflex articulations. According to Mannel (2009), the muscle may also raise the sides of the

tongue to produce grooved articulations of the [s] and [z] sounds. Its functions resonate with those

of the inferior longitudinal, which retracts the tongue’s tip to produce some consonant sounds.

Speech Production Structures

Larynx

It is popularly identified as the sound maker because of the vocal folds which remain

open as air whooshes through. Speech is produced during the process of exhalation, where air

whooshes through the vocal folds. They ripple in response, besides snapping and humming to

produce a sound whose pitch varies depending on the speed at which they vibrate.

The glottis

This structure is found between the two vocal folds, opening and closing each time a

person inhales and exhales. Its closure prevents the entry of food into the windpipe and therefore

delineates the respiratory system from the digestive system.

THE DYNAMICS OF NORMAL SPEECH PRODUCTION

The vocal tract

It is made up of the throat, the oral cavity and the nasal passages. Each of these structures

works in a complex and complimentary manner to change the buzzy sound produced during

vibration into a recognizable voice.

Muscles

The diaphragm, abdominal muscles, lungs, ribs and chest are all geared towards the same

function-regulating air pressure to allow the rhythmic vibration of the vocal folds to produce

sound.

The Physiology of Speech Production

Speech is produced during the process of exhalation whereby the diaphragm relaxes by

retracting to its original position and this expels air from the lungs. The air moves through the

windpipe to the larynx, and the puffs vibrate the vocal folds in a complex manner to produce a

buzzy sound.

The sound leaving the vocal cords has no meaning unless it is fashioned into words with

the help of articulators (Lieberman and Blumstein, 2013). Before getting to the mouth, the sound

passes through the pharynx, although there is very little articulation at this point. The tongue is

perhaps the most agile of all the articulators because of a complex musculature which allows it to

assume multiple shapes and therefore produce different sounds Lieberman, P., & Blumstein, S. E.

(2013). Besides changing its shape, the tongue moves rapidly to establish complete or partial

occlusions of the vocal tract and these account for the articulation of different words.

THE DYNAMICS OF NORMAL SPEECH PRODUCTION

Theories of Speech Production

The Source-filter Theory

This framework summarizes speech production into two basic steps:

1. Generation of a particular sound source

2. Filtration of sound by the vocal tract

The sources of sound according to this theory, are either periodic or aperiodic and the

subsequent filtration to produce speech depends on the nature of the sound in question. A sound is

filtered using the precise vocal tract that is anterior to the source of that particular sound (Tatham

and Morton, 2015). If a glottal source is voiced, it contains a special spectrum and spectral slope

that differentiates between harmonics and noise.

Mortor Theory

This theory emphasizes the link between speech perception and production, supporting the

assertion that there are articulatory gestures which individuals are capable of perceiving innately.

Research on this theory extends to pre-lingual infants in an attempt to determine whether they are

capable of discriminating phonetic contrasts. The major assumption made here is that speech is an

innate disposition and the physiological processes only facilitate nature.

Logogen Theory

This model is mainly associated with the process of speech recognition with the help of

small units called logogens. The units explain in detail the process by which people understand

THE DYNAMICS OF NORMAL SPEECH PRODUCTION

words, whether they are spoken or written. As a downside, however, the theory dwells on the

recognizable units of words rather than explaining the process of speech production.

THE DYNAMICS OF NORMAL SPEECH PRODUCTION

References

Lieberman, P., & Blumstein, S. E. (2013). Anatomy and physiology of speech production. Speech

physiology, speech perception, and acoustic phonetics, 90-139.

doi:10.1017/cbo9781139165952.007

Mannel, R. (2009, August 01). An Introduction to Speech Production. Retrieved July 09, 2017,

from http://clas.mq.edu.au/speech/phonetics/phonetics/introduction/

Perrier, P., & Fuchs, S. (2015). Motor Equivalence in Speech Production. The Handbook of Speech

Production, 223-247. doi:10.1002/9781118584156.ch11

Tatham, M., & Morton, K. (2015). Two Theories of Speech Production and Perception. The

Handbook of Psycholinguistic and Cognitive Processes, 63-98.

doi:10.4324/9780203848005.ch14

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The dynamics of normal speech production

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