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Chapter 10
The Anatomical and Physiological Bases of Speech, Language, and Hearing
Chapter Overview
It is impossible to understand human speech without examining the anatomical structures and physiological
processes that produce speech. Speech is, after all, the direct result of muscle contractions innervated by the nervous
system that move structures in ways that force air out of the lungs, vibrate that air, resonate it, and break it up into
Learning Outcomes
• Describe the four processes of speech production.
• Discuss how the brain is the control center for speech, language, and hearing.
• Explain the mechanism of hearing.
Key Terms and Concepts
• Vocal-auditory channel, p. 393
• Larynx or voice box, p. 394, p. 400
• 4 processes of speech, p. 394
• Respiration, p. 394, p. 396-399
• Phonation, p. 394, p. 400-405
• Resonation, p. 394, p. 405-406
• Vocal folds, p. 400
• Hyoid, p. 400
• Significant laryngeal cartilages, p. 400: thyroid, cricoid, epiglottis, arytenoids
• Glottis, p. 402
• Intrinsic muscles of the larynx, p. 403
• Abductor muscles of the larynx, p. 403
• Adductor muscles of the larynx, p. 403
• Glottal or laryngeal tone, p. 405
• Articulators, p. 407
• Vertebral column, p. 409
• Peripheral nervous system, p. 409
• Neuron, p. 409
• Cerebrum, p. 410
• Corpus callosum, p. 410
• External auditory meatus or ear canal, p. 414
• Tympanic membrane, p. 414
• Ossicles, p. 414: malleus, incus, stapes
• Ossicular chain, p. 416
• The inner ear, p. 417-418
• Semicircular canals, p. 416
• Cochlea, p. 417
• Modiolus, p. 417
• Auditory nerve, p. 417
Points of Emphasis
1. All of the structures involved in producing speech are designed for other, more basic biological purposes.
2. Speech can be most easily understood as the product of four separate but inextricably related processes:
respiration, phonation, resonation, and articulation. Speech is the product of the successive and simultaneous
interactions of these four processes.
3. The primary biological function of respiration is the exchange of life sustaining oxygen for carbon dioxide.
Respiration provides the power for speech. The speaker inhales to capture air in the lungs and then, in a
controlled manner, exhales to force a column of air into the larynx.
a. Breathing depends on the very practical application of Boyle’s law and the simple principle of equilibrium.
b. Breathing for speech necessitates delicate control of each respiratory cycle and particularly the exhalation
portion of the cycle.
c. When we breathe for speech, we extend and control exhalation for up to 15 seconds. If we were unable to do
this, talking time would be restricted to 2.5-second spurts, the average duration of exhalation during quiet
breathing. We would be able to produce only a few words at a time instead of the lengthy sentences that
characterize normal speech.
b. The secondary function of the larynx is sound production, a purpose for which it is ideally constructed.
i) The vocal folds are relatively long and are capable of the wide range of adjustments in length and
tension that are essential for voice production.
ii) During normal quiet breathing, the vocal folds are relatively wide open, but during speech, they are
drawn together to obstruct the flow of air from the lungs, setting up the conditions necessary for vocal
fold vibration.
c. Muscles in the larynx allow the speaker to open and close the vocal folds, and the muscles making up the
vocal folds allow the speaker to make the folds tense or relax. These adjustments are basic to producing the
voice.
d. During a single cycle of vocal fold vibration: (1) the vocal folds are adducted to restrict the flow of air from
the lungs. (2) At the same time as the folds are being adducted, exhalation is producing increased air
e. This five-step sequence is repeated 120 to 145 times per second in adult males and 200 to 260 times per
second in adult females.
f. Pitch changes are accomplished by varying the length and mass of the folds. In general, pitch rises when
there is an increase in length and a decrease in mass; adjustments that result in more rapid vocal fold
vibrations.
5. As the vibrating air column passes through the throat, the mouth, and sometimes the nasal cavities, it undergoes
resonation, which means that the tone of the noise from the vocal folds is modified according to the size and
shape of the resonating cavities, including the pharynx, mouth, and nasal cavities.
6. The final process of speech, articulation, is most simply understood as the breaking up of the airstream into the
sounds of speech by the structures of the mouth.
7. The reason speech is produced with so little conscious effort is that the speech machine is directed by a central
nervous system unmatched in any other animal on earth.
a. The nervous system can be arbitrarily divided into two major divisions:
i) The central nervous system includes the brain and the spinal cord.
ii) The peripheral nervous system consists of all the cranial and spinal nerves that carry information to the
for speech. These motor commands are then transmitted to the motor cortex. The neural messages
carrying speech and language information are eventually sent to the speech musculature.
c. The right hemisphere is less involved with speech and language than the left, but it does contribute to the
processing of emotional content that often underlies speech and language, in addition to the melodic patterns
we superimpose on speech when we sing.
8. The child learns to talk by listening to the speech around her. Hearing is as crucial to normal speech as any other
part of the complete anatomical and physiological speech package.
a. The outer and middle ears function together to transform acoustic energy into mechanical energy.
b. Sound travels to the outer ear in the form of sound waves that are disturbances of air particles characterized
by compressions and rarefactions.
c. These waves are caught by the pinna, the visible fleshy part of the ear attached to the side of the head, which
serve to direct sound waves into the external auditory meatus or ear canal. At the end of the canal is the
tympanic membrane or eardrum.
d. The tympanic membrane absorbs the acoustic energy of sound waves and transforms it into mechanical
energy, which is the vibration of a solid material.
e. The ossicles operate together in transferring energy from the tympanic membrane to the oval window and
the increased concentration of energy achieved by the tympanic membrane and the ossicular chain is
necessary to set the dense fluids of the inner ear into motion.
Discussion Topics
• What does it mean to say that speech is the product of borrowed structures?
• What role does Boyle’s law play in normal respiration? How does this explanation of breathing compare to a
naive and uninformed understanding of breathing?
• Identifying as many laryngeal structures as possible, describe one cycle of vocal fold vibration.
• Identifying as many structures of the nervous system as possible, trace the neurological relay race from the
cerebrum to the muscles of speech.
Suggested Activities
• Examine the oral structures of a normal child and the oral structures of a normal adult. Compare and contrast
what you observe relative to size, shape, color, and function.
• Listen to a television with both ears and then with a hand covering one ear. Compare and contrast the binaural
and monaural listening experiences. Next, using your hand, cup your pinna and reflect on the difference in
acoustics. Observe a cat or dog, specifically watching their ear movements. How are these movements different
from the movements our ears are capable of?
• Read aloud for two minutes as normally as possible. Read the same passage, but try to maintain a 50:50 ratio
for duration of inhalation and exhalation. What does this experience indicate to you about the nature of
breathing for speech in comparison to vegetative breathing?
as possible. What does this experience indicate to you about the physiological limitations of the articulatory
mechanism?
• Read aloud for two minutes as normally as possible. Read the same passage, but as you say each word try to
separate the processes of respiration, phonation, resonation, and articulation. What does this experience
indicate to you about the need to integrate and synchronize these processes of speech?
Assignment Suggestions
• Readers may assess their understanding by completing these brief, self-check quizzes:
o 10.1 (p. 408): the four processes of speech
o 10.3 (p. 418): the ear as an energy transformer
• Chapter Review 10.1 (p. 419)
Websites to Explore
