26 Chapter 2
Consonants
Consonant phonemes can be classified in two dif fer ent ways: by place and by manner of produc-
tion. In classification by place, consonants are categorized by where in the oral cavity they are pro-
duced. The glottal phoneme /h/ is produced at the level of the vocal cords, and the lingua- velar site is
the tongue and soft palate. Lingua- palatal, lingua- alveolar, and lingua- dental sites are the tongue and
palate, tongue and alveolar ridge, and tongue and teeth articulatory sites, respectively. Labio dentals
are sounds produced at the lips and teeth, and bilabials are produced by the action of both lips.
By categorizing the manner in which the airstream is shaped into speech sounds, consonants
can be divided into two categories: stops and continuants. Stops involve the complete cessation
of the airstream and acoustic energy, whereas continuants have continuous airf low during their
production. Nasals involve increased nasal resonance due to the opening of the velopharyngeal
port, and glides require movement of the articulators. Fricatives are produced by constriction of
the airstream, and plosives have an abrupt explosion of air. Affricates are explosions of air shaped
into continuants. A blend is two or more consonants without a vowel separating them, sometimes
called a consonant cluster.
Vowels
All vowels are voiced and depend on the height and front- to- back position of the tongue in the
oral cavity. For example, some vowels are classified as low- back, high- front, high- back, and so on,
depending on the tongue’s prominence in the oral cavity. Lip rounding also plays a role in their
acoustic qualities. A diphthong is produced by moving the articulators from one vowel articulatory
position to another. The vowel is central to the syllable— a unit of speech with a vowel as its central
physiological and acoustic property. The types of syllables are represented using V for vowel and C
for consonant: for example, CV (be), CVC (bun), VC (up), and CCV (sleigh).
Coarticulation and Assimilation
Rarely do people produce individual speech sounds in isolation (static articulation) uncon-
nected to strings of other phonemes. Most speech sounds are produced in rapid succession as
part of longer utterances (dynamic speech). Oral movements during dynamic articulation occur
very rapidly, involving more than 100 muscles and thousands of neurological impulses per sec-
ond. Because of the rapid movement of the articulators during speech, units of speech run into
each other. As a result, articulatory movements only approximate their ideal points of contact. In
dynamic utterances, speech sounds become more like each other. Coarticulation is the overlapping
of articulatory movements during dynamic speech. Assimilation is the effect that one sound has
on another. Coarticulation leads to assimilation.
Phonology
Whereas the sensorimotor approach to articulation development and disorders considers
speech sound learning a product of auditory perception and the development of fine motor skills,
the phonological approach involves language. Phonology is the rule- governed way humans pro-
duce the sounds of language. It is one aspect of language, with the others being semantics, syntax,
and grammar. When an individual has a phonologically based articulation disorder, learning the
phonological rules is the treatment objective. Rather than teach the production of one and only
one sound, clinicians use several sounds to teach the rules of phonology.
In the phonological approach to articulation development and disorders, speech sound devel-
opment is considered the discovery and fusion of syllable formation princi ples. In this approach,
articulation disorders are thought to result from delayed acquisition of the phonological rules of
the language. Phonological rules or pro cesses are simplified linguistic be hav iors used by children