Phonetics - Unit Two - Lesson No. 9
According to Crystal (2008), coarticulation is an articulation which involves simultaneous or overlapping between more than one point in the vocal tract, as in the combination of stops such as [pk], [bg], [pt] and [bd], often heard in West African languages.
When the speaker articulates CCV sequence, the tongue body may begin to move towards the vowel even during the first consonant. Similarly, in VCC sequences, anticipatory movements towards the second consonant can start during the vowel. Some authors use the term coarticulation to refer to the simultaneous movement of two different articulators.
Thinking of speech sounds as a series of autonomous units runs the risk of dismissing the coarticulatory overlaps as a sort of needless complication which interferes with the ideal properties of speech. However, coarticulation is an essential characteristics of speech sounds. Speech production depends on very rapid, highly coordinated articulatory movements. It is almost impossible to speak or produce speech without making overlap in articulators.
According to Ladefoged, all utterances involve coarticulation, which is the overlapping of adjacent articulations. English consonants often vary their place of articulation so that they become more like the next sound. For example, /t,d/ are usually alveolar stops but they are pronounced with tongue contact of the teeth, so that they become somewhat dental when they occur before dental fricatives as in “eighth” /eitθ/. Another change occurs in the pronunciation of /k,g/ before a front vowel as in “key, geese” /ki, gis/ as compared to a back vowel as in “cow, gauze”.
Coarticulation can be classified into two types: anticipatory coarticulation and perseverative coarticulation.
According to Clark and Yallop (2007), anticipatory coarticulation effects are known as Right-to-Left (L < R) coarticulation. In the string ----CD---, for instance, the sound C is influenced by sound D. This type of coarticulation is thought to happen due to the deliberate high-level organization of the neuromuscular commands for the relevant sounds. Such high-level planning is complicated by the difference in innervation latencies among the various articulatory muscle systems.
The same kind of articulatory configurations happens with respect to gestures of the lips. Lip rounding is an essential part of /w/ sound. Because there is a latency for gestures to overlap with those of adjacent sounds, stops are slightly rounded when they occur in clusters in which /w/ is the second element, as in “twice”. This type of gesture overlapping is called anticipatory coarticulation.
In anticipatory coarticulation, an articulator not involved in a particular sound begins to move in the direction of an articulation needed for a later sound in the utterance. An example is the /ʃ/ of /ʃu:/, which is normally pronounced with lip rounding, anticipating the influence of the following /u:/.
Clark and Yallop (2007) stated that the perseverative coarticulation is known as Left-to-Right (L > R). Therefore, in the string ---AB---, the sound A influences sound B. Perseverative coarticulation is thought to be largely due to lag in articulatory movement, induced by inertia. The relevant ingredients are the biomechanical properties of the articulators, e.g. their size and mass, and the nature of the muscles involved in the articulation process, the speaker’s rate of articulation, and the extent to which the speaker is exercising voluntary neuromuscular effort in the control and movement of the articulators.