This paper adopts the framework of Articulatory Phonology to explore the timing patterns of two-stop clusters in Tripolitanian Libyan Arabic (TLA), a colloquial form of Arabic used in everyday spoken communication in Tripoli. By means of electropalatography (EPG) and acoustic analysis, the influence of syllable position and speaking rate on the inter-gestural coordination of the clusters /gt/, /gd/, /kt/, and /kd/ is investigated.
The data were collected from one male speaker of TLA who repeated the target words in a carrier sentence three times, and in two speaking rates: normal and fast. The results provide evidence that syllable-initial (onset) clusters are coordinated differently from syllablefinal (coda) clusters. The coordination pattern in syllable-initial clusters is characterised by an overlap between the gestures of the first consonant (C1) and the second consonant (C2) in the cluster. This is the result of the simultaneous closure of the tongue-body (TB) gesture, and the following tongue-tip (TT) gesture. Another coordination pattern in onset clusters allows a short delay between the release of C1 and forming the closure of C2. This coordination is marked by a short inter-consonantal interval (ICI) 5–15 ms in duration, between the two articulatory closures. On the other hand, the coordination pattern in syllable-final clusters is distinguished by a longer ICI separating the two consonantal gestures. The syllable-final ICI emerges as a result of the long delay between the release of C1 and forming the closure of C2. The duration of this ICI is between 30–50 ms. As speaking rate is increased, the duration of syllable-initial clusters decreases. However, the coordination pattern remains stable in /gt/, /gd/ and /kt/, but more gestural overlap between the two consonantal gestures is observed in /kd/. In coda clusters, the increase in speaking rate results in a decrease in duration of C1 and C2, some reduction in the percentage of contact, particularly in the velar region and finally, a tighter coordination between the two gestures. This leads to the decrease in the duration of the ICI in syllable-final clusters.