This thesis acoustically investigates the impact of emphasis on the degree of gestural overlap in consonant sequences in Najdi Arabic. It has been reported that the identity of the articulators influences the degree of gestural overlap in consonant sequences. Lingual/lingual sequences, such as /ɡt/, tend to exhibit lower degree of gestural overlap than labial/lingual sequences, such as /bt/, because the former involve two interdependent articulators (tongue tip and tongue dorsum), while the latter involve two independent articulators (lips and tongue tip). The emphatic coronals /tˤ/, /sˤ/ and /ðˤ/ are considered in this thesis. They differ from their plain counterparts /t/, /s/ and /ð/ in that they are produced with a secondary articulation involving a movement of the tongue back. This thesis aims to examine whether the secondary articulation of emphatic coronals will influence the degree of gestural overlap. The state of the glottis has also been reported to influence the degree of gestural overlap. When both consonants in a sequence share the same state of the glottis, they exhibit greater degree of gestural overlap than when they differ in the state of the glottis. The emphatic coronals /tˤ/ and /sˤ/ are reported to be produced with a less open glottis than /t/ and /s/. Another aim is to examine whether the less open glottis of the emphatic coronals will influence the degree of gestural overlap. A third aim is to find out whether the two types of vowel insertion (intrusive and epenthetic vowels) occur in Najdi Arabic; the thesis also aims to examine whether emphasis impact will be observed in intrusive, epenthetic vowels or in both.
The hold phase, frication, inter-consonantal interval (ICI), Voice Onset Time, sequence durations and ICI voicing proportion were examined. The sequence position in the word, the order of place of articulation, the identity of the articulators, the speech rate and gender were all considered.
The results reveal that there is an impact of emphasis on the degree of gestural overlap in consonant sequences in Najdi Arabic. Two features of emphasis reflect this impact. First, the secondary articulation of emphatic coronals influences the degree of gestural overlap. Lingual/lingual sequences in an emphatic context are found to exhibit lower degree of gestural overlap than those in the plain counterpart. This has been attributed to motor constraints. Second, the state of the glottis of the emphatic coronal /tˤ/ influences the degree of gestural overlap, but that of the emphatic /sˤ/ does not. The state of the glottis of /sˤ/ was found to be the same as that of the plain /s/; the ICI voicing proportion was similar between sequences including /sˤ/ and sequences including /s/. The state of the glottis of /tˤ/ was found to be different from that of the plain /t/; the ICI voicing proportion was higher in sequences including /tˤ/ than in sequences including /t/. Accordingly, sequences including /tˤ/ exhibit greater degree of gestural overlap than sequences including /t/; this has been attributed to the role of the state of the glottis which is less open in /tˤ/ than in /t/.
The results also reveal that the two types of vowel insertion occur in Najdi Arabic. These types vary as a function of the word position and the place order. Intrusive vowels occur in CC# (in front-back place order), in C#C and in #CC word positions. Epenthetic vowels occur in CC# (in back-front) and at the word boundary in CC#CC positions. Emphasis impact was observed in intrusive vowels, but not in epenthetic vowels. Intrusive vowels were variable in duration and voicing, depending on surrounding consonants, unlike epenthetic vowels that were longer in duration and mostly voiced regardless of surrounding consonants.
The findings contribute to our understanding of timing relations in consonant sequences and of emphasis, and to the study of phonetics of Arabic, particularly Najdi Arabic. The findings reveal that not just the primary articulation, but also the secondary articulation, can influence gestural overlap. The findings reveal that not just the state of the glottis of voiced consonants, but also the less open glottis of the emphatic /tˤ/, can influence gestural overlap. The findings also reveal that the two types of vowel insertion exist in Najdi Arabic, and emphasis impact is observed in intrusive vowels. Future work, using instruments such as Magnetic resonance imaging, has been suggested to have a clearer view of emphasis impact on gestural overlap.
