Contributions of cochlea-scaled entropy and consonant-vowel boundaries to prediction of speech intelligibility in noise

published_or_final_versio

An Acoustic & Articulatory Analysis of Consonant Sequences across Word Boundaries in Tripolitanian Libyan Arabic

The main goal of this thesis is to provide a description of the articulatory and temporal interaction between stops spanning the word boundary in the four sequence types VC#CV, VC#CCV, VCC#CV, and VCC#CCV in Tripolitanian Libyan Arabic. A general aim of the study is to contribute to the Phonetic description of Libyan Arabic and to provide a better understanding of speech production and the temporal organisation of articulatory gestures. One of the principal objectives of this study is to investigate what effect an increase in the number of stops in a sequence will have on the timing of stop gestures. Furthermore, the study aims to identify the different patterns of gestural coordination and the types of inter-consonantal intervals occurring between stops in the four sequence types. Another aim of the study is to investigate the nature of the resulting inter-consonantal intervals occurring between these stops in order to understand the patterns of epenthesis. Factors affecting gestural coordination such as the order of place of articulation of stops and speech rate are also an objective of this study. Voice assimilation across the word boundary is also investigated in addition to the influence of inter-consonantal intervals on the process. The study adopts Articulatory Phonology as a theoretical framework to carry out the investigations. The data was collected through recordings of participants’ speech and was subjected to EPG and acoustic analysis. Ten native speakers of Tripolitanian Libyan Arabic took part in the acoustic part of the study. Two of the speakers also took part in the EPG part of the study. Results show that the effect of the number of stops in a sequence on gestural timing is not limited to within syllable-initial and final clusters but also spreads across the word boundary. The timing of syllable-final and syllable-initial stops decreases as a result of the increase in the number of stops across the word boundary. The results also show that the timing of syllable-final clusters is more variable than syllable-initial clusters in across word boundary sequences. Different sequences types exhibit different degrees of gestural coordination and epenthesis patterns between adjacent stops. Inter-consonantal intervals occurring as a result of lag durations between adjacent stop gestures fall into two types. The first type are typical of transitional excrescent vowels with a mean duration ranging from 14ms-20ms and their voice values exhibit more variation as a result of the voice context in which they occur. Inter-consonantal intervals of the second type are typical of epenthetic vowels with a mean duration ranging from 43ms-51ms and are usually specified as voiced. The patterns of epenthesis also show that Tripolitanian Libyan Arabic belongs to the VC type of languages where sequences of three stops CCC are broken up by epenthesis occurring between C1 and C2 of the sequence. Statistical tests show a significant effect for order place of articulation on gestural coordination across the word boundary in TLA in the C#C sequence where gestures are more closely coordinated in the coronal-dorsal order. Regressive voice assimilation is more frequent and the voice context of the stops involved plays a major role in determining the direction of voice assimilation spreading. Progressive voice assimilation is limited to the –V+V voice context and whereas regressive assimilation of voicelessness occurs in both. Furthermore, excrescent vowels are found to be transparent to voice assimilation and are dependent on the voicing of the trigger segment. On the other hand, epenthetic vowels block voice assimilation and are more dependent usually specified as voiced