| Summary: | This thesis uses acoustic measurements as a basis for the phonological analysis of the interaction of tone with voicing and foot structure in Kera (a Chadic language). In both tone spreading and vowel harmony, the iambic foot acts as a domain for spreading. Further evidence for the foot comes from measurements of duration, intensity and vowel quality. Kera is unusual in combining a tone system with a partially independent metrical system based on iambs. In words containing more than one foot, the foot is the tone bearing unit (TBU), but in shorter words, the TBU is the syllable. In perception and production experiments, results show that Kera speakers, unlike English and French, use the fundamental frequency as the principle cue to 'Voicing" contrast. Voice onset time (VOT) has only a minor role. Historically, tones probably developed from voicing through a process of tonogenesis, but synchronically, the feature voice is no longer contrastive and VOT is used in an enhancing role. Some linguists have claimed that Kera is a key example for their controversial theory of long-distance voicing spread. But as voice is not part of Kera phonology, this thesis gives counter-evidence to the voice spreading claim. An important finding from the experiments is that the phonological grammars are different between village women, men moving to town and town men. These differences are attributed to French contact. The interaction between Kera tone and voicing and contact with French have produced changes from a 2-way voicing contrast, through a 3-way tonal contrast, to a 2-way voicing contrast plus another contrast with short VOT. These diachronic and synchronic tone/voicing facts are analysed using laryngeal features and Optimality Theory. This thesis provides a body of new data, detailed acoustic measurements, and an analysis incorporating current theoretical issues in phonology, which make it of interest to Africanists and theoreticians alike.
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