Clear speech production and perception of Korean stops and the sound change in Korean stops
The current dissertation investigated clear speech production of Korean stops to examine the proposal that the phonetic targets of phonological categories are more closely approximated in hyperarticulated speech. The investigation also considered a sound change currently underway in Korean stops: younger speakers of the Seoul dialect produce the aspirated and lenis stops differently from older speakers of the same dialect. Hyperarticulated, clear speech provided evidence for difference in the phonetic targets of the stops between the two age groups. Compared with conversational and citation-form speech, younger speakers primarily enhanced the F0 difference between the aspirated and lenis stops in clear speech, with only a small VOT enhancement, whereas older speakers solely enhanced VOT difference between the two stops. These different clear speech enhancement strategies were interpreted to indicate that younger speakers have developed different phonetic targets for stop production than older speakers. The results from a perceptual experiment using re-synthesized stimuli indicated that the production differences between the younger and older speakers are linked to perceptual differences. The perceptual processing of the stops differed between the groups in a manner parallel to the production differences. When identifying aspirated and lenis stops, younger listeners evidenced greater cue weight for F0 than older listeners, whereas older listeners evidenced greater cue weight than younger listeners for VOT and H1-H2. In addition, the results from a perceptual experiment using noise-masked stimuli confirmed an intelligibility improvement effect of clear speech and also indicated that the three speaking styles were on a continuum from the most casual, conversational speech, to the most careful, clear speech, with citation-form speech in the middle. In the final chapter, the different findings of the current study were discussed in view of various theoretical models and hypotheses. This dissertation includes previously published co-authored material.