Abstract
This paper examines the devoicing rates of high vowels in five dialects, namely Akita, Tokyo, Osaka, Hyogo and Kumamoto. The data were collected in 2006 and 2007 and include information from 306 participants between the ages of 10 and 87. The paper examines the factors affecting vowel devoicing, and analyzes age differences of devoicing rates for each dialect. The main findings of the paper are as follows. First, the devoicing rate of each dialect is strongly affected by sound environments. As for the relationship between the word accent and the devoicing rate, the sound environment is more important than the word accent even in Osaka and Hyogo. Second, this study confirms Byun's argument that there are generational differences in devoicing rates in most dialects. Indeed, the study clearly shows that generational gaps in devoicing rates differ from dialect to dialect. The gap exists between those in their 60s and 50s in Akita while gaps are evident between those in their 40s and 30s in Osaka and Kumamoto. There is also a possibility that a gap exists between those in their 40s and 30s in Hyogo. However, there are no significant differences among the age groups of Tokyo. Finally, a comparative analysis of current and previous data collected twenty years ago shows that devoicing rate of the same cohort of speakers is almost the same.
