Kim, Hyun-ju. 2018. Diachronic change in vowel length contrast in North Kyungsang Korean. Studies in Phonetics, Phonology and Morphology 24.3. 273-295. 

This study investigates the phonemic status of the vowel length contrast in North Kyungsang Korean (NKK), responding to the vowel length contrast merger in contemporary Seoul Korean. A phonetic study was designed to examine whether the vowel length contrast is maintained phonemically in the speech of younger NKK speakers by comparing their vowel production with that of older NKK speakers at two different speech rates. The results showed that younger NKK speakers produced long vowels with the same length as their corresponding short vowels, differing from older NKK speakers, whose long vowels were significantly longer than their short ones. The differences in vowel duration and in vowel-to-word ratios between long and short vowels were unaffected by different speech rates. These findings suggest that the vowel length contrast has been losing its phonemic status in younger NKK speakers, and that this change is robust and nearing completion. The loss of the vowel length contrast should involve changes in NKK accent patterns, since the vowel length distinction is crucial in NKK accent assignment, which is sensitive to syllable weight as long vowels attract a high tone in the accent system. It is also suggested that word frequency plays a role in the accent change triggered by the loss of long vowels. (The State University of New York, Korea, Assistant Professor) 

Keywords: vowel length contrast, speech rate, vowel duration, vowel-to-word ratio, age group, accent patterns, word frequency