Abstract
This is a follow-up study on Han and Kang (2013) which argued that the Euclidean distances between /o/ and /u/ in Seoul Korean decreased in the first syllable position as speakers were among younger female speakers but not for male speakers, whereas in the second syllable position both gender groups showed a cross-generational decreasing effect of the Euclidean distance between /o/ and /u/. This study normalized the same data in Han and Kang (2013) which measured 12 speakers (six males and six females) for each Age group and investigated the spectral changes vowels /o/ and /u/ between age and gender, using the log-mean normalized statistical results. This study also examined overlap fraction values generated in SOAM 2D ($F1{\times}F2$) (cf. Wassink, 2006), which may also indicate the proximity of two vowels in question. The results showed that /o/ and /u/ vowels were making closer with /o/ raising for female speakers in $V_1$ and $V_2$ positions but only in the $V_2$ position for male speakers. That is, females led the upward movement of peripheral /o/ vowel, just like the raising of 'e' and 'o' in New York City (Labov, 1991). The results also showed that younger speakers used a rather narrow vowel space for the vowels. This also contributed to the proximity of the vowels /o/ and /u/, resulting in rather large overlap fraction values for younger speakers between these two vowels.
