Change and stability in the tonal contours of King Rama IX of Thailand, 1959-1997

Studies of change across the lifespan have enabled a more nuanced understanding of segmental sound change, but this method has hardly ever been used in tone change research. This study, one of the first longitudinal studies of tone, investigates the tonal contours of King Rama IX of Thailand across a 38- year period (1959-1997). During the 20th century, Thai Tone 3 (“Falling”) changed from mid-falling to high-falling. The study examines whether King Rama IX’s T3 pronunciation changed during the period of investigation, and if so, whether the change was in the same direction as the community trend. The data consist of 16 recordings of the King’s commencement speeches at Chulalongkorn University. F0 was extracted from 1317 T3 tokens and fitted to a cubic polynomial function. Linear mixed model results and post-hoc analysis of estimated marginal means indicate a period of change followed by stability: T3’s F0 onset raised and the slope became steeper between the 1960’s and the 1980’s (in line with community trends), but not between the 1980’s and 1990’s. These findings align with previous research showing that adults have the potential to change in the post-adolescent period, but they also may resist change when that aligns with their identity.