Aspects of vowel raising in Southern Sotho and Setswana: An acoustic approach

The investigation and its results reported in this article focus on the presence and acoustic characteristics of the process of vowel raising as found in two branches of Sotho, namely Setswana and Southern Sotho. This article presents a contribution with respect to the acoustic description of vowel raising concerning the extent and nature of vowel raising especially, as measured in two ‘e’-like vowels1, viz. the stem vowel of reka ‘(to) buy’ supposedly raised to reke and rekile, as well as the stem vowel of tena ‘(to) dress’, allegedly not subjected to raising, at any rate not in the case of Southern Sotho (Doke & Mofokeng, 1957). In light of our findings, we reflect on some methodological matters with respect to the choice of a number of speakers' readings to be elicited, as well as on the sensibleness of taking one language branch to be representative of the other branches of Sotho. On a general linguistic level, we assessed the theoretical soundness of the dispersion theory (Manuel, 1990; Lindblom, 1990; Diehl, 2008); a theory concerned with the density of distributions of vowels within its acoustic space. Finally, we assume that such results could be of considerable value in the speech technological area; such information being of great importance for the development of Human Language Technologies, for instance automatic speech recognition systems or text-to-speech systems.