The Five Phonemic Vowel Heights of Southern Sotho: an Acoustic and Phonological Analysis

This study examines the vowels of Southern Sotho, a South African language of the South Eastern Bantu group. The purpose of this work is to determine the actual number of Southern Sotho phonemic vowel heights and their acoustic characteristics. Some authors claim that there are seven phonemic vowels, making four phonemic heights, and that this number of vowels increases as a result of the process of vowel raising giving then eleven phonetic vowels and six phonetic vowel heights.

An acoustic analysis of all Southern Sotho vowels was made in order to determine their spectral qualities. Measurements were taken of the first three formants and their corresponding bandwidths. Two male speakers were recorded uttering the vowels under the same conditions. The speakers varied significantly in age, dialect, formant frequencies, bandwidth and pitch.

Despite these differences, however, variation in formant frequency according to vowel height was the same for both speakers. This indicates that the vowel heights are realized acoustically in the same way by both speakers. The acoustic measurements support the claim made in this work that there
are nine phonemic vowels, which constitute five phonemic heights. Since standard Sound Pattern of English (SPE) features do not distinguish five phonemic heights, the additional feature [Expanded], suggested by Lindau (1975), is recommended in order to distinguish these vowels.