An acoustic study of Luganda liquid allophones

Transcription-based descriptions of Luganda (Bantu, Uganda) have stated that there is a rhotic (r) in the language that occurs only after a front vowel, in complementary distribution with a lateral (l) that occurs only elsewhere. However, these descriptions of the pattern have disagreed about the nature and distribution of the sounds involved. Such a pattern has been reported in a number of Bantu and non-Bantu languages, and it is intriguing because its phonetic basis is not obvious, since there is nothing rhotic about a front vowel or lateral about a non-front vowel. To clarify the facts and provide insight into this kind of pattern, a production study was conducted in which Luganda speakers produced the liquid in varying vocalic contexts. F1, F2, duration, mean harmonics-to-noise ratio (HNR), and intensity were measured. The results support the characterization of the liquid after a front vowel as a nonlateral tap, and elsewhere as a lateral sonorant. But the intensity data also show a continuum in the degree of tongue tip constriction, ranging from approximant to tap, depending on the frontness of both the preceding and following vowels. The pattern of distribution is thus more complex and gradient than has been evident from transcriptions alone.