The nonexistence of the plain bilabial trill phoneme

Abstract

Phonetic studies of bilabial trills in phonemic systems show that they are preceded immediately by an oral stop closure, e.g., /mbʙ, bʙ, pʙ̥/. A plain bilabial trill without a preceding oral stop closure /ʙ/ is not known to occur as an individual phoneme in any language. On the contrary, plain apical /r/ and uvular /ʀ/ trill phonemes that lack a preceding oral stop closure occur in many languages. The nonexistence of /ʙ/ is likely due to the fact that it does not meet the specific aerodynamic conditions necessary for its production (Maddieson 1989). In this paper, I examine a crosslinguistic sample of consonant inventories containing both bilabial and apical trills. I find that these inventories show an implicational tendency: For each phoneme containing a bilabial trill, there is usually a corresponding phoneme containing an apical trill that shares the same values for voicing and prenasalization. These phonemes always include an oral stop closure preceding the trill, and they pattern as obstruents. In addition, these consonant inventories usually include a plain apical trill phoneme (which patterns as a sonorant), but lack a plain bilabial trill phoneme. The most common such inventory (e.g., found extensively in Austronesian) includes three trills /mbʙ, ndr, r/, while larger inventories are found in the Democratic Republic of the Congo and South Sudan, e.g., Mangbetu /pʙ̥, bʙ, mbʙ, tr̥, dr, ndr, r/. While a plain bilabial trill does not emerge due to aerodynamic constraints, resulting in a gap in the system, symmetry appears to favor the emergence of bilabial stop-trill phonemes in languages that have corresponding apical stop-trill phonemes.