Length and Spectral Dynamics of Rising Diphthongs in Nuer

Nuer, a West Nilotic language spoken in South Sudan and Ethiopia, is typologically unusual in that it exhibits intraparadigmatic alternations across a three-way division of vowel length categories: short /V/, long /VV/, and overlong /VVV/. Nuer has a series of rising-sonority diphthongs, e.g., /wa/, /we/, /ja/, that participate in this three-way length distinction (e.g., /lwaak/ ∼ /lwaaak/, cow byre.nom ∼ gen). In this study, we investigate the relationship between vowel length category and spectral dynamics in Nuer’s rising diphthongs. In particular, we find that when short, onglides overlap with the preceding consonantal constriction to such a degree that the vowel often sounds homophonous with the corresponding monophthongal phoneme (/lwak/ → [lw are minimal (e.g., both /lwaak/ and /lwaaak/ can have similar duration, but still differ in their spectral dynamics). This suggesting that these temporal patterns are phonemicized rather than falling out mechanically from durational differences.both vocalic components have prominent steady states (/lwaaak/ → [luːaːk]). Furthermore, we show that these dynamic characteristics of vowel length are present even in tokens where differences in vowel duration are minimal (e.g. both /lwaak/ and /lwaaak/ can have similar duration, but still differ in their spectral dynamics). This suggesting that these temporal patterns are phonemicized rather than falling out mechanically from durational differences.