Acoustic and ultrasound investigation of word-initial gemination in Moroccan Arabic

Moroccan Arabic uses geminate/singleton contrasts in medial position but it is controversial whether it maintains them utterance-initially. To address this issue, we made simultaneous ultrasound and acoustic recordings of five native speakers producing target words containing /t/-/tt/ and /d/-/dd/ contrasts utterance-initially and -medially, 10 times each. The ultrasound data were analysed via a novel method of using pixel-derived principal components and linear discrimination to generate a time-varying articulatory “closure” signal directly from the ultrasound images, without the need for manual tracing. This articulatory signal was subsequently used to measure closure duration by determining gestural landmarks from its velocity function. The results provide clear articulatory evidence that speakers produce utterance-initial singletons versus geminates with significantly different closure durations, although the contrast provides no acoustic evidence of closure duration per se. Rather, our results reveal that speakers realize geminate/singleton contrasts via acoustic dimensions not related to consonant duration: The vowel is significantly longer following geminates than singletons, and the stop bursts have greater amplitude for geminates than singletons. Together these findings provide evidence that the gemination contrast is maintained in initial position in Moroccan Arabic, and challenge traditional assumptions that consonant length contrasts are primarily carried by acoustic closure duration differences.