Coronal-Triggered Voicing Assimilation in Najdi Arabic: A Phonetic and Phonological Analysis

This paper investigates voicing assimilation across morpheme and word boundaries in Najdi Arabic (NA) from both phonetic and phonological perspectives. Although voicing assimilation has been widely documented cross-linguistically, its realization in NA remains underexplored. Using autosegmental theory and feature geometry, the study examines how the alveolar stop /t/ in the proclitic /mit-/ behaves when followed by different consonants and whether assimilation in NA is categorical or gradient. Acoustic data were elicited from eight native male speakers, yielding 288 tokens produced in controlled elicitation tasks. Vowel duration, F1, and F2 were obtained in Praat and statistically compared across voiceless (VL) and voiced (VD) contexts. The results reveal systematic regressive assimilation when /t/ precedes a coronal obstruent, producing a fully identical geminate through delinking and reassociation of the C-place node. In VD contexts, vowels preceding assimilated segments were longer, exhibited lower F1 and higher F2 values, and showed continuous voicing, providing clear acoustic evidence of assimilation. Assimilation was consistently blocked before non-coronal and sonorant consonants, confirming feature-geometry predictions. The same mechanism operated across both morpheme and word boundaries, indicating a unified assimilation rule in NA. Overall, the findings show that voicing assimilation in NA is categorically implemented yet phonetically grounded, situating the dialect within the broader Arabic typology.