Phonological Variation in Igbo Across Six Geopolitical Zones: Evidence from the Nigerian Igbo Speaker Diaspora

This study conducts an empirical investigation of phonological variation in Igbo as spoken by native speakers residing across Nigeria's six geopolitical zones, generating the first systematic cross-zonal phonological comparison of diaspora Igbo speech. The phonological profile of Igbo in diaspora contexts is shaped by both contact-induced changes from dominant zone languages and internal variation inherited from speakers' communities of origin. The study elicits speech samples from one hundred and eighty Igbo speakers, thirty from each geopolitical zone, using a standardised wordlist and connected speech instrument. Acoustic phonetic analysis using Praat software measures fundamental frequency for tonal contrasts, vowel formant patterns, and consonantal duration in key minimal pair environments. Statistical comparison of phonological variables across zones employs analysis of variance and post-hoc Tukey tests. Findings document statistically significant inter-zonal differences in high-tone realisation levels, vowel height fronting patterns, and the frequency of tonal downstep application, with Northern Zone speakers demonstrating the most pronounced phonological deviation from South East speaker norms. Contact effects from Hausa, Yoruba, and Efik are identified in specific phonological variables. The study contributes to the variationist sociolinguistics of Igbo and provides a phonological baseline for dialect contact research. Keywords: Igbo phonology, phonological variation, diaspora, acoustic phonetics, geopolitical zones.