Diphthongisation of /i:/ in West Frisian

Contemporary West Frisian (ISO 639-2 fry; henceforth: Frisian) has a rich and symmetrical vowel system, with nine short and nine long monophthongs as well as numerous rising, falling and centring diphthongs. However, the vowel system of this minority language is changing, some of these changes are induced by contact with Dutch, others are more likely to be internal changes. One such sound change in progress is observed in the long high vowel /iː/, which younger speakers tend to realise as a centring diphthong [iˑə]. Consequently, the traditional minimal pair wiid /ʋiːt/ ‘wide’ ~ wiet /ʋiˑət/ ‘wet’ becomes homophonic [ʋiˑət].
We present the first analysis of this sound change in progress. Based on acoustic analyses of the trajectory of /iː/ of 51 speakers from Boarnsterhim, we show that the youngest speakers use this centralising diphthongisation more often than older speakers. Moreover, analyses show that diphthongisation occurs more often before alveolar consonants.