Influence of Velars and Uvulars on Vowel Context in Four Typologically Unrelated Languages

We investigate the coarticulation between velars~uvulars and surrounding vowels in four languages from three unrelated families where velars and uvulars as phonemes: Alutor (Chukotko-Kamchatkan), Chukchi (Chukotko-Kamchatkan), Mehweb (East Caucasian), and Shughni (Southeastern Iranian < Indo-European). Following the Laryngeal Articulator Model (LAM), the articulation of uvulars requires tongue rising and retraction. As the articulation of velars does not require retraction of the tongue, we expect the quality of vowels to exhibit changes in the uvular environment compared to velar. Various acoustic properties of vowels in the context of velar and uvular stops are investigated including static and dynamic properties with the quality of vowels at the stationary and transition periods. To confirm that the coarticulatory processes are connected to the uvular environment, we compare the contribution of various properties of vowels to the differentiation between velars and uvulars using Random Forests (RF) classification tool. While vowel quality changes in the uvular environment in all four languages; the quality of vowels at the midpoints, onset/offset, dynamics of formants show different contribution to the differentiation between velars and uvulars across the four languages. The variability concerns the type of changes (retraction or centralization of vowels), direction of coarticulation, whether coarticulatory effects are observed only on transitions or affect the quality at the midpoint.