F2 locus equations: phonetic descriptors of coarticulation in 17- to 22-month-old children.

The general purpose of this research was to describe coarticulation across voiced stop consonant place of articulation in 10 children younger than 2 years of age. A total of 1,182 voiced stop CV productions was analyzed using the locus equation metric, which yielded 3 regression lines that described the relation of F2 onset and F2 vowel for /bV/, /dV/, and /gV/ productions. The results revealed significant differential effects for slope and y-intercept as a function of stop consonant place of articulation. The ordering of the mean slope values for stop consonant place of articulation was /g/>/b/ and /d/, indicating that /g/ was produced with significantly greater coarticulation than /b/ or /d/. However, the unique vowel allophonic pattern of [g] coarticulation reported in the literature for English-speaking adults was generally not learned by these young children. Group and individual coarticulation trends are described in relation to developmental theories of sound acquisition. Results suggest that early coarticulation patterns are phoneme specific.