Acoustic analysis of correct and misarticulated semivowels.

Four children who produced correct (w,r,l,j), four children with developmental w/r and w/l substitutions, and four articulation impaired children with w/r and w/l substitutions were subjects. They produced sets of minimally contrasted words with (w,r,l,j) in word-initial position with four vowels and with (w,r,l) in two types of consonant clusters. Children's utterances were spectrographically analyzed for three formant frequencies and transition rate of the second formant. Children with correct semivowels produced distinctive formant frequency patterns for semivowels that were similar to those previously reported in the literature for adults and children. Developmental and articulation impaired children produced acoustic features for (j) that were similar to the (j) produced by the control group; but neither group differentiated among (w,r,l) by either formant frequencies or transition rate. Some individuals in both groups produced formant frequency and/or transition rate differences among semivowels in some phonetic contexts. The (w) produced for target (w) and in substitution for (r) and (l) by three developmental children and two articulation-impaired children did not match the acoustic pattern of control (w). These productions had higher second formants, occurring between control (w) and (r,l) or in the range of correct (r,l).