A phonetic analysis of vowel errors during the course of treatment

The vowel patterns displayed by one phonologically disordered child were ev aluated during the course of a 10-week treatment period using a combination of acoustic and transcriptional methods. At the conclusion of treatment th e size of the child's vowel inventory and overall vowel accuracy improved. Although the child's vowel inventory increased, a chronological mismatch in vowel mastery occurred, whereby vowels that were expected to be mastered e arly [i, o, a] were the least accurate, while vowels that were not expected to be mastered [I, ae] were highly accurate. Those vowels with the highest accuracy also showed the most significant acoustic changes with regard to fundamental frequency and vowel duration. Vocal tract resonance measures of formant frequency were not discriminating of changes in vowel accuracy acr oss the course of treatment. Discussion focuses on the nature of vowel deve lopment in phonologically disordered children, as depicted along transcript ional and acoustic phonetic domains.