Perceptual and acoustic analysis of lexical and sentential stress in children with developmental apraxia of speech

Lexical and sentential stress patterns were compared for children with developmental apraxia of speech (DAOS) (n = 5) and children without speech disorders (n = 5). Audio recordings were made of imitative production of 10 bisyllabic and 10 multisyllabic words, and 5 sentences (3 interrogative, and 2 emotive). Ten listeners judged the accuracy of stress in both the words and sentences. Fundamental frequency (F₀), root mean square (RMS) amplitude, and duration also were measured for each word for two of the sentences. Listeners perceived the control subjects to more accurately mark syllabic stress than DAOS subjects for both the bisyllabic and multisyllabic words and to more accurately imitate intonational contours. Group differences were small, however, and the range of listener judgments was large. Acoustic analysis revealed that the subjects with DAOS used the same acoustic parameters as the control group to mark stress, although they exhibited greater intersubject variability.