Vowel Acoustics in Adults with Apraxia of Speech

Purpose: To investigate the hypothesis that vowel production is more variable in adults with acquired apraxia of speech (AOS) relative to healthy individuals with unimpaired speech. Vowel formant frequency measures were selected as the specific target of focus. Method: Seven adults with AOS and aphasia produced 15 repetitions of 6 American English vowels in /hVC/ context ("hid, head, hat, hot, hub, hoot"). Vowel formant frequency measures (F1, F2) were Bark transformed and compared with data from archival sources. Results: Measures of vowel acoustics in speakers with AOS did not differ from those of unimpaired speakers, including absolute Bark formant values, vowel space area, intervowel distance, and individual trial-to-trial formant variability. Conclusion: Comparison with normative acoustic measures suggested that vowel production at the word level is unimpaired in the current speakers with AOS, supporting previous studies that have shown vowel production is relatively intact in AOS.