| Sumario: | Purpose: This study aimed to investigate the acoustic changes in vowel production with different forms of auditory feedback via cochlear implant (CI), hearing aid (HA), and bimodal hearing (CI + HA). Method: Ten post–lingually deaf adult bimodal CI users (aged 50–78 years) produced English vowels /i/, /ɛ/, /æ/, /ɑ/, /ʊ/, and /u/ in the context of /hVd/ during short-term use of no device (ND), HA, CI, and CI + HA. Segmental features (first formant frequency [F], second formant frequency [F], and vowel space area) and suprasegmental features (duration, intensity, and fundamental frequency [f]) of vowel production were analyzed. Participants also categorized a vowel continuum synthesized from their own productions of /ɛ/ and /æ/ using HA, CI, and CI + HA. Results: Fs of all vowels decreased; Fs of front vowels but not back vowels increased; vowel space areas increased; and vowel durations, intensities, and fs decreased with statistical significance in the HA, CI, and CI + HA conditions relative to the ND condition. Only fos were lower, and vowel space areas were larger with CI and CI + HA than with HA. Average changes in f, intensity, and F from the ND condition to the HA, CI, and CI + HA conditions were positively correlated. Most participants did not show a typical psychometric function for vowel categorization, and thus, the relationship between vowel categorization and production was not tested. Conclusions: The results suggest that acoustic, electric, and bimodal hearing have a measurable impact on vowel acoustics of post–lingually deaf adults when their hearing devices are turned on and off temporarily. Also, changes in f and F with the use of hearing devices may be largely driven by changes in intensity.
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