Electronic Thesis and Dissertation Repository


Master of Science


Health and Rehabilitation Sciences


Dr. David W. Purcell


The envelope following response (EFR) has proven useful for studying brainstem speech processing. Previous work, however, demonstrates that its amplitude varies across stimuli. This thesis investigates whether this variation is attributable to the consonant or vowel context of the stimulus, or some interaction of the two. Experiment 1 evoked EFRs in 30 participants using seven English vowels embedded in four CVC environments. A strong effect of vowel and a minor effect of consonant on EFR amplitude were found. In Experiment 2, 64 listeners heard four different tokens of one of four possible English vowels (16 participants/vowel), embedded in the same CVC environments as before. A significant three-way interaction between vowel, vowel trial, and consonant was found, indicating that the EFR is highly sensitive to subtle acoustic differences in stimuli. To effectively utilize the EFR in research, future studies should carefully explore the mechanisms driving these complex context effects.