An examination of the effect of talker familiarity on the sentence recognition skills of cochlear implant users

Three experiments examined normal-hearing and cochlear-implant listeners’ abilities to perceive and use talker-specific information in the speech signal. In Experiment 1 voice similarity judgments were gathered from normal-hearing listeners to maximize variability across talkers used in Experiment 2. These judgments were submitted to a multidimensional scaling (MDS) analysis; this solution was used to select the talkers. Experiment 2 was an approximate replication of Nygaard and Pisoni’s (1998) work. In this study cochlear-implant and normal-hearing listeners were trained to recognize 6 different voices. The cochlear-implant users recognized the voices with 59.31% accuracy and the normal-hearing listeners achieved 92.64% accuracy. After training the listeners completed a sentence recognition task in noise. In the task 6 familiar talkers spoken half of the sentences and 6 novel talkers spoke the other half. It was predicted that sentences spoken by the familiar talkers would be more accurately perceived than those spoken by the novel talkers. However, there was no difference in accuracy, nor was there a difference in performance across the groups of listeners. The factors contributing to these null results were discussed at length. Experiment 3 gathered voice similarity judgments from the normal-hearing and cochlear-implant listeners of Experiment 2. These data were submitted to both classical and weighted MDS analyses. The voice maps showed notable differences in the perceptual spaces of the two groups of listeners. The participant space yielded from the weighted MDS showed great variation across all of the participants’ judgments, but no clear trend supporting the listeners’ group membership. In conclusion, despite listening via a constrained, electric signal, the cochlearimplant users were successfully trained to recognize voices with notable accuracy (as were the normal-hearing listeners). Nevertheless, Experiment 2 failed to provide insight AN EXAMINATION OF THE EFFECT OF TALKER FAMILIARITY ON THE SENTENCE RECOGNITION SKILLS OF COCHLEAR IMPLANT USERS by Brittan Ann Barker A thesis submitted in partial fulfillment of the requirements for the Doctor of Philosophy degree in Speech and Hearing Science in the Graduate College of The University of Iowa