Purpose: Recent bimodal studies identified a lack of bimodal evaluation and fitting protocols to improve bimodal benefits. The purpose of this study is to measure bimodal benefits in speech and sound quality recognition and identify bimodal fitting issues with adult cochlear implant listeners to establish bimodal fitting guidelines and evaluation protocol. Methods: A total of 20 adult cochlear implant users were participated in this study. The experimental procedures included basic evaluation, hearing aid evaluation, and bimodal benefits evaluation. In order to evaluate bimodal benefits, speech and sound quality recognition tests were performed. Matrix sentences in quiet and noise (5 and 10 dB sound pressure level), consonant-vowel-consonant words, and story comprehension tasks were provided. Participants judged sound qualities for six sound quality dimensions and a tester performed real ear measurements to verify hearing aid gains. Results: Results showed that bimodal listeners had some bimodal benefits in the sentence and monosyllabic word recognition in quiet. The benefits of sound quality judgments were also observed for six sound quality dimensions. Bimodal cochlear implant listeners of this study demonstrated less real-ear insertion gains than target gains across test frequencies. Conclusion: Speech and sound quality recognition tests are useful tools to measure bimodal benefits. Additional care for bimodal listeners is needed to optimize bimodal fitting and improve the quality of bimodal hearing aid fitting services.
MATERIALS AND METHODS