Bimodal cochlear implants: the role of acoustic signal level in determining speech perception benefit.

The aim of this project was to determine for bimodal cochlear implant (CI) patients, i.e. patients with low-frequency hearing in the ear contralateral to the implant, how speech understanding varies as a function of the difference in level between the CI signal and the acoustic signal. The data suggest that (1) acoustic signals perceived as significantly softer than a CI signal can contribute to speech understanding in the bimodal condition, (2) acoustic signals that are slightly softer than, or balanced with, a CI signal provide the largest benefit to speech understanding, and (3) acoustic signals presented at maximum comfortable loudness levels provide nearly as much benefit as signals that have been balanced with a CI signal.