Bimodal hearing and speech perception with a competing talker.

Purpose: The objective of the study was to investigate the influence of bimodal stimulation upon hearing ability for speech recognition in the presence of a single competing talker.

Method: Speech recognition was measured in 3 listening conditions: hearing aid (HA) alone, cochlear implant (CI) alone, and both devices together (CI + HA). To examine the use of low-frequency cues, the competing masker voice was manipulated with respect to fundamental frequency (F0) and formant frequencies. Twelve implanted adults were included in the study.

Results: Group results revealed only a relatively small benefit of CI + HA compared with the CI alone. A detailed analysis of errors, which was assumed to be an indicator for the release from masking, revealed that this benefit was not attributed to improved target-masker segregation. The variable determined to be responsible for segregating target and masker talkers was a large difference in F0 of the voices. This held true for all CI alone, HA alone, and CI + HA listening conditions.

Conclusions: Bimodal hearing improved overall speech recognition of both the target and the masker. No evidence for better target-masker separation with bimodal fitting could be found.