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Purpose: The objective of the study was to investigate the influence of noise (energetic) and speech (energetic plus informational) maskers on the head shadow (HS), squelch (SQ), and binaural summation (SU) effect in bilateral and bimodal cochlear implant (CI) users. Method: Speech recognition was measured in the presence of either a competing talker or modulated speech-shaped noise in 10 bimodal and 10 bilateral adult CI users. HS, SQ, and SU effects were calculated. The interfering signals were manipulated with respect to F0 to consider the influence of different speaker voices. Results: The effects HS, SQ, and SU differed depending on the type of masker. A detailed analysis of errors was used to dissociate energetic and informational masking effects. The analysis showed a release from energetic than from informational masking. Conclusion: Noise interferers are not sufficient to reflect difficulties experienced with speech understanding in noise for bilateral and bimodal CI users. Key Words: bilateral hearing, bimodal hearing, hearing aid, cochlear implant, informational masking, fundamental frequency, To communicate successfully in a listening situation with more than one talker, listeners must be able to attend selectively to a target talker while ignoring other competing talkers. In a [...]

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. Key Words: bimodal hearing, hearing aid, cochlear implant, informational masking, fundamental frequency, formant frequencies, In many communication settings, people are exposed to speech from multiple concurrent talkers (e.g., in a cocktail party situation). Typically the listener does not need to attend to all talkers [...]