After several years of trying to recruit participants, it was decided to stop the study after recruiting only 12 participants.

When providing amplification post-implantation to residual acoustic hearing in the implanted ear, the lower frequency boundary can be modified to minimize or avoid overlap between the frequencies coded through acoustic hearing and those presented through electrical stimulation. This boundary is termed the cross-over frequency (Fc) and the effect of modifying this parameter will be investigated in this study. To avoid the research being confounded by prior bias for a particular frequency allocation, the study will be conducted with newly implanted recipients.

This study will also investigate whether tests which measure the ability to use low frequency hearing and objective measures can predict the preferred Fc and speech performance benefit.

Inclusion Criteria:

1. Adult (≥18 years of age)
2. Post-operative residual hearing in the implanted ear (defined as having an unaided threshold better than or equal to 80 dB HL at the 500 Hz frequency).
3. Implanted with the CI500 or CI24RE-series cochlear implants
4. User of the commercially available Nucleus 6 sound processor
5. User of the ACE strategy
6. Native speaker in the language used to assess speech perception performance
7. Willingness to participate in and to comply with all requirements of the protocol

Exclusion Criteria:

1. Additional handicaps that would prevent participation in evaluations
2. Unrealistic expectations on the part of the subject, regarding the possible benefits, risks and limitations that are inherent to the procedure and investigational device