The rationale is to determine (in individuals with limited perceived bimodal benefit) whether the CROS device may be a better solution for obtaining two-sided input. If yes, this study would be practice-changing.

It is well accepted that bilateral input can significantly improve speech understanding in noise for patients with cochlear implants. For cochlear implant (CI) recipients who have a CI on only one side, two sided input can be provided with simultaneous use of a hearing aid (HA) or a CROS device on the opposite side. The decision about which device to use depends on the level of residual hearing a recipient has in non CI-implanted ear, and more specifically what level of useable residual hearing s/he has. Access to useable low frequency hearing can not only improve speech understanding in noise, it can also improve sound quality, pitch perception and music perception.

Clinicians can reasonably predict that a recipient with hearing thresholds better than 60 dB HL at low frequencies (below 750 Hz) would benefit from amplification. For recipients with no measurable acoustic hearing in the contralateral ear, CROS would be a reasonable option, especially if bilateral implantation is not feasible or desired. However, it is more difficult to predict the appropriate device in individuals who have some measurable acoustic hearing but may be receiving limited benefit from it. This can be especially challenging because audiometric thresholds are not a reliable predictor of bimodal benefit. Additionally, acoustic hearing can provide subjective benefits which could hold different intrinsic value or significance for different individuals depending on their life style and listening needs.

Inclusion Criteria:

• Adults (> 18 years of age)
• Unilaterally implanted with an Advanced Bionics implant (CII or later)
• At least six months of CI use
• Limited bimodal benefit as perceived by the recipient and/or the clinician
• Participants may or may not currently be using a hearing aid in the unimplanted ear.
• Open set performance with current device configuration:
• ≥40% AzBio sentence score in quiet (S0) and? (i.e. do both these apply)

If currently bimodal:

• Hearing aid ear only CNC score <50%
• AzBio Scores bimodal benefit <15% increase in score compared to CI only?
• Unaided audiometric threshold of ≤100 dBHL up to 500 Hz
• Ability and willingness to participate in multiple sets of open speech testing (and ongoing evaluation of HA and CROS benefit)

Exclusion Criteria:

• Patients who are not proficient in English as the AzBio testing is available in English only.
• Patients with agenesis of the contralateral ear