Clinical Evaluation of a Cochlear Implant Sound Processor

General Inclusion Criteria: * Ability to provide Informed Consent * 18 years of age or older * Unilateral user of a HiResolutionTM Bionic Ear System (HiRes 90KTM, HiRes 90KTM Advantage, HiResTM Ultra, HiResTM Ultra 3D), including bilaterally implanted subjects that only use one implant in their everyday listening modality * Minimum of 6 months of CI experience * Having used a Naída CI Q70 or a Naída CI Q90 as their primary processor for a minimum of one month * Presently using a current steering strategy * At least moderate open-set speech recognition abilities with implant alone, as defined by achieving a score of ≥ 60% words correct in the AzBio in quiet test using the Naída CI Q90 research processor * English language proficiency as determined by the investigator * Willingness to use a BTE processor for the duration of the study ARH Arm Inclusion Criteria * Residual low frequency hearing sensitivity (pure tone average of \< 70 dB HL for 125, 250, and 500 Hz) and a severe-to-profound high-frequency sensorineural hearing loss (pure tone average of ≥ 70 dB HL for 1,000, 2,000, 3000, 4,000, and 8,000 Hz) in the implanted ear * Willingness to use an in-canal acoustic earhook for the duration of the study EO Arm Inclusion Criteria • Severe-to-profound sensorineural hearing loss in the low (pure tone average of ≥ 70 dB HL for 125, 250, and 500 Hz) and high frequencies (pure tone average ≥ 70 dB HL for 1,000, 2,000, 3000, 4,000, and 8,000 Hz) in the implanted ear Exclusion Criteria: * Unrealistic expectations regarding potential benefits, risks and limitations of the investigational device as determined by the investigator * Unwillingness or physical / cognitive inability of subject to comply with all investigational requirements as determined by the investigator