A Feasibility Study Evaluating the Performance of Focused Multipolar Stimulation and Sound Coding in Adults.

Inclusion Criteria: 1\) Candidate for unilateral cochlear implantation according to bilateral sensorineural hearing loss criteria, who has decided to proceed with implantation through routine processes. a) Bilateral sensorineural hearing loss criteria for clinics in the United States: i) Ear to be implanted: 1. Moderate to profound sensorineural hearing loss, defined as a pure-tone average (PTA) (250 - 1000 Hz) ≥ 40 dB HL and a PTA (2000 - 8000 Hz) ≥ 65 dB HL 2. Aided word score ≤ 40% ii) Contralateral ear: (1) PTA (500, 1000, 2000, and 4000 Hz) \> 30 dB HL (2) Aided word score ≤ 80% b) Bilateral sensorineural hearing loss criteria for clinics in Belgium: i) Both ears: 1. PTA (500, 1000, 2000, and 4000 Hz) ≥ 70 dB HL for average of 3 out of 4 frequencies 2. Unaided phoneme score ≤ 50% on CVC in quiet at 70 dB SPL in free field 3. ABR peak ≥ 75 dB nHL 2\) 18 years of age or older. 3\) Fluent in the language used for speech testing. 4\) Willing to comply with all investigational requirements. 5\) Willing and able to provide written informed consent \- Exclusion Criteria: 1. Previous or existing cochlear-implant recipient. 2. Severe or greater sensorineural hearing loss in the ear to be implanted prior to five years of age. 3. Duration of severe to profound hearing loss \> 20 years in the ear to be implanted. 4. Ossification or other cochlear anomaly that might prevent complete insertion of the electrode array. 5. Diagnosis of auditory neuropathy. 6. Deafness due to lesions of the acoustic nerve or central auditory pathway. 7. Pregnant at the time of surgery. 8. Additional handicaps that would prevent or restrict participation in the audiological evaluations. 9. Unrealistic expectations on the part of the subject regarding the possible benefits, risks, and limitations that are inherent to the surgical procedure and prosthetic device. 10. Unable or unwilling to comply with the requirements of the clinical investigation as determined by the Investigator. 11. Investigator site personnel directly affiliated with this study and/or their immediate families; immediate family is defined as a spouse, parent, child, or sibling. 12. Cochlear employees or employees of Contract Research Organisations or contractors engaged by Cochlear for the purposes of this investigation. 13. Currently participating, or participated within the last 30 days, in another interventional clinical investigation/trial involving an investigational drug or device