A Study of Objective Fitting for Focused Multipolar Stimulation

Inclusion Criteria: 1. Moderately severe to profound sensorineural hearing loss in both ears. (i.e., \>55 dB HL pure-tone average loss) 2. Candidate for unilateral cochlear implantation according to locally approved criteria. 3. Aged 18 years or over. 4. Fluent speaker in the language used to assess speech perception performance. 5. Willing and able to provide written informed consent. Exclusion Criteria: 1. Unable or unwilling to comply with the requirements of the clinical investigation as determined by the Investigator. 2. Investigator site personnel directly affiliated with this study and/or their immediate families; immediate family is defined as a spouse, parent, child, or sibling. 3. Cochlear employees or employees of Contract Research Organisations or contractors engaged by Cochlear for the purposes of this investigation. 4. Pregnant at the time of surgery. 5. Prisoners, or anyone in custody. 6. Current participation, or participation in another interventional clinical study/trial in the past 30 days, involving an investigational drug or device. 7. Previous or existing cochlear-implant recipient. 8. Evidence of severe or greater sensorineural hearing loss in the ear to be implanted prior to five years of age. 9. Duration of severe to profound hearing loss \>20 years in the ear to be implanted. 10. Ossification or other cochlear anomaly that might prevent complete insertion of the electrode array. 11. Diagnosis of auditory neuropathy. 12. Deafness due to lesions of the acoustic nerve or central auditory pathway. 13. Additional handicaps that would prevent or restrict participation in the audiological evaluations. 14. 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.