Inclusion Criteria:  Individuals 18 years of age or older Obtain limited benefit from appropriately fitted hearing aids Bilateral severe-to-profound sensorineural hearing loss _ Severe-to-profound hearing loss is determined by a pure-tone average (PTA) superior or equal (≥) to 70 dB HL at 500, 1000 and 2000 Hz. Limited benefit from amplification is defined by scores of 50% or less on a validated sentence recognition test in quiet (AzBio sentences), in the best-aided listening condition _  Exclusion Criteria:  Previous cochlear implantation Ossification or any other cochlear anomaly that might prevent complete insertion of the electrode array Active external or middle ear infections or tympanic membrane perforation in the ear to be implanted Presence of medical contraindications to middle-ear or inner-ear surgery or anesthesia as required Diagnosis of retro-cochlear pathology Diagnosis of auditory neuropathy Unrealistic expectations on the part of the subject regarding the possible benefits, risks, and limitations that are inherent to the surgical procedure and use of the prosthetic device Unwillingness or inability to comply with all investigational requirements Additional cognitive, medical, or social handicaps that would prevent completion of all study requirements