Evaluation of the Nucleus Hybrid™ L24 Cochlear Implant System

Inclusion Criteria: 1. Eighteen years of age or older at the time of implantation. 2. Severe to profound (a threshold average of 2000, 3000, \& 4000 Hz \> 75dB HL) sensorineural hearing loss for frequencies \> 1500 Hz. Low-frequency thresholds up to and including 500 Hz should be no poorer than 60 dB HL. 3. Consonant Nucleus Consonant (CNC) monosyllabic word recognition score (mean of two lists) between 10% and 60%, inclusive (i.e., 10% \<= score \<= 60%), in the ear to be implanted. 4. CNC word recognition score in the contralateral ear equal to, or better than, the ear to be implanted but not more than 80%. 5. English spoken as a primary language. Exclusion Criteria: 1. Duration of severe-to-profound hearing loss greater than 30 years. 2. Congenital hearing loss (for the purpose of this study, onset prior to 2 years-of-age). 3. Medical or psychological conditions that contraindicate undergoing surgery. 4. Ossification or any other cochlear anomaly that might prevent complete insertion of the electrode array. 5. Conductive overlay of 15 dB or greater at two or more frequencies, in the range 250 to 1000 Hz. 6. Hearing loss of neural or central origin. 7. Diagnosis of Auditory Neuropathy. 8. Active middle-ear infection. 9. Unrealistic expectations on the part of the subject, regarding the possible benefits, risks, and limitations that are inherent to the surgical procedure(s) and prosthetic devices. 10. Unwillingness or inability of the candidate to comply with all investigational requirements. 11. Additional handicaps that would prevent or restrict participation in the audiological evaluations.