Population 2: 30 Children (ages 5-12 years) and adolescents (ages 13-15 years) who have a sensorineural hearing loss with a pure-tone average (PTA) between 60-90 dB HL between 125-1500 Hz and profound loss at higher frequencies will be implanted with the Cochlear® Nucleus™ Hybrid L24 Implant or the Cochlear® Nucleus™ Hybrid S12 Implant. Those that have hearing thresholds between 60-90 dB HL at 1500 Hz would be implanted with the less invasive shorter 10 mm Hybrid S12 in attempt to better preserve the middle frequency range. Those with hearing thresholds >90 dB HL at 1500 Hz would receive the longer 16 mm Hybrid L24 electrode. The potential subject will present with Phonetically Balanced Kindergarten (PB-K) monosyllabic word scores between 0-50% in the ear to be implanted and up to 60% understanding in the contralateral ear in the best-aided condition.