Population 1: 15 Adults who have a severe sensorineural hearing loss with a pure-tone average (PTA) between 60-90 decibels (dB) hearing level (HL) between 125-1500 Hz and profound loss at higher frequencies will be implanted with the Cochlear® Nucleus™ Hybrid L24 Implant. The potential subject will present with Consonant-Nucleus-Consonant (CNC) monosyllabic word scores between 0-35% in the ear to be implanted and up to 60% understanding in the contralateral ear in the best-aided condition.