Inclusion Criteria:  No previous experience with any auditory implant 18 years of age or older Postlingual onset of severe hearing loss (≥ 4 years of age) Limited benefit from appropriately fitted hearing aids, defined as scoring 60% or less in Freiburger Monosyllabic word test German language proficiency Willingness to participate in all scheduled procedures outlined in the protocol  Exclusion Criteria:  Cochlear malformation or obstruction that would preclude full insertion of electrode array. Presence of additional disabilities that would prevent or interfere with participation in the required study procedures Medical or psychological conditions that contraindicate surgery or impact the ability to manage an implanted device or the study related procedures Evidence of central auditory lesion or compromised auditory nerve Pregnancy at time of surgery.