Safety and Performance of HiRes Ultra/Ultra 3D Cl Mid-Scala Electrodes in Adults With Severe-to-profound Hearing Loss

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.