• Sixty-five years of age or older at the time of the study and CMS-eligible as primary source of medical insurance coverage.
• Bilateral moderate to profound hearing loss in the low frequencies (up to 1000 Hz) and profound sensorineural hearing loss in the high frequencies (3000 Hz and above).
• Preoperative aided sentence score in quiet greater than or equal to 40% correct but less than or equal to 60% correct in the best aided condition on recorded AzBio sentences.
• English spoken as the primary language.
• Congenital hearing loss (for the purpose of this study, onset pror to 2 years-of-age).
• Preoperative aided sentence score less than 40% or greater than 60% correct in the best aided condition on AzBio sentences in quiet
• Ossification, absence of cochlear development or any other cochlear anomaly that might prevent complete insertion of the electrode array.
• Hearing loss of neural or central origin (e.g., deafness due to lesions on the acoustic nerve or central auditory pathway).
• Active middle-ear infection.
• The audiologist and/or surgeon will review the study protocol with the patient prior to having him/her sign the consent form. If the patient indicates he/she is unwilling or unable to comply with all investigational requirements, he/she will not be enrolled in the study.
• Using best clinical judgment based on professional interaction with the patient and his/her family, the managing audiologist and surgeon will determine if there are any disabling cognitive limitations that would prevent the patient from providing reliable data for this study.

• Cystic fibrosis patients about to receive IV tobramycin for acute pulmonary exacerbation.
• Voluntarily consent to participate in the study.
• Females of childbearing potential should be using and committed to continue using one of the following acceptable birth control methods:
• Sexual abstinence (inactivity) for 14 days prior to screening through study completion; or IUD in place for at least 3 months prior to study through study completion; or Barrier method (condom or diaphragm) with spermicide for at least 14 days prior to screening through study completion; or Stable hormonal contraceptive for at least 3 months prior to study through study completion.
• Ability to perform all behavioral tests as indicated.
• Current use or within 60 days prior to study enrollment the following IV ototoxic medications: aminoglycoside antibiotics (gentamicin, tobramycin, amikacin, streptomycin); platinum-containing chemotherapies (cisplatin, carboplatin, oxaliplatin); or loop diuretic (furosemide).
• History of idiopathic sensorineural hearing loss, otosclerosis, or vestibular schwannoma.
• History of middle ear or inner ear surgery.
• Current conductive hearing loss or middle ear effusion.
• Significant cardiovascular, hepatic, renal, hematologic, endocrine, immunologic, or psychiatric disease.
• History of hypersensitivity or idiosyncratic reaction to compounds related to ebselen.
• Participation in another investigational drug or device study within 30 days prior to study enrollment.
• Female patients who are pregnant or breastfeeding.