This pivotal study examines the clinical efficacy and safety of an investigational totally implantable cochlear implant (TICI) system. The system includes a microphone placed under the skin to detect speech and sound from the environment, providing the option to hear without any visible external parts. This study will involve adults with sensorineural hearing loss, a type of hearing loss caused by damage to the inner ear or auditory nerve (the nerve that carries sound signals from the ear to the brain). Participants will complete hearing tests and questionnaires to evaluate how well the system works and how it affects their daily life.

Inclusion Criteria:

• Individuals aged 18 years and older at time of consent.
• Clinically established sensorineural hearing loss (SNHL) defined by a four frequency (500, 1000, 2000, 4000 Hz) pure-tone average unaided threshold (PTA4) of ≥70 dB HL in the ear to be implanted.
• Compromised functional hearing in the aided condition defined as ≤40% correct on a word recognition test in the ear to be implanted.
• Clinically established SNHL defined by a four-frequency (500, 1000, 2000 & 4000 Hz) pure-tone average unaided threshold (PTA4) of ≥30 dB HL in the contralateral ear.
• Candidate is a fluent speaker in the language used to assess speech perception performance as determined by the investigator.
• Direct access to a compatible Smart Phone.
• Willing and able to provide written informed consent.

Exclusion Criteria:

• Prior cochlear implantation, in either ear, or medical plan for cochlear implantation during the clinical investigation, contralateral to the ear to be implanted.
• Candidates with single-sided deafness as determined by the investigator.
• Intra-axial (within-the-brain) lesions or deafness due to lesions of the acoustic nerve affecting the ear to be implanted.
• Middle ear infection (including acute otitis media, chronic otitis media, suppurative otitis media, or serous drainage) in the ear to be implanted either at the time of surgery or within 3 months prior to enrolment.
• Presence of a tympanic membrane perforation or a history of otologic surgery within 3 months prior to enrolment, in the ear to be implanted.
• Previously reported diagnosis of auditory neuropathy, in the ear to be implanted.
• Ossification, malformation or any other cochlear anomaly, such as common cavity, that might prevent complete insertion of the electrode array, in the ear to be implanted.
• Current cerebrospinal fluid (CSF) shunts or drains, existing perilymph fistula, skull fracture or CSF leaks.
• Severe, or poorer, bilateral sensorineural hearing loss prior to 5 years of age, as reported by the participant.
• Severe, or poorer, sensorineural hearing loss for more than 20 years, as reported by the participant, in the ear to be implanted.
• Medical or psychological conditions that contraindicate general anaesthesia, surgery, or participation in the clinical investigation as determined by the investigator.
• Pre-existing skin condition that could jeopardize wound healing as judged by the investigator e.g., psoriasis, dermatitis, use of corticosteroids, uncontrolled diabetes.
• Unrealistic expectations on the part of the participant, regarding the possible benefits, risks, and limitations inherent to the surgical procedure(s) and prosthetic devices, as determined by the Investigator.
• Additional disabilities that may affect the participant's participation or safety during the clinical investigation.
• Unable or unwilling to comply with all requirements of the clinical investigation, as determined by the investigator.
• Pregnant or breastfeeding women.
• Investigator site personnel directly affiliated with this study and/or their immediate families. Immediate family is defined as spouse, parent, child or sibling.
• Cochlear employees or employees of Contract Research Organisations or contractors engaged by Cochlear for the purposes of the investigation.
• Current participation, or participation in another interventional clinical study/trial in the past 30 days, involving an investigational drug or device (unless Cochlear sponsored and determined by Investigator or Sponsor to not impact this investigation).