In this study, the performance with the CI is investigated over time in three groups of freshly implanted CI users. Both the standard frequency-band distribution and anatomy-based fitting will be used to compare outcomes.

In this study, the performance with the CI is investigated over time in three groups of freshly implanted CI users. The first group is fitted using the standard frequency-band distribution as implemented in MAESTRO 9. In the second group of users, an anatomy-based frequency distribution is used as per anatomy-based fitting in MAESTRO 9. The performance with anatomy-based fitting is assessed by comparing performance with the CI in these two groups over time.

The third group constitutes the within-subject design. These subjects are both fitting using the standard frequency-band distribution and the anatomy-based frequency distribution in MAESTRO 9. So, subjects will have both study maps on their audio processor throughout the whole study. They will have to change weekly between both fittings: standard fitting and anatomy-based fitting. Here, the performance with anatomy-based fitting is assessed by comparing performance with standard fitting and anatomy-based fitting.

Inclusion Criteria:

• Age ≥ 18 years
• Post-lingual onset of severe to profound sensory-neural hearing loss in the implanted ear(s)
• Post-OP CT scan of the CI electrode available
• Subject implanted with MED-EL cochlear implant(s)
• Subjects received a Flex28 or FlexSoft electrode
• Subject planned to receive a SONNET 2 /RONDO3 audio processor on the newly implanted side
• Audio processor not yet activated on the newly implanted side
• The most apical active electrode contact has to be inserted at least 450°
• Minimum of 10 active channels can be activated
• Fluent in Spanish
• Signed and dated ICF before the start of any study-specific procedure

Specific inclusion criteria for the possible study groups • Bilateral CI users: Bilateral CI implantation SONNET 2/RONDO3 audio processor on the first ear implanted

• 40% speech recognition a monosyllabic word Test in quiet at 65 dB SPL (last time tested) on the already implanted side

• 40% speech recognition in a sentence test in noise (10 dB SNR) on the already implanted side First activation of the already implanted side between 3 and 12 months prior to study inclusion

  • Unilateral CI users: Unilateral CI implantation CI user with contralateral hearing ≥ 60 dB (PTA measured at 500, 1000, 2000, and 4000 Hz)

  • SSD CI users: Unilateral CI implantation CI user with contralateral hearing ≤30 dB (PTA measured at 500, 1000, 2000, and 4000 Hz) Interaural threshold gap ≥40 dB

  • Bimodal CI users: Unilateral CI implantation Contralateral ear adequately fitted with a hearing aid CI user with contralateral hearing ≥30 dB (PTA measured at 500, 1000, 2000, and 4000 Hz) CI user with contralateral hearing ≤55 dB (PTA measured at 500, 1000, 2000, and 4000 Hz) Interaural threshold gap ≥15 dB

Exclusion Criteria:

• Lack of compliance with any inclusion criteria
• EAS user (user of an EAS audio processor)
• Implanted with C40+, C40X and C40C
• Implanted with an ABI or Split electrode array
• Known allergic reactions to components of the investigational medical device
• Anything that, in the opinion of the Investigator, would place the subject at increased risk or preclude the subject's full compliance with or completion of the study