Cochlear implants (CI) are used to help patients with severe to profound hearing loss regain auditory perception by electrical stimulation of the auditory nerve. The electrical stimulation consists of trains of charge balanced, biphasic current pulses. For each patient, individual stimulation parameters (perception threshold, most comfortable level - MCL) are determined for each electrode during fitting sessions. However, an important parameter, pulse duration, cannot be individualized for each electrode. There are certain circumstances where it would be advantageous to have the possibility of introducing variable pulse durations into the fitting strategy (e.g., optimization of energy consumption, development of combined cochleo-vestibular implants). However, since in current CI systems pulses are transmitted sequentially, introducing varying pulse widths would also introduce "gaps" (zero-stimulation periods) into the stimulation profile. The influence of such auditory gaps on speech recognition and on the quality of hearing has not been explored yet, but can be investigated in current CI users. The objective of this study is to investigate the impact of time-fixed gaps (zero-stimulation periods) in the cochlear stimulation strategy on speech performance and hearing quality.

Auditory gaps can be induced in standard CI users by temporarily deactivating one to three electrodes. These gaps can be configured to have different gap durations.

The different variations of auditory stimulation with gaps will be presented to study participants via a standard MED-EL audio processor (Opus 2) bearing conformity marking. The programming of the processor will be performed using standard clinical hardware and software interfaces. These include the hardware interfaces "MAX interface box" and the "Diagnostic Interface Box" (DIB II) as well as the "MAESTRO" fitting software. After programming the respective configurations to the audio test-processor, a clinical word recognition test (Fournier) and a clinical consonant recognition test will be presented to the participants in a sound-shielded chamber using a free-field loudspeaker system.

Inclusion Criteria:

• Informed Consent as documented by signature
• CI recipients using MED-EL implants (C40+, Pulsar, Sonata, Concerto, or Synchrony) and standard electrode arrays (Standard, FLEXSOFT, FLEX28, or FLEX24)
• >1 year post-implantation
• Regular CI use (at least 4 hours/day)
• At least 9 active electrodes in the device
• Good knowledge of French (at least B1 level according to the Common European Framework of Reference for Languages)

Exclusion Criteria:

• Patients with electro-acoustic stimulation (EAS) systems
• Unwillingness or inability to perform investigational tests
• Known or suspected drug or alcohol abuse
• Inability to follow the procedures of the study (e.g. due to language problems, psychological disorders, dementia, etc.)
• Previous enrolment into the current study
• Enrolment of the investigator, his/her family members, employees and other dependent persons