Cochlear implants

Also known as Cochlear implant, Bionic ear

Cochlear implants are electronic devices that stimulate the auditory nerve to give a sense of sound to people with profound deafness or severe hearing loss. About 736,900 devices had been implanted worldwide by December 2019, but results vary between people and hearing in noise and music remains difficult.

CommercialDemonstratedReviewed 21 Oct 2026
AI illustration · Illustrative scene, not a photograph of the specific device or experiment.

In plain language

A cochlear implant is for people who get little benefit from hearing aids, usually because the inner ear, the cochlea, is badly damaged. A microphone and processor worn outside the head pick up sound and turn it into a pattern of electrical pulses. Surgery places a thin array of electrodes inside the cochlea, and these electrodes send the pulses straight to the auditory nerve, the bundle of fibres that carries sound signals to the brain.

The brain learns to interpret these pulses as sound, so hearing through an implant is not the same as normal hearing. People differ a lot in how well they do, and many need time to learn to make sense of the signals. Newer work extends implants to younger children, to people with hearing in only one ear, and to designs that have no external parts. Researchers are also testing light instead of electricity to stimulate the nerve more precisely.

Technical explanation

Most implants use an external processor that splits incoming sound into frequency bands and sends each band to electrodes placed along the cochlea. The electrodes stimulate the spiral ganglion neurons, and the brain receives these patterns as sound. Because each electrode spreads current into neighbouring tissue, the number of independent channels that can be used is limited. This restricts frequency detail. McDermott's 2004 review of music perception reports that, in one study of 12 well-known tunes, implant users averaged about 19% correct against about 83% for listeners with normal hearing, and that implant users tend to rate musical sounds as less pleasant. The same review notes that earlier processors struggled to estimate speech in high background noise, while many users of recent systems understand speech reasonably well even in moderately noisy conditions.

Indication expansion has followed improved devices and evidence. In March 2020 Cochlear announced FDA approval to lower the labelled age from 12 months to 9 months for children with bilateral profound sensorineural hearing loss who get limited benefit from binaural hearing aids. In January 2022 the FDA approved Cochlear Nucleus implants for unilateral hearing loss and single-sided deafness. Cochlear's release describes this as the first time it can offer cochlear implants for this group, alongside its bone conduction systems. Research is also moving beyond electrical stimulation. Dieter and colleagues (2020) used micro-LED optical implants in gerbils that had been made light-sensitive by a viral vector. Light evoked tonotopic activation of the auditory pathway with high spectral selectivity, but the work is acute and limited to small animal groups. Lefebvre and colleagues (2025) report initial results from a totally implantable device in six adults, in which the components are combined in one implant that removes the need for an external processor, with a primary aim of safety. These results come from secondary summaries and need checking against the primary paper.

What the evidence says

Each statement is typed by the strength of its evidence and linked to the source that supports it.

Demonstrated Shown in a published experiment, test or shipping product.

The WHO fact sheet dated 3 March 2026 states that over 5% of the world's population, or 430 million people, need rehabilitation for disabling hearing loss, including 34 million children, and projects that over 700 million people will have disabling hearing loss by 2050.

Sources: [1] · Overview · medium confidence

NIDCD reports approximately 736,900 registered cochlear implant devices implanted worldwide as of December 2019, with roughly 118,100 in adults and 65,000 in children in the United States.

Sources: [2] · Number of recipients · medium confidence

NIDCD states that not everyone performs at the same level with a cochlear implant, and that an implant does not restore normal hearing.

Sources: [2] · How outcomes vary

In gerbils, micro-LED optical cochlear implants evoked tonotopic activation of the auditory pathway with high spectral selectivity. Only 15 of 35 virus-injected animals showed robust optically evoked responses, and 206 of 528 individual micro-LEDs evoked responses.

Sources: [5] · Results and key numbers

In a non-randomised feasibility study of a totally implantable cochlear implant, six adults with bilateral severe-to-profound hearing loss were implanted from September 2020 and followed for 52 weeks. One anticipated serious adverse device effect occurred and resolved, and speech perception in quiet and in noise was comparable with a conventional external processor. The device is a study device, not a commercial product.

Sources: [6] · Abstract (Europe PMC) · medium confidence

In a study of 12 well-known tunes cited in McDermott's 2004 review, implant users averaged about 19% correct, against about 83% for listeners with normal hearing. The review also says implant users tend to rate musical sounds as less pleasant than listeners with normal hearing.

Sources: [7] · Music perception section · medium confidence

McDermott's 2004 review states that many users of recent implant systems understand speech reasonably well even in moderately noisy conditions, while earlier processors struggled to estimate speech in high background noise.

Sources: [7] · Speech and feature-extraction discussion · medium confidence

Reported, unverified Stated by a company or team but not independently confirmed.

On 11 January 2022 the FDA approved Cochlear Nucleus implants for unilateral hearing loss and single-sided deafness. Cochlear's release describes this as the first time it can offer cochlear implants for this group, alongside its existing bone conduction systems.

Sources: [3] · Press release · medium confidence

On 18 March 2020 Cochlear announced FDA approval to lower the labelled age for implantation from 12 months to 9 months, for children aged 9 to 24 months with bilateral profound sensorineural hearing loss who get limited benefit from binaural hearing aids, and extended the approval to all current Nucleus models.

Sources: [4] · Press release · medium confidence

Limitations and open problems

  • Outcomes differ widely between people, and an implant does not restore normal hearing (NIDCD).
  • In a 2004 review, implant users averaged about 19% correct in one melody recognition study. The review predates many current processing strategies (McDermott, 2004).
  • Earlier processors struggled to estimate speech in high background noise, and that review predates current processing strategies (McDermott, 2004).
  • Optical stimulation has so far been tested only in acute studies in gerbils. Only 15 of 35 virus-injected animals showed robust responses, and about a third of individual micro-LEDs (206 of 528) evoked responses (Dieter and colleagues, 2020).
  • Totally implantable devices have only initial results from six adults (Lefebvre and colleagues, 2025), reported in secondary summaries that need checking against the primary paper. The device is not available for commercial use.
  • The NIDCD figure counts registered devices rather than individual people, and it is dated December 2019. Current global totals were not found in the sources reviewed.

Possible future uses

Speculative

Ideas, not predictions. None of these has been demonstrated.

  • Fully implanted systems that remove the need for an external processor, so that users can wear their hearing device all day without visible parts, if trials confirm long-term safety and speech performance.
  • Optical implants with finer frequency selectivity than electrodes, which could improve pitch and music perception if light delivery can be scaled to human cochleae.
  • Music-focused processing strategies for implant users, designed around the detail that current devices lose.

Timeline

  1. 2004McDermott's review in Trends in Amplification reports that implant users averaged about 19% correct in one melody recognition study, against about 83% for listeners with normal hearing. Sources: [7]
  2. Dec 2019NIDCD's figures show approximately 736,900 registered cochlear implant devices implanted worldwide, including roughly 118,100 adults and 65,000 children in the United States. Sources: [2]
  3. 18 Mar 2020Cochlear announces FDA approval to lower the labelled age for implantation from 12 months to 9 months for children with bilateral profound sensorineural hearing loss. Sources: [4]
  4. 29 Jun 2020Dieter and colleagues publish micro-LED optical cochlear implants that evoke spectrally selective activation of the auditory pathway in gerbils. Sources: [5]
  5. 11 Jan 2022FDA approves Cochlear Nucleus implants for unilateral hearing loss and single-sided deafness. Cochlear says this is the first time it can offer implants for this group. Sources: [3]
  6. 8 Jan 2025Lefebvre and colleagues publish initial results from a totally implantable cochlear implant in six adults, with a primary aim of assessing safety. Sources: [6]

Futures this could help bring about

AI illustration
How far away?

Restoring hearing to deaf children with gene therapy

Pilots · 4 of 8 steps done

Glossary

Cochlea
The spiral, fluid-filled organ of the inner ear that turns sound vibrations into nerve signals.
Auditory nerve
The nerve that carries sound signals from the inner ear to the brain.
Electrode array
A thin set of electrical contacts placed inside the cochlea to stimulate the auditory nerve.
Single-sided deafness
Severe to profound hearing loss in one ear with normal or near-normal hearing in the other.

Sources

  1. government report
    Deafness and hearing loss: Fact sheet
    World Health Organization, 3 Mar 2026. Accessed 21 Oct 2026.
  2. government report
    Cochlear Implants
    National Institute on Deafness and Other Communication Disorders, 13 Jun 2024. Accessed 21 Oct 2026.
  3. company announcement
    FDA approves Cochlear Nucleus Implants for unilateral hearing loss/single-sided deafness
    Cochlear Ltd, 11 Jan 2022. Accessed 21 Oct 2026.
  4. company announcement
    Cochlear receives FDA approval to lower the age of pediatric cochlear implantation to 9 months
    Cochlear Ltd, 18 Mar 2020. Accessed 21 Oct 2026.
  5. peer reviewed paper
    μLED-based optical cochlear implants for spectrally selective activation of the auditory nerve
    Alexander Dieter, Eric Klein, Daniel Keppeler et al.. EMBO Molecular Medicine, 29 Jun 2020. DOI: 10.15252/emmm.202012387. Accessed 21 Oct 2026.
  6. peer reviewed paper
    Rehabilitation of human hearing with a totally implantable cochlear implant: a feasibility study
    Philippe Pierre Lefebvre, Joachim Müller, Gerhard Mark et al.. Communications Medicine, 8 Jan 2025. DOI: 10.1038/s43856-024-00719-0. Accessed 21 Oct 2026.
  7. review article
    Music Perception with Cochlear Implants: A Review
    Hugh J. McDermott. Trends in Amplification, 2004. DOI: 10.1177/108471380400800203. Accessed 21 Oct 2026.

Revision history

4 changes since this profile was created.

Changes on 21 Oct 2026
Published on owner instruction (content loop iteration 48)d9ec0d4
Totally implantable implant study checked against its abstract and Crossref; claim updated from secondary summaries to the paperc1ad9ee
Sources and claims re-checked against originalsfbb434c
Initial profile drafted from primary sources7e66249