Cochlear Implant Simulator

If one implant had 22 electrodes in 1985, why do others have fewer?

Having 22 electrodes never meant hearing 22 separate pitches. The first 22-electrode implant, the Nucleus 22, used only one electrode at a time in its earliest version, then two (1985), then four (late 1980s). Its processor looked for the strongest parts of a voice and sent each one to the electrode in the matching spot. From the early 1990s it has picked about six to ten of the 22 for each moment of sound, whichever bands are loudest. So 22 gives many places to choose from, not 22 things happening at once.

When did all 22 start working at once? They never have. All 22 have been available since the first version, but even today the implant fires only one electrode at a time, switching between them thousands of times a second, because electrodes fired together blur into each other. Since about 2000 its processor can be set to use up to 20 in each sweep, but a typical setting still uses about 8 to 10.

The makers still use different counts today because they made different trade-offs, and no count has proved best:

Cochlear (22): many closely spaced electrodes, with only the loudest several used at each moment.
MED-EL (12): fewer electrodes spaced farther apart on a longer, softer wire, and all of them are used every time. Wider spacing means less overlap between neighbors, and the longer wire reaches deeper, toward the low-pitch end of the cochlea.
Advanced Bionics (16): each electrode has its own power source, so two neighbors can fire together and place a pitch between them. That is how 16 electrodes are set up to give many more pitch steps than 16.

Why more is not simply better: the cochlea is filled with fluid that carries electricity, so the current from one electrode spreads to the nerves near its neighbors. In studies, most implant users get about as much from 22 electrodes as from roughly 8 well-separated ones, and people with 12, 16 and 22 electrodes understand speech about equally well on average.

What surgery can cost the ear

Many people who get an implant can still hear a little, usually low pitches. This is called leftover hearing, or residual hearing. Sliding the wire into the cochlea can damage it.

About half of patients lose some or all of their residual hearing after surgery. Sometimes it happens right away, and sometimes it fades over the following months.
The trend is toward protecting it. Surgeons now use thinner, softer wires, slide them in slowly, often go through the cochlea's natural opening (the round window), and give medicine to calm swelling. Some watch the ear's own signals during surgery so they can stop if it is being damaged.
Why it matters: a person who keeps their residual low-pitch hearing can use a hearing aid and an implant in the same ear. That mix helps with music and with speech in noise.
It is still not a promise. Anyone considering an implant is told that the residual hearing in that ear may be lost.

Who can get an implant?

Not everyone with hearing loss can. It depends on the ear itself and on the person's situation.

The ear and body (anatomy)

There has to be a working vestibulocochlear nerve (often called the auditory nerve). The hearing part of this nerve connects the cochlea to the brain. The implant's electrodes sit inside the cochlea, where the ends of this nerve are. Their tiny electric pulses skip the damaged parts of the cochlea and set off the nerve directly, and the nerve carries the signal to the brain. If the nerve is missing, the signal has no way to get there, so an implant cannot help.
There has to be a cochlea the wire can fit into. Some people are born with a cochlea that formed differently before birth (a congenital difference). Doctors look for these on a CT scan or an MRI before surgery. A CT scan shows the bone and the shape of the cochlea, and an MRI shows the vestibulocochlear nerve:
- No cochlea at all. The inner ear never formed. An implant is not possible, because there is nowhere to put the wire.
- One open space instead of a spiral (called a common cavity). The cochlea and the balance organ formed as a single pocket. An implant is sometimes possible with a specially shaped wire.
- Too few turns (often called a Mondini malformation). The cochlea has about one and a half turns instead of two and a half, and the inner walls are partly missing. Many of these ears can be implanted.
- A small cochlea. It has the right shape but is undersized, so a shorter wire is used.
Separately, after meningitis the cochlea can fill with bone within weeks or months, which can block the wire. Children who lose hearing from meningitis are often implanted quickly for this reason.
The person has to be well enough for surgery, with no ear infection at the time.

The situation (in the United States)

How much hearing aids help. Implants are for people who get little benefit from hearing aids. A common guide is understanding 60% or less of test words, with a hearing loss of 60 dB or more. Medicare raised its cutoff from 40% to 60% of test sentences in 2022, so more people now qualify.
Age. The youngest approved age has dropped over time: 2 years (1990), 18 months (1998), 12 months (2000) and 9 months (2020, for one maker's implant).
One deaf ear. Implants for people with one deaf ear and one hearing ear were first approved in 2019. Other devices are sometimes preferred. They work in different ways:
- CROS hearing aid. A microphone worn on the deaf side sends sound to the hearing ear. No surgery.
- Bone conduction device (such as a Baha). A small device behind the deaf ear sends sound as vibration through the skull to the hearing ear's cochlea. There are two ways to wear one:
  - With surgery: a small metal post or magnet is placed in the skull bone behind the ear, and the device snaps onto it.
  - Without surgery: the device is held against the head by a soft headband. This is common for young children and for people trying one out before deciding.
- Cochlear implant. The only one of the three that makes the deaf ear itself hear.
Why the difference matters: the first two move sound over to the good ear, so the person still hears with one ear. They help with sound coming from the deaf side, but not with telling where a sound is coming from. In a trial that compared all three, only the implant improved locating sounds and eased ringing in the ear (tinnitus).
Why someone might still choose a CROS aid or a Baha: the deaf ear may have no working vestibulocochlear nerve or cochlea; the ear may have been deaf so long that the brain would struggle to use it; they work right away, with no months of learning; they can be tried out before deciding; and the surgery is smaller or not needed at all.
Access. Insurance, cost, distance from a clinic, and whether a doctor ever suggests it all matter. It is estimated that fewer than 1 in 10 adults in the United States who qualify have an implant.
Choice. An implant is a choice, not a requirement. Many Deaf people and families choose sign language and do not want one. The box "Do deaf people need to be fixed?" below says more.

Why timing matters: the brain's windows for learning

An implant only gives the brain access to sound. The brain still has to learn what sounds are and connect meaning to them. Young brains are very flexible (this is called plasticity), so babies and young children learn this most easily, which is why they are implanted early.

The brain learns sound and language most easily during certain years of life. Scientists call these sensitive periods. They are not hard deadlines, and the ages below are averages, but learning gets harder as each window closes.

Learning to hear: about the first 3½ years. A study of 104 children who were born deaf measured how their brains responded to sound after an implant. Children implanted by about age 3½ developed typical brain responses within months. Some children implanted up to about age 7 still did. After about age 7, the brain's flexibility for this was greatly reduced.
Younger is better, even within that window. Studies of babies implanted before 12 months, and even before 9 months, find better spoken language than in children implanted later. This is why the youngest approved age keeps dropping.
A first language: from birth through the early years. Babies begin learning language from their first days. A child who has no full access to any language in the first few years, spoken or signed, can have lasting difficulty with language. This is called language deprivation. Sign language is a full language and counts: a deaf child who signs from birth is learning a first language on time.
An early first language also helps with every language that comes after it. A study published in the journal Nature in 2002 compared adults who had language from infancy with deaf adults who had little language in early life. Those who had language from infancy learned a new language well later in life. Those who had little early language did poorly. This held whether the early language was signed or spoken, and whether the later language was signed or spoken. What mattered was having a language early, not which kind. This is why researchers who study this advise keeping the time a child spends without language as short as possible.
A new language later on: easiest before about age 10 to 12. A study of about 670,000 people found that the ability to learn a new language's grammar stays strong until about age 17 or 18 and then declines. To end up with grammar like a native speaker's, people usually needed to start by about age 10 to 12. Adults can still learn new languages well, with more effort. (This study was about hearing people learning English grammar, not about deaf children.) Accent has been studied separately. The later a person starts a new language, the stronger their accent tends to be: adults usually keep more of an accent than children do, and in one study even children who started young still had an accent that listeners could hear.

What this means for implants: a baby with an implant is using these windows while they are wide open. It is much harder for an older brain that has never heard, or has gone many years without sound, because the window for learning sound has mostly closed. Adults who lost their hearing after they learned to listen and talk usually do well, because their brains already know what sounds mean.

The hard part: who decides, and when?

The argument for waiting. Many people feel a person should have a say in elective surgery on their own body. (Elective means it is planned ahead and is not an emergency.) An implant is an operation, it can destroy residual hearing, and a baby cannot agree to it. Waiting until the child is old enough to take part in the decision feels morally right to many people, and it is a view often heard in the Deaf community.
The cost of waiting. The windows above do not wait. A child old enough to help decide, at 8 or 12 or 18, is past the years when the brain learns to hear most easily. An implant at that age usually gives much less than the same implant would have given in the first year or two of life.
There are consequences for waiting to decide. Deciding to wait is also a decision, made by the parents, with results that last. That is why this is one of the hardest choices families of deaf babies face, and why thoughtful people debate it.
One thing that does not have to wait: language. Whatever a family decides about an implant, a child who has full access to a language from the start, including sign language, keeps the language window from closing.

After surgery: mapping the implant

An implant does nothing until it is switched on and tuned for the person wearing it. That tuning is called mapping (or programming), and the saved settings are called a map. An audiologist does it.

What a session looks like

Switch-on usually comes a few weeks after surgery (often three to four), once the ear has healed. The outside part of the implant (the sound processor) is plugged into the audiologist's computer.
The computer checks every electrode to see that it is working. This is not the first check: the same kind of test is usually run in the operating room during surgery, so that a problem can be found while the surgeon can still do something about it.
The audiologist finds two levels for each electrode, one electrode at a time:
- the softest pulse the person can just hear (the threshold, or T-level);
- the pulse that is loud but still comfortable (the comfort level, or C-level).
Sound is then fitted into the space between those two levels.
The person says what they hear. An adult points to a loudness chart ("too soft", "comfortable", "too loud"). A young child plays a listening game, such as dropping a block in a bucket each time they hear a beep.
For babies, the implant can measure the nerve itself. It sends a pulse and records how the vestibulocochlear nerve responds, so the audiologist has a starting point even when the child is too young to take part or give feedback.
The map is saved to the processor, and the person goes out and listens with it.

What the audiologist can adjust

How soft and how loud each electrode is (the T-level and the C-level). This is most of the work.
Which electrodes are on. An electrode can be switched off if it sounds bad, does nothing, or makes a face muscle twitch. This is like the history buttons on this page switching electrodes off.
Which pitches go to which electrode. These are the "pitch each electrode plays" numbers on the chart above.
How fast the electrodes pulse, and, on one maker's implants, how many are used for each moment of sound.
Separate programs for different places, such as a noisy room, music, or the phone. The person wearing the implant can switch between these programs themselves, to suit where they are and what they are doing.

It is not done once. The first map is usually quiet and careful. As the brain and nerve get used to the sound, the levels change, so there are several sessions in the first months and then checkups for life. A new map can make the implant sound noticeably different, and usually better.

Bluetooth: sound sent straight to the implant

Today's sound processors have Bluetooth, like wireless earbuds. Phone calls, video calls, music, podcasts and TV sound can be sent straight from a phone or other device to the processor.
Why it helps: streamed sound does not have to cross the room to reach the microphone, so it does not pick up background noise on the way. One user described a streamed phone call as much clearer than holding the phone up to the processor.
Extra gadgets that do the same job for things that are not a phone:
- A TV streamer is a small box that plugs into a television. It sends the TV's sound straight to the processor, so the person hears the show clearly without turning the volume up for everyone else.
- A remote microphone is a small microphone that someone else wears, clipped to their shirt. A teacher is a common example. The teacher's voice goes straight to the student's processor, so it sounds close and clear even from across a noisy classroom. People still often call these "FMs" or "FM systems", because the older ones sent the voice over FM radio. Most newer ones use digital signals instead, but the name has stuck.

MRI scans: from "not allowed" to "allowed, with rules"

An MRI machine is a very strong magnet. A cochlear implant has a small magnet in it too, under the skin, which holds the outside processor in place. For years that made MRI scans a real problem.

The problem. The MRI machine can pull on the implant's magnet and move it under the skin.
The old answer: surgery. With many earlier implants, a surgeon had to take the magnet out before the scan and put it back afterward. The implant did not work in between.
Early 2000s: weak scanners. The first implant was approved in the United States for a low-strength MRI (0.2 tesla) with its magnet left in place.
Next: standard scanners. Some implants were then approved for the common 1.5 tesla scanners without removing the magnet, while others still needed it taken out.
2015: strong scanners. The first implant was approved in the United States for a 3 tesla MRI without removing the magnet. Its magnet can turn freely inside its case and line itself up with the scanner, so it is not pulled out of place. The other makers followed with their own versions in 2018 and 2019.

Doctors do not call an implant "MRI safe". The term is MRI conditional: a scan is allowed only under set conditions, which depend on the exact implant and the strength of the scanner. The implant also leaves a shadow on the picture near the ear. A person with an implant always tells the MRI staff before a scan.

New in 2026: an implant with nothing on the outside

Every implant described so far has two parts: the part inside the head, and a sound processor worn on the outside that holds the microphone and battery. In September 2026 the maker MED-EL launched the first cochlear implant with no outside part at all, called the TICI UNICO.

How it is different

The microphone is under the skin, above and behind the ear. It cannot be seen.
The battery is inside too. It runs for up to 40 hours and is recharged in about an hour to an hour and a half by holding a charger against the head. The implant keeps working while it charges.
It can still use an outside processor if the person wants or needs one.

What is expected to change

Hearing all day and all night. People can hear while sleeping, showering and swimming, the times when an outside processor comes off.
Nothing to see, lose or knock off. Helmets, sports and rough play are simpler, and no one can tell the person has an implant. The maker hopes this will lead more people to consider one.

What is still unknown or harder

It is very new. As of late September 2026, 40 people had received one. Early testing found speech understanding with the inside microphone was similar to an outside one, but larger studies are still under way.
It is approved in Europe, for adults. It is not approved for sale in the United States, and there is no known date for that.
The inside battery will not last forever, and it cannot be swapped on its own. The maker says it should give a full day of hearing on one charge for at least 15 years. When it wears out, replacing it means another surgery, or the person can switch to wearing an outside processor. The inside electronics are also harder to upgrade than an outside processor.

Different companies are making different choices. Fully internal implants are still being developed, and the makers have not settled on one design. They differ on where the battery goes, how it is charged, and even on how sound gets in: a microphone under the skin, or a sensor that uses the ear's own parts. Only one is on the market so far. The other two below are still being tested and cannot be bought.

	MED-EL TICI UNICO	Envoy Medical Acclaim	Cochlear (not yet named)
Can you get one?	Yes, in Europe, for adults (launched September 2026). Not approved in the United States.	No. In a clinical trial in the United States. Its maker hopes for approval in late 2027 or early 2028.	No. For research use only, with no date given.
How sound gets in	A microphone under the skin, above and behind the ear.	No microphone. A sensor in the middle ear picks up the movement of the ear's own tiny bones.	A microphone under the skin behind the ear.
Where the battery is	In the head, inside the implant.	In the chest, joined to the implant by a wire under the skin.	Under the skin behind the ear.
How it charges	A charger held against the head, for about 1 to 1½ hours.	A charger at the chest.	Not stated in the sources I found.
Time between charges	Up to 40 hours.	Several days.	Not stated.
How long the battery should last	At least 15 years, the maker says.	About 10 to 15 years, the maker says.	Not stated.
Can it also use an outside processor?	Yes.	Not stated.	Not stated.

The biggest differences:

Microphone or sensor. A microphone under the skin hears through a layer of tissue, which changes the sound and took years to get right. A middle-ear sensor skips that problem by letting the outer ear and tympanic membrane (eardrum) do their usual job, but it depends on those parts of the ear working.
Head or chest. A battery in the head keeps everything in one place. A battery in the chest can be bigger and last longer between charges, but it means a second site for surgery and a wire under the skin.
Proven or not yet. Only one of the three has been approved anywhere. The battery lifespans are the makers' own estimates, because none of these has been in anyone's head for that long.

This does not change the questions in the next box. An implant with nothing on the outside is still an implant, and a person who has one is still deaf.

Do deaf people need to be "fixed"?

Many deaf people say no. Deaf people have a rich culture that does not rely on sound, with its own languages, stories, poetry, humor, art and traditions passed down through generations. This is one of the most important things to understand about cochlear implants.

Two ways of seeing deafness

The medical view sees deafness as a hearing loss, something missing that a doctor should try to repair. An implant is the repair.
The cultural view sees Deaf people (often written with a capital D) as a community with its own language, such as American Sign Language, and its own history, schools, humor and art. In this view a deaf child is not broken. A person who is whole does not need to be "fixed".

How the Deaf community's views have changed

1980s: adults. The first implants went to adults who had grown up hearing, lost their hearing later, and chose the surgery for themselves. For that group, implants were generally seen as a good thing. The results were modest, though. With the early one-electrode implants, most people could notice sounds and found lip-reading easier, but could not understand speech by listening alone.
1990 to 1991: children, and strong opposition. In 1990 the United States approved implants for children as young as 2. In 1991 the National Association of the Deaf called that decision "unsound scientifically, procedurally and ethically": the benefit for children had not been proven, Deaf people had not been asked, and a child cannot agree to the surgery for themselves. There was also concern that children with implants would be placed in programs that did not value sign language.
2000: a shift. The National Association of the Deaf replaced its statement. The new one was much milder. It stressed parents making informed choices, and it said: "Cochlear implantation is a technology that represents a tool to be used in some forms of communication." It also said that implants "do not by themselves impart the ability to understand spoken language through listening alone."
Today: less "implant or sign", more "language first". Some Deaf people now have implants and also sign. In its later statements, the National Association of the Deaf says it is critical that signing also be used with a child who has an implant. The main concern has moved from the device itself to making sure every deaf child has full access to language from the start, whether or not they get an implant. Views still differ, and some Deaf people remain opposed to implanting children.

Things both sides agree on: an implant does not turn a deaf person into a hearing person. They are still deaf in the pool (without a waterproof processor), when the battery dies, and every night while the processor is off and charging for the next day. And children do best when the adults around them make sure they are never left without language.

An implant and sign language together

The National Association of the Deaf, and a number of researchers, recommend giving a deaf child both: an implant if the family chooses one, and a sign language such as American Sign Language (ASL). The goal is that the child has full access to language at every moment, not only when the implant is working well.

The months or years before the implant matter most. A baby cannot get an implant on the day they are born. There is testing, waiting, surgery, healing and switch-on, and then more months before speech starts to make sense. Those are some of the most important months for language. A baby who is signed with during that time is already learning language. A baby who is not may be getting very little.
An implant does not work the same for everyone. Some children understand speech very well with one, and some get much less. No one can tell ahead of time. Sign language means the child has a full language either way.
There are times with no implant. At night, in the bath, at the pool (without a waterproof processor), when a part breaks or the battery dies, the child is deaf and needs a way to communicate.
Most deaf children have hearing parents. More than 90 percent of deaf children are born to hearing parents. Gallaudet University's yearly survey of deaf and hard-of-hearing students in the United States found that about 23 percent had family members who regularly signed (in both 2009–10 and 2013–14). The ASL textbook Signing Naturally gives about 30 percent as the share of hearing parents who learn to sign. A Boston University article puts it at "at most, 40 percent" of families using sign language at home, and says that perhaps as many as 70 percent of deaf children are deprived of language.

Why so few families sign. Parents report that sign language is hard to learn, that classes can be costly, hard to find or hard to fit into family life, and that some professionals discouraged them from signing.

What families are told after the hearing screening. When a baby does not pass a hearing screening, the first people the family hears from are medical professionals, and every family sees an audiologist for the diagnosis. Researchers report that hearing families "often experience pressure from health care professionals to pursue spoken language as a primary form of communication", and that some professionals say signing will get in the way of learning to speak. In a small 2025 interview study, some families said an audiologist or implant team told them they did not need sign language, and ten families said no one had talked with them about language choices at all. One long-standing approach, auditory-verbal therapy, teaches listening and speaking without sign language or lip-reading; families who want a spoken-language outcome may choose it. Advice like this steers families toward a spoken-language-only approach, now usually called Listening and Spoken Language and historically known as oralism.

Does signing get in the way of speech? Studies have not found that it does. A 2023 study looked at 56 deaf and hard-of-hearing children who had hearing parents and were learning both ASL and spoken English. Children with bigger ASL vocabularies were more likely to have spoken English vocabularies in the normal range. Its authors wrote: "Acquisition of sign language does not harm spoken vocabulary acquisition," and "We found no evidence to support recommendations that families with DHH children avoid learning sign language." (DHH means deaf and hard of hearing.) A 2017 review found no evidence "that using sign language impairs spoken language development." A 2022 article written for speech-language pathologists says that using a signed language alongside a spoken one "can be highly beneficial for a child who is deaf."

Researchers do not all agree. Some studies have found that children with implants whose families did not sign scored higher on spoken language tests, and some programs still advise families to focus on listening and speech alone. Other researchers answer that those studies did not compare against families who sign fluently, and that a child with a strong first language of any kind learns a second one more easily. What nearly everyone agrees on is that no child should go without language while the adults decide.

How accurate is this?

An implant, as users describe it is built from studies of people who have an implant in one ear and normal hearing in the other, so they can compare the two directly. The changes they chose most often were to narrow the sound to roughly 500 to 3,000 Hz and to blur neighboring pitches together. This page does both. Those studies also found large differences from person to person: there is no single implant sound. Many listeners also asked for a flatter voice pitch, which this page does not do.

The electrode demonstration is the method researchers have used for about 30 years, called a vocoder. It shows how much information a given number of electrodes can carry. In the same studies, implant users rated it a poor match for what an implant actually sounds like, so use it to compare electrode counts, not to imagine the experience.

More electrodes do not add detail one for one. Electric current spreads inside the cochlea, so neighboring electrodes overlap. Studies find that people understand speech in quiet quite well with about eight working channels.

The history is not a straight line. The year on each button is roughly when that number of electrodes first reached patients. The 22-electrode Nucleus came early, in 1985, only a year after the single-electrode House/3M implant was approved. The 8, 12 and 16 channel designs came afterward from other makers, and 12, 16 and 22 are all still made today. So the count did not climb step by step; different makers chose different numbers.

The cochlea chart is a simplified drawing. The natural pitches come from a standard formula for the human cochlea (Greenwood's), with the electrodes drawn about 1.2 turns deep, which is typical for a 22-electrode implant. Real ears and real surgeries vary, so treat the natural pitch numbers as approximate.

A new implant user's brain also takes months to learn the new signal. No simulation can show that.