What Does a Cochlear Implant Sound Like?
This is a perfectly natural question—after all, you are choosing a cochlear implant to hear.
Are Cochlear Implant Simulations for Natural Hearing Accurate?
You might have come across cochlear implant sound simulations online. These popular videos or sound samples are often simulations made using a vocoder, which is an audio tool that can be used to artificially synthesize voices.
It is very important to understand that a vocoder “cochlear implant simulation” is not at all an accurate representation of what a cochlear implant sounds like. These simulations sound very robotic and uncomfortable to listen to, and do not at all match real user experience.[ft] [ft]
To answer this question, there has been extensive research on cochlear implant recipients with single-sided deafness, which is hearing loss in only one ear. These unique recipients are able to directly compare the sounds of their cochlear implant to the same sound played to their natural hearing ear.[ft] [ft] [ft] [ft] [ft] [ft] [ft] [ft]
“I have never found a CI simulation that even comes close to how I hear with my CIs. I think the simulations all sound robotic and lacking in full tones.”
Mary Beth
Bilateral Cochlear Implant Recipient
”If you Google ‘cochlear implant simulation’, you’ll find noise-band vocoders. I’m pleased to say that a cochlear implant does not sound like a vocoder. It would be painful if you had to listen to something like a vocoder all your life. No, it doesn’t sound like a noise vocoder or a sine vocoder, thankfully.”
Prof. Michael Dorman[ft]
Cochlear Implant Researcher
The MED-EL Philosophy: Closest to Natural Hearing
Above all else, the purpose of a cochlear implant system is to help restore the human sense of hearing. In fact, a cochlear implant is one of the only medical devices that can help restore a sense. But our sense of hearing is not just the ability to detect sounds or understand words.
Hearing is the joyful laughter of a child, the crackle of leaves beneath your step, the emotional lift of your favorite song—our hearing goes so much beyond just understanding a sound.
More natural hearing doesn’t just mean a more enjoyable sound quality. It also helps your brain understand and comprehend complex sounds more easily. This can make it easier to take part in group conversations or hear better in noisy restaurants.[ft] [ft]
That’s why our philosophy at MED-EL is to provide the closest to natural hearing with our cochlear implants. We want the sound quality of our cochlear implants to match the sound quality of natural hearing. To achieve this, we’ve spent more than 30 years developing unique technologies that no other cochlear implant system can match. How? By designing our cochlear implants to follow nature as closely as possible.[ft] [ft] [ft] [ft] [ft] [ft] [ft] [ft] [ft] [ft]
“My ideal cochlear implant would be one that the hearing experience is so natural that they do not ‘realize’ they have an implant.”
Dr. Peter Nopp
Director of Sound Coding Research, MED-EL
What Is Natural Hearing?
As you may know, in natural hearing, sounds travel as vibrations from your outer ear, through the tiny bones of your middle ear, to your inner ear, known as the cochlea. The cochlea is a tiny, fluid-filled, spiral-shaped organ and is responsible for turning sound vibrations into nerve signals, your brain can understand as sound.
Along the whole length of your cochlea, there are thousands of tiny hair cells. Each hair cell corresponds to a specific sound frequency or pitch and works like a light switch. When sound waves move through the cochlea, they rock these hair cells back and forth. This mechanical switching motion from the tip of the hair cell instantly triggers a natural electrical nerve signal at the base of that hair cell, like a switch turning on a light bulb. This nerve signal is then instantly carried along the natural hearing pathway to the brain.
When hearing loss affects the sensory hair cells of your inner ear, this is known as sensorineural hearing loss.
About Sensorineural Hearing Loss
In sensorineural hearing loss, the hair cells in the inner ear are not working any more. Sensorineural hearing loss can be caused by noise exposure, genetic factors, viral infections, and many other conditions.
In mild sensorineural hearing loss, only some hair cells stop working, so hearing is only partially lost. As more hair cells stop working, the sensorineural hearing loss becomes more severe. This is often the case with progressive sensorineural hearing loss in adults.
So, as you can see, sensorineural hearing loss is caused when these sensory hair cells do not function properly. However, it’s important to understand that these hair cells are just one step in the natural hearing process—and in sensorineural hearing loss, all of the rest of your natural hearing structures are intact.
It may sound odd, but even in profound sensorineural hearing loss, the rest of the delicate structures of the cochlea can be healthy. There is an incredibly intricate network of nerve cells that are just waiting to be reactivated. If a light switch is broken, you don’t need to replace all the wiring in the walls—you just need to replace the switch. This is exactly where cochlear implants come in.
“A deaf ear is not a dead ear! The human auditory nerve function persists after hair cell loss and deafness; a blessing for the deaf and implanted.“
Prof. Helge Rask-Andersen
How Cochlear Implants Work
A cochlear implant system consists of an audio processor 1 , which sits on your ear, and the cochlear implant itself 2. A cochlear implant does not replace your cochlea—instead, it is designed to bypass the non-functioning hair cells by using precise electrical stimulation. A flexible electrode array is inserted into the cochlea during surgery, which provides a series of electrical contacts near the hair cells.
Get to Know How CI Systems Work
How can electrical pulses from a cochlear implant replace natural hearing?
In natural hearing, when a hair cell is activated by a sound, it triggers a natural electrical nerve signal. These natural electrical signals are actually how all of our nerves transmit information to our brain—so in reality, everyone has “electrical hearing”.
When a cochlear implant provides electrical stimulation, it activates the nearest functioning nerve structure—for example the hearing nerve cells right beyond the non-functional hair cells. These activated nerve cells instantly pass the signal all the way up the natural hearing pathway.
So what is the most important factor in sound quality of a cochlear implant system? You might think it’s the audio processor, the part that is worn on your ear, because that has the microphones and “processes” the sounds. However, the audio processor is just the first part of the chain of hearing.
The truth is that every single sound you hear through a cochlear implant goes through the tiny electrode array that is implanted in your cochlea. This intricate bridge between technology and nature is the point where sounds flow from an electronic implant system to your natural hearing pathways.
This is why having the right implant and the right electrode array is such an essential factor in what a cochlear implant will sound like. The more natural this connection in your cochlea is, the more natural your hearing experience can be.[ft] [ft] [ft] [ft] [ft] [ft] [ft] [ft] [ft]
You might upgrade your audio processor as often as you upgrade your mobile phone, but the implant, the part that is inserted into the cochlea, is a decision for many, many years. That’s why it’s important to choose your cochlear implant system based on the implant, not the audio processor.
What Is Sound?
If a cochlear implant works together with our natural auditory system, why do some cochlear implant recipients report that their implants sound robotic, electronic, or distorted? One of the most important factors that influences what a cochlear implant system sounds like is how closely the implant follows and replicates the natural function of the cochlea.[ft] [ft] [ft] [ft] [ft] [ft] [ft] [ft] [ft] [ft] [ft] [ft] [ft] [ft]
Especially important for sound quality is how accurately the cochlear implant can represent natural pitch perception. It’s important to understand that there are two main components to every sound: Loudness, and frequency or pitch.[ft] [ft] [ft] [ft] [ft]
The Right Place
Let’s look at how your cochlea identifies different sound frequencies in different places.
In natural hearing, each specific pitch or frequency of sound always activates a corresponding specific hair cell on a specific place in your cochlea. It’s just like a piano keyboard laid out all along the cochlea, from the beginning to the tip. This means a high-pitched bird chirp activates hair cells at the beginning of your cochlea, while a lower-pitched dog’s bark activates hair cells deeper in near the tip of your cochlea.[ft]
In fact, this place-pitch matching is so precise and reliable, that if you activate a certain hair cell, your brain will automatically perceive it as that specific pitch. Just like a piano keyboard, pressing the same key always plays the same sound.
This is how your brain understands the frequency of sounds—pitch perception is determined by which hair cells are being activated.
Electrode Length and Cochlea Coverage
To provide an accurate perception of a sound, you have to stimulate that sound frequency in the correct place in the cochlea. A cochlear implant electrode array has to be long enough to cover the whole cochlea, up to 720°, so that it can stimulate the full natural range of sound frequencies. You can’t accurately stimulate sound frequencies if the electrode array doesn’t cover that part of the cochlea—just like trying to play piano keys you can’t reach.[ft] [ft] [ft]
Unlike MED-EL, other companies use shorter arrays that can generally only stimulate the first turn of the cochlea (up to 450°), sometimes marketed as the hearing zone, which would mean only middle-to-high frequencies can be stimulated.[ft] [ft] [ft]
If a cochlear implant just ignored all the frequencies it could not reach, you would be missing so many sounds in everyday life, for example, the dog's bark at 300 Hz. Instead, these systems simply shift all the missing sounds into the part of the cochlea they can reach. That means the dog's bark would be much higher pitched, closer to 800 Hz.
A significant upshift in frequencies often causes sounds to be “tinny”, meaning that they sound thin, metallic, and lacking depth. This is because the lower frequencies that created the depth and body of sounds are lost.[ft] [ft] [ft] [ft] [ft]
Don’t Miss Half of Your Cochlea
Our philosophy at MED-EL is to enable the closest to natural hearing with our cochlear implants. This is why our cochlear implants use electrode arrays that are long enough to cover your whole cochlea—from low pitches like the dog barking to high pitches, like the birds chirping and everything in between. This is only possible because our arrays are especially soft and flexible, so they can be safely inserted more deeply into the cochlea.
Our arrays are available in the most comprehensive range of lengths so that your surgeon can choose the array that optimally covers your unique cochlea. This makes it possible for the widest range of sounds to be stimulated in their natural place in the cochlea. [ft] [ft] [ft] [ft] [ft]
How long is long enough for a cochlear implant electrode array? The natural hearing nerve structures go about two turns in the spiral shape of the cochlea, so the electrode array should cover one and a half to two turns (540°–720°) to provide complete cochlear coverage.
This is the key to a more natural sound quality with a cochlear implant. Extensive research has shown that this accurate place-pitch matching is the only reliable way to provide a more accurate pitch perception with a cochlear implant.[ft] [ft] [ft] [ft] [ft] [ft] [ft]
This is why the electrode array could be considered the most important part of your cochlear implant—it is the foundation of every single sound that you will hear through your cochlear implant.
What about perimodiolar electrode arrays that are promoted as being “closer to the hearing nerve”?
One of the most common cochlear implant electrode array designs from other companies is a perimodiolar electrode array designed to cover the first turn, up to 450°, of the cochlea. These shorter arrays are marketed as “closer to the hearing nerve”.
The hearing nerve is your auditory nerve. In the cochlea, your auditory nerve is shaped a bit like a Christmas tree: the tips of the branches are individual nerve fibers that reach your hair cells, while closer to the trunk of the tree is called the spiral ganglion, which continues on to the auditory nerve. Perimodiolar arrays wrap closer to the center of the cochlea, so they are more likely to stimulate the spiral ganglion than the tips of the fibers.
Although this feature is often marketed as a benefit, it is actually more of a necessity for the basic function of the design. If these perimodiolar arrays are not close enough to the spiral ganglion, there can be a significant loss in performance. The electrode contacts are closely spaced, so there can be issues with overlapping stimulation if they’re not close enough to the center of the cochlea.[ft]
Most importantly, pitch perception has nothing to do with how close the electrode is to the center of the cochlea. The nerve fibers of the hair cells and the spiral ganglion share the exact same place-pitch map up to about two turns. This means being “closer to the hearing nerve” certainly does not mean “more natural sound quality”. The nerves in your elbow are closer to your brain than your fingertips, but of course your fingertips have more precision. And if you are missing any electrode coverage of half of those natural hearing nerve structures, can you honestly call that “closer to the hearing nerve”? This is why electrode length is such an essential point.[ft]
There are also claims that these electrodes are “on the inside track” of the cochlea, so they can stimulate just as much as longer arrays. This is not at all supported by clinical evidence—post-operative imaging consistently shows that these arrays only cover the first turn of the cochlea.
What about number of electrode contacts? Are 22 better than 12?
As you research cochlear implants, you may have heard “22 active contacts are better than 12” on an electrode array. This certainly seems like a logical argument because an electrode contact is where the implant stimulates the cochlea. This path of stimulation is often called an “electrode channel”. However, there are two things to consider. Is the implant system limited to physical electrode channels or is the implant advanced enough to create virtual channels, and where are the electrode contacts located in the cochlea?
MED-EL up to 250 channels
More advanced cochlear implant systems can use parallel or coordinated sequential stimulation on two or more electrode contacts. By precisely coordinating the stimulation between two adjacent electrode contacts, it’s possible to create additional “virtual” electrode channels, which act like additional electrode contacts between those two real physical electrode contacts. This means the need for numerous physical electrode contacts is effectively replaced by these virtual electrode contacts.[ft]
This makes it possible for a MED-EL implant with 12 physical electrode channels to stimulate up to 250 virtual channels in the cochlea, which can provide a rich, full hearing experience that is not limited by number of electrode contacts. You can think of this like being able to play all the different keys on a piano, even though you only have 10 fingers. If you can reach both ends, you can reach the spaces in between. This powerful technology is part of our default FineHearing sound coding.
Other Systems up to 22 channels
On the other hand, if an implant has 22 contacts, but isn’t designed to create virtual channels, this may be more like playing only 22 piano keys. And with current sound coding strategies on these implants, it’s only 8 of 22 electrodes active at a given moment, so “most active electrodes” isn’t really accurate. It’s certainly possible to provide acceptable outcomes with such a design, but it certainly couldn’t be called more advanced just because it has more electrode contacts. More electrode contacts on a short array can also make the array stiffer, and more likely to damage the natural structures of your cochlea.[ft]
But most importantly, it matters where those electrode contacts are. If you have 16 or 22 physical electrode channels, but they only cover the first half of the cochlea, then half of the natural frequency range will be missing. Even if you theoretically put 1,000 electrode contacts on an implant, but the array only covered half the cochlea, the result is the same. The unnatural “tinny” sound is caused by forcing frequencies upwards, not by limiting the number of physical electrode contacts.
You may hear that the electrode array doesn’t matter, because our brain will just adapt to correct any mismatch. Numerous studies have shown that even after years of experience, cochlear implant users with short electrode arrays do not reliably adapt enough to correct mismatches.
And most importantly, why force adaptation if you don’t need to? This is why our goal at MED-EL is to provide as close to natural sound input from the very beginning. We want to let your brain focus on fine-tuning your listening experience and improving your abilities for more challenging environments.[ft] [ft] [ft]
@2x.jpg?auto=format&sfvrsn=e8344d43_2 "Closest to Natural Hearing")
The Right Timing
In the second turn of the cochlea, there is a second type of sound coding for even more precision in natural hearing. In addition to place coding, which we have described above, the second turn of the cochlea uses time or rate coding. Basically, place coding looks at which hair cell is activated, while rate coding looks at how fast or slow that hair cell is switched on and off by a sound wave.
This means you have to be at the right place and have the right timing.
Why is rate coding important?
In this natural rate coding, the timing of the nerve signal is locked to the timing of the sound wave. For example, a dog’s bark with a frequency of 120 Hz will cause the hair cell at the 120 Hz location in the cochlea to trigger 120 nerve signals per second. Your brain can then precisely understand this as a 120 Hz sound.
This rate coding is especially important for cochlear implant sound quality, because in the second turn, rate coding can override place coding. So even if you are at the right place, you still need to have the right timing.
For example, for a 120 Hz sound stimulated at the correct place in the cochlea, if you use a standard fixed stimulation rate of 800 electrical pulses per second, you will activate the nerve cells to send signals 800 times per second, and your brain would likely understand this as shifted upwards in pitch, closer to a 800 Hz sound signal. And this, of course, would have an unnatural effect on sound quality, and is sometimes described as “pitch confusion”.[ft] [ft] [ft]
Why do we at MED-EL care about such precise details in the cochlea? With long MED-EL electrodes, you can reach the widest range of natural frequencies, up to the second turn where this rate coding is important to enable the closest to natural hearing.
For other companies that only offer short electrode arrays and only cover half of the cochlea, this rate coding doesn’t matter, because they usually can’t reach the second turn of the cochlea. And without the ability to provide accurate rate coding, it wouldn’t make sense for these other systems to have longer electrodes, because they still would likely not be able to experience accurate pitch perception in the lower frequencies.[ft] [ft] [ft]
FineHearing
If you can combine accurate place and also accurate timing information, you can provide a very close match to natural pitch perception. This is why we developed our unique rate-matched FineHearing technology.
FineHearing is the only sound coding for cochlear implants that instantly adapts the stimulation rate for electrode contacts in the second turn to match the natural frequencies of the incoming sounds.
By combining long electrode arrays with FineHearing, you get a more accurate and more natural stimulation of the whole cochlea. This is designed to give the closest to natural hearing experience with a cochlear implant.[ft] [ft] [ft] [ft] [ft] [ft] [ft]
Closest to Natural Hearing
Having closest to natural hearing is a benefit for everyday listening. Your favorite sounds can sound more natural and familiar. Many of our recipients report being able to enjoy music, which would be very difficult if you had an unnatural sound quality.
More natural sound quality also means using our incredible natural auditory system as it was intended. This can make it easier for your brain to interpret complex listening environments, so you can hear better in noisy settings.[ft] [ft] [ft] [ft] [ft] [ft] [ft] [ft]
- Closest to natural sound quality
- Using the full potential of the natural cochlea
- Richer, fuller hearing experience
- More natural music quality/perception
- Better hearing in quiet and noise
- Improved sound localization
Free Music Training With Meludia
Build your listening skills with Meludia—a fun and playful music training tool ideal for hearing implant users. myMED-EL users get 12 months of free access.
Offer may not be valid in all countries due to local laws and restrictions.
What Does a MED-EL Cochlear Implant Sound Like?
Much like learning to play a musical instrument, learning to hear with a cochlear implant takes time, practice, and patience. Every person’s hearing experience will be different. On activation day, many recipients may only hear beeps or unfamiliar sounds, while others may already be able to understand voices. Thankfully, this effort is worth it, because cochlear implants can effectively restore the ability to hear the sounds of life.
Real Life Experiences
Cochlear implants can provide so much more than just being able to understand words. With MED-EL, your cochlear implant can mean enjoying a lively conversation, picking up the phone with confidence, and rediscovering the music you love.
Experiencing more natural hearing can help restore your freedom to live independently, your confidence to face new challenges, and the happiness of truly reconnecting with your friends and family.
“This implant gave me the ability to hear high tones to such a degree that it is possible for me to tune the piano.“
Grzegorz, MED-EL cochlear implant recipient
“My fear that hearing with a CI would sound unnatural or like a robot turned out to be completely unfounded. My hearing feels completely natural—it’s how I remember it being before I got hearing aids.“
Chris, MED-EL cochlear implant recipient
“I can recognize people I know just by hearing their voices. I can recognize singers’ voices as well in songs. I notice people’s accents. This is what I mean when I say things sound natural to me with my CI. There is no robotic, computerized, flat sound to the voices I hear.“
Mary Beth, MED-EL cochlear implant recipient
