Our ability to hear helps us interact with our surrounding world. When hearing loss is severe, bionic hearing devices are increasingly a viable solution.
How Natural Hearing Works
Here is a basic description of how natural hearing works:
- Sound enters the ear canal through the ear and travels toward the eardrum.
- The sound wave causes the eardrum and the three small bones in the middle ear to vibrate.
- Tiny hair cells inside the cochlea in the inner ear convert the vibrations to electrical signals that are picked up by the auditory nerve.
- The auditory nerve sends the signals to the brain, which then interprets them as sounds.
In reality, the system is more complex. The hair cells sit on a membrane that vibrates in response to the incoming sound, but these vibrations vary at different locations on the membrane depending on the frequencies in the sound. This allows us to hear different pitches. The amplitude of the vibrations also increases with louder sounds, allowing us to detect volume.
The following video provides a more complete explanation:
What is Hearing Loss?
Humans have a hearing threshold of 0 decibels (dB). In other words, the softest sound that an average person can hear is at 0 decibels. Here are the decibel levels for some typical sounds:
- breathing: 10 dB;
- whispering at 5 feet: 20 dB;
- quiet rural area: 30 dB;
- bird calls: 40 dB;
- large office environment: 50 dB;
- sewing machine or average dishwasher: 60 dB;
- TV audio: 70 dB;
- noisy restaurant: 80 dB;
- tractor or large truck: 90 dB;
- snowmobile100 dB;
- power saw 110 dB;
- rock concert 120 dB.
If you cannot hear sounds below 20 dB, you are said to have a hearing loss of 20 dB (i.e. the loss compared to the normal hearing threshold of 0 dB). Here are the typical classifications for hearing loss:
- mild: a loss of 26 to 40 dB, meaning you can hear some speech but not soft sounds;
- moderate: loss of 41 to 55 dB — cannot hear normal speech;
- severe: 71 to 90 dB — can hear only some loud sounds;
- profound: above 90 dB — can only hear a sound if it is very loud.
Hearing loss can vary at different frequencies. For example, it is common for people to lose their hearing at high frequencies first.
In addition to these factors, there are also different types of hearing loss:
- Conductive: hearing loss caused by something that blocks sounds from getting through the outer or middle ear.
- Sensorineural: hearing loss caused by a defect in the inner ear or hearing nerve.
- Mixed: a combination of Conductive and Sensorineural loss.
- Auditory Neuropathy Spectrum Disorder: sound enters the ear normally but isn’t organized in a way that the brain can understand it due to damage to the inner ear or hearing nerve.
The Global Scale of Hearing Loss
According to the World Health Organization, 430 million people have “disabling” hearing loss, which is defined as a hearing loss of greater than 35 decibels in the better hearing ear.
Most hearing loss can be addressed by hearing aids, which simply amplify the sounds going into the ear. They are best suited for mild to moderate sensorineural hearing loss. Also, they don’t require surgery and are reasonably affordable in most modern countries.
Bionic hearing devices are best suited for severe to profound hearing loss. Based on various sources, it is estimated that as many as 40 million people in the world could benefit from this technology.
What is Bionic Hearing?
For many decades, the definition of a bionic ear was synonymous with a Cochlear Implant, which was first conceived in the 1950s. However, other types of implants were developed over time. More recently, we’ve begun to see innovative new technologies emerge that don’t require surgery.
As a result, our definition of bionic hearing has expanded to include any electronic device that allows a person to hear when traditional hearing aids are no longer sufficient to do so.
In the next few sections, we’ll provide brief descriptions of each of these technologies.
Existing Bionic Hearing Technologies
The following video is specific to one brand of Cochlear implant but it does a great job of explaining the general concepts:
The key points to know about Cochlear implants are:
- They do not actually restore hearing. Instead, they bypass the damaged parts of the inner ear to directly stimulate the auditory nerve. This creates the sensation of sound rather than the actual sound.
- Patients need significant time and effort to learn how to properly interpret the “sounds” generated by the implant. This may take anywhere from a few months to a couple of years.
- Cochlear implants are expensive, typically costing between $30,000 and $50,000 US.
BAHA stands for “bone-anchored hearing aid”, though it is not a hearing aid in the traditional sense. This type of implant is used when the cochlea is intact and functioning, but damage to the outer or inner ear prevents the transmission of sound waves to the cochlea.
A BAHA system consists of an external sound processor, a small titanium bone implant, and an abutment that connects the two. The sound processor picks up external sound vibrations and passes these vibrations through the abutment/implant into the bone, where they are carried to the cochlea. From this point onward, the vibrations are processed naturally:
The following video provides a good description of this system:
This is a specific product from Medel.com. We are referencing it here because it represents a slightly different way of achieving the same goal as a BAHA implant, namely to bypass a damaged outer and/or middle ear to directly stimulate an intact cochlea. Another video provides an excellent description:
Electric Acoustic Stimulation(EAS)
Electrical Acoustic Stimulation is a hybrid approach that combines the technologies of hearing aids and cochlear implants. It is designed for people who can still hear low-frequency sounds but not high frequency sounds. Symptoms of this form of hearing loss include the ability to hear conversations in quiet environments but not in noisy ones.
Again, because of the high quality of their videos, we use a product presentation from Medel.com to explain:
Auditory Brainstem Implant (ABI)
An auditory brainstem implant provides a sensation of hearing to deaf people by bypassing the cochlea and directly stimulating the brainstem. It is intended for people with nonfunctioning or absent cochlear nerves, which often occurs due to neurofibromatosis type II (NF-2), a disease that causes tumors to form on the balance and hearing nerves.
We couldn’t find a great animated video to explain the procedure, but this patient-story video provides a good description of the technology and its implications.
One thing to note about an ABI is that it doesn’t provide a full range of hearing. It allows patients to hear sounds that give them a greater awareness of their surroundings. While some patients achieve good word recognition, others must use more general sound cues along with lipreading to understand what is being said.
Newer Types of Bionic Hearing Technology
As is the case with almost every aspect of human bionics, we are seeing an explosion of new research, prototypes, and devices around the world.
In the case of bionic hearing, below are some new technologies that we’re tracking. We will continuously add to this list going forward.
Buzz from Neosensory
This is really cool technology, mainly because it promises to restore a level of hearing to the deaf for a fraction of the cost of other solutions. It uses a wrist band to convert sounds into 4 billion possible vibration patterns against the skin. What’s fascinating about this is that, over time, the brain can learn to convert these patterns into specific sounds!
The best explanation that we can find for Buzz starts at 1:28 to 1:56 of this video, and then resumes from 3:34 to 7:03:
A Non-Surgical Bionic Ear by Augmented Bionics
There is no official product name for this device yet because it is still in an early stage of development. However, the goal is to create a headset as an alternative to a cochlear implant that:
- will not require surgery;
- is more affordable;
- will be more accessible because hearing aid audiologists can fit the device instead of needing specialized surgeons.
These innovations are necessary because only between 5 and 10 % of the people who need a cochlear implant can get one, mainly due to cost.
The following video provides a good description of this exciting idea:
We do not yet have any related information, as we have just started the Bionic Hearing section of our website. However, you can count on us to follow the same blueprint that has been so successful for our sections on Bionic Arms & Hands and Bionic Legs & Feet. Specifically, we will create:
- articles on each bionic hearing device currently on the market or in the late prototype stage;
- all background technologies related to bionic hearing; these technologies are often shared between similar devices;
- a complete guide on bionic hearing;
- User Satisfaction Surveys for each bionic hearing device;
- new research news snapshots to keep you up-to-date as developments unfold;
- periodic articles from industry experts.
It will take us time, but we will eventually create a complete bionic hearing resource for you, free, as always, from any form of commercial influence.