The Electronic Ear is a cochlear implant, a tertiary medical device, so what kind of people would need a cochlear implant? What does it make up for in terms of what we're missing in the ear? A man-made device that can recreate the lost world of the hearing impaired? Through this article, let us briefly understand the basic design of a cochlear implant.
Cochlear Implant - A Perspective. *** The Most Common Types of Hearing LossSu Shi (石钟山记) said, "It's not a matter of seeing and hearing, but of assuming that there is a focal point, is it? Our eyes and ears are almost equally important in recognizing the world.
According to a WHO report in March this year, 460 million people in the world are suffering from disabling hearing loss, and by 2050, the number of people with hearing loss will reach 900 million. It means that 1 in 10 people around you will be hard of hearing in the future.
pixabayBut only a tiny percentage of people with hearing loss have microtia, which is the main group of people for whom we talked about bone-conduction hearing aids in the previous post.
The vast majority of patients have sensorineural hearing loss, and these people can be treated with air-conduction hearing aids (the most common type of hearing aid on the market). However, have you ever thought that people with severe sensorineural hearing loss can just wear normal hearing aids? The answer may be different, and that's what we're going to talk about today.
What is sensorineural hearing loss?Before we get to the main topic of the day, let's take a quick look at the aforementioned what is sensorineural hearing loss?
There are many causes of hearing loss, including prolonged exposure to noise, disease, medication, and even aging, genetic inheritance, and so on. If you look at the location of the ear lesions, hearing loss can be divided into Conductive hearing loss (Conductive hearing loss), Sensorineural Hearing Loss (SNHL), and Mixed Hearing Loss (Mixed Hearing Loss). Three directions. [
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Of these, sensorineural hearing loss accounts for the largest proportion, and is caused by damage to the hair cells of the cochlea in the inner ear, or by abnormalities in the functioning of the fibers of the auditory nerve, which affects the transmission of sound from the inner ear to the brain. In such cases, traditional hearing aids may be sufficient for mild cases, but in more severe cases, the cochlear implant, the subject of today's article, may be needed to hear sound.
How does a cochlear implant work?What is a cochlear implant? What does "artificial" mean here? Is it the same as the artificial skin, the artificial heart, or the artificial tears we often hear about?
A cochlear implant uses a long electrode that goes into the deepest part of the ear, the inner ear, and bypasses the hair cells to apply electrical signals directly to the *** auditory nerve to "help us restore our hearing".
A diagram of the cochlear implant. Image embedded from Advanced Bionics Bio+Engineering, the design principle of cochlear implantsA large part of the design and improvement of the Cochlear Implant depends on the relationship between the electrodes and the cochlear auditory nerve, and we would like to explore this mystery. To explore this, we can look at the biological side and the engineering side of the equation.
1. The biological side: the inner ear, which uses **** vibration to distinguish frequenciesThe mechanism by which we hear sound is extremely complex. How the inner ear processes the complex frequencies in sound plays a big role. Imagine how we can hear different instruments at different pitches at the same time during a concert.
Simply put, the inner ear distinguishes between frequencies by utilizing the "*** vibration" principle that you and I know so well. As I learned in junior high school, if the natural frequency of an object is close to or in line with the frequency of an external force, the object will swing involuntarily, and the amplitude of the swing is very large. The most famous cases are the Taa bridge collapse, in which the frequency of the wind coincidentally coincided with the natural frequency of the bridge, and the bridge collapse caused by British infantrymen crossing the bridge at too uniform a pace
When sound from the outer ear travels to the middle ear and the inner ear, the stapes (the end point of the sound in the middle ear) begins to knock on the cochlea's oval window (the beginning point of the sound in the inner ear), and the lymphatic system in the cochlea is affected by this sound.
However, the Basilar membrane in different parts of our cochlea reacts differently to the traveling wave, with high-frequency traveling waves causing *** vibrations in the Basilar membrane at the base of the cochlea, and low-frequency traveling waves causing *** vibrations in the Basilar membrane at the top of the cochlea. From this, we can understand that different frequencies of sound will cause different parts of the cochlea to produce large vibrations, and these vibrations will then drive the hair cells in the area to oscillate, and then *** the auditory nerve to produce action potentials, which are transmitted to the brain. (For more details, please refer to this movie.)
The basilar membrane inside the cochlea is *** vibrating in relation to different sounds. Jared E. (Piezoelectric-Based, Self-Sustaining Artificial Cochlea)〈〈Piezoelectric-Based, Self-Sustaining Artificial Cochlea〉The cochlea is the means by which we dismantle different frequencies of sound, and then sends the dismantled signals to the brain by the auditory nerve to make us feel the highs and lows of the sound.
The basilar membrane in different parts of the cochlea **** vibrates to different sound frequencies.
2. The engineering side: triggering the auditory nerve with an electrical *** deviceOnce we understand how the brain perceives such complex sounds through the cochlea, we can start to think about the engineering side of designing the electrodes for the cochlear implant. First, because cochlear hair cells are damaged in patients with severe sensorineural disease, the basilar membrane*** is not able to oscillate the hair cells when it vibrates, triggering action potentials in the auditory nerve at that site.
So we need a long electrical ****er to replace the hair cells. It has to be able to **** different parts of the cochlea according to the frequency of the sound, and it has to be soft enough to follow the spiral shape of the cochlea from the base all the way up to the top, and the array of electrodes on the electro ****er is a key point, with a higher number of electrodes representing a higher frequency resolution.
An enlarged view of the electrodes and their position in the ear. Pawe? R. From cochlear implants to brain-puter interfacesIn addition to the electrodes, we need a receiver, which not only receives the radio waves from the signal transmitter on the surface of the body, but also has a function of the basement membrane that decodes the radio waves and separates them from the different frequencies, and then transmits them to the electrodes, which further form the commands that drive the electrodes.
Typically, a person with cochlear hearing loss will have a microphone and an audio processor behind the ear. The microphone is the equivalent of an artificial outer ear, which receives sound from the outside world and, after filtering by the audio processor, transmits it wirelessly to a subcutaneous signal receiver, which creates the aforementioned signal that can ***** the auditory nerve.
Figure Cochlear implant system schematic. Centre for HearingThis is a brief discussion of the cochlear implant, and we hope that after reading this article, readers will understand a few important design points and the role of the cochlear implant in the human body.
In fact, in the design of every medical device, the engineering and biological considerations are very important. How to make the engineered device meet the needs of our human body structure, and at the same time make our human body produce the original perceptions through the instrumentation *** ...... and so on. These are all things that require constant communication between engineers and clinicians, and careful cultivation. We hope that this article will help readers understand how a medical device is designed to meet clinical needs, and what level of knowledge is required to connect the dots.
Additional information: If you are reading this article and are a user of the Electronic Ear, or if you know someone who is a wearer of the Electronic Ear, you are welcome to join us in our research on the Electronic Ear at the Institute of Theological Studies at National Yang Ming University, and to work together to improve the quality of hearing! For more information, please visit: link.
This article is reprinted from the Unmet Needs Clinical Engineering column "Electronic Ear? Cochlear implants? The world of hearing aids may be more complicated than you think.