The ear is made of the outer ear, the middle ear and the inner ear and contains the eardrum, ossicles, cochlea, and auditory nerve.
The outer ear portion of the ear that you can see is called the Pinna. The purpose of the Pinna, and it's unique shape, is to collect sound and amplify/boost the sound pressure, and concentrate the sound to travel down the ear canal to the ear drum, like a funnel but for sound waves. It's the natural amplification of sound that makes the ears so sensitive to frequencies and the human ear can hear in a certain certain pitch range. The Pinna is always pointing forward, because of this it helps to locate the direction sound is coming from. Sound coming from each direction bounces off the outer ear in a different way, this alters the pattern of the wave. Your brain analyzes and recognizes patterns and compares the different waves ,which then determines what the sound is and where the sounds are coming from, but it takes both of your ears to truly be able to tell sound direction. Your brain compares the information collected from both ears and then comes to a conclusion. For example, when you hear a sound to your left the sound will be louder in your left ear than your right, and the sound will be heard in your left ear before its heard in the right. When your deaf in one ear you hear the sound, but unless it's immediately to the side of the good ear determining location based on hearing alone is very hard.
The eardrum is a tiny flap of skin that separates the ear canal and the middle ear and is one of two sensory parts of the ear. It serves to detect sound, protect the middle ear physically, and also protects the inner ear from noise extremes especially loud, low-pitched noises. To help you further understand the eardrum, it acts like the diaphragm in microphones. Sound waves cause the diaphragm (ex: paper) to vibrate back and forth and the vibrations travels down the intended path (the ossicles aka ear bones), becomes an electric signal which in this case is the audio signal (the cochlea and auditory nerve), interpreted by audio equipment (the brain). The higher the pitch the more rapidly the eardrum vibrates, and the louder noises cause the eardrum to move back and forth further than soft noises. One element that isn't needed in microphones is your Eustachian tubes. These tubes connect your middle ear to your throat, so air moves up these tubes into your ears and creates a pressure balance from both sides of the eardrum allowing it to move back and forth freely.
When the brain receives information the ear needs to be protected from a sound, a natural reflex happens where certain muscles connected to the eardrum contract. This causes the eardrum to become more taut and rigid which in turn pulls the ear bones in the opposite direction decreasing the effectiveness of the vibration pathway. This makes it harder to hear the lower sound vibrations, thus dampening some of the noise, making the sound less damaging to the middle ear. This reflex also helps you dampen background noise (low pitched sound) so you can hear higher pitched noises you desire to hear better, like speech. When you're talking your eardrums use this reflex the same way so your voice does not drown out the sound around you while your talking.
So I've mentioned a part of the ear called the Ossicles a few times already. They are also known as "ear bones". This is essentially what the ossicles are, they are three tiny bones (the tiniest in your body) connecting the eardrum to the cochlea. In order they are called the Malleus, Incus and Stapes, also referred as the hammer, anvil and stirrup. The Malleus is connected to the center of the inside of the eardrum so vibration and movement from the eardrum moves and vibrates and malleus. Then from the malleus to the incus to the stapes. The end of the stapes rests against the cochlea and transfers the sounds waves to the cochlea. The vibration of the eardrum itself does not have the momentum and power to affect the cochlea by itself, so the bones act to amplify the momentum or pressure of the vibration.The cochlea is a snail like structure that is divided into three fluid filled canals. The fluid is almost identical to spinal fluid. The cochlea uses this fluid to conduct sound as opposed to air. Fluid is harder to move than air, which is why the vibration of the eardrum is inefficient to affect the cochlea. The vibrations cause ripples like in a pond that travels along the canals to the other end of the cochlea where the auditory nerve is located. (Hint: the cochlea is the part of my ear and is completely non-functioning.)
The cochlea is the most complex part of the ear. It's job is to take the physical vibrations it receives from the Stapes and translates and transforms the vibration signal into an electrical signal the brain can receive, interpret and understand. I'm going to mostly skip how different parts of the cochlea helps interpret different parts of sound but it is fascinating if you want to look it up.When the ripples get to a certain part of the cochlea called the organ of corti, which has thousands of miniscule hair cells, the energy caused by the vibration/ripples hit against and move these hair cells. When this happens the hair cells send a complex pattern of electrical impulses through the auditory nerve to the brain.
I'm going to stop here. I know I've promised more, and it's coming, just not as fast as I'd hoped. Writing is not the easiest for me and it's slow going. I posted a video just before this blog that is a visual of the process that I just explained and also touches on how a cochlear implant works.
My cochlear implant activation is on Thursday March 13th at 1pm!!! I'll receive the outer part of my implant. They will connect it, turn it on and start the slow process of programming it. This happens at the hearing rehabilitation clinic which is not at the U of M hospital. The next day I have an appointment with Dr. Telian which is at the hospital, and plan to stop by and visit the OR. Hopefully the appointment won't be long and I can catch people on their lunch. I'm so excited!!! I hope everyone is well!!
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