To get a better grasp of tinnitus, how it comes about, and what can be done about it, it helps to understand something about how our sense of hearing works. This second article in a three part series introduces the basic anatomy of the middle ear, what it does, how it can go wrong to give rise to tinnitus, and how it can be treated. The other two articles focus on the outer ear and the inner ear and tinnitus. With no further ado, let’s get a look at the middle ear.
The tympanic membrane or ear drum marks the division between the outer ear and middle ear. The external side of the tympanic membrane is considered part of the outer ear, and the internal side of the tympanic membrane is part of the middle ear.
As sound energy moves through the auditory canal, the wave runs into the tympanic membrane or ear drum. The ear drum constantly responds to changes in the air pressure surrounding us. Every sound wave that travels through the ear canal, striking the eardrum, sets a reaction in motion, with purely mechanical motion.
Being a specialized, taut skin membrane, the ear drum vibrates back and forth in response to the energy of the sound wave, according to the qualities of the sound, such as pitch and volume. The vibrations move quickly for the shorter waves of high-pitch sounds, and more slowly for the longer waves of low-pitch sounds. The energy of a loud sound will impress the eardrum more deeply, while the softest detectable sound of a healthy young adult moves the membrane only about 1 millionth of an inch Indeed a wonder!
The process that transforms sound waves into information that the brain interprets as the sounds we hear begins with the tympanic membrane. Most of the time we are bombarded with multiple competing sounds. Imagine sitting in a restaurant conversing with your friend. The eardrum helps you to focus and concentrate on what your friend is saying, while putting all of the other sounds of the restaurant in the background.
To a certain extent, the tympanic membrane can also shield our inner ears from damage resulting from very loud sounds. The tympanic muscle contracts in reaction to very loud sounds, and does not vibrate normally. Thereby it reduces the amount of energy that will reach the brain, protecting you. As helpful as that natural mechanism may be, we still have to take responsibility for shielding ourselves from the hearing damage caused by exceedingly loud sounds.
Our modern, industrial world produces sound volumes that are not experienced by pre-industrial peoples. Our ears and hearing have not had the time needed to adapt or evolve enough to protect us from the damage caused by the sounds we now experience in our modern world. Whether it is the screaming of jet engines at an airport, or the high decibel speakers of a night club, such loud sounds or noises are well-known as one of the primary causes of hearing loss and tinnitus today.
As remarkable as the protective mechanism of our ear drums might be, it can protect us from the sound volumes we experience in nature, not the volume and intensity of sound that we experience when standing 100 yards from a pile driver on a construction site. For that reason, we ourselves must take responsibility for shielding our ears from the extremely loud sounds produced today.
With that caution noted, let’s take the next step into the middle ear. Up to this point, we have traced the movement of sound waves through the air, then gathered by the pinna, funneled through the auditory canal, at the end of which the sound energy caused the eardrum to vibrate. From there the middle ear functions to amplify the sound, so that when it is transferred to the inner ear, which is fluid filled, the sound will carry properly through the denser medium. Because of the denser, fluid medium of the inner ear, the sound energy needs the amplification that the middle ear provides in order to overcome the greater inertia posed by the fluid-filled inner ear. Just how the middle ear carries out that amplifying function can only magnify our appreciation for our sense of hearing.
Within the chamber of the middle ear, which is usually dry, are the ossicles. The word ossicle literally means “tiny bone.” The ossicles of the middle ear are the three smallest bones in the human body. As sound waves vibrate the tympanic membrane (eardrum), it in turn moves the nearest ossicle, called the malleus, which is attached to the ear drum. With falling domino like action, the malleus then strikes the next ossicle, called the incus, transferring the energy. The incus then strikes the third ossicle, the stapes, again, transferring the energy. In turn, the stapes passes the energy on to the inner ear to which it is attached.
It is an incredible mechanism, and mechanism is the right word for it, because our sense of hearing is a mechanical process, as opposed to our senses of sight and taste which involve chemical processes. Our hearing is based on mechanics.
The ossicles, working like levers, increase the mechanical power of the tympanic membrane, focusing the energy force from the larger membrane to the smaller oval window of the cochlea of the inner ear. The result is an amplification of the sound energy, because the ossicles, those three tiny bones, are perfectly designed to work together to pass on greater, more compacted energy to the cochlea of the inner ear. That amplification produced by the leverage action of the ossicles is required for when the vibrations encounter the denser medium within the fluid-filled inner ear. Is it not fantastic?
The eustachian tube, at the far end of the middle ear, connects the dry chamber of the middle ear with the nasopharynx or part of the throat. Most of us who have experienced a common cold understand that the ears, nose, and throat have common connections. The connection for the ear comes via the eustachian tube.
The eustachian tube keeps the air pressure on either side of the tympanic membrane equal. It also provides a drain tube for the middle ear, keeping it free of fluid and congestion, and thereby helping to prevent infections.
It is very common when you fly in an airplane or drive in the mountains to experience the feeling of different air pressure on either side of the eardrum. Maybe you yawned or made a chewing motion or swallowed, and heard a popping or clicking sound that was accompanied by a sense of relief. That was the eustacian tube functioning to keep the air pressure on either side of the eardrum equalized.
When tinnitus arises within the middle ear, it is most commonly when the eustachian tube becomes stopped up from inflamed, swollen tissues due to sinusitis, rhinitis, or an allergy episode. When the eustachian tube stops up, it can trap fluid within the middle ear which can then become a breeding ground for bacteria or viruses, leading to otitis media, or inflammation or infection of the middle ear, which can engender tinnitus symptoms. While proper treatment of the infection and inflammation usually resolves the ringing in ears, chronic sinusitis or allergies can lead to chronic tinnitus. In that case, a good holistic tinnitus treatment regimen offers the best chance for a permanent tinnitus cure.
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