To understand tinnitus better, what causes it, and what can be done to stop ringing ears, it helps to know something about our hearing and how it works. This article is the second of a three article series that deals with tinnitus and the three major parts of the human ear, the outer ear, the middle ear, and the inner ear. This second part focuses on the middle ear, how it works, what can go wrong to engender tinnitus, and what can be done to resolve it. Now, let’s look at the middle ear.
The tympanic membrane or ear drum marks the division between the outer ear and middle ear. The outer surface of the eardrum is considered part of the outer ear, while the inner surface of the eardrum is part of the middle ear.
As sound waves travel through the outer ear the energy quickly hits what we commonly call the ear drum. The ear drum constantly responds to changes in the air pressure surrounding us. When a sound wave moves through the ear canal and strikes the tympanic membrane, a chain reaction is set in motion, which is a purely mechanical reaction.
The eardrum, consisting of a taut, specialized membrane of skin, vibrates in accordance with the various characteristics of the sound, such as pitch and volume. The membrane vibrates quickly in reaction to a high-pitch sound, and vibrates more slowly for a low-pitch sound. 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 Truly a marvel!
The tympanic membrane begins the process of changing sound waves into the form that the brain can interpret. Usually the ear receives more than one sound at once. For example, think of speaking with a friend at a restaurant. The eardrum responds by helping you filter out most of the restaurant sounds so that you can focus on what your friend is saying.
Up to a certain point, the eardrum will also protect you from loud and harmful sounds. In response to a very loud sound, the tympanic muscle contracts and reduces the vibrations. The amount of sound energy that gets beyond the tympanic membrane is thereby reduced. Of course, that does not relieve us of our own responsibility to protect our ears from excessively loud sound.
In our modern, technological world we’re exposed to many loud sounds that pre-industrial peoples, for example, never experience. 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 constant noise of a machine shop, or the excessive volume of an over-charged car stereo, exposure to such high level sounds is clearly known as the most common cause of hearing loss and tinnitus.
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. So, it’s really up to us to protect our ears from such excessively loud sounds.
Having issued that caution, let’s go deeper within the middle ear. So far we have tracked the journey of sound waves that are collected by the outer ear, channeled through the ear canal, and received by the ear drum that vibrates in response. The sound is then transferred to the mechanism of the middle ear which amplifies and focuses the sound energy, preparing it to be transferred to the inner ear which is fluid filled. Because the inner ear is fluid-filled rather than air filled, and a denser medium by nature, the amplification that the middle ear performs is really necessary. Just how the middle ear carries out that amplifying function can only magnify our appreciation for our sense of hearing.
The primary components within the usually dry chamber of the middle ear are called ossicles. The literal meaning of the word ossicle is “tiny bone,” and the ossicles are indeed the three smallest bones found in the human body. When the tympanic membrane is vibrated by a sound wave, those vibrations are transferred to the first ossicle, the malleus, which is attached to the eardrum membrane. The malleus then transmits the vibrations to the next ossicle, called the incus. The sound energy is then transferred to the stapes, the third ossicle. And the stapes then transmits the vibrations to the inner ear, to which the stapes 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 mechanical by nature.
The ossicles work together like a series of levers giving mechanical advantage to the eardrum, reducing the area of force distribution from the larger ear drum to the much smaller oval window that leads to the inner ear. As a result, the ossicles pass on amplified energy with greater concentration to the inner ear. As stated before, because the inner ear is fluid-filled and denser, the kick of amplification that the ossicles leverage is necessary for overcoming the greater inertia of the inner ear’s medium. Is it not fantastic?
Before leaving the middle ear, we need to take a look at the eustachian tube, which connects the dry chamber of the middle ear with the nasopharynx or part of the throat. Those of us who have experienced a common head cold understand that the ears, nose, and throat share common connections. The eustachian tube provides the ear connection.
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.
Anyone who has flown in a plane or driven in the mountains probably has experienced the sensation of unequal pressure on either side of the tympanic membrane. You may also have experienced a popping sound that produced a sense of relief by yawning or swallowing. That was the eustacian tube functioning to keep the air pressure on either side of the eardrum equalized.
The most common tinnitus problem to arise within the middle ear involves the eustachian tube which can become blocked by swollen, inflamed tissues brought on by sinusitis, rhinitis, or allergy episodes. 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. Usually, once the infection and inflammation are treated properly, the ringing in ears goes away, but chronic sinusitis or allergy episodes can give rise to chronic tinnitus. In that case, a good holistic tinnitus treatment regimen offers the best chance for a permanent tinnitus cure.