This article assumes that you already know that tinnitus is a ringing in the ears or some other form of unwanted ear noise for which there is no outside stimulus, and in order to get a better grasp of tinnitus, you would like to get a better understanding about our sense of hearing, how it functions, what can go wrong to engender tinnitus, and what can be done to get rid of the unwanted noise. This article focuses on the inner ear, while the two other articles, which can be found under my author name, focus on the outer ear and the middle ear. Now, let\’s look at the inner ear.

Up to this point, we have followed sound waves as they are gathered by the outer ear and channeled through the ear canal and come in contact with the tympanic membrane. The tympanic membrane then vibrates with the energy of that sound, and transmits it to the middle ear via the ossicles,those three tiny bones, the hammer, anvil, and stirrup, which amplify and focus the sound, leveraging the sound energy for when the stirrup or stapes strikes the cochlea, which takes us to the starting point of the inner ear.

The medium through which the sound has traveled up to this point has been air, which is much less dense than fluid, but within the inner ear the sound energy encounters the much denser medium of the fluid-filled cochlea. Overcoming the greater inertia or resistance of the denser fluid medium of the inner ear is the reason for the amplification of the sound energy performed by the ossicles of the middle ear. And, here in the inner ear, the way that the sound continues its journey to the brain changes significantly.

The cochlea has been so named because its shape resembles a snail or spiral shell, which \”cochlea\” literally means. The cochlea functions to transduce or convert the mechanical vibrations into electrical nerve impulses which are sent to the brain to be processed into the sound forms we recognize.

When we get inside the cochlea, we find three fluid filled tubes. Two of them, the vestibular canal and the tympanic canal, transmit the pressure caused when the stapes presses against the oval window of the cochlea. The third canal is the cochlear duct in which the organ of corti is found. The organ of corti picks up the pressure impulses and sends out electrial impulses to the brain via the auditory nerve in response. These three canals or ducts fit together in the curved cochlear shape. A thin membrane, known as the basilar membrane, separates the three canals.

The basilar membrane functions as a base for the sensory cells of hearing, the hair cells of which there are about 20,000. These hair cells react with the various frequencies of the sound waves that are being transferred through the cochlea, creating tiny electrical impulses. Then, the organ of corti is housed within the cochlear duct, and it\’s located on the basilar membrane. It operates something like a microphone, sending electrical impulses along the auditory nerve to the brain, which interprets those impulses as the sounds that we hear. For the sake of understanding tinnitus, that\’s about all we really need to know about the cochlea and how it functions.

If you\’ve been finding this look at hearing fascinating, and would like to dig deeper into the subject, I certainly understand. Wikipedia is a great resource for starting out, if you want to dig deeper. Wikipedia offers good information and, more importantly, it provides a lot of references that will allow you to go as deep as you like. But, for right now, let\’s stay with our focus on tinnitus.

The way our inner ear enables us to hear is amazing enough all by itself, but this incredible little component of the body is also command central for the body\’s mechanism of balance. Certain other functions of the body also contribute to balance, such as the sense of sight, and input from muscles, but the vestibular system of the inner ear is the centerpiece for maintaining balance.

Three essential components make up the vestibular system: the utricle, the saccule, and the three semi-circular canals. The utricle and saccule keep track of the head\’s position. Thus, they help keep the head in proper alignment with the body. The utricle and saccule are both sensitive to gravity and acceleration. Because of the way they are situated, the utricle detects changes in horizontal movement, while the saccule detects changes in vertical movement, such as when you ride in an elevator. Working together, these two tiny organs keep track of head movement in all 3 dimensions, and keep the brain informed, and that helps us to keep our head aligned and our bodies in balance.

Yet another marvel is how these tiny organs work. The utricle and saccule are filled with thick fluid in which calcium carbonate particles are suspended. Inside of them are also hair-like sensor cells. Whenever the head is moved, the particles suspended in the fluid are also moved by gravity or acceleration and come in contact with the sensors which respond by sending signals to the brain for processing. The brain then determines whether the head alone is moving or if the entire body is in motion. Of course, the brain can use input from the eyes and muscles to help make its assessment, but the inner ear is doing by far most of the work for keeping the head aligned with the body, and keeping the entire body in balance.

Simultaneously, the three semi-circular ducts are performing much the same function. But instead of focusing primarily on head position, they are providing information about the body\’s movement overall. These three semi-circular ducts are called, superior, posterior, and external. In order to take into account all three spatial dimensions, these ducts are in perpendicular alignment to each other, so that any motion, forward or backward, left or right, up or down, or any combination of motions can be processed properly. The semi-circular canals work pretty much the same way that the utricle and saccule work. The semi-circular ducts are fluid filled and have hair cells that are sensitive to gravity and acceleration, and respond to motion by sending electrical impulses along nerve fibers to the brain.

Whether we are conscious of it or not, the inner ear is constantly at work performing all of these functions. To maintain our sense of balance, we depend on the vestibular system to gather motion information and send it on to the brain. The brain then processes the information, making sense of all the competing signals, and sends out signals of its own to the muscles in order to keep us in balance.

When balance and tinnitus both become problematic together, it\’s often an indicator of Meniere\’s Disease, which accounts for nearly one percent of all tinnitus cases. However, much more common is another tinnitus issue that develops in the inner ear, namely noise-induced damage to the tiny hair receptor cells in the cochlea, and noise damage or acoustic trauma accounts for 80-85% of all tinnitus cases. Except for freak, accidental exposure to excessively loud sound, noise damage is mostly preventable by avoidance of loud sounds or by using ear muffs or ear plugs to protect our ears.