Jun 17, 2016

Massdrop 101: The Anatomy of the Ear

We might not give them much thought, but while we go about our day-to-day lives, our ears do some pretty incredible stuff. By transforming vibrations into electrical impulses that our brains can perceive as sound, they allow us to hear the world around us, tune into that new album, groove out at a live show, and so much more. The process is complex, occurs in a split second, and goes on around the clock. It’s happening right now. (And now... And now...) Plus, these little organs pull double duty by helping us maintain our balance, too.
Sweet, Sweet Sound
The three parts of the ear (outer, middle, and inner) work in tandem, like three bakers in a kitchen working together to make a cake. Think of the sound waves traveling through the air as the batter, and the electrical impulses as the cake: The sound must be in this finished form for our bodies to be able to digest it. And like one baker might be in charge of mixing the ingredients, one building the tiers, and one adding the icing, each part of the ear has a different job—each as important as the last.
The Outer Ear
First up is the outer ear, whose job is to collect sound waves. The ear’s most recognizable component is the auricle (or pinna), the piece of skin-covered cartilage that sticks out from either side of the head. The auricle has a dozen or so external components, like the triangular fossa, Darwinian tubercle, and antitragus. But its primary function is to gather those sound waves and tunnel them into the auditory canal (also called the ear canal) toward the eardrum outer layer (also called the tympanic membrane).
Did you know? In Buddhist iconography, large ears are considered auspicious because they signify wisdom, compassion, and virtue. That’s why, in many statues and images, Buddha and the Bodhisattvas are portrayed with ears that reach down to their shoulders. In other cultures, the length of your ears (or the thickness of your earlobes) is said to predict the length of your life or the wealth you’ll acquire.
The Middle Ear
Next, sound waves move through the middle ear, which includes a thin sheet of connective tissue known as the eardrum, plus the air-filled, mucosa-lined tympanic cavity and the ossicles. The latter is comprised of three tiny bones: the malleus or “hammer” (a long handle attached to the eardrum), the incus or “anvil” (the bridge between the malleus and the stapes), and the stapes or “stirrup” (the footplate). The last in line, the stapes, is the smallest bone in the human body, and together, all three could easily fit on a penny.
Did you know? Ever wondered why your ears sometimes pop mid-flight? The Eustachian (or pharyngotympanic) tube, which connects the middle ear to the throat, is to blame. This tube is responsible for maintaining equilibrium between the air pressure in your middle ear and the atmospheric pressure, and when it fails, discomfort (and even temporary hearing loss) can occur. The pop you hear is that pressure finally equalizing.
The Inner Ear
When sound travels through the middle ear, it causes the ossicles to vibrate. As it enters the inner ear, these vibrations set the fluid within the cochlea into waves of motion. The spiral-shaped cochlea is lined with tiny cells covered in tiny hairs, and the vibrations also cause these hairs to move. All this creates nerve impulses that are sent via auditory pathways to the brain, and the brain then translates this information into recognizable sound patterns.
The semicircular ducts, three small loops above the cochlea, are filled with fluid, as well, and these transmit information on balance and head position. Meanwhile, the auditory tube drains fluid from the middle ear into the throat behind the nose. The middle ear is flanked by a bony wall, and the inner ear is surrounded and protected by both the membranous labyrinth and the bony labyrinth.
Imperfect Pairs
Beyond the basic presence of sound, our ears allow us to detect various tones, volume levels, and the direction a specific sound is coming from, often despite lots of background noise. Different people have different ear shapes and ear canal sizes, which is why an earbud or headphone that fits your friend comfortably may not suit you as well. And because humans aren’t perfectly symmetrical, your left ear canal may be larger or smaller than your right one. Think about your favorite ring, which may fit perfectly on one finger on your left hand—yet on the same finger on your right hand, it might not even be able to fit over the knuckle.
Did you know? Not all living things use ears to hear. Fish respond to pressure changes, and male mosquitoes hear via thousands of tiny hairs on their antennae. Snakes have two distinct hearing mechanisms, and use their jawbones alongside a traditional inner ear to hear and catch prey. Birds have ears, but they look nothing like ours, and parrots in particular have a remarkable sense of hearing. During World War I, they were kept on the Eiffel Tower to warn citizens of approaching enemy planes before any human ear could detect them.
Comfortable fit is one consideration among many that people take into account when choosing their listening devices. Some look for completely accurate sound reproduction, while others are all about that big, thumping bass. Some value wireless, some need portability, and some care about design as much as sound. When nothing off the shelf will do, audiophiles turn to custom in-ear monitors (and earplugs for hearing protection). These ensure the best fit and seal, and require personalized ear impressions from an audiologist.
Any Questions?
Leave ‘em in the comment section below, and someone from the community will be happy to help. Have personal recommendations to share? We’d love to hear those, too! Want to learn more about how to keep your ears healthy? Check out our profile on musician and health education advocate Kathy Peck (https://www.massdrop.com/talk/56/music-profile-kathy-peck-the-h-e-a-r-organization), and hit "Follow" to be notified about future articles from this account.
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Have you guys of Aumeo? It's an amp/dac combo that has a custom equalizer that tailors for frequency differences in both ears! I still haven't received my unit from indiegogo so I can't really say much about it yet but they look pretty cool.
Hi, thanks for setting up this informative platform! :)
I was just wondering if our hearing would be adversely affected due to pressure build up if we were to simply stuff our earbuds straight into our ears
I always listen at low volume. Just enough to register all the details. One can check their listening ability/defects using an app like this https://play.google.com/store/apps/details?id=mobile.eaudiologia&hl=en
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