How the Mind Processes Music

What?

You heard me. I'm going to explain you how you hear—how your ears work.

The process of how humans hear is quite fascinating. In fact, is very much like recording sounds on your computer. You're auditory system, the system that allows you to hear, turns sound waves into digital information that your brain can understand.

Another interesting note about hearing, the process is completely mechanical. It involves no chemical reactions even though listen to music often involves quite a bit of chemicals. The technical name for this mechanical process is mechanosensation.

Before you run off in fear because this article might have you feeling like you're back at school, keep in mind that while learning about how we hear you're bound to come across some really cool vocabulary words. So not only will you learn something new but you just might find the perfect name for your newly formed grindcore-ambient- electro-cyber metal-trance band.

WHAT'S THAT SOUND?
Before we start with how we hear, let's first define sound. Sound is a waveform that generally moves through air but as we will soon see it can also move through liquids. Sound has two components: frequency and amplitude. Frequency is pitch while amplitude is loudness. If you picture a drawing of a sound wave the height of the peaks is amplitude while the space between peaks is frequency.

Any sound we can hear is called audio or sonic. There is a finite range of audio humans can hear. This range is typically 20Hz to 20,000HZ (your grandfather can only hear about half of this range once your grandmother starts talking). Any sound that is below the threshold of human hearing is called infrasonic (see, there's a good band name). Any sound that's above the range of human hearing is called ultrasonic.

EAR WE GO!
Since we now know what sound is we can move on to how it gets into our brain? Obviously, it gets into our brain via our ears just like smell gets to our brain via our nose and guilt gets into our brain via our mothers. But did you know that the appendage we call the ear—the thing that holds up our sunglasses and is the perfect target for a wet Willie—is only a third of the ear?

PINNA
Our ear is made up of three parts: the outer, middle, and inner ear. The ear we're most familiar with, the outer ear, also known as the pinna, directs sound into our head. The pinna is directed slightly forward so we can hear sounds in front and to the sides of our position the best. The way sounds hit the pinna also helps the brain determine their direction.

EAR CANAL & EAR DRUM
Once a sound hits the pinna it enters the ear canal. The ear canal is a tube made out of cartilage and bone. The hole in your ear (the thing you jam a Q-tip into) is the canal's beginning. So now we're moving away from the ear we can see and moving inside the old noggin to parts of the ear we can't see. The ear canal, or auditory canal, ends at the ear drum. Another name for the ear drum is the tympanic membrane. We'll stick to calling the ear drum the ear drum because it sounds cooler and the word "membrane" is kinda gross.

MIDDLE EAR
The ear drum, which separates the outer ear from the middle ear, is a lot like a microphone. It's very sensitive and moves at the slightest sound. High frequency sounds move the ear drum rapidly while loud sounds (like when you crank up the Boz Scaggs) moves the ear drum great distances. The ear drum's job is to transmit sound from the outer ear to the middle ear. It's not, as some assume, to keep a steady beat.

OSSICILES
The middle ear, not to be confused with Middle Earth, contains the ossiciles. The ossicles is made up of the three smallest bones in the human body: the malleus, incus, and stapes. Or as cool people call them: the hammer, the anvil and the stirrup (respectively). The ossiciles' job is to convert lower-pressure sound waves into higher-pressure sound waves because the next step of the hearing process involves liquid and sound waves need more energy to move through liquid than they do through air.

OVAL WINDOW
The way ossiciles amplifies sound is quite ingenious— a lot like Frampton Comes Alive. The ossiciles uses the principles of hydraulics and Work (Work = Force x Distance) to amplify sound waves. The ossiciles interacts with the ear drum via the malleus and the ossiciles interacts with the next stage of the hearing process, the inner ear, via the stapes. The stapes moves the oval window—the oval window separates the middle ear from the inner ear. And you thought this was going to be complicated.

INNER EAR
The inner ear is where sound is finally converted into nerve impulses that the brain can understand (that silly brain, always needing things translated into nerve impulses). This translation is done by the star of the inner ear, the cochlea.

COCHLEA
Incidentally, the word cochlea is Latin for "snail." The cochlea bears a slight resemblance to a snail shell. The cochlea contains three fluid-filled sections: scala vestibuli, scala media, and scala tympani. The tympani and vestibuli sections have the responsibility of converting the movement of air into the movement of liquid. The scala media contains the organ of Corti (I swear these names are real, I'm not making this stuff up).

CILIA
The organ of Corti contains hairs called cilia. Sound waves, now moving through fluid, bend the hairs back and forth creating an electrical impulse which are sent to the cochlear nerve (auditory nerve). In turn, this nerve sends the impulses to the cerebral cortex where the brain can finally make sense of it all. And of course some brains make more sense than others.

BRAIN
The data sent to the brain is pretty raw. The brain takes the raw data and interprets it. The brain says "that's a kicking solo" or "that's a gnarly beat" or "so that's what Boots Randolph sounds like." While this process seems fairly defined, there's a lot about hearing scientists still haven't figured out. It's one of those things that due to its simplicity and effectiveness is extremely difficult to fully understand—kinda like country pop.

RECAP
You play some music in iTunes which causes your computer's speakers to produce sound waves. These waves are corralled by your "pinna" which sends them down the "ear canal" to the "ear drum." The ear drum moves the "ossiciles" which turns the low pressure sound waves into high pressure sound waves. The ossiciles then moves the "oval window" which sends the hulked up sound waves to the "cochlea." In the cochlea the sound waves, now traveling through liquid, move hairs called "cilia." The movement of the cilia creates "nerve impulses." These nerve impulses are sent to cochlear nerve which then sends them to the "cerebral cortex" where they can be fully interpreted by the brain. And in this case they are interpreted rather poorly because you accidently played your mother's Peter Cetera album.

Oh well, at least you now know how your ears work.

Copyright 2011 mind-funk-music.com