Loud and Clear – the science of sound

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I’ll bet her hand tells the best jokes

 

You may not know this but…

we are in possession of ancient technology. I’m talking about Men in Black, Star trek phaser-level technology. Forget about your smartphone or the connectivity of your Wi-Fi to your oh so shiny tablet (yeah..your tablet is boring). We have ears! Do you understand how remarkable the phenomenon of hearing is?! Mammalian ears are a curiously sophisticated adaptation. They’ve crossed species borders and traveled the millennia just to stay virtually the same. As far as mammals are concerned, version 1.0 is still the best thing out there and those cute little ears of our furry ancestors have been around since the dinosaurs. Archaeologists in China discovered the fossil of a 195 million year old mouse-like mammal (Hadrocodium) with a fully developed inner ear, not unlike what we have today. That’s the physiological equivalent of finding King Tut’s blue-ray collection.

philos

Do we hear with our ears or with our brains?

Sound Waves and Philosophy

Sound is a physical property. Sound happens because people and animals and objects interact with the physical environment and the resulting energy of those interactions is transferred into sound waves that travel through air, water, asphalt or whatever. What we “hear,” on the other hand, is what our brains say we hear. Our brain translates that physical phenomenon into an experience and our brain instantly labels that experience as familiar or unfamiliar, safe or dangerous, pleasing or Nickelback.

Ear Anatomy

The pinna, that floppy, fleshy, flap of skin and cartilage on the outside of our heads is a total cover girl. It’s the most recognizable part of the ear and it helps to funnel a small portion of the infinite variety of sound waves whizzing pass our heads every second of the day. However, to learn the secret to the riddle of sound we need to look beyond the pinna, down the icky, wax filled canal (external auditory meatus) into the middle and inner ear where the tiny bones and membranes play percussion for our central nervous system.

ear-anatomy

The path of sound…

Tempanic > malleus > incus > stapes > oval window > vestibules > cochlea > Brain!

Once sound waves slinky down our ear canal they reach the tempanic membrane (ear drum) and that’s where the magic really happens. Waiting just behind the tympanic membrane is a highly specialized set of tiny bones (ossicles) that move in sync with each vibration.

At this point we have this nifty domino effect happening where vibrations move from one tiny bone to the next. That’s right, I said “vibrations.” Sound is energy and it behaves the way all energy does, never destroyed just moving from one form to another.

Anyway, vibrations move from the tympanic and then pass the baton to the malleus, along to the incus, and then to the tiniest bone of all, the stapes.

Here’s where it changes up a little. Those 3 bones I mentioned occupy this air filled space (tympanic cavity), kind of like a hallway in your head and at the end of that hallway is a door (or rather a window), the oval window. This window is a part of the next compartment of the ear. When that vibration reaches the stapes it basically knocks on that window, handing off the remaining sound energy to the inner ear.

Keep in mind that this is all happening at the speed of sound. Sound waves gallop along at a healthy pace of 1,126ft/sec through the air. Just imagine jumping 13 train cars in a fraction of a sec. Of course, your ear canal is only about an inch long so this all happens MIGHTY quick.

The inner ear is like another dimension. There are fluid filled vessels and a chamber at the end shaped like a snail shell with hairy receptor cells transmitting signals to the brain. I mean What?! It sounds like the hallucination of a band groupie at a Pink Floyd concert, but it’s real.

So what happens?

The stapes knocks on the oval window, transferring the sound vibration to fluid contained behind the window that will move along tubular ventricles.

So in case you got lost, sound moved down the pinna, through the canal, to the tympanic, shaking hands with the malleus, incus, and stapes hanging out in the hallway of the tympanic cavity where the stapes bangs on the oval window to stir up some nasty fluid on the other side.

This fluid (endolymph) now surging with sound energy, will transmit vibrations within the coiled vestibules where they connect with a spiraled chamber called the cochlea.

OK…here it is..

Tucked inside the cochlea is a layer of epithelial receptor cells that make up the Organ of Corti. As the energy charged fluid passes over the tiny hairs of these cells an electrochemical signal (neural transmitter) is released. Neural transmitters are basically like biochemical text messages, but instead of going through Verizon or Sprint this message travels down a bundle of nerves called the spiral ganglion where the temporal lobe of your brain is waiting to…well..”hear” it.

Stay curious, stay classy, and never stop learning my friends 🙂

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