Vocal Folds

What better way to start the new year than to play games with your larynx?!

The larynx is, after all, where the sound of your voice actually begins.  It is the source of your voice.  So let's start off the year by talking about where your voice starts.

Remember how I showed you guys my larynx model a while back?  Go ahead and touch your throat again to find it—remember it's the adam's apple in dudes.  Now I'm going to tell you about what's inside the larynx.

Inside of your larynx, you have two sets of vocal folds.  On top are the "false" vocal folds, which really just provide extra protection for the larynx.  The bottom set of vocal folds are the "true" vocal folds—they are the part of the larynx that vibrate when you make voiced sounds.  Remember how your throat feels different when you say "buzzzz" vs. "hissss"?  When you voice the "z" in "buzzzzzzz", your vocal folds are vibrating, flapping open and closed, open and closed.

 

The speed at which the vocal folds are vibrating provides the fundamental frequency of your voice—which is perceived as pitch.  If you are singing an A, at 440 Hz, that means your vocal folds are opening and closing 440 thousand times a second.

You want to know how they do it?  It's super exciting.

A long time ago, back in the cave days or something, people thought that each flap of the vocal folds was a muscular contraction—that the vocal fold muscles were purposefully flapping open and closed bajillions of times per second.

Now we know that's just silly—no nerve could tell the vocal folds to move that fast!  Instead, the muscles of the larynx hold the vocal folds tightly closed.  As air pressure builds up in your throat below the vocal folds, it pushes them open!  But the muscles of the vocal folds are still trying to hold them closed.  Thanks to the force from the muscles and also Bernoulli's principle, the vocal folds quickly return to their closed position.  You're still breathing out at this point, so air pressure builds up again and pushes the vocal folds open again, and then they close again, and you get the idea.  Lather, rinse, repeat.  Thousands of times per second.

Are you read for a fancy phrase?  You just learned the myoelastic aerodynamic theory of phonation.  Cool, huh?

And if you're ready for a pretty gross video, check out these gorgeous vocal folds!  This video gives a good slow-mo vision of vocal folds.  It doesn't have sound until the end for some reason.  It was taken by shoving a camera back into someone's throat; the bottom of the video is the front of the larynx (the epiglottis), and the top of the video is the back of the larynx (the arytenoid cartilages).

Happy 2014, everyone!