The Vocal Mechanism, Part I

The voice box, or larynx, is an amazingly complex apparatus of sound production, (Oh, and it's pronounced "lehr-inks" not "lehr-in-icks").  As with many bodily structures and functions we take for granted, the larynx rests humbly and unnoticed in the throat above the lower airway, or trachea, as seen here:

A summary of the vocal mechanism vocal tract upper airway vocal folds

It is inconspicuous until we engage it for communication, at which time it, in conjunction with surrounding muscles and cartilages, can perform a surprising array of tilts and twists to produce a multitude of pitches and registers (more on this in another post).  

The larynx plays a vital role not only  for speech, but for breathing and swallowing as well.  In fact, from an evolutionary perspective, the larynx's primary purpose in development is for airway protection, with voicing a pleasant gratuity that developed over time.  

The parts of the whole

In speech science the prevailing explanation of the vocal mechanism is the Power-Source-Filter Theory which breaks down speech production in three components:

  • The lungs provide the Power, or supply of air and pressure need to set the vocal folds into motion to create noice
  • The vocal folds are the Source of sound, which are set into vibration with airflow passing through them.  The vocal folds are housed within the larynx in the throat.
  • The vocal tract is the Filter through which the sound produced by the vibration of the vocal folds.  The vocal tract consists of the structures of the throat, mouth, and nose above the level of the larynx that shape this sound into the voice you hear when speaking.
We have a general idea of the function of the lungs, but the workings of the vocal folds and vocal tract might be more obscure to many of us, so let's talk a bit more about those.

The Larynx

A simplistic but sufficient labeling of the larynx is below.

The larynx muscle cartilage ligaments

Above we can see cartilages, muscles, and ligaments that comprise the major structure of the larynx.  Each part of the whole serves a specific role in voice production and modulation, or changes in strength, tone, and/or pitch.  The most obvious part we can see and feel is the thyroid notch or "Adam's Apple".  This notch is formed by the shield-like projection of the largest cartilage of the larynx.  Although it is most observable in males, females have this notch as well, albeit smaller.  

Hidden within this muscle and cartilage lies the hidden crux of the voice, the vocal folds (or more colloquially, vocal cords).  These folds attach anteriorly to the thryoid cartilage and posteriorly to the arytenoid cartilages, stretching from front to back across the larynx, as seen here:

The upper airway and vocal tract with vocal fold closure and opening or adduction and abduction

The Vocal Tract

When we voice, or phonate, the vocal folds are brought together and vibrate from airflow underneath from the lungs, setting into motion a wave movement of the folds that creates a simple buzz.  This noise ascends into the upper airway of the throat, mouth, and nose (i.e., the vocal tract), where it is filtered by these tissues to create our unique voice.  Through articulation with the lips, teeth, and other oral and pharyngeal structures we create a speech pattern exclusive to each of us.  

The size and shape of the vocal tract (everything above the vocal folds) varies between each of us--no two people are exactly alike.  Thus, our voice is similar to a fingerprint, identifying us to the listener even when other cues aren't available (seeing our face, for instance).  This is how we determine a familiar voice on the telephone.  

Our Unique Voice

Accordingly our voice becomes a part of our identity--something listeners use to discriminate us from a crowd.  Those of us that are able to modulate the voice and change its characteristics can deceive the listener on identity.  Consider the late Mel Blanc, who voiced multiple characters in Looney Tunes, including Bugs Bunny, Daffy Duck, Porky Pig, Tweety Bird, Sylvester the Cat, Yosemite Sam, Foghorn Leghorn, Marvin the Martian, Pepé Le Pew, Speedy Gonzales, Wile E. Coyote, Road Runner, and the Tasmanian Devil.  Who could believe that the same person could modulate the voice in such a way as to have so many distinct "personalities"!?  

For now, consider variations you are capable of making.  What sorts of pitches, "accents" and varying vocal "qualities" can you produce from your typical speech?  We'll continue our talk in The Vocal Mechanism, Part II.

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