Over the past weeks, I have described components of the vocal instrument working my way upward, and now we arrive at the source of sound, the vocal tract.
First a definition, the vocal tract is the cavity where sounds are both initiated and potentially crafted. It consists of the laryngeal cavity, the pharynx, the oral cavity and the nasal cavity. For our purposes today we will focus on the laryngeal cavity with a brief nod at the entire vocal tract.
The larynx (sometimes called the voice box) is the organ through which we breathe, prevent swallowed items from entering the lungs, and create sound. Its outer structure consists of cartilages which create a flexible house for a dynamic intrinsic and extrinsic muscular system. The operation of the larynx is a monument to muscle coordination and interconnectedness. One could write a book solely on the function of these muscles (and people have done just that), which is to say the following descriptions are by no means all there is to know. They should provide a light primer on this subject which you can study further if you are curious.
Intrinsic Muscles of the Larynx
The intrinsic muscles are named for the cartilages they attach to. Like all muscles of the body, the origin is listed first and the insertion point, last. They are:
Thyroarytenoid muscles – The internal thyroarytenoids are the actual vocal cords, but the muscle as a whole does much more which we will visit in the function portion of this post.
Cricothyroid – Responsible for lengthening and tensing the vocal cords.
Posterior and Lateral Cricoarytenoids – Responsible for opening, closing, and rotating the vocal cords as well as creating necessary compression in the vocal cords when together (lateral).
Transverse and Oblique Arytenoids – These muscles assist vocal function by helping the cords come together and narrowing the space between the arytenoids.
The Extrinsic Muscles of the Larynx
If this graphic of the extrinsic musculatures looks complicated, it is sort of. All of these function to support and position the larynx within the trachea. I won’t go into all of these individually because they don’t actually function individually. In fact, these musculatures all interconnect via fascia all the way to the psoas (and beyond), making the vocal instrument inseparable from the human body as a whole.
That was a quick and dirty overview of the physical structures of the vocal tract. I recommend that all voice users have a clear mental picture of the vocal tract and where it rests within the body. Knowing what each muscle is called is not necessary.
The most important function of the larynx is to keep foreign bodies out of the lungs. The musculatures of the larynx, the vocal cords among them, are responsible for sealing when we swallow to prevent food from entering the lungs. Related to this function, these muscles are also responsible for coughing and throat clearing to dislodge anything that gets through.
The last of the primary roles of the larynx are creating of air pressure for physical exertions such as lifting heavy objects and bearing down. The creation of grunts is an aural component of this function.
These primary functions will always override production of sound.
How do we make sound?
To produce sounds, we need a few things.
- A power source
- A vibrator
You’ve already met your power source, the lungs, and the muscles which permit their function. The vibrator is the vocal cords and their supporting musculatures. The resonator is the part of vocal tract we haven’t discussed yet, your throat, mouth, nose, and sinuses. The articulators are your lips, jaw, teeth, palates, and tongue. The Impulse comes from the Brain and your nervous system.
We went into breathing for voice use in a previous article. I won’t break down the inhalation process again here, but it is worth checking out.
First, you have an impulse to communicate. This can take the form of specific speech or something to be sung. That impulse regulates the breath as it exits the lungs causing the vocal cords to vibrate.
The air passes between the vocal cords causing them to vibrate very quickly depending on the pitch you are trying to produce. Impulses coordinate and send the signals for which pitch is to be sounded. The pitch we are vibrating is not under our discrete control, it is operating on a meta level. This is crucial to remember and will be discussed at length in a future blog post.
Sound exits the vocal cords, but that sound is not yet recognizable as human. The journey through the throat and mouth, and its relationship to the nose and sinus, converts the sound wave into what we know as speech and singing. Much of the “magic” of how we sound and how far it travels after leaving our body is in direct relation to how the sound exited the vocal cords and how well it goes through the resonators.
The articulators also help with the crafting and specificity of sound. It is the articulators (again driven by impulse) that guide sound into language as it travels out of our body. Human beings are the only animal that possesses articulators making the human voice unique.
There is a wealth of great information out there on the anatomy of the vocal tract and voice use. My favorites are:
Basics of Vocal Pedagogy by Clifton Ware – Geared mostly towards singing but a wealth of information on the voice for the academically minded.
Just for fun: Here are a couple of videos of the vocal cords in use. One is a view of the vocal cords from above as they are singing. The other is a video of Michael Volle singing in an MRI machine.
See you next week for Focus Friday!