About the Voice

Anatomy 101: Parts of the Voice

1. Larynx (pronounced LAIR-inx, not LAHR-nix)
The larynx is the voice box. The vocal folds (also called vocal cords; refer to our explanation to clarify this terminology) are part of the larynx. The vocal folds vibrate to create the sound of the voice.

2. Pharynx (pronounced FAIR-inx)
The pharynx is the throat. It goes up from the larynx and divides into the laryngopharynx (just above the larynx), oropharynx (going into the mouth) and nasopharynx (going into the nose).

3. Trachea (pronounced TRAY-key-ah)
The trachea is your windpipe. It's the tube that connects your lungs to your throat. The larynx sits on the top of the trachea.

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4. Esophagus
The esophagus is your food pipe. It's just behind the larynx and trachea. Your pharynx carries both air and food/water. The air goes through the larynx and trachea, and food and water go into your esophagus.

5. Spinal column
The spinal column is behind the esophagus. You can feel it by pressing the back of your neck.

6. Diaphragm
The diaphragm is underneath the lungs, inside the rib cage. It's shaped like a dome. The diaphragm is your main muscle for controlling respiration (breathing).

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Vocal FOLDS or Vocal CORDS???

You've probably heard the term "vocal cords" used to describe the part of the body that creates sound for the voice. You've probably also heard the term "vocal folds" in the same context. So what's the difference between the two? Well . . .

Vocal folds are the same as vocal cords. The two terms refer to the exact same part of the body performing the exact same functions. The term "vocal cords" is less technically correct but more often used among singers and laypersons.

Why, then, do voice scientists and otolaryngologists refer to them as vocal folds? Years ago, vocal folds were thought of as being two cords stretched across the airway, like strings on a piano (hence the term "cords"). Now we know that vocal folds are multilayered folds of tissue that are continuous with other tissues in the throat. Therefore, vocal "folds" is a more accurate term, but it's OK with us if you call them vocal cords. Just don't get confused and call them vocal "chords!"

ANATOMY 201: CARTILAGES AND MUSCLES OF THE LARYNX

laryngeal [pronounced lah-RIN-jul or lair-in-JEE-al] = having to do with the larynx

In the picture on the right, part of the thyroid cartilage is cut away to show the extent of the cricothyroid muscle, insterting into the inside of the thyroid cartilage.

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Anatomy of the Larynx:

1. Cricoid (rhymes with "thyroid") cartilage - As the top ring of the trachea, the cricoid cartilage is shaped like a signet ring, wider in the back than the front.

2. Thyroid cartilage - the thyroid cartilage fits over the cricoid cartilage, and is hinged so that it can slightly rock forward and downward. The thyroid cartilage comes to a point in the front; this point is termed the thyroid notch, but is commonly called the Adam's Apple. The vocal folds (also called vocal cords; refer to our explanation to clarify this terminology) attach at the inside of the thyroid notch.

3. Arytenoid (pronounced ah-RIHT-uh-noid) cartilages - These sit atop the back of the cricoid cartilage and hold the back end of the vocal folds. The arytenoid cartilages can rock, glide, and pivot, thus controlling the movement of the vocal folds.

4. Vocal Folds (Vocal Cords) - These remarkable structures provide a valve for the airway and also vibrate to produce the voice. The vocal folds are multilayered structures, consisting of a muscle covered by a mucosal covering.

5. Glottis - This is the space between the two vocal folds. When the vocal folds adduct, the glottis closes; when the vocal folds abduct, the glottis opens. The adjectives "glottal" and "glottic" are used to describe many aspects of vocal fold movement. The glottis opens and closes during vibration. Refer to the corresponding pictures.

6. Epiglottis - This soft cartilage serves as part of the protective swallowing mechanism. It folds backward over the glottis during a swallow so that food and water do not go into the lungs. It is not involved in normal voice production.

7. Hyoid (rhymes with "thyroid") Bone - This horseshoe-shaped bone is positioned slightly above the thyroid cartilage and is the only bone in the body not connected to any other bone. The hyoid bone provides the attachment for many of the muscles of the tongue, jaw, and neck.

IMPORTANT TERMS

  • Abduction - The vocal folds abduct (come apart) in order to let air in and out of the lungs during breathing.
  • Adduction - The vocal folds may adduct (come together) to trap air in the lungs. They may also adduct to vibrate to produce vocal sound

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ANATOMY 202: STRUCTURE OF THE VOCAL FOLD

Vocal folds used to be called vocal cords (and are still often referred to that way) because it was thought that they vibrated much like strings on a violin. This has been shown to be untrue.

The figure below shows the cross section of a vocal fold. As you can see, it is a multilayered structure. The innermost layer is the thyroarytenoid (a.k.a. vocalis) muscle, which runs the entire length of the vocal fold, from the thyroid cartilage to the arytenoid cartilage. The thyroarytenoid muscle is the most dense portion of the vocal fold.

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This drawing shows a cross section of a vocal fold. Deeper layers of mucosa are more stiff than shallower ones. At the core is a muscle with fibers stretching from front to back.

Surrounding the thyroarytenoid muscle is a sheath of mucosal tissue, that varies in stiffness from the stiffest portion surrounding the muscle, to the outermost layer, which is quite floppy.

The mucosal covering is divided into three sections, deep, intermediate, and superficial. All three layers are composed of collagen fibers, but the fibers are arranged differently in each layer. The fibers of the superficial layer are sparsely arranged, and are like thin, loose threads. The intermediate fibers are arranged along a different direction, and are more like a bundle of soft rubber bands. The fibers of the deep layer lie in yet a different direction, and they are arranged in dense, stiff bundles, like clumps of cotton thread. The overall looseness or stiffness of the mucosa depends on the state of contraction of the laryngeal muscles, but in general, the mucosa is similar in consistency to soft-set Jell-O.

The mucosa is covered by a thin layer of epithelial covering, similar to the loose skin on the back of your hand. This epithelium contains the mucosa but allows it to take on an endless variety of shapes.

The interesting thing about the multilayered structure is that the vocal fold can be stretched or contracted and made to vibrate at many different lengths. It can also adapt to different degrees of impact, and can withstand the forces and strain of extremely rapid vibration by rapidly changing its configuration.

ANATOMY 301: THE ROLE OF THE NERVOUS SYSTEM

Nerves come from the brain to the brain stem (a lower, more primitive center of the brain) or to the spinal cord, and then go out to muscles and tissues of the body. Signals from the nerves activate the muscles and control their movement. Nerves also carry information about sensations in the muscles and tissues back to the brain. This two way process is called "innervation," and nerves are said to "innervate" the organs. There are two nerves that innervate the larynx: the recurrent laryngeal nerve and the superior laryngeal nerve. The recurrent laryngeal nerve is the more important of the two nerves, and the one most likely to be damaged. Both the recurrent laryngeal nerve and the superior laryngeal nerve are part of one of the 12 cranial nerves. They branch off from the tenth cranial nerve, called the Vagus nerve. The recurrent laryngeal nerve comes out of the brain stem and descends all the way down to wrap around the aorta (the main artery leading out of the heart) on the left side. It then comes back up and attaches to the larynx.  Below diagrams the nerves that connect the larynx to the brain.

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Physiology 101: How It Works

1. Air comes out of the lungs, through the trachea, and into the larynx.

2. The air makes the vocal folds vibrate.

3. When the vocal folds vibrate, they alternately trap air and release it.

4. Each release sends a little puff of air into the pharynx; each puff of air is the beginning of a sound wave (see Acoustics 101: Sound Waves and How They Move).

5. The sound wave is enhanced as it travels through the pharynx; by the time it leaves the mouth, it sounds like a voice.

To see how the vocal folds vibrate, purse your lips and blow; this is similar to vocal fold vibration. Or, hold two pieces of paper so close together that they almost touch, and blow through them. Surprised? They don't blow apart -- they vibrate together.

PHYSIOLOGY 201: VOCAL FOLD VIBRATION AND PITCH

This chart shows how fast your vocal folds are vibrating (in Hertz) when you're singing certain pitches. Notice that every time you go up an octave, you double the frequency of vibration.

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The faster the vocal folds vibrate, the higher the pitch. Extremely slow vocal fold vibration is about 60 vibrations per second and produces a low pitch. Extremely fast vocal fold vibration approaches 2000 vibrations per second and produces a very high pitch. Only the highest sopranos can attain those extremely high pitches. In general, men's vocal folds can vibrate from 90 - 500 Hz, and they average about 115 Hz in conversation. Women's vocal folds can vibrate from 150 -1000 Hz, and they average about 200 Hz in conversation.The faster the vocal folds vibrate, the higher the pitch. Extremely slow vocal fold vibration is about 60 vibrations per second and produces a low pitch. Extremely fast vocal fold vibration approaches 2000 vibrations per second and produces a very high pitch. Only the highest sopranos can attain those extremely high pitches. In general, men's vocal folds can vibrate from 90 - 500 Hz, and they average about 115 Hz in conversation. Women's vocal folds can vibrate from 150 -1000 Hz, and they average about 200 Hz in conversation.

For all you singers . . .

Different voice types have different average speaking pitches. Here is a table of average speaking pitches and frequencies by voice type.

  • Soprano B3 (246.9 Hz)
  • Mezzo-Soprano G3 (196.0 Hz)
  • Contralto F3 (174.6 Hz)
  • Tenor E3 (164.8 Hz)
  • Baritone B2 (123.5 Hz)
  • Bass G2 (98.0 Hz)

Source: Titze, Ingo R. 1994. Principles of Voice Production. Englewood Cliffs, NJ: Prentice Hall, Inc., p. 188.

Vocal folds (also called vocal cords; refer to our explanation to clarify this terminology) vibrate faster as they're pulled longer, thinner, and more taut. This is done by contracting the cricothyroid muscle, which pulls the thyroid cartilage down and forward on its hinge, away from the arytenoid cartilages, thus lengthening the vocal folds. When they're lengthened they also get thinner and more taut (like a rubber band - try it).

Vocal folds vibrate more slowly when they're shorter, thicker, and floppier. This is done by contracting the thyroarytenoid muscle, which pulls the arytenoid end of the vocal folds closer to the thyroid end, thus bunching them up. The thyroarytenoid muscle is contracted, so it's firmer, but the mucosa overlying the vocal fold becomes floppier, so it vibrates slower.

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 The vocal folds on the left are singing rather high (733 Hertz) while the vocal folds on the right were singing much lower (about 200 Hertz).

It sounds pretty simple, but it's usually more complex than that. The cricothyroid muscle and thyroarytenoid muscle coordinate with each other to create different pitches. They can also coordinate differently to produce the same pitch with a different sound quality. The amount of airflow from the lungs also impacts the pitch. In addition, the other muscles in the larynx can affect pitch and loudness adjustments in very complex ways.

PHYSIOLOGY 202: VOCAL FOLD VIBRATION AND LOUDNESS

Loudness is pretty complex -- lots of factors affect loudness.

The loudness of the sound coming directly from the vocal folds has to do with one thing: the strength of the explosion of air into the glottis (the space between the 2 vocal folds) each time the glottis opens during a cycle of vibration. The loudness of the sound coming out of the MOUTH is a different matter. We'll get to that later.

Remember that the vocal folds alternately trap and release air; each trap/release is one cycle of vibration. This cycle is often referred to as the glottic cycle, and it is divided into phases: opening phase, open phase, closing phase, closed phase (see the diagrams on the left and right; follow along from top to bottom).

During the closed phase, the air pressure builds up below the vocal folds. When the glottis opens, the air explodes through the vocal folds, and that's the beginning of the sound wave. The strength of that explosion determines the loudness of the sound coming directly from the larynx.

Keep in mind that, depending on the pitch of the sound, each cycle of vibration can be occurring within one-sixtieth of a second or at any speed up to nearly one two-thousandth of a second! Regardless of how fast the vocal folds are vibrating, each cycle is still divided into phases, and those phases can have different proportions. 

What causes stronger explosions of air going into the glottis?

The longer the closed phase, the more the air pressure builds up -- thus the stronger the explosion. With soft phonation, the closed phase is proportionately short, and air pressure doesn't get as much chance to build up. The explosion is weaker. With loud phonation, the closed phase is proportionately longer, and the air pressure builds up more. Therefore, the explosion is stronger.

How does the closed phase get longer?

The muscles in the larynx that bring the vocal folds together contract more strongly, squeezing the vocal folds together harder, so they can resist the air pressure longer. Those muscles are the thyroarytenoids, lateral cricoarytenoids, and interarytenoids. The muscles in the neck may also help provide stabilization, or may actually help produce the squeezing effect. The muscles in the larynx that bring the vocal folds together contract more strongly, squeezing the vocal folds together harder, so they can resist the air pressure longer. Those muscles are the thyroarytenoids, lateral cricoarytenoids, and interarytenoids. The muscles in the neck may also help provide stabilization, or may actually help produce the squeezing effect.

What happens to the opening phase when more air pressure builds up?

When the air pressure builds up for a longer time, not only does the air explode more strongly through the larynx, but the vocal folds are blown more strongly apart, and that opening phase is more sudden. The open phase is actually shorter because the forces that suck the vocal folds back together are stronger. The closing phase, therefore, is also more sudden, and the vocal folds snap back with high impact. The sudden closing phase helps produce a brighter, "ringier" sound but it is also harder on the vocal folds

The other thing that affects loudness is how the sound wave is enhanced by the vocal tract. Think of blowing into the mouthpiece of a trumpet, and then blowing into the mouthpiece when it's connected to the rest of the trumpet. This difference in sound is similar to the difference of when the sound leaves the glottis and when it leaves the mouth.

Physiology 301: Types of Voice Disorders

Structural

Structural disorders are caused by some lesion (physical abnormality) of the larynx.

  • Contact Ulcers
  • Cysts
  • Granuloma
  • Hemorrhage
  • Hyperkeratosis
  • Laryngitis
  • Leukoplakia
  • Nodules (nodes)
  • Papilloma
  • Polyps
  • Trauma
  • Miscellaneous growths

Neurogenic

Neurogenic Voice Disorders are caused by some problem in the nervous system as it interacts with the larynx. See the Anatomy 301 section in our page about the voice for more information. Briefly, two nerves come from the brain to the larynx and control the movement of the larynx. The most important of the two nerves, the recurrent laryngeal nerve, comes down and wraps around the aorta before going back up to attach to the larynx on the left side. Because of this position in the neck, the recurrent laryngeal is vulnerable to damage during cardiac, pulmonary, spinal and thyroid surgeries. When the nerve is damaged, it causes a paresis (weakness) or paralysis (complete lack of movement) in the vocal fold of the affected side. Other neurogenic voice disorders are related to other kinds of problems in the central nervous system.

  • Paralysis/Paresis
  • Spasmodic Dysphonia (Laryngeal Dystonia)
  • Tremor (Benign Essential Tremor)
  • Voice problem caused by another neurological disorder (e.g. Parkinson's disease, myasthenia gravis, ALS/Lou Gherig's Disease)

Functional

Functional disorders are caused by poor muscle functioning. All functional disorders fall under the category of muscle tension dysphonia. The different disorders listed here refer to different patterns of muscle tension.

  • Muscle tension dysphonia (general)
  • Anterior-posterior constriction
  • HyperABduction
  • HyperADduction
  • Pharyngeal constriction
  • Ventricular phonation
  • Vocal fold bowing

Psychogenic

Psychogenic disorders exist because it is possible for the voice to be disturbed for psychological reasons. In this case, there is no structural reason for the voice disorder, and there may or may not be some pattern of muscle tension. While it is quite common for a psychogenic component to exist in a voice disorder, voice disorders that are caused by a psychological disorder are relatively rare. The two most common types of psychogenic disorders are listed on the right.

  • Conversion dysphonia or aphonia
  • Puberphonia (mutational falsetto)