Understanding How Voice is Produced

Key Glossary Terms

Larynx
voice box

Vocal Folds or Vocal Cord
"fold-like" soft tissue that is the main vibratory component of the voice box; comprised of a 1) cover = epithelium + superficial lamina propria; 2) vocal ligament = intermediate and deep laminae propria; 3) body = thyroarytenoid muscle

Glottis
opening between the two vocal folds; the glottis open during breathing and close during swallowing and sound production

Glossary

The "spoken word" results from three components of voice production: voiced sound, resonance and articulation.

• Voiced sound: The basic sound produced by vocal fold vibration is called "voiced sound." This is frequently described as a "buzzy" sound. Voiced sound for singing differs significantly from voiced sound for speech.
• Resonance: Voiced sound is amplified and modified by the vocal tract resonators (the throat, mouth cavity, and nasal passages). The resonators produce a person's recognizable voice.
• Articulation: The vocal tract articulators (the tongue, soft palate, and lips) modify the voiced sound. The articulators produce recognizable words.

Sound is produced when aerodynamic phenomena cause vocal folds to vibrate rapidly in a sequence of vibratory cycles with a speed of about:

• 110 cycles per second or Hz (men) = lower pitch
• 180 to 220 cycles per second (women) = medium pitch
• 300 cycles per second (children) = higher pitch
  higher voice: increase in frequency of vocal fold vibration
  louder voice: increase in amplitude of vocal fold vibration

The vocal fold vibratory cycle has phases that include an orderly sequence of opening and closing the top and bottom of the vocal folds, letting short puffs of air through at high speed. Air pressure is converted to sound waves.

Vocal folds vibrate when excited by aerodynamic phenomena; they are not plucked like a guitar string. Air pressure from the lungs controls the open phase. The passing air column creates a trailing "Bernoulli effect," which controls the close phase.

Voice production involves a three-step process:

1. A column of air pressure is moved towards the vocal folds: Air is moved out of the lungs and towards the vocal folds by coordinated action of the diaphragm, abdominal muscles, chest muscles and rib cage
2. Vocal fold vibration – sequence of vibratory cycles:
   • Vocal folds are moved to mid-line by voice box muscles, nerves, and cartilages
   • The vibratory cycle occurs repeatedly. One vibratory cycle is as follows:
     1. Column of air pressure opens bottom of vocal folds
     2. Column of air continues to move upwards, now towards the top of vocal folds and opens the top
     3. The low pressure created behind the fast-moving air column produces a "Bernoulli effect" which causes the bottom to close, followed by the top
     4. Closure of the vocal folds cuts off the air column and releases a pulse of air
     5. New cycle repeats
   • The rapid pulses of air created by repeat vibratory cycles produce "voiced sound" which is really just a buzzy sound, which is then amplified and modified by the vocal tract resonators, producing voice "as we know it." (see table below)
     • Loudness: Increase in air flow "blows" vocal folds wider apart, which stay apart longer during a vibratory cycle – thus increasing amplitude of the sound pressure wave
     • Pitch: Increase in frequency of vocal fold vibration
     
     
     Diagram of Vocal Fold Vibration

     1 Column of air pressure moves upwards towards vocal folds in "closed" position	click for larger image	6–10 The low pressure created behind the fast-moving air column produces a "Bernoulli effect" which causes the bottom to close, followed by the top.
     2, 3 Column of air pressure opens bottom of vibrating layers of vocal folds; body of vocal folds stay in place		10 Closure of the vocal folds cuts off the air column and releases a pulse of air
     4, 5 Column of air pressure continues to move upwards, now towards the top of vocal folds and opens the top		New vibratory cycle – repeat 1-10

   
   
3. Vocal tract: resonators and articulators: The nose, pharynx and mouth amplify and modify sound, allowing it to take on the distinctive qualities of voice

The way that voice is produced is analogous to the way that sound is produced by a trombone. The trombone player produces sound at the mouthpiece of the instrument with his lips vibrating from air that passes from the mouth. The vibration within the mouthpiece produces sound, which is then altered or "shaped" as it passes throughout the instrument. As the slide of the trombone is changed, the sound of the musical instrument is similarly changed.

The human voice can be modified in many ways. Consider the spectrum of sounds – whispering, speaking, orating, shouting – as well as the different sounds that are possible in different forms of vocal music, such as rock singing, gospel singing, and opera singing.

In order to vibrate efficiently, vocal folds need to be:

• At the midline or "closed": Failure to move vocal folds to the midline, or any lesion which prevents the vocal fold edges from meeting, allows air to escape and results in breathy voice.

  Key players: muscles, cartilages, nerves

• Pliable: The natural "built-in" elasticity of vocal folds makes them pliable. The top, edge and bottom of the vocal folds that meet in the midline and vibrate need to be pliable. Changes in vocal fold pliability, even if limited to just one region or "spot," can cause voice disorders, as seen in vocal fold scarring.

  Key players: epithelium, superficial lamina propria

• "Just right" tension: Inability to adjust tension during singing can cause a failure to reach high notes or breaks in voice.

  Key players: muscle, nerve, cartilages

• "Just right" mass: Changes in the soft tissue bulk of the vocal folds – such as decrease or thinning as in scarring or increase or swelling as in Reinke's Edema produce many voice symptoms – hoarseness, altered voice pitch, effortful phonation, etc. (For more information, see Vocal Fold Scarring and Reinke's Edema.)

  Key players: muscles, nerves, epithelium, superficial lamina propria