Understanding How Voice Is Produced
Key Glossary Terms
Highly specialized structure atop the windpipe responsible for sound production, air passage during breathing and protecting the airway during swallowing Vocal Folds (also called Vocal Cords)
"Fold-like" soft tissue that is the main vibratory component of the voice box; comprised of a cover (epithelium and superficial lamina propria), vocal ligament (intermediate and deep laminae propria), and body (thyroarytenoid muscle) Glottis (also called Rima Glottides)
Opening between the two vocal folds; the glottis opens during breathing and closes during swallowing and sound production
Voice as We Know It = Voiced Sound + Resonance + Articulation
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.
Voice Depends on Vocal Fold Vibration and Resonance
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
Vibratory Cycle = Open + Close Phase
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 into sound waves.
Not Like a Guitar String
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.
The Process of Voice
Voice production involves a three-step process.
- 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
- Vocal fold vibration – sequence of vibratory cycles:
- Vocal folds are moved to midline by voice box muscles, nerves, and cartilages
- The vibratory cycle occurs repeatedly; one vibratory cycle is as follows:
- Column of air pressure opens bottom of vocal folds
- Column of air continues to move upwards, now towards the top of vocal folds, and opens the top
- The low pressure created behind the fast-moving air column produces a "Bernoulli effect" which causes the bottom to close, followed by the top
- Closure of the vocal folds cuts off the air column and releases a pulse of air
- 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 raises pitch
Diagram of Vocal Fold Vibration
1 Column of air pressure moves upward towards vocal folds in "closed" position
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 stays 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 upward, now towards the top of vocal folds, and opens the top
New vibratory cycle – repeat 1-10
In the closed position (---) maintained by muscle (), the key vibrating layer of the vocal fold () opens and closes in a cyclical, ordered and even manner (1 – 10) as a column of air pressure () from the lungs below flows through. This very rapid ordered closing and opening produced by the column of air is referred to as the mucosal wave. The lower edge opens first (2-3) followed by the upper edge thus letting air flow through (4-6). The air column that flows through creates a "Bernouli effect" which causes the lower edge to close (7-9) as it escapes upwards. The escaping "puffs of air" (10) are converted to sound which is then transformed into voice by vocal tract resonators.
Any change that affects this mucosal wave – stiffness of vocal fold layers, weakness or failure of closure, imbalance between R and L vocal folds from a lesion on one vocal fold – causes voice problems. (For more information, see Anatomy: How Breakdowns Result in Voice Disorders.)
- Vocal tract – resonators and articulators: The nose, pharynx, and mouth amplify and modify sound, allowing it to take on the distinctive qualities of voice
Similarities With Trombone
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.
Amazing Outcomes of Human Voice
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.
Key Factors for Normal Vocal Fold Vibration
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