Learning About the Voice Mechanism
Speaking and singing involve a voice mechanism that is composed of three subsystems. Each subsystem is composed of different parts of the body and has specific roles.
3 Voice Subsystems
||Role in Sound Production
Air Pressure System
Diaphragm, chest muscles, ribs, abdominal muscles
Provides and regulates air pressure to cause vocal folds to vibrate
Voice box (larynx)
Vocal folds vibrate, changing air pressure to sound waves producing "voiced sound," which is frequently described as a "buzzy sound"
Varies pitch of sound
Vocal tract: throat (pharynx), oral cavity, nasal cavities
Changes the "buzzy sound" into a person's recognizable voice
The Airflow Source
The ability to produce voice starts with airflow from the lungs, which is coordinated by the action of the diaphragm and abdominal and chest muscles.
The Vibratory System
The voice box (larynx) and vocal folds (sometimes called vocal cords) comprise the vibratory system of the voice mechanism.
The Resonating + Modifying System
The vocal tract is comprised of resonators which give a personal quality to the voice, and the modifiers or articulators which form sound into voiced sounds.
Key Functions of The Voice Box
The key function of the voice box is to open and close the glottis (the space between the two vocal folds).
- Role in breathing open glottis:
- The voice box brings both vocal folds apart during breathing.
- Role in cough reflex close, then open glottis:
- The voice box closes the glottis to build up pressure, then opens for the forceful expelling of air during cough.
- Role in swallowing close glottis:
- The voice box coordinates closing the glottis by bringing both vocal folds to the midline to prevent choking during swallowing.
- Role in voice close glottis and adjust vocal fold tension:
- The voice box brings both vocal folds to the midline to allow vocal fold vibration during speaking and singing.
- The voice box adjusts vocal fold tension to vary how high or low (pitch) voice is, and during changes in voice volume, such as loud voice production.
Key Components of the Voice Box
- Vocal Folds
Voice Box Cartilages
There are three cartilages within the larynx.
- Forms the front portion of the larynx
- Most forward part comprises the "Adam's apple"
- Houses the vocal folds
- Vocal folds attach just below the Adam's apple
- Below the thyroid cartilage
- Ring-like: front to back
- Becomes taller in the back of the voice box
- Platform for the arytenoid cartilages
(left and right)
- Pair of small pyramid-shaped cartilages
- Connect with the cricoid cartilage at the back of the vocal folds
- With the cricoid cartilage, forms the cricoarytenoid joint
Voice Box Muscles
Voice box muscles are named according to the cartilages to which they are attached.
Voice Box Muscles Cartilage Attachments, Role, Nerve Input
|Muscles, Cartilage Attachments and Their Roles
Muscles That Move Vocal Folds to the Midline (close glottis)
- Thyroarytenoid muscle: key muscle in vocal fold
- Lateral cricoarytenoid muscle
- Inter-arytenoid muscle
- work coordinately to move arytenoid cartilages in such a way that brings both vocal folds to the middle closing the V-shaped opening or glottis
- role in voice production
- role in protection of airway during swallowing
recurrent laryngeal nerve (RLN)
Muscle That Moves Vocal Folds Apart (open glottis)
- Posterior cricoarytenoid muscle
- move arytenoid cartilages so as to move both vocal folds apart "open vocal folds"
- role in breathing
recurrent laryngeal nerve (RLN)
Muscle That Adjusts Length and Tension of Vocal Folds
- Cricothyroid muscle
- Tilts the thyroid cartilage, thus increasing tension of vocal folds
- Role in high pitch singing
- Role in pitch glide in singing
superior laryngeal nerve (SLN)
Diagram of Voice Box Cartilages and Muscles
Nerve Input to the Voice Box
- The brain coordinates voice production through specific nerve connections and signals.
- Signals to the voice box for moving voice box muscles (motor nerves) come from
- motor branches of recurrent laryngeal nerve (RLN)
- superior laryngeal nerve (SLN)
- Signals from the voice box structures for feeling (sensory nerves) travel through
- sensory branches of the RLN and SLN
"Recurrent" Laryngeal Nerve: The recurrent laryngeal nerve is so named because on the left side of the body it travels down into the chest and comes back (recurs) up into the neck to end at the larynx. [see figure below]
Long Path of Left RLN: The circuitous path of the left RLN throughout the chest is one reason why any type of open-chest surgery places patients at risk for a recurrent laryngeal nerve injury, which would result in vocal fold paresis or paralysis. (For more information, see Vocal Fold Scarring and Vocal Fold Paresis and Paralysis.) [see figure below]
Shorter Path of Right RLN: The right recurrent laryngeal nerve continues in the upper chest and loops around the right subclavian artery, just behind the clavicle (collarbone), then travels the short distance in the neck to the larynx.
- The left and right vocal folds are housed within the larynx. The vocal folds include three distinct layers that work together to promote vocal fold vibration.
1. Covering/Mucosa: loose structure that is key to vocal fold vibration during sound production; comprised of:
- basement membrane
- superficial lamina propria (SLP)
2. Vocal Ligament: The vocal ligament is composed of:
- intermediate lamina propria
- deep lamina propria: contains collagen fibers that are stronger and more rigid than the superficial lamina propria
3. Body: The vocal fold body is composed of the thyroarytenoid muscle. This muscle helps close the glottis and regulate tension of vocal fold during speaking and/or singing. The medial portion of this muscle is also called "vocalis muscle"
"Wiper-Like" Movement of Vocal Folds
The vocal folds move similar to a car's windshield wipers that are attached to the middle of the windshield and open outwards.
- The front ends of both vocal folds are anchored to the front-middle (anterior commissure).
- The back ends of both vocal folds are anchored to the arytenoid cartilages.
- When arytenoids are moved to the open position by the posterior cricoarytenoid muscle, vocal folds open, resulting in glottal opening.
- When arytenoids are closed by the lateral cricoarytenoid and inter arytenoid muscles, vocal folds are brought to the midline resulting in glottal closure.
(click photographs for larger images)