assignment eng 21 journal 4

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Normal Voice Function

Voice is produced by vibration of the vocal folds. The vocal folds are a pair of pliableshelves of tissue that stretch across the top of the trachea . They are enclosed within the thyroid

cartilage, which is the hard structure that forms the mass in the neck known as the Adam¶s apple.The vocal folds, together with the muscles and cartilages that support them, are known as thelarynx .

Biologically, the larynx evolved as a valve to protect the airway and lungs. Thus, it is positioned where the airway and the esophagus separate. The vocal folds open to allow breathing and close during swallowing to prevent food from entering into the lungs and duringvoicing.

y Vocal fold - is the modern term for µvocal cord.¶ The change in terminology came about because of a better understanding of the anatomy and function of the larynx. µVocal cord¶suggests a band or string suspended in the air that vibrates when it is plucked or struck. Infact, the vocal fold is a part of a muscle on the side of the larynx, covered with specialtissues that can vibrate at a high speed. It resembles a lip of tissue much more than a cord.Only its outer covering vibrates.

y L arynx - Highly specialized structure atop the windpipe responsible for sound production, air passage during breathing and protecting the airway during swallowing.

y G lottis (also called Rima G lottides) - Opening between the two vocal folds; the glottisopens during breathing and closes during swallowing and sound production

Aspect of Voice:

Sound

In order to produce voice, the lungs blow air against vocal folds that are closed, but moreloosely than they would be during swallowing. Air pushes through the very small space betweenthem and in so doing, makes the covering of the vocal folds, known as the mucosa, vibrate. Thisoccurs by means of a phenomenon known as the venturi effect. As air passes through aconstriction (or venturi), it speeds up and creates a suction in its wake. This suction draws in the

pliable mucosa from each vocal fold, which meets in the midline, only to be pushed aside bymore air from the lungs. This cycle creates a repeating undulation which is known as

the mucosal wave . The regularity of the mucosal wave is essential to the production of goodvoice.

The pliability of the mucosa depends on the integrity of the layer immediately beneath it,known as the superficial lamina propria , or Reinke¶s layer , named after the man who

described it. It is a special network of substances, unique in the body, that can support thestresses of vocal fold vibration over the long term.

L oudness

The volume of sound is principally a result of the pressure of the air that is blown past the

vocal folds. A more forceful expulsion of air from the lungs raises this pressure. Of course, thevocal folds must increase tension to maintain the near-closure that is needed for the venturieffect. If they do not, the increased air pressure will simply blow them aside and interruptvibration. This tensing of the vocal folds usually happens instinctively, without conscious effort.People with vocal fold paralysis or other types of vocal fold weakness are often unable to do this,

and frequently complain of an inability to increase the volume of their voice.

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P itch

The frequency of the mucosal wave determines the pitch of the voice. In addition to

opening and closing, the vocal folds are able to lengthen and shorten, and this forms an importantmeans of increasing vocal fold tension. Just as tuning a guitar string will adjust its pitch, so will

changing tension on the vocal folds. In the case of vocal folds, however, tension must be alteredsymmetrically. A person performs this activity rapidly and precisely, and many times over the

course of a short conversation.

Hoarseness

Hoarseness is the result of irregularity of mucosal vibration. Very many factors influencethe formation and maintenance of the mucosal wave, but broadly speaking, these can be

simplified to two: vocal fold closure and the integrity of the superficial lamina propria. Inabilityof the vocal folds to close sufficiently, as in some cases of vocal fold paralysis, may make it

impossible to create the venturi effect which underlies mucosal vibration. Tethered or stiff

mucosa resulting from a change in the lamina propria, as in vocal fold scar, will not vibrate wellor at all, regardless of the vocal fold closure. Sometimes, a large mass like a cyst or polyp blocks

both the vocal folds from closing and the mucosa from vibrating.

Vocal Sound Production

Diaphragm action pushes air from the lungs through the vocal folds, producing a periodictrain of air pulses. This pulse train is shaped by the resonances of the vocal tract. The basicresonances, called vocal formants, can be changed by the action of the articulators to producedistinguishable voice sounds, like the vowel sounds.

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Phonation

The process of speech production by the human voice may be divided into

phonation, resonation, and articulation. Phonation is the process by which energy from the lungsin the form of air pressure is converted into audible vibrations. One method of phonationinvolves using the air pressure to set the elastic vocal folds into vibration, a processcalled voicing.

The other involves allowing air to pass through the larynx in to the vocal tract wheremodifications of the airstream produce transient or aperiodic sound waves.

Understanding Voice Disorders

Knowing how normal voice is produced and the roles the voice box and its parts play inspeaking and singing helps patients understand their voice disorders

Voice "As We Know It"The "spoken word" results from three components of voice production: voiced sound,

resonance, and articulation.

y Voiced sound: The basic sound produced by vocal fold vibration is called "voicedsound." This is frequently described as a "buzzy" sound. Voiced sound for singing differssignificantly from voiced sound for speech.

y Resonance: Voice sound is amplified and modified by the vocal tract resonators (thethroat, mouth cavity, and nasal passages). The resonators produce a person's recognizablevoice.

y Articulation: The vocal tract articulators (the tongue, soft palate, and lips) modify thevoiced sound. The articulators produce recognizable words.

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 in voice

production.

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T hree Voice Subsystems

Subsystem Voice Organs Role in Sound P roduction

Air pressuresystem

Diaphragm, chestmuscles, ribs, abdominal

muscles

Lungs

Provides and regulates air pressure to causevocal folds to vibrate

Vibratorysystem

Voice box (larynx)

Vocal folds

Vocal folds vibrate, changing air pressure tosound waves producing "voiced sound,"frequently described as a "buzzy sound"

Varies pitch of sound

Resonating

system

Vocal tract: throat

(pharynx), oral cavity,nasal passages

Changes the "buzzy sound" into a person's

recognizable voice

Key Function of the Voice Box

The key function of the voice box is to open and close the glottis (the space between the twovocal folds).

y Role in breathing: Open glottisy Role in cough reflex: Close, then open glottisy

Role in swallowing: Close glottisy Role in voice: Close glottis and adjust vocal fold tension (plus additional functions for

singing)

Key Components of the Voice Box

Cartilages

y Musclesy Nervesy Vocal folds

Abnormalities or Changes in the Vibratory System Result in Voice Disorders

Breakdowns can occur in any one or all three subsystems of voice production. This patient education series focuses on voice disorders, specifically breakdowns in the vibratorysystem.

Footnotes:

1. Voice Medicine by Dr. Lucian Sulicahttp://www.voicemedicine.com/normal_voice_functioning.htm

2. Hyperphysics by R. Nave http://hyperphysics.phy-astr.gsu.edu/hbase/music/voice.html 3. Ronnie Lederman, Vocalfucus.com http://www.vocalfocus.com/voice.html 4. Voice Foundation

http://www.voicefoundation.org/index.php?option=com_content&view=article&id=85%3Aanatomy-and-physiology-of-voice-production-highlights-&catid=47%3Avoice-problems&Itemid=49

5. Hyperphysics http://hyperphysics.phy-astr.gsu.edu/hbase/music/voice2.html