Phonation

Functions of the larynx

• Controls airflow in and out of lungs

• Protects pathway to lungs during swallowing

• Increases intrathoracic pressure during exertion, coughing, etc.

• Provides sound source for speech

Abduction

Folds separated for voiceless sounds and breathing (rest position)

Adduction

Folds brought together for phonation (voiced sounds)

Myoelastic Aerodynamic Theory

• Negative pressure causes vocal folds to be sucked together, causing a closed airspace below the glottis

• Continued air pressure from the lungs builds up underneath the closed folds

• Once the pressure is high, folds are blown outward, opening the glottis which releases a single “puff” of air

• Lateral movement of the folds continues until the natural elasticity of the tissue takes over and folds move back to original position

Breathy Voice

Vocal folds only slightly apart so that they vibrate while allowing a high rate of airflow through glottis

Loose adduction

Creaky Voice

Arytenoid cartilages hold posterior end of vocal folds together so they can vibrate at other end

Irregular vibration

Spasmodic Dysphonia

Vocal fold paralysis yields inability to initiate or maintain phonation; strangled voice quality

Involuntary muscle spasms

Alaryngeal Speech

Caused by surgical removal of larynx which requires the speaker to use other structures as a sound source

Stuttering

Simultaneous contraction of adductor and abductor muscles may yield delayed phonation and cause a “block”

Disrupted coordination of adduction/abduction

Hoarseness

Irregularities in laryngeal tissue

Ex: Swelling

Contact Ulcers

Lesions produced by impact of vocal folds (vocal fold collisions) during phonation (often reflects excess muscle tension)

Fundamental Frequency

Rate of vocal fold vibration

Depends on:

• Length

• Mass

• Tension

Controlled by:

• Cricothyroid muscles (stretches folds)

• Suprahyoid/Infrahyoid muscles (raise/lower larynx)

Intensity Control

Increased subglottal pressure = louder voice

Vocal folds blown apart more forcefully

Faster closing and higher amplitude waveforms

Phonatory Sound Sources

Periodic

Involved in vocal fold vibration

Supraglottal Sound Source

Aperiodic

Involved in airflow obstructions (stops, fricatives, etc.)

Posterior Cricoarytenoid

Rotate arytenoids and separate vocal folds

Interarytenoid Muscles

Draws arytenoids together posteriorly and adducts vocal folds

Lateral Cricoarytenoid Muscles

Assists in adduction

Draws arytenoids forward and down