Foundations of Speech and Language Development · 4 min read
Phonation
Section Overview
The Foundations of Speech and Language Development section comprises approximately 25% of the Praxis 5881 exam, consisting of roughly 30 selected-response questions. This section assesses your understanding of how speech and language develop in children, the anatomical and physiological structures involved in speech production, and the various disorders that can affect communication. Mastery of this content area requires knowledge of normal developmental milestones, the mechanics of speech production, and the characteristics of common speech and language disorders.
Understanding Phonation
Phonation refers to the production of sound by the vibration of the vocal folds (also called vocal cords) located within the larynx. The larynx, commonly known as the voice box, sits at the top of the trachea and houses the vocal folds. When air from the lungs passes through the larynx, it causes the vocal folds to vibrate, producing sound. This sound is then modified by the resonating chambers of the throat, mouth, and nasal cavities to create speech.
Anatomy of the Phonatory System
The phonatory system consists of several key structures:
The larynx is a cartilaginous structure composed of the thyroid cartilage (the largest, forming the Adam's apple), the cricoid cartilage (a complete ring below the thyroid cartilage), the arytenoid cartilages (two small pyramidal cartilages that control vocal fold movement), the epiglottis (a leaf-shaped cartilage that protects the airway during swallowing), and the corniculate and cuneiform cartilages (small cartilages that support the aryepiglottic folds).
The vocal folds are two bands of muscle tissue covered by mucous membrane that stretch horizontally across the larynx. They attach anteriorly to the thyroid cartilage and posteriorly to the arytenoid cartilages. The space between the vocal folds is called the glottis.
The Process of Phonation
Phonation occurs through a complex process called the myoelastic-aerodynamic theory. First, the vocal folds are brought together (adducted) by the intrinsic muscles of the larynx. Air pressure builds up below the closed vocal folds (subglottal pressure). When subglottal pressure exceeds the resistance of the closed vocal folds, air bursts through, causing the folds to separate. The elastic properties of the vocal folds, combined with the Bernoulli effect (which creates negative pressure as air flows rapidly through the glottis), cause the folds to snap back together. This cycle repeats rapidly, creating a series of air pulses that we perceive as sound.
Parameters of Voice
Voice has three primary characteristics:
Pitch is the perceptual correlate of frequency, determined by how many times per second the vocal folds vibrate. Higher frequency equals higher pitch. Factors affecting pitch include the length, mass, and tension of the vocal folds. Adult males typically have a fundamental frequency of 100-150 Hz, while adult females typically have a fundamental frequency of 180-250 Hz. Children have higher fundamental frequencies due to smaller vocal folds.
Loudness is the perceptual correlate of intensity, determined by the amplitude of vocal fold vibration and subglottal pressure. Greater subglottal pressure and larger amplitude of vibration result in louder voice.
Quality refers to the distinctive characteristics of a voice that make it unique. Voice quality is affected by the pattern of vocal fold vibration, resonance characteristics, and any irregularities in the phonatory system.
Voice Disorders Related to Phonation
Voice disorders occur when voice quality, pitch, loudness, or flexibility differs from voices of others of similar age, sex, and cultural background. Common phonation-related voice disorders include:
Vocal nodules are bilateral callous-like growths on the vocal folds, typically at the junction of the anterior one-third and posterior two-thirds. They result from chronic vocal abuse and misuse. Symptoms include hoarseness, breathiness, and reduced pitch range. Treatment involves voice therapy to eliminate abusive behaviors, with surgery rarely necessary.
Vocal polyps are soft, fluid-filled lesions that typically occur unilaterally on the vocal fold. They may result from a single traumatic event or chronic irritation. Symptoms are similar to nodules but may be more severe. Treatment often involves surgical removal followed by voice therapy.
Laryngitis is inflammation of the larynx that causes temporary voice changes. Acute laryngitis results from viral infection, vocal strain, or irritants. Chronic laryngitis may result from ongoing irritation such as gastroesophageal reflux disease (GERD), smoking, or environmental factors.
Vocal fold paralysis occurs when one or both vocal folds cannot move due to nerve damage. Unilateral paralysis affects one fold and may cause breathiness and reduced loudness. Bilateral paralysis affects both folds and can cause airway obstruction. Causes include surgical trauma, tumors, stroke, and viral infections.
Spasmodic dysphonia is a neurological voice disorder characterized by involuntary spasms of the laryngeal muscles. Adductor spasmodic dysphonia causes strained, strangled voice quality. Abductor spasmodic dysphonia causes breathy voice breaks. Treatment includes botulinum toxin injections and voice therapy.
Phonation in Children
Children's phonatory systems differ from adults in several ways. The infant larynx is positioned higher in the neck than the adult larynx. Vocal folds are proportionally shorter and thinner. The larynx descends during the first years of life, contributing to changes in voice pitch. Voice changes during puberty are more dramatic in males due to greater laryngeal growth.
Teachers should be alert to signs of voice problems in children, including persistent hoarseness lasting more than two weeks, frequent voice loss, strain or effort during speaking, pitch breaks or inappropriate pitch, and complaints of throat pain or fatigue when speaking.
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