Hoarseness, medically known as dysphonia, is a common change in voice quality that signals a problem with the vocal apparatus. The resulting sound is often characterized by a rough or strained texture, or an excessive breathy quality.
Defining the Acoustic Qualities of Hoarseness
Voice specialists commonly break down the perception of hoarseness into three primary acoustic components: roughness, breathiness, and strain.
Roughness describes a perceived irregularity in the vocal sound, often giving the voice a raspy, gravelly, or harsh texture. This quality arises from non-periodic, erratic changes in the frequency and amplitude of the vocal fold vibration.
Breathiness refers to the audible escape of air during speech, making the voice sound weak, airy, or whispery. This occurs when the vocal folds fail to close completely during phonation, allowing air to leak through the gap.
Strain is the perception that the speaker is using excessive effort or tension to produce the voice. Listeners perceive this as a tight, squeezed, or effortful quality in the sound. This component is typically associated with muscle tension, where the laryngeal muscles are hyperactive, causing the vocal folds to press together too tightly.
The Physical Cause of the Sound
The hoarse sound originates in the larynx, or voice box, where two bands of tissue known as the vocal folds produce sound. Normally, these folds meet in the midline and vibrate in a smooth, wave-like, and periodic pattern when air from the lungs passes over them.
Hoarseness occurs when the vocal folds are prevented from achieving this smooth, symmetrical, and complete closure. Conditions like laryngitis, which is inflammation of the vocal folds, cause swelling that makes the folds stiff and heavy. This alters their ability to vibrate consistently, leading to the erratic sound waves perceived as roughness.
Irregular vibration can also be caused by masses like vocal nodules, polyps, or cysts that form on the folds. These growths prevent a full closure, creating an asymmetrical vibration pattern and a persistent gap. The incomplete closure allows air to leak, resulting in the breathy quality, while the mass itself disrupts the normal vibratory cycle, causing roughness.
Vocal fold paralysis, often due to nerve damage, can also lead to hoarseness because one or both folds fail to move properly. If a fold is paralyzed in an open position, the gap is wide, causing excessive air escape and a severely breathy and weak voice.
Differentiating Hoarseness from Other Voice Changes
Hoarseness is fundamentally different from aphonia, which represents a complete or near-complete loss of the voice, reducing it to a whisper.
While hoarseness involves a change in the quality of the voice, a simple pitch change only involves an alteration in the vocal frequency. For example, severe laryngitis often lowers the voice pitch due to swelling, but the defining characteristic remains the rough, noisy quality of the sound, not just the lower frequency. A temporary shift in pitch without accompanying roughness is not classified as hoarseness.
Vocal fatigue is another distinct condition, describing a feeling that the voice tires easily and requires significant effort to maintain. While fatigue can occur alongside hoarseness, it is primarily a sensation of muscular exhaustion in the throat after speaking. Hoarseness, by contrast, is an objective change in the audible sound quality, even if the speaker is not feeling tired.