Fonasjon

Fonasjon, or phonation, is the process by which the vocal folds in the larynx vibrate to convert a stream of exhaled air into audible sound. During phonation, the glottis—the opening between the vocal folds—alternates between closure and separation as the airflow from the lungs builds subglottal pressure. The interaction of airflow and the vocal fold tissue produces a periodic vibration, often described as a mucosal wave, which shapes the sound that becomes voice and speech.

Anatomy and mechanism: The larynx contains the true vocal folds, arytenoid and cricoid cartilages, and intrinsic muscles such as the cricothyroid and thyroarytenoid. The tension, length, and mass of the vocal folds are adjusted by these muscles, allowing changes in pitch (fundamental frequency), loudness (via subglottal pressure and degree of vocal fold closure), and timbre. The glottal configuration and closing pattern influence voice quality.

Phonation types and quality: Normal conversational speech typically uses modal phonation. Other voice qualities include creaky voice (low, irregular F0 with a tense vocal fold configuration), breathy voice (incomplete glottal closure with more air leakage), and pressed voice (tense, tightly closed folds). Whispering eliminates vocal fold vibration, resulting in no phonation.

Measurement and clinical relevance: Phonation can be described by metrics such as fundamental frequency, intensity, and spectral characteristics. Instrumental methods (eg, electroglottography, high-speed imaging) aid in assessing vocal fold function. Phonation is central to voice production in speech and singing, and disturbances can indicate or contribute to voice disorders or laryngeal pathology.