Adduction
Quick Definition
The medial movement of the vocal folds toward midline, creating the closure pattern necessary for phonation.
Factual Definition
The approximation of the vocal folds controlled primarily by the lateral cricoarytenoid and interarytenoid muscles, quantified by parameters including prephonatory glottal width, inter-vocal fold contact area, and the adduction quotient (Jiang & Titze, 1993).
Full Explanation
Adduction is the process by which the vocal folds come together to create the closure necessary for phonation. The degree of adduction is controlled primarily by the lateral cricoarytenoid (LCA) muscle, which rotates the arytenoid cartilages to bring the vocal processes together, and the interarytenoid muscles, which approximate the posterior portions of the arytenoids (Hirano, 1975).
The relationship between adduction and phonation is complex. Titze (1988) demonstrated that the primary purpose of vocal fold approximation is to lower phonation threshold pressure to initiate vibration. However, adduction alone does not guarantee glottal closure during phonation; the interaction between fold stiffness, geometry, and subglottic pressure also determines the actual closure pattern (Zhang, 2016).
Critically, the degree of adduction interacts with vocal tract inertance. When supraglottal inertive reactance is high (as in semi-occluded vocal tract exercises), it provides a ‘push-pull’ mechanism that assists fold closure during the closing phase of vibration, reducing the adductory effort required from the laryngeal muscles (Titze, 2006). This interaction explains why exercises like straw phonation can help singers find more efficient adduction patterns.
Too little adduction results in breathiness as air escapes through incompletely closed folds. Excessive adduction produces pressed voice with extended closed quotient and elevated phonation threshold pressure. The optimal balance produces efficient phonation with minimal effort.