Subglottic pressure (Psub) and Phonation Threshold Pressure (PTP) influence both the initiation and maintenance of phonation, provided the vocal cords are adducted and close to the median line of the glottis.
Depending on the levels of adduction, vocal cord tension, and pressures (Psub and PTP), three main types of glottic vocal onsets can be identified:
Hard Onset: Characterized by a high degree of adduction and tension in the vocal cords, as well as high Psub and PTP. When the airflow manages to separate the vocal cords, the sound is released abruptly and acoustically perceived as a "burst." This type of onset creates impact stress on the cords.
Breathy Onset: Air is expelled while the vocal cords are in an open position and gradually approach the median line until the vibratory cycle is triggered. Just before the sound becomes perceptible, a noise or turbulence is heard, resembling an aspirated /h/. When used exclusively and persistently, this pattern can lead to hypofunction.
Soft Onset: Sound is produced at the exact moment air passes through the glottis, initiating the vibratory cycle with all systems in full balance. The sound emerges smoothly, cleanly, and ergonomically.
The assistance of an osteopath in removing rigidity in phonation onset patterns and/or improving glottic competence is a valuable aid in speech therapy.
Valentina Carlile - Osteopath specializing in Osteopathy for Voice and Speech Disorders since 2002. For information and bookings, visit the Contact page.
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