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Onset Delay

Onset delay is the phenomenon of slight delay from the moment of intended phonation until sound actually commences. Often there is a faint hiss of air heard before the start of vocal cord vibration.

Basic Vibratory Blur Example: Photo 2 Is What to Study…

This young singer is struggling with loss of vocal strength and phonatory onset delays. She has been resting her voice for several weeks after a long illness with laryngitis.

After evaluation, it appears that the primary issue is deconditioning and the onset delays are due to gap between the cords, rather than margin swellings.

By studying photo 2 below, one can see that when the examiner pays attention to vibratory blur, the stroboscopy findings are previewed and analysis of the vibratory blur can even predict the findings of the subsequent stroboscopy.

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vocal folds are seen just before phonation begins

Continuous Light — Pre-phonatory Instant (1 of 4)

Under continuous illumination, the vocal folds are seen just before phonation begins. The phonatory airstream is about to initiate vibration. Because there is no vibration here, the cord margins are sharp. The next image will reveal the vibratory blur that occurs once vibration starts. This frame captures the baseline configuration immediately prior to oscillation.
With phonation, the characteristic vibratory blur appears as a thin grey blur band

Continuous Light — Vibratory Blur Appears with Voicing (2 of 4)

With phonation, the characteristic vibratory blur appears as a thin grey blur band. It is similar in width bilaterally, suggesting symmetrical vibration. Importantly, the black line between the cords remains visible; it is not completely obliterated by the blur. This predicts an incomplete closed phase during the vibratory cycle.
open phase approximately equals the combined lateral extent of the gray blur bands

Stroboscopic Light Validates Blur Predictions — Open Phase (3 of 4)

Under stroboscopic illumination the distance between the vocal fold margins in open phase approximately equals the combined lateral extent of the gray blur bands observed in Photo 2 under continuous light. In other words, if one mentally replaces the grey blur bands with black space, effectively expanding the glottal gap to include the blur bands, the resulting distance between the revisualized vocal cords approximates the actual separation in this stroboscopic image of the open phase of vibration. This confirms that the lateral extent of the vibratory blur represents the lateral excursion of the vocal cord margins during vibration—as seen under strobe light.
persistent black gap between the cords

Stroboscopic Light — Closed Phase (4 of 4)

During this closed phase image, a persistent black gap between the cords confirms that the cords do not make complete contact during the vibratory cycle. The stroboscopic image therefore validates the prediction from photo 2 that the closed phase of vibration is incomplete.

Key Words: Vibratory Blur, vibration, open phase, closed phase, stroboscopy

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