Dynamics of the Driving Force During the Normal Vocal Fold Vibration Cycle.
Philippe Henri DeJonckere, Jean Lebacq, Ingo R Titze
PMID 28495329WHAT IT FOUND
In one trained vocalist, computed pressure inside the vocal folds was higher while the folds opened than while they closed.
The pressure ratio between opening and closing rose with loudness up to about 76.5 dB, then fell.
Key findings
01In the selected recordings shown as examples, calculated intraglottal pressure during opening was higher than during closing, with the ratio near 1 at 58.92 dB and about 7 times larger at 76.84 dB.
02The opening-to-closing pressure ratio increased with loudness up to around 76.5 dB, then decreased at higher intensities.
03Closed quotient increased with intensity but reached a plateau at around 76 dB, and peak flow did not significantly change above that level.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
Only one trained vocalist was tested, so the pattern may not apply to other voices or to voice disorders. The intraglottal pressure was computed from glottal area and flow using Bernoulli assumptions, not measured directly inside the glottis. A fixed pressure loss coefficient was assumed, and the paper says it is not accurately known. Some recordings were rejected because the photoglottographic signal was too small. The task was a sustained vowel in a laboratory mask, not everyday speech. The study did not test an intervention or patient outcomes. The authors note likely interindividual differences in the critical intensity zone.
The easy way to misread this
Do not tell patients to aim for 76.6 dB as an optimal vocal intensity. The value came from one trained vocalist, and the paper did not test a voice treatment or patient outcomes.