Narrowing constrictions self-amplify until the lips slam shut and cut airflow

Evidence

Since airflow increases as it flows through the constriction, the force required to curve the airstream is greater, so the reduction in pressure is greater at the curved surface of the lips (vocal folds), and there is a greater force pulling them toward each other, so they accelerate toward each other. This process continues as the constriction narrows further, until finally they smack together, cutting off the airflow. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1241

Categorization

• QUESTION: This positive-feedback collapse-then-release cycle is the core of self-sustaining oscillation — worth tracing how it maps onto understanding why sustained tones feel effortful.
• XREF: connects to: Lip and vocal fold vibration is driven by Bernoulli pressure reduction from airflow — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1240

Broader Connections

• Lip and vocal fold vibration is driven by Bernoulli pressure reduction from airflow #expands (0.78) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1240