Which parameter is determined by the rate at which air passes between the vocal folds during phonation?

• A. Subglottal pressure (Psub)
• B. Phonation threshold pressure (PTP)
• C. S/z ratio
• D. Average airflow rate

Answer: (D)

Airflow through the glottis during phonation is the average airflow rate—the amount of air passing per unit time as the vocal folds vibrate. The speed and duration of air passage set how much air leaves the lungs each second, which is exactly what this measure captures. Subglottal pressure is the driving force behind that flow, influencing how much air can pass but not itself quantifying the flow. Phonation threshold pressure is the minimum pressure needed to start phonation, not the ongoing flow rate. The S/z ratio relates to voice quality and articulation, not the actual glottal air passage.