What it is
Normalized Amplitude Quotient. It describes how efficiently the glottis — the opening between the folds — completes one open-close cycle per vibration: closing too tightly is pressed phonation, failing to close is leaky phonation, and between the two lies an efficient zone.
NAQ normalizes “the air volume flowing through the glottis per cycle” by “the slope of glottal closing”, yielding a quantity comparable across pitches.
Where it comes from
Estimated by inverse-filtering the audio signal to recover the glottal volume-velocity waveform, then measuring on that waveform.
It is the one parameter invisible on the spectrum that still decides pressed versus leaky.
How to read it
A low NAQ leans pressed (folds clamped too hard, a tight timbre); a high NAQ leans leaky (incomplete closure, a hollow timbre); inside the middle channel the folds do maximum work at minimum air pressure.
The Airflow Balance chart plots the NAQ-versus-pitch trajectory inside that “high-efficiency channel”.
Where it is used
Phonation Balance — Shared edge · closure efficiency feeds this composite score, not just the airflow face.
Airflow Balance — Shared edge · defines the efficient channel: NAQ separates pressed, flow and leaky phonation.