Below 0.3 average absorption, Sabine’s simpler equation is accurate enough.

Evidence

Equation 6.21 is also known as the “Millington-Sette equation.” Although Equation 6.21 can be used irrespective of the absorption level, it is still more complicated than the Sabine equation and, if the average absorption coefficient is less than 0.3, it can be approximated very effectively by it, as discussed previously. Thus in many contexts, the Sabine equation, Equation 6.20, is preferred. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1894

Categorization

• DEFINE: Names the Millington-Sette equation and states its relation to the Sabine equation.
• SEED: Angle: engineered approximations and thresholds — how a numeric cutoff (0.3) licenses practitioners to ignore theoretical rigor.