Millington-Sette Equation

The Millington-Sette equation is a reverberation time prediction formula that sums the absorption contribution of each surface independently using natural logarithms, rather than averaging the absorption coefficient across all surfaces as in the Eyring equation. Published by Millington (1932) and Sette (1933), it is considered more appropriate for rooms with a mix of highly absorptive and highly reflective surfaces. The equation prevents the mathematical error that occurs in the Eyring equation when the average absorption coefficient approaches 1.0 in rooms with some fully absorptive surfaces. However, the Millington-Sette equation can underestimate reverberation time because it overweights highly absorptive surfaces. It is most useful as a lower-bound estimate complementing the Sabine equation as an upper bound, with the true value typically falling between the two predictions.