Weighted geometric means of absorption coefficients let reverberation equations handle mixed materials

Evidence

Because there are only a finite number of different materials in the room, but of differing areas, it is necessary only to consider an average based on just the number of different materials but weighted to allow for their dif­ fering surface areas. Because logarithms convert products to additions, this weighted geometric mean can be simply expressed as a sum of the indi­ vidual absorption terms and so the Norris-Eyring reverberation time equa­ tion can be rewritten in a modified form, which allows for the variation in material absorption due to both nature and frequency, as: Equation A5. — David Howard, Jamie Angus, coustics and Psychoacoustics, 2847

Categorization

• DEFINE: Explains the Millington-Sette equation as the log-transform of weighted geometric mean over surface areas.