Logarithms convert weighted geometric means into simple absorption sums

Evidence

Because logarithms convert products to additions, this weighted geometric mean can be simply expressed as a sum of the individual absorption terms, and so the Norris-Eyring reverberation time equation 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 M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2860