A systematic study of power‐law decays in reverberation rooms

A space‐ensemble average decay curve {〈S2(t)〉}NO, obtained in a reverberation room, shows a smooth but notable curvature at low frequencies, implying a lack of diffusion. It is closely approximated by L(t), the theoretical curve for power‐law decays given by Schroeder [5th ICA, paper G31 (1965)], and can be quantitatively characterized by only two parameters for L(t), i.e., by T0 (initial decay time) and Q30 (curvature index). This allows a quantitative evaluation of the diffusion condition in the decay process, always relating it to the absorption coefficient (αrev) evaluated from the identical {〈S2(t)〉}NO. The validity of {〈S2(t)〉}NO has been verified by its application in the design of a large‐scale reverberation room (570 m3) provided with a huge rotating vane (6 m in diameter) on the ceiling. A large contribution of the vane to the linearization of {〈S2(t)〉}NO, and hence, to the increase in measured αrev has been clearly established after the construction. Theoretical analysis of the effectiveness of...