โ Scribed by Giuliana Benedetto; Renato Spagnolo
No coin nor oath required. For personal study only.
Standardized methods for the measurement of the sound absorption coefficient, or, of materials in a reverberant room use well known relations between ~ and the reverberation time of the room. Actually, these relations are correct only in rooms with high diffusion at low โข values and for uniform distribution of the absorption on the surfaces. The introduction of acoustic materials with high ~ values concentrated on only one surface, as recommended by standards, causes a derandomization of the sound field, which may overcome the "randomization strength' of the enclosure and therefore make the use of traditional formulae incorrect. This paper proposes a computer-ray tracing model, which enables these phenomena to be described, and operatively defines the 'randomization strength' of room design. Lastly, an alternative approach is suggested for evaluating the sound absorption coefficient, based on the characterization of the reverberant room by its own "calibration curve'.
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## It has not yet been established if stationary diffusers are effective in the measurement of the sound absorption coefficients of materials in a reverberation room. Although the results of such measurements may be strongly influenced by the use of diffusers, the conditions under which diffusing
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