Page 176 - Master Handbook of Acoustics

FIGURE 9-3 The nonexponential form of this decay is attributed to acoustically coupled spaces. The
absence of a diffuse sound field is indicated.

Spatial Uniformity of Reverberation Time

When reverberation time for a given frequency is reported, it is most accurately stated as the average
of multiple observations at each of several positions in the room. This accounts for the fact that
reverberatory conditions differ from place to place in the room. Figure 9-4 shows the results of

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measurements in a video studio of 22,000-ft volume. The multiple uses of the space require variable
reverberation time, which is accomplished by hinged wall panels that can be closed, revealing
absorbent sides, or opened, revealing reflecting sides. Multiple reverberation decays were recorded
at the same three microphone positions for both “panels-reflective” and “panels-absorptive”
conditions. The open and filled circles show the average values for the reflective and absorptive
conditions, respectively, and the solid, dashed, and dotted lines represent the average reverberation

time at each of the three microphone positions. It is evident that there is considerable variation, which