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ARCHITECTURAL, ACOUSTICS
317
lation tests the writer has conducted in a small room in which the percentage articulation increased as the time of reverberation was reduced from 1.0 to .60 seconds.
It is now possible, from the upper curve in Fig. U, to derive kr, the reduction factor owing to reverberation, for times of reverberation between .5 and 8.0 seconds. The value of kr is taken as unity for a time of reverberation of .5 second. The value of kr for any other time of reverberation is the ratio of the articulation at that time to the articulation for a time of .5 second. The curve in Fig. 5 gives the value of kr, obtained in
1.0 • d ■ 6 4\
^
I ix,_ . .
— — i i i i i i r
1.0 2.0 3.0 6.0 5.0 6.0 70 8.0 9.0
Rei/erberot /on Seconds
FIGURE 5.
Curve giving the reverberation reduction factor kr for different times of reverberation.
this manner, for different times of reverberation. It will be noted that kr decreases almost uniformly as the time of reverberation increases from 1.0 to 6.0 seconds. Above 6.0 seconds the rate of decrease of kr appears to be less rapid.
The deviations of the observed points from the smooth curve in Fig. U can be accounted for by such factors as the shape of the rooms, the variation in reverberation for tones of different pitch, and the distribution of absorptive materials in the rooms. Time will not permit us to enter into a discussion of these factors, although it may be stated that these various factors do not seem to produce a very marked effect upon articulation. In