Larson Davis 831, User Manual

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Model 831 Manual 1/1 and 1/3 Octave Filters A-29
Minimum Residual Filter Decay Time for RT 60 (option 831-RT)
Table A-21 on page A-26 shows the residual decay time (TR) and the bandwidth-time product (BT)
for each of the filters on the Model 831. This data was taken by feeding the output of the internal pink
noise source into the input of the Model 831 using a CBL09x. The residual decay time for each
frequency is the T30 of the ensemble average of 50 decays.
Table A-22 Residual Decay Times
Pink Noise Generator Levels
Pink Noise Generator Levels are pseudo-random, uncorrelated, and produced by digital algorithm.
Frequency
1/3 Octave 1/1 Octave
TR (ms) BT TR (ms) BT
50.0 Hz 378 4.37
63.0 Hz 301 4.38 160 7.12
80.0 Hz 216 3.96
100 Hz 181 4.18
125 Hz 153 4.43 86 7.63
160 Hz 119 4.34
200 Hz 94 4.32
250 Hz 75 4.36 40 7.10
315 Hz 55 4.04
400 Hz 43 3.93
500 Hz 37 4.26 16 5.62
630 Hz 29 4.18
800 Hz 24 4.44
1000 Hz 13 3.11 8 5.56
1250 Hz 17 4.97
1600 Hz 16 5.85
2000 Hz 12 5.38 6 8.87
2500 Hz 11 6.30
3150 Hz 11 6.30
4000 Hz 10 9.45 5 13.63
5000 Hz 8 9.42
6300 Hz 5 7.27
800 Hz 10 18.69 5 28.50
10000 Hz 7 17.05