The symbol dBrn or dB(rn) is an abbreviation for
decibelsabove reference noise.
With C-message weighting, a one-
milliwatt, 1000 Hz tone will read +90 dBrn, but the same power as white noise, randomly distributed over a 3 kHz band will read approximately +88.5 dBrn, because of the frequencyweighting.
With 144 weightings, a one milliwatt, 1000 Hz white noise tone will also read +90 dBrn, but the same 3 kHz power will only read +82 dBrn, because of the different
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