The title given to this article is incorrect due to technical limitations. The correct title is dBrn.

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dBrn or dB(rn) is an abbreviation for decibels above reference noise.

Note 1: Weighted noise power in dB is referred to 1.0 picowatt. Thus, 0dBrn = -90 dBm. Use of 144 line, 144-receiver, or C-message weighting, or flat weighting, must be indicated in parentheses as required.

Note 2: 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 (rounded off to +88 dBrn), because of the frequency weighting.

Note 3: 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 frequency weighting.

Source: from Federal Standard 1037C and from MIL-STD-188