The dB Above Reference Noise (dBrn) specification is a characteristic value for the level that lies above the weighted noise power. This refers to 1.0 picowatt (pW), which corresponds to a dBm value of -90 dBm
. Weighting plays a role in the dBrn value. According to Decibel Filter (C) weighting (dB(C)), a 1,000 hertz tone with a power of 1 mW has a dBrn value of +90 dBrn. The same power as white noise distributed over a bandwidth of 3 kHz gives 88.5 dBrn because of the frequency weighting.