What is dBrnC0 and what is ICN?
ICN is Idle Channel Noise, or the noise present in a circuit output with no input signal present. [Or when a PCM zero code is received.] It is usually measured through the C-, or Psophometric, weighting curves and referenced to either the 0TLP or to 90 dB below 0TLP (1 picowatt.) Using the North American technique, an expected value of ICN might be 11 dBrnC0. This is explained as being 11 dB greater than –90 dB reference noise when measured through a C-Message weighting filter referenced to 0TLP.
