1. The calculated or measured noise power, within the bandwidth being used, at the receive end of a circuit, channel, link, or system.
2. The absolute power of the noise measured or calculated at a receive point.
Note: The related bandwidth and the noise weighting must also be specified.
3. The value of noise power, from all sources, measured at the line terminals of telephone set's receiver.
Note: Either flat weighting or some other specific amplitude-frequency characteristic or noise weighting characteristic must be associated with the measurement.
Source: from Federal Standard 1037C and from MIL-STD-188