In telecommunications, the term noise power has the following meanings: The measured total noise in a given bandwidth at the input or output of a device when the signal is not present; the integral of noise spectral density over the bandwidth. The power generated by a random electromagnetic process. Interfering and unwanted power in an electrical device or system. In the acceptance testing of radio transmitters, the mean power supplied to the antenna transmission line by a radio transmitter when loaded with noise having a Gaussian amplitude-vs.-frequency distribution.
Thermal noise power can be calculated by multiplying the noise spectral density with the signal bandwidth
where: is the Boltzmann constant ≈ is the absolute temperature of the device; and is the bandwidth.
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