Equivalent noise resistance

In telecommunication, an equivalent noise resistance is a quantitative representation in resistance units of the spectral density of a noise-voltage generator, given by R _n = (πW _n)/(kT ₀), where W _n is the spectral density, k is Boltzmann's constant, T ₀ is the standard noise temperature (290 K), and kT ₀ = 4.00 × 10^-21 watt-seconds.

Note: The equivalent noise resistance in terms of the mean-square noise-generator voltage, e ², within a frequency increment, Δf , is given by R _n = e ²/(4kT ₀Δf ).

Source: from Federal Standard 1037C