A quantitative representation in resistance units of the spectral density of a noise-voltage generator, given by Rn = (Wn) / (kT0,) where Wn is the spectral density, k is Boltzmann's constant, T0 is the standard noise temperature (290 K,) and kT0 = 4. 00 × 10-21 watt-seconds. Note: The equivalent noise resistance in terms of the mean-square noise-generator voltage, e2, within a frequency increment, f, is given by Rn = e2/ (4kT0f. )