Formula for the RMS noise voltage:

Vn =sqrt( 4 * kB * T *If *R )
where,
Lu in dBu has the reference voltage V0 = 0.7746
and LV in dBV has the reference voltage V0 = 1 V
Boltzmann constant k_B = 1.3806505*10^-23 J/K (joule/kelvin); J=W·s
Absolute temperature in kelvin T = 273.15
Bandwidth being considered .If = f2 - f1 = fmax - fmin in Hz; 20 kHz - 20 Hz = 19980 Hz
Resistance of the circuit element R.
R does not mean the universal gas constant!

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