Formula for the RMS noise voltage:

Vn =sqrt( 4 * kB * T *If *R )

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);

Absolute temperature in kelvin T = 273.15

Bandwidth being considered .If = f2 - f1 = fmax - fmin in Hz; 20 kHz - 20 Hz = 19980 Hz。