When the transfer function is measured in diaggui, several choice could be used for measurement. Especially, when performing FFT measurement, there is 'Gaussian' and 'uniform' noise to be chosen. I checked today what is the difference of them.

I used Diaggui to generate these two noise as shown in the first figure. Then the spectrum of them was measured and shown in attached figure 2.

The conclusion is that both of them are white noise. But the 'Gaussian' noise is about twice the amplitude of 'uniform'.