# Are questions about physical applicability of noise models appropriate here?

I'd like to ask the following question:

Why are physical noise processes (e.g. Johnson noise from a resistor) frequently assumed to be Gaussian processes? It seems that the central limit theorem, which says that the sum of many random variables is Gaussian distributed, is not enough, because a Gaussian process not only has $x(t)$ Gaussian distributed for each $t$, but also has $x(t_1)$ and $x(t_2)$ jointly Gaussian for any $t_1$ and $t_2$.

Is this question appropriate for this site? I posted a version of it on Physics Stack Exchange but I'd like to know if the users here would welcome this type of question in the future.

• In my opinion, questions like that would be welcome. – MBaz Jun 28 '15 at 0:49
• i think it's appropriate. – robert bristow-johnson Sep 19 '16 at 23:23

Indeed, no actual signal or noise realization can be perfectly modeled by a particular distribution, for several reasons: discretized data, limited numbers of samples, the non-perfect behavior of the acquisition chain (nonlinearity, saturation, jitter) are common limits. For instance, the idea that an average of $n$ uncorrelated Gaussian noises reduce in amplitude as $1\sqrt{n}$ is greatly limited by quantization or rounded data.