Electrical noise
Johnson noise
Also known as resistor noise. Johnson noise is temperature dependent, it appears everywhere in nature where there is a dissipative element. It is caused by the fluctuation dissipation theorem, it also appears in (small scale) mechanical systems. If there is a damper you get automatically this sort of noise. The resistor noise has a Gaussian distribution function. It is white noise, which means it is equally distributed over all frequencies.
A solution to attenuate it is to keep resistor values as small as possible. Other options are lowering the bandwidth or temperature.
Shot noise
Also called current noise. Shot noise is caused by a barrier, as particles come in discrete parts instead of a continuous stream. This means this electrical noise type occurs only when the charges arrive independently. In many cases the particles are not independent. Electrons in a metal wire for example feel each other, if one of them moves it drags the others along. Shot noise for example occurs in a Pn junction, vacuum, electron tube, diode or transistor diode. In simple resistor circuits this current noise does not show up.
The solution to make shot noise less dominant is to increase the current.
Flicker noise
Also known as excess noise or 1/f noise. This is all noise which is not due to Johnson noise, thermal fluctuations or shot noise. It is caused by imperfections of the system. Flicker noise is frequency dependent, while Johnson noise and shot noise are in their intensity not frequency dependent. The intensity decreases with increasing frequency.
The solution is to move up in frequency to a range where excess noise is small.