And sometimes electrical noise is a desirable trait as in pink and white noise generators used to output wide spectrum audio signals to measure frequency response of circuits or components, or as when wanting a hardware noise generator to be used as a source of random number generators.
All electrical circuits and components generate noise to some degree just by the energy of electron movement. One does not eliminate electrical noise, but one can manage it in a circuit such that it does not effect the desired function(s) of the device or circuit.
http://en.wikipedia.org/wiki/Johnson%E2%80%93Nyquist_noise
Lefty