Noise in Electronics Noise is present in all electronic circuits. In electronics the term noise can be applied to anything that obscures the desired signal. The 50 Hz interference noise from power supplies and ground paths is very common. It sounds like a low hum or e.g. generates horizontal moving bars to the TV picture. As an example all resistors generate noise voltage across its terminals called Johnson noise.
White noise is completely uncorrelated from point to point.
It has equal energy in each octave, whereas white noise has equal energy for any given bandwidth. The frequency response of pink noise drops with frequency - lower frequencies have more energy than higher frequencies. Pink noise sounds softer, less harsh than white noise, a little bit like a low hiss. It is usually artificially generated by low-pass filtering white noise. Pink noise is often used in audio measurements as a test signal.