Each mechanism can put either type of noise into some portion of an electronic system. Any pair of traces or wires on a PCB, IC, or cable assembly can experience two types of noise: common mode and differential mode noise. Common mode noise will have the same magnitude and polarity on each side of the interconnect, while differential mode noise has opposite polarity. Note that we haven’t considered intrinsic random noise sources like Johnson noise, which does not need an external source. http://www.softmagneticmaterials.com/