Differential lines are extensively used in high-speed digital circuits due to their ability to improve signal integrity by rejecting common-mode noise. However noise is injected into differential signals when there are irregularities in the signaling setup. These anomalies may be via transitions of differential lines through power planes in power distribution systems, via stubs, asymmetric lengths of differential lines, different transition points for each of the differential vias etc. This paper quantifies noise due to irregular differential structures in frequency domain. Presence of noise in differential signaling is verified through a set of test vehicles. The effect of signal to power coupling from differential lines on signal jitter is also investigated.