If you have digital signals, you have switching and switching transients. Those transients may be coupled to other circuits.
Roughly speaking, the energy in a transient depends on the transient's transition time and the change in voltage/current. So to minimise transient energy, have a balanced signal and maximise the transition time. The latter is one reason many ADCs/DACs have two outputs, one the inverse of the other.
The power in the transients can be measured over many transient periods (e.g. clock cycles), and is proportional to the frequency at which the transients occur. The power may or may not be relevant in your system.
Depending on your system, it may be possible to avoid transients during a measurement period and have the transients when no measurements are being made.