A general model for electrical interference is quite simple and very powerful.
Any interference problem is composed of 3 elements:
1) Source
2) Coupling path
3) Victim
If any of the 3 components are removed or hardened then the interference problem is resolved.
Contents
Sources
Sources are what generate the electrical noise that causes the interference.
Often noise is a high frequency phenomenon but not necessarily.
In actuality it is the rate of change, or fast, large edges that create the most problems.
A pulse of 1 V amplitude and 1 ns rise time has theoretically the same coupled amplitude as 100 V with 100 ns rise time.
Low frequency noise is also possible with certain coupling paths.
Coupling Paths
A coupling path is what allows the energy from the source get to the victim.
This includes electric field, magnetic field, EM waves, and common impedance.
Common impedance is when two different circuits share a conductor, coupling energy through its non-zero impedance (V = IZ). This is the only mechanism that can couple DC energy betwren circuits.
Victims
A victim is a circuit, typically a sensitive one, that cannot function correctly in the presence of the electrical interference.
Often this means analog systems such as audio or RF communication, but even digital systems are susceptible to strong interference.