Stuck with demonstrating effect of output impedance from EMI in SPICE simulation
There are two main near field coupling mechanisms for interference, inductive (magnetic field) or capacitative (electric field).
You can simulate the capacitative interaction by putting a mother ac source in your simulation coupled into the junction of the source and destination.
The actual value of the capacitance will depend upon the frequencies you wish to simulate. It should be low enough value that most of the source voltage is dropped across the capacitor.  You will find that as the source impedance increases the amount of interference increases.
For magnetic field coupling you can use a transformer driven by your noise source and rather than in parallel, you put the secondary in series between the signal source and the load - you will find that the interference either is not affected by the source impedance or is worse at low impedances.