If I understand the way the snake renders it's oil in an AFCI they are looking for current spikes, not voltage spikes, that is why I would start with a scope and a current probe.
Triplen harmonics are not really noise, they are very regular beat frequency waves within the base wave that get superimposed on it.
You can certainly start easter egging around throwing anti-noise hardware at the problem but at a certain point you may need to take a look at what is really happening.
If this is not one of the new breakers that has indicators of whether they tripped on an arc or a ground fault, I would eliminate the possibility of this being a ground fault problem first.
