I have dedicated lines, but why is this happening?

When my central air kicks on, I hear a pop through each speaker.

Now the odd part is, I just started hearing this recently. I never remember hearing it for the first several months after I had the dedicated lines installed.

I have made several changes to my system recently that has taken the transparency of my system to a level I didn't think was possible, but I don't think that could explain why I am just now hearing the pops. Or could it?

But the primary question remains. Why is the air conditioning popping through my speakers when I have dedicated lines.

Could this be coming back through the main bus bar ground in my panel?

What would fix it?

I obviously know crap about this stuff.