We've lived in this house for over a year, and this issue started just over a week ago.
When the AC is running, we have an intermittent bass pulsing, roughly every 3-4 seconds. The AC cools great (it's 95 during the day and can cool to 73 with no issues); it's just loud and getting louder.

It doesn't seem to do it during the day; just in the evening. It's most noticeable in the bedroom (of course), and it makes it hard to even be in the room because it's just a constant bass noise. Like those neighbors you hate that throw parties at night, but only inside the walls.

Some basic research has shown that it could be the TXV regulating the flow of the refrigerant.
My thought is that maybe the evap coil needs more refrigerant to cool during the hot day so the TXV is open more, and it needs less refrigerant to cool in the cooler evening, so it closes more and the condenser 'queues up' when giving it refrigerant, hence the pulsing?
If that's the case, if the noise just recently started, is that indicative of a dying TXV?

I've also read about the refrigerant lines not being properly insulated. Rubbing on the walls and transferring the sound, etc. It all looks good upon inspection, but within the last 2 weeks, I've trapped and removed 2 raccoons from my attic. We could hear them thumping around, etc, but from what I can see, did not cause any real damage. Possible that they chewed up the insulation within the walls, etc?

It's worth noting that this is a rental house, so we have limited say in what can be done. I cannot do much to the house myself, as we don't own it, but I'd like to at least research and have a strong case for what the issue might be before I relay it to the landlord. The last thing I want to do is make waves when the lease renewal is coming up.