Soundproofing Added to Shared Wall

When we tore out the plaster on the east wall of the sunroom (which seems like eons ago), we realized that our sunroom was separated from our neighbour's sunroom by just a 2x4 wall. In the photo below you can see the plaster poking through the lath on their side of the wall. This is obviously not great for protecting against sound or fire penetration.

I did not think to take "during" photos, so you'll have to just trust me on this one. In order to improve sound control on this wall, we installed sound control insulation between the existing studs. I then drywalled, taped and mudded the wall. Finally, I framed a new 2x4 wall on our side of this drywall.

When we're ready to finish the room, we will install more sound control insulation between these studs, and then install drywall. Who knows how much quieter this room will be, but at a cost of 4" of space, $50 of materials, and 2 hours of time, it was worth a try.