The dimensions of the area are roughly 12 x 16 1/2 but the rear of it opens to basically the whole rest of the house - both up and downstairs. Therefore, I'm not even going to attempt to do anything acoustically like I've done in the past. One, I think it would be mostly futile, two, my neighbor's house is about 15 feet away from that window wall so I can't get too crazy with the sound no matter what I do and, three, I want to be able to easily revert this area to "normal" use if I need to when I sell the house.
So, the first order of business is that window. The plan is to build a false wall right in front of it. This will do a couple of things for me. It will seal off the light from the window and it will give me at least some both extra sound barrier to next door and absorption possibility for the room itself.
First, a little cover up for the window itself.
I tacked a sheet up first just to protect the blinds and frame from the stuff I put next which is some left over 2" OC 703. Then, a couple of moving pads over that.
The false wall itself will be framed basically "friction-fit" into the area - right on top of the carpet.
It goes right against the existing baseboard so I need a little spacer block in the top corners.
Now, just a few screws in the corners and the whole wall will be easily removable with minimal patches required.