Crown Molding and Textured Ceiling

I have a unique situation. I am trying to figure out something that I can put in place of drywall walls in order to close in my staircase. I have bought a home with an inlaw suite for my parents and we all use the same entry door. They then go into the apartment downstairs by another door and we walk up the stairs. I want to build a door at the top of the stairs and therefore close in a half wall that is on the one side (finishing off my living room). There is a large window that I would love to be able to still benefit from its light and I want something that would maybe keep out a little more noise than having nothing there. I could install a drywall wall although it would be hard to reach as its cathedral-like and I still want the light. I cannot find anything that I can install between the ceiling and the half wall except maybe a shoji screen which wouldnt save any noise. And as I'm sure everyone else is..I am working on a budget! Please help!!

Hi everyone hope all is well.. My situation is.. I will be having a 4" duct pass through interior drywall and exterior particle board. I will need to cut drywall and particle board so the duct pass through. I've read some previous posts and I think I want to make the cut with a keyhole saw (does anyone agree?) My question is.. what is used to seal the duct and walls? Chalking? :confused: Do I need different sealers for drywall and particle board? Any suggestions would be greatly appreciated. Beer 4U2