Vinyl is a hard surface, and for obvious reasons, the sound will 'bounce' off this surface, no matter how thick the Vinyl. I would recommend a heavier cloth drapery effect for a couple of these windows, so you can realize a small amount of acoustic room treatment...
Vinyl Blinds
Wondering if anyone here can tell me whether cheap vinyl blinds act as diffusors in a listening room. I'm renting a studio and there are many windows, all with vinyl blinds on them.