Curtains do damp office noise

One of our offices has no curtains (yet). The others do. I went from one office to the other, a couple of minutes ago and I immediately noticed the difference in sound. Both offices have parquetry and a light carpet on the floor. They have similar furniture. The main difference is the absence of a wall-wide curtain in that one office. And that gives a clear difference in echo and surround noise. My advice to office architects? Textile !