The open office was supposed to spark collaboration, more talking, more ideas bouncing around. What actually happens is the average person gets pulled out of focus dozens of times a day, and each time it takes a few minutes to get back in.
The brain isn't great at tuning out a voice in the background or motion at the edge of your vision. Headphones alone don't fully fix it, because your eyes are still catching the movement even when your ears aren't.
What actually helps isn't changing the room, it's building a consistent layer of sound. Starting work with the same sound every time tells your brain it's focus time now, no matter how loud the office gets.