Unless they feel the need to yell, they are probably interrupting a small number of people and not hundred plus people. The difference in the open floor plan is that at least they aren't entering the private space of another team. What we saw is that when each team is in their own little silo, people are reluctant to go invade another team's private space unless they knew the person very well. Inter-team knowledge sharing and collaboration really dropped.

While team silos create additional problems, obviously the hundred plus style open floor plans are still pretty horrible. The best approach I have seen is individual offices with shared collaboration areas nearby. People can do deep work by closing their office door. People can pair-program, have someone look over their code, have a private conversation etc. by going to another's office without disturbing everyone else. A shared collaboration area allows for quick easy group discussion when helpful.

in a 100 people room there will always be people walking around. what an open office does is to train people to ignore the noise around them (pity those that can't adjust). you'll see people walking by and you'll ignore them. in a team room, if someone enters, you know that it's for the team, and everyone will perk up to see what the 'intruder' wants.