Most large companies have converted their work area for employees to have an open floor plan. The purpose of this is not to take away your privacy but to allow more natural light into the office from the outside windows and also promotes a more unified work environment. So the days of closing the door to your office are over! I have discovered that wearing headphones in the office during select times sends a signal to your co-workers that you are focusing and need to have some privacy (in effect, a closed door moment).
Give it a try.