hmm...It sounds like a very challenging problem to solve with the "passive" approaches you have tried, and others have suggested. I think maybe moving onto an

hmm...It sounds like a very challenging problem to solve with the "passive" approaches you have tried, and others have suggested. I think maybe moving onto an "active" strategy might be the way to go. You can easily devise a device using an Arduino, a mic, and an air horn. Anytime people are being loud and annoying, and the decibels exceed a certain threshold, you automate the system to sound the airhorn. I guarantee within a week everyone in the office will be trained to keep quiet. Either that, or you won't be allowed in the building. In any case, you won't need to deal with the loud office environment anymore!