Perhaps its just a cultural difference, but I am positively taken aback at the thought that the use of earplugs could be seen as rude??!!!! The rudeness is in people making so much noise that they have driven their colleague to consider having to use earplugs to be able to work. The rudeness is the noise and lack of consideration of others need to work, NOT in doing what is necessary to get your PhD work done.

No one should be an apologist for doing what they need to be able to get their work done, and I would be tempted to point out to colleagues that I had been forced to resort to ear plugs due to their incessant rude noise.

If people were making noise and bothering me, I would also ask them to please be quiet, because they WERE bothering me. Its like being on the quiet car of a train. If you have to make noise, go elsewhere, so you do not disturb the people that are around you. I would have no qualms insisting on a quiet shared workspace. Those who had a problem with that, well, how are they going to defend a position of being noisy and disruptive?!!

Further, you might suggest to your supervisor that you cannot do good work under those conditions. How badly do they want you to finish your PhD v. conform to some arbitary idea of control? Are you stuck at this university or even with this particular department? Can you ask for a transfer of supervisor, or department? Is it feasible to find another university that promotes good working conditions and is supportive of students and their needs in accomplishing the PhD over petty tyranny?

I think you need to ask the others to be quiet! There are plenty of places to socialise but not in the office. I have a noisy three year old at home, if I couldn't work in the office I would go mad.