I face the same problem at my workplace.

Here are some of the things that I do when noise around in the office starts distracting me:

1) Put on headphones and play music that I like.

2) If the work is really demanding, would need absolute concentration and that too for a long time, I prefer leaving office early in the day and come next morning at least 2-3 hours before others start filling in. Or sometimes, I come back to office after dinner.