If you want to block out the noise in the office and work without any distractions, noise-cancelling headsets should be on your shopping list.
The best noise-cancelling headsets protect your ears from the outside world, cutting out frequencies and rumbles that would otherwise detract from your work.
Some simply allow you to turn noise-cancelling on or off, which is fine if you're listening to them on a train or plane. Other models give you greater flexibility and the ability to adjust the strength of the noise-cancelling based on where you're using them. You might want to allow some noise through if you're using them in built-up areas where there's loads of traffic around.