If you, like me, find it hard to concentrate in a noisy environment, you may want to consider looking into a random noise generator to help.
Put simply, the human ear is very good at picking up patterns in sound, and focusing your attention on them. That was a good evolutionary thing when it was, say, a tiger creeping up behind to eat you, but not so good when it's an old couple on the bus gossiping about their grand children.
If you listen to a noise source, the noise will break up the patterns, so that you don't get disturbed. You don't need a particularly loud noise source to do this. And because the noise is patternless, your brain will quickly tune it out, leaving you in (and this is the unintuitive bit) peace and quiet.
Random noise = peace and quiet
There are several types of noise, some harsher sounding than others. Without going into the details, pink noise is the best to start with for masking out sounds.
I recommend that you check out a site I have come across called SimplyNoise.com.
On here, you can choose between various noise sources without having to download anything.
Try it, I think you'll be surprised at how well it works.