This app plays White Noise that helps sleep or concentrate better. I find that the nights I use this app I fall asleep quicker and sleep deeper. You can also create a combination of sounds that work best for you. I like to use the fan mixed with the train and the heartbeat. There is also a sleep timer that will slowly turn down the noise and turn off so it isn't running all night long.

I also use this app at work when I need to concentrate or ignore my very noisy office mate. I can put my earbuds in and really focus on the work that I need to get done and it drowns out all the sighing and tapping he does all day long.