If you are like me, you have a hard time working in a “quiet” environment because it is never really quiet. I am writing this in my office today, and I can hear the clock ticking, the heating system, and someone walking by outside the door. Usually, I put on a television show or a movie, but for a lot of people, this will distract them further.
White Noise is a free app that, as the name suggests, makes white noise.

The app has dozens of background sounds to choose from, including nature and industrial sounds as well as a series of “White Noise,” “Brown Noise,” “Pink Noise,” “Blue Noise,” “Violet Noise,” and “Gray Noise.” I am not sure how they decide what color different sounds are, but they are all very nice.
If none of the sounds that come pre-loaded work for you, you can record your own. You can also create mixes – multiple white noise sounds played simultaneously. For example, I took Beach Waves Crashing and Camp Fire to create the sound of a camp fire on the beach.

You can set timers so that the noise plays as you fall asleep but does not go all night, or the timer can cue you to stop working on a project when the noise ends.
This is a handy app that you can use for meditation, background noise as you work, or help with sleep. Basically, it has something for everyone!