A free app for Android, by Avalunt.

The app contains a list of various types of sounds to help you relax and fall asleep. You can listen to them at any time and place. Some of them are very effective in helping you fall asleep, while others are better for adults. You can listen to all of them on your Android device. Just download the app, choose the sound you like, set the time and distance, and you will be able to listen to it at home, on your way to school, or while you are at work. This app is also useful for those who suffer from insomnia or who have a sleeping problem.