2. Relax and Sleep plus
For Android at: play.google.com
There are many different ambient noises on this app and the app mixes them up in various orders and then plays the track as long as you like. It means you do not have to keep the noises going all night long if you do not want, and the aim of the ambient noises is to relax you and to drown out any noises that may otherwise keep you awake, such as the noise of traffic passing by.