The Windows Phone app which has gone free next as myAppFree app of the day is Sounds to Sleep.

Sounds to Sleep Details and Features:

Can’t sleep? Listen to nature sounds to help you fall asleep. Nature Sounds to Sleep is an amazing health app, allowing you to cure insomnia, increase your quality of sleep and help you relax. You will relax and sleep like baby
-One touch access to favories and recently played
-Sleep Timer: automatically stop playing sound after a set time.
-Run under locked screen
-Relax and sleep sounds: only natural music, no musical instruments.
-High-quality sounds of bird, wave, ambience, campfire,….
-Auto decrease volume

Install Link