ANoise - Ambient Noise Player  

The Ambient Noise Player aka ANoise Player is a simple but very useful app that plays sounds that help you boost your productivity, stay focused or it can even help you fall asleep. You can access the Ambient Noise options from the Ubuntu Sound Menu which allows you to play various relaxing sounds like storm, rain, wind, forest, night, fire, coffee shop, sea and other custom relaxing sounds provided by community members.

sudo add-apt-repository ppa:costales/anoise
sudo apt-get update
sudo apt-get install anoise