Power Nap App - Best napping timer with relaxing sleep sounds
Noizio - Feeling that the noise of the big city is too much for you to bear?
Earth.fm - Earth.fm is a non-profit, growing library of pure, high quality nature sounds from around the world.
Noizer - Ambient sounds like Noisli, but free
White Noise - White Noise to help you sleep and games to wake you up.
Defonic - Create a unique sound environment at home or in the office