Lots of ambient-sound apps out there, but many are too complicated. "Relax Melodies Seasons" has an easy interface: easy to see which sounds are playing (swinging icons) and easy volume control for setting up your favourite sound mixes. With "binaural beats" and a user-friendly alarm/timer, this app is a great aide for sleep or timed relaxation breaks.
BBoeckel about Relax Melodies Seasons Premium: Mix Rain, Thunderstorm, Ocean Waves and Nature Ambient Sounds for Sleep, Relaxation & Meditation