You can play the sounds while you sleep or take a nap. They will continue playing while your device is sleeping or locked. Includes the following 9 sounds: Dusk in the Country Night Ambience 1 (with crickets and frogs) Night Ambience 2 (with crickets and frogs) Gentle Ocean Waves Cascading Waterfall Thunderstorm 1 Thunderstorm 2 Heavy Raining Mystical Ice