The sounds of MOONIE humming toys are authentic, non-computer-generated recordings of natural pink noise. The heartbeat is a recording from inside a mother’s belly, helping babies feel calm and safe with a familiar sound. The sea waves come from the Baltic Sea, while the mountain stream was recorded in the Tatra Mountains. MOONIE also plays a soothing kalimba lullaby, along with two classical pieces by Claude Debussy: Clair de Lune and Rêverie.