Tibetan singing bowl. 🔥 #howitsdone The water-filled bowls, when rubbed with a leather-wrapped mallet, exhibit a lively dance of water droplets as they emit a haunting sound. At the heart of the phenomenon are what are known as Faraday waves, which arise when a fluid such as water vibrates, constrained by a closed boundary such as the edge of a singing bowl. As the frequency of the rubbing reaches that at which the bowl naturally vibrates, the bowl's edge begins rhythmically to change shape, from one slightly oval shape into another. The energy of this shape-shifting partly transfers to the water, in which a range of interesting patterns can arise as the intensity of the rubbing increases.