When singing bowls don't sing: a numerical and experimental investigation on the subtle dynamics of Tibetan bowls

Tibetan bowls have been traditionally used for ceremonial or meditation purposes, but also in contemporary music-making. They are handcrafted and produce different tones depending on their shape, size, mass and their alloy composition. Most important is the sound producing technique by impacting and/or rubbing, as well as the excitation location, the hardness and friction characteristics of the excitation stick. In a previous paper, we developed a physically-based method for nonlinear time-domain simulation of Tibetan bowls. Our computational approach, based on a compact modal formulation, produces realistic dynamical responses. In the present paper we focus on an interesting feature of Tibetan bowls: in order to produce self-excited responses, the stick must rub the bowl against the external side of the rim, e.g.
adially\pressing outwards the bowl center. Indeed, experimenting with many bowls showed that they do not sing when rubbed internally. We start documenting this claim with experimental results from representative bowls, and then exploit our computational model in order to reproduce the observed behavior qualitatively. Our results are in good agreement with experiments, thereby demonstrating that internally excited bowls are dissipative and hence unable to sing.