Why does water change the pitch of a singing wineglass the way it does?
Yih-Yuh Chen · American Journal of Physics · 2005
When the rim of a fine wineglass is rubbed with a moist finger, a pure tone can be heard. The frequency of this tone is lowered if a liquid such as wine or water is added to the glass. Although it is tempting to ascribe this change to the extra effective mass contributed to the wineglass by the liquid, we argue that this explanation leads to several counterintuitive phenomena. We use a simplified model to compute the frequency shift as well as a variational approach for a more general derivation and demonstrate how a more appropriate physical interpretation accounts qualitatively for all the observed phenomena.