Variations on a theme by a singing wineglass

Abstract

A "singing wineglass" is a glass which generates a more or less pure tone when one rubs its rim with a wet finger. The frequency of this tone is lowered when water or wine is poured into the glass. One usually associates this downward frequency shift with an effective mass contributed by the liquid to the vibrating wineglass. We present experimental work and simplified theoretical models to show that this idea requires modifications for a couple of counter-intuitive phenomena.