ACOUSTICS OF THE GLASS HARMONICA

Glass harmonicas or glass harps, consisting of sets of tuned glasses, were already popular in Europe when Benjamin Franklin designed an improved style of instrument that he called an armonica. The modes of a wineglass resemble the flexural modes of a bell. Striking the glass excites a number of these modes, but rubbing the rim with a finger or bowing it radially with a violin bow generally excites a single mode. As the player's finger moves around the rim of the glass, the nodes and antinodes move with it, resulting in a pulsating sound.