Everyone knows the phenomenon: Someone moves his finger along the edge of a glass and lets it "sing". Andy Piacsek and Dennis Hamilton from the Central Washington University in Ellensburg studied differently shaped glasses and the corresponding pitches. But contrary to the intuitive expectation that larger glasses produced deeper sounds than smaller ones, it turned out that the shape is more crucial for the frequency.
James Woodhouse of the University of Cambrigde tells New Scientist that the effect may be related to how the glass vibrates: for round glasses, the vibration can develop through bending, for glass with straight walls, the glass must straighten out in a straight line. This requires more energy, triggering higher frequencies and thus higher tones.Jutta Perkert