Glass is in actuality a solid liquid. To break glass, the static molecule structure must be interrupted. Shattering with sound will not work with just any glass (in less it is so intense the SPL would shatter everything else, including your eardrums). Fine crystal, as is usually found in a good wine glass, is the best candidate. What is needed is a sound at one of the natural (resonant) frequencies of the wine glass. You could find the frequency needed to shatter the wineglass by tapping it sharply with a spoon (not hard enough to break it!) - the sound you hear is the one you require. You need to put enough energy into the object to actually break it, so that the amplitude (size) of the resonant response is sufficient to propagate cracks in the material, and so shatter the glass.