What sound should be used to shatter the glass?
The sound used must contain a large amount of energy at the resonant frequency of the glass. We used a sine wave generator, which creates sound at one frequency only. This is ideal. It is very important to tune the frequency of the signal to match the resonant frequency of the glass. We first measured the resonant frequency using an FFT analyser. I this case we excited the glass by rubbing a damp finger on the top of the glass. We then fine tuned the signal’s frequency until a maximum displacement was reached. We found it useful to balance small pieces of folded paper on the edge of the glass as when resonance was reached the paper jumped up and down. The tuning for resonance was done when the sine wave signal was small. It may be possible to generate the sound from a synthesizer.
