A special compression driver speaker is mounted to the left of the glass. When the speaker is set to the resonance of the glass - vibrations will constructively interfere with each other until the glass breaks. This demonstration takes a special speaker, a frequency generator, and an amplifier that can drive the speaker at 120 watts. The action is captured with a high speed flash operating at 1/20,000th of a second. This image is one out of a set of two showing before and during the glass shattering..