I modified a stereo speaker (basic transducer) so that all its energy went to a metal plate instead of a speaker cone. I generated pure sine tones in Pure Data (PD) and sent them through the metal sheet causing sound. I then poured salt on it and intricate patterns appeared (different patterns correlate to different pitches). Because only certain parts of the plate are vibrating to create the tones, the parts that are not vibrating collect salt, revealing patterns. This is a phenomenon belonging to the field of Cymatics (the study of wave behavior).
This was for a performance class actually, so i performed unannounced mock salesman style demo/infotainment pieces at bars. I was selling free information about a scientific phenomenon.
The process took several days, during the first week of Obama's presidency.
It didnt work on the first six speakers; this involved a lot of craigslist purchases.
The winning design involved a deadbolt door knob receiver piece.