The three stages of technology in undertoe include: Sensation, Processing, and Output.

In the prototype, the Sensation portion used accelerometers to detect the vibrations in footsteps. The Processing section used custom software built in MSP to filter and threshold the vibration data obtained from the accelerometers, in order to isolate footsteps. When a footstep was detected, the software then amplified and routed the vibration data to the Output section. The Output portion consisted of bass shakers (speakers optimized to send waves through solid media) to generate waves in a pool of water, which was then projected (using an overhead lamp) onto the ceiling. The prototype did not have a grid of bass shakers, so only ever created ripples in the center of a small tank.

The final version of undertoe will not look much different from the prototype, only repeated and on a larger scale. My current research shows that piezo film, which works similarly to accelerometers, will work best for the Sensation portion of the project. Sixty of these will each be placed in small wooden resonator box pads, to optimize footstep detection, and the grid of these will be laid on a small pile carpet, to minimize false triggers that could be caused by neighboring footsteps. The Processing section will use microcontrollers instead of computers, to keep down costs. For each piezo sensor, a simple pic chip will threshold the footstep data, then generate square waves at an optimally tested frequency for the “prettiest” ripples. The duration of the wave-generating tone will depend on the amplitude of the footstep: stomp hard and get a long tone – lots of ripples – tread lightly and create only a few. This tone will then be amplified in a separate chip, still part of the Processing section of the piece. Finally, the amplified tone will be Output to a sub-woofer / speaker, which has a long plexiglass rod attached to its sound-generating core. At the bottom of this rod sits another larger piece of plexiglass, one with a greater surface area and submerged surface of the water, and this will produce our ripples.