A Piezo driver and contact mic on a resonant object create a cheap plate reverb or sculptural signal processor

By coupling a Piezo driver (which vibrates an object using audio signal) and a Piezo contact mic (which captures the object’s resonance) on the same physical surface, the object becomes a filter and reverb unit: the object’s mass, material, and shape determine the frequency response. Thin materials (pie tins, balloons, vinyl records) work better than thick ones. Flexing or dampening the object changes the reverb character. This is the same principle as classic plate reverb (an electromechanical transducer driving and picking up a large metal plate). David Tudor’s famous Rainforest installation used sculptural objects to transform sound material by this same method. The resulting reverb can be patched through a matrix mixer like any other effect.

Examples

Solder a Piezo driver to a pie tin, clamp a Piezo contact mic to the same tin, send a send-bus signal through the driver and return the mic to a mixer channel — instant plate reverb.

Assessment

Explain why a thin metal plate produces a different reverb character than a thick wooden block in this configuration, and describe how to adjust the reverb decay time.