Tapping out a TAI-CHI tune.

Main Crevoisier had reckoned that it would be easy to turn almost any hard surface into a keyboard, drum head, or other input for a computer-controlled musical instrument. Just place a few sensors somewhere under a tabletop to read sound waves traveling through it. Then, assign spots on the table to correspond with various digital sounds stored in the computer. Begin tapping, and the computer would triangulate the positions of those taps to figure out what sounds to play.

In fact, creating such a system proved quite difficult, says Crevoisier, an artist and engineer at the University of Applied Sciences Vaud in Yverdon-les-Bains, Switzerland. But now, after working with researchers from seven research centers in five countries for the past 2 years, Crevoisier and his colleagues have created prototype kits for transforming household surfaces into computer-input devices.

The team calls its new systems tangible acoustic interfaces for computer-human interactions (TAI-CHI). The devices are made of inexpensive acoustic sensors wired to specially designed computer chips. The sensors, which could operate wirelessly, pick up sound waves moving through a solid surface that can be any shape and can be made of wood, plastic, glass, metal, or even the plaster of a wall.

Crevoisier's colleague Ming Yang of Cardiff University in Wales is looking to use TAI-CHI systems for more than making music. The technology allows the creation of virtual buttons anywhere in a room to control devices such as a lamp or ceiling fan, he notes. The system can even acoustically interpret what's being written on a sensor-tagged marker board and reproduce that script on a computer screen. Eventually, Yang predicts, diners will relay orders to restaurant kitchens by tapping to select items from a menu painted on a tabletop.