In Sonic constructs, two robotic devices move and interact while performing trajectories that produce sound as a by-product of the movement itself. Direction, speed, acceleration, position, scratching, and collision characterize an environment for kinetic and acoustic participation.
This according to “Sonic constructs: Robotics and the residue of sound” by Rebelo and McAllistair, an essay included in Systems research in the arts. VI: Music, environmental design, and the choreography of space (Windsor: International Institute for Advanced Studies in Systems Research and Cybernetics, pp. 58–62).
Images, sound clips, and a video are here.