The sounds of physical shapes

We propose a general framework for the simulation of sounds produced by colliding physical objects in a virtual reality environment. The framework is based on the vibration dynamics of bodies. The computed sounds depend on the material of the body, its shape, and the location of the contact. This simulation of sounds allows the user to obtain important auditory clues about the objects in the simulation, as well as about the locations on the objects of the collisions. Specifically, we show how to compute (1) the spectral signature of each body (its natural frequencies), which depends on the material and the shape, (2) the "timbre" of the vibration (the relative amplitudes of the spectral components) generated by an impulsive force applied to the object at a grid of locations, (3) the decay rates of the various frequency components that correlate with the type of material, based on its internal friction parameter, and finally (4) the mapping of sounds onto the object's geometry for real-time rendering of the resulting sound. The framework has been implemented in a Sonic Explorer program which simulates a room with several objects such as a chair, tables, and rods. After a preprocessing stage, the user can hit the objects at different points to interactively produce realistic sounds.