Multi-dimensional Synchronization for Rhythmic Sonification

Human locomotion is fundamentally periodic, so when sonifying gait, it is desirable to exploit this periodicity to produce rhythmic sonification synchronized to the motion. To achieve this rhythmic sonification, some mechanism is required to synchronize an oscillator to the period of the motion. This paper presents a method to synchronize to multidimensional signals like those produced by a motion capture system. Using a subset of the joint-angle signals produced by motion capture, the method estimates the phase of a periodic, multidimensional model to match data observed from a moving subject. It does this using an optimization algorithm applied to a suitable objective function. We demonstrate the synchronization with data from a publicly available motion capture database, producing sonifications of drum beats synchronized to footfalls of subjects. The method is robust and shares some common features of phase-locked loops used for synchronizing onedimensional sinusoidal signals. We foresee applications to sonification for athletics and clinical treatment of gait disorders.