Kinematic synthesis of auditory motion

A technique is presented for headphone simulation of sounds moving in auditory space using the mathematics of kinematics, or mechanics of pure motion. Doppler shifts, as well as changes in interaural time delays and interaural intensity differences can be shown to have transformation invariant dependencies based on kinematics. For example, the Doppler effect represents a pattern of change that is invariant for a particular velocity and distance, and independent of the frequency and amplitude of the sound pressure waveform. In principle, these invariants intrinsic to the sound pressure wave of a moving object are available to the listener. The continuous kinematic approach differs from the more traditional approach of considering static localization cues strung together to reconstruct the dynamic event, and allows programmatic simulation of arbitrary acoustic trajectories through the environment. A series of experiments was designed to assess the sufficiency of synthesized kinematic information for simulating sounds moving in the horizontal plane. Subjects were asked to judge the trajectory and direction of a simulated moving sound under headphones using the combination of a visual display of the path and a pointing device. Results support the sufficiency of kinematic information in judging trajectory and direction. Furthermore, the variability of judgments was comparable to other studies of headphone simulation of static free‐field listening. [Work supported by ONR and Wisconsin Alumni Research Foundation.]