Measurement of head movement during auditory localization

Abstract

Head movement can have a significant effect on the ability to locate the direction of a sound source. A system has been designed to track the head movement in response to sound originating at different azimuth locations with respect to the head. A videotape record is made of a light approximating a point source carried on a lightweight “beanie” mounted on the listener’s head. Movement of the light is monitored by the video camera and recorded on tape, along with the sound stimulus and information concerning loudspeaker location and time. The horizontal and vertical coordinates of the light-spot image are determined in relation to the video synch pulses defining the field borders. Synch signals are available from a video monitor either in real-time or from tape replay to define each TV frame and horizontal scan line. The circuitry interfaces to a computer programmed to take the information, apply a calibration, and process the data into records of time-varying head position and velocity. Examples of both digital and graphic printouts of head movement are given. The system is capable of expansion to three-axis operation.