Abstract. In a stereoscopic system, both eyes or cameras have a slightly dierent view. As a consequence, small variations between the projected images exist (`disparities') which are spatially evaluated in order to retrieve depth information (Sanger 1988; Fleet et al. 1991). A strong similarity exists between the analysis of visual disparities and the determination of the azimuth of a sound source (Wagner and Frost 1993). The direction of the sound is thereby determined from the temporal delay between the left and right ear signals (Konishi and Sullivan 1986). Similarly, here we transpose the spatially de®ned problem of disparity analysis into the temporal domain and utilize two resonators implemented in the form of causal (electronic) ®lters to determine the disparity as local temporal phase dierences between the left and right ®lter responses. This approach permits real-time analysis and can be solved analytically for a step function contrast change, which is an important...