Binaural Lateralization of Cophasic and Antiphasic Clicks

Results from a computational model for middle ear and basilar-membrane operation suggest several binaural phenomena. The effects are sought experimentally in tests on the binaural lateralization of pulses. The interaural times for producing centered images are measured as functions of pulse polarity and noise masking. To a large extent. the interaural disparities appear explicable in terms of the mechanical response of the basilar membrane together with simple hypotheses about the mechanical-to-neural transduction in the inner ear. The time disparity can be manipulated by symmetrically masking with high-pass or low pass noise. By this means, the coherent neural information is elicited from a restricted place on the membrane and reflects the mechanical properties of that place. Similarly, asymmetrical masking (for example, high pass in one ear and low pass in the other) yields interaural times that reflect the transit times to specific membrane places. Calculations from the mathematical model for the middle ear and basilar membrane are used to interpret the psychoacoustic behavior in terms of physiological response. The results are discussed in the context of related findings, and an effort is made to assess the relative influence of mechanical and neural factors.