A Space-Time Theory of Pitch and Timbre Based on Cortical Expansion of the Cochlear Traveling Wave Delay

Introduction The displacement pattern of basilar membrane motion is tonotopically organized, with high frequencies reaching their apogee towards the base of the cochlea and low frequencies achieving their maximum near the apex (von Békésy, 1960). This systematic relationship between peak displacement and cochlear location serves as the linchpin of the "place" model of spectral representation and of auditory theory in general. In recent years this "classic" place model has come under increasing scrutiny in light of experimental observations demonstrating that this spatial organization of excitatory activity is generally discernible only under a restricted set of conditions in the auditory periphery, thus calling into question its ability to subserve frequency coding at sound pressure levels typical of speech communication and musical performance. In place of classic tonotopy, many recent models of pitch and frequency analysis focus on the temporal properties of peripheral activ