Cochlear mechanics: nonlinear behavior in two-tone responses as reflected in cochlear-nerve-fiber responses and in ear-canal sound pressure.

Over the last five years, we have studied spatial distributions of cochlear responses to single‐ and two‐tone stimuli by recording sequentially from as many as 418 cochlear nerve fibers in each cat and obtaining plots of amplitude and phase of response components at primary and distortion frequencies. We have observed: (1) that such responses to two‐tone stimuli of sound pressure levels (SPL) as low as 34 dB re 20 μN/m2 rms show noticeable deviations from linear behavior; (2) that two major forms of nonlinear behavior in responses to two‐tone stimuli are distortion products and two‐tone suppression; (3) that the spatial distributions of amplitude and phase of (2f1‐f2) and (f2‐f1) components in response to two‐tone stimuli are similar, in the region near and apical to the distortion‐frequency place, to those of the fs component in response to a single‐tone stimulus whose frequency fs is equal to the particular distortion frequency, and dissimilar in the more basal region; and (4) that each of the f1 and f2...