An Improved Model of Mechanical Neural Transduction in the Cochlea, the Robinson Ear Model 2

The Robinson Ear Model 2, an improved version of the original Robinson ear model, is presented. The Robinson ear model is based on the anatomy of the cochlea and the theory that sound induced neural firings are stimulated by the interaction of two waves, a pressure wave moving through the fluid of the inner ear at the speed of sound and a transverse wave moving much more slowly along the basilar membrane. Neural tuning curve sharpening without the need of a second filter is exhibited by both models, but Model 2 shows considerable additional sharpening. The original model predicts cubic difference tones, their cancellation, and the perception of residue pitch, but Model 2 significantly reduces the prediction errors in several areas. The errors in the predicted frequencies for cubic difference tones and residue pitch are reduced from about three percent to less than one percent. The error in the predicted amplitude for cancellation tones, associated with cubic difference tones, is reduced from about twelve decibels to less than two decibels. As for the original model, predictions of the model are compared to data from both psychoacoustic and neural firing experiments. Model 2 makes specific predictions about the acoustic neural firing patterns associated with the perception of residue pitch. The reason why a cubic difference tone can be canceled and a residue pitch cannot be canceled is explained.