The stretching nonlinearity of the basilar membrane in a cochlear model.

Recently it has been suggested that the stretching nonlinearity of the basilar membrane might be responsible for the observed nonlinear behaviour of basilar membrane motion. In the present study this type of nonlinearity is investigated, both by estimating its influence in an analytical manner, and by calculating its effect numerically, using a regular pertubation method. The conclusion reads that the stretching nonlinearity does not explain the observed nonlinear phenomena; not only is stretching negligible at normal sound levels, but it also fails to fit the data qualitatively, because of its typical hard-spring effect. In consequence, the origin of cochlear nonlinearity is not to be sought in the macromechanics of the inner ear, but in the more detailed processes in th organ of Corti-tectorial membrane complex.