Published online by Cambridge University Press: 20 April 2006
Previous contributions made by physical models to the understanding of cochlear mechanics suggested that a new cochlear model should be constructed. This paper illustrates the results obtained with a rectilinear, three-chamber model. The model was geometrically scaled 50:1 and contained the constituent elements of the cochlear cross-section including the basilar membrane, Reissner's membrane, the tectorial membrane and the organ of Corti. The basilar membrane was stretched crosswise in order to simulate real basilar membrane anisotropy. Two kinds (rigid and elastic) of tectorial membranes were used. The ductus and the sulcus were made visible and the model was also provided with displacement transducers to measure the axial and cross components of the oscillating fluid motion in the scala media. The adoption of a highly flexible membrane, simulating Reissner's membrane, made it possible to vary the viscosity of the scala media compared to that of the other two scalae. The reasons why the simplifications of the previous models were partially rejected and the criteria adopted to assure dynamic similitude between the model and the real cochlea are described in the paper. The results of tests carried out to determine the partial distribution of the amplitude maximum, the phase velocity along the axis of the model and the dispersion curves are shown. The same tests were repeated with partially filled scala vestibuli. Lastly a typical nonlinear feature, that is a continuous flow in the scala media, is described.