Effects of Scalae Tapering, Perilymph Viscosity, Helicotrema and the Cochlear Map Function on Models of the Cochlea

We calculate the basilar membrane (BM) frequency response and the cochlea input impedance (Z sub c) by cascading two-port ABCD matrices formulated to include effects due to scalae tapering (scalae area variation along the length of the cochlea), perilymph viscosity, and helicotrema, for various cochlea maps. Previously Koshigoe et.al. [JASA 74(2), 1983] showed that perilymph viscosity has an important effect on Z sub c in the frequency region below 500 Hz. We show that Z sub c is affected more by scalae tapering than by perilymph viscosity, and it is affected very little by the helicotrema.