Figure 9: Force-displacement relation for the stapes footplate (red) and the tympanic membrane (black) in case of axial displacement in direction of the vestibulum. Because of the visco-elastic properties, the behavior for loading and releasing is different which explains the hysteresis curves. It is obvious that the annular ligament stiffens already in case of low forces and allows only little deflection. The eardrum, however, shows a nearly linear course with constant stiffness in the examined area.