The mechanism of the middle ear: Part II. The drum

The ear drum is considered to be a thin circular membrane with radial and circular fibers, whose center is pulled inwards by the handle of the hammer. It is shown that such a membrane is equivalent to a rigid piston connected by a lever to the handle of the hammer, and subjected to elastic forces. The stability of the equivalent system is great, and the flexibility of the lever is very small. The lever is such that small pressures in the auditory canal are transformed into larger forces on the hammer. The leverage ratio increases with the tension of the tensor tympani and decreases with the number of circular fibers.