Middle ear bones amplify pressure over 30-fold via lever and area ratios.

Evidence

This is just what a lever does. Work is force times distance, so to keep force low (within human ranges, say), we use levers with large displacements (and lower force and impedance) at one end, but connecting at the other to small displacements with high force and high impedance. … Each has a ligament attached near its center to act as a fulcrum. This combined lever action provides a factor of 2 to 3 increase in pressure at the oval window, which doesn’t sound too spectacular. … A part of the impedence transformation is won as a result of the ratios of areas of the tympanum to the oval window—about 17:1. If there were just a straight bone connection between them, the pressure times area of the tympanum would be the same as the pressure times area of the oval window, meaning 17 times the pressure on the oval window, which is a good step in the right direction (see figure 21.6). Including the lever action pressure factor of 2 to 3, there should be above a 30-fold increase in pressure at the oval window compared to the tympanum, or more than a 1000-fold increase in power. — Eric J. Heller, Why You Hear What You Hear- An…, 1943

Categorization

• DEFINE: Explains impedance transformation: how the ossicles trade force for distance to match air pressure to cochlear fluid.