The ossicles in the Middle Ear

The ossicles transform small changes in pressure (sound wave) to a much greater pressure on the oval window using:

1. a lever action: a small force acts through a larger distance resulting in a larger force acting through a smaller distance.
   
2. a smaller oval window: smaller area transmits greater pressure,
      pressure = force/area$$.$$

The lever action, a force factor of about 1.5, and the smaller oval window (1/20th the size of the eardrum), increase the pressure transmitted to the inner ear by a factor of $20 \times 1.5 = 30$.