The Ossicles and the Cochlea

The ossicles and the cochlea are the two main parts of the ear that take the vibrations of the eardrum and convert them into information that the brain can understand.

The ossicles are three bones within the middle ear that aim to increase the amount of sound that passes from the eardrum to the cochlea. To achieve this, the ossicles apply a process rooted in Archimedes' Principle of Lever Action. This image of a balanced teeterboard provides a nice picture of this principle:

(The Physics of Music and Color)

Though the smaller figure weighs more than the other, the teeterboard remains balanced because of the distance between the point where the board pivots (F). Because of this difference in distance between the pivot point, moving closer end of the board will move the other end by a larger magnitude. The ossicles operate in a similar way by using a pivot point to increase the amplitude of the vibrations of sound waves that pass into the ear. 

The amplified vibrations of the ossicles pass into the inner ear where they meet the cochlea. The cochlea is the part of the ear that is able to distinguish the frequency of sound and also converts sound energy into information that the brain can interpret. The cochlea relies on a small amount of fluid that is similar to water, but has twice the viscosity. The different parts of the cochlea take the vibration of sound and cause vibrations within the cochlear fluid. Stem cells, which are nerve cells, interpret the vibrations in the cochlear fluid and convert them into information that the brain can understand. 

Works Cited:

1.  Gunther, Leon. The Physics of Music and Color. New York, New York: Springer, 2012.