Its function of directing sounds toward the inner structures is demonstrated by a person who may cup a hand around the ear to focus on a sound. Sound enters the ear canal or meatus and vibrates the ear drum or tympanum . The vibrations of the ear drum are transmitted to a set of three bones or ossicles which transmit the sound energy to the oval window of the cochlea. The cochlea contains the receptor end organs which generate the neural impulses corresponding to sound. The middle ear is connected to the throat by the eustacian tube and this structure allows regulation of pressure on the ear drum and the oval window of the cochlea.
Ossicles Think of the three bones as a lever system with three components.
The hammer muscle or tensor tympani is able to pull the mallues away from the ear drum. The stirrup muscle or tensor stapedius is able to pull the stirrup away from the oval window of the cochlea. When the muscles are tensed the level system undergoes the attenuation reflex which is able to reduce sound intensity by as much as 30 decibles. However, the time lag between a loud sound triggering the attenuation reflex and contraction of both muscles as about 10 milliseconds. The sense of balance will be covered later, however since both structures share the eighth cranial nerve there is some interaction between them.