Give a brief account of mechanism …

The ears are the sense organs which help us in hearing sound. It consists of three compartments – outer ear, middle ear and inner ear. 
i.    The outer ear consists of a broad part called pinna having a long passage called ear canal. At the end of the ear canal is a thin, elastic and a circular membrane called ear drum. It is also called tympanum. The outer ear contains air.
ii.    The middle ear contains three small and delicate bone called hammer, anvil and stirrup. These bones are linked to one another. The middle ear transmits the amplified pressure variations received from the sound wave to the inner ear. 
iii.    In the inner ear, the pressure variations are turned into electrical signals by the cochlea. These electrical signals are sent to the brain via the auditory nerve, and the brain interprets them as sound.