Explain the mechanism of hearing.

1.The pinna collects sound waves and conducts them through the external auditory canal. They finally strike on the ear drum and the vibration is set. 

2.The Eustachian tube equalises the air pressure on either side of the ear drum allowing it to vibrate freely. 

3.The vibrating ear drum sets the three ear ossicles into vibration. The vibration of the first two ossicles, i.e. malleus and incus, magnifies the vibration in stapes. 

4.The stapes transmits vibration to the membrane of the oval window which sets the fluid in the cochlea into vibration. 

5.The vibrating movement in the fluid stimulates hair-like processes of sense cells of the cochlea and the impulses are transmitted to the brain via the auditory nerve.