question_answer

Explain how the human ear works.                         

Answer:

                      The sound waves reaches  the   eardrum,   the  pressure on the outside of membrane increases and pushes the eardrum inward. Similarly, when a rarefaction falls on the eardrum, the pressure on the outside of the membrane decreases and it moves outward. In this way, the eardrum begins to vibrate. The vibrations of eardrum causes the vibrations in the small bone, called hammer. From hammer these vibrations are passed to second bone anvil and finally to third bone stirrup. The vibrating stirrup strikes on the membrane of the oval window and passes its vibrations to the liquid in the cochlea. The vibrating liquid of cochlea converts the pressure variations of sound waves into electrical signals. These electrical signals are sent to the brain via the auditory nerve. The brain interprets these electrical signals as sound and we get the sensation of hearing. Human beings hear only sounds with frequencies from about 20 Hz to 20,000 Hz. These are the limits of audibility; the upper limit decreases with age. A hearing aid can be used to send an amplified sound to the eardrum when someone can hear only quite loud sounds. If the eardrum of the middle ear is damaged, an aid can pass on vibrations to the cochlea directly through the skull bones. Deafness occurs if the cochlea or auditory nerve is damaged.