After sight, hearing is the sense that provides the brain with most information about the surroundings. Then human ear can register a wide range of sounds compared to animals. This system, the auditory system, also gives us the sense of balance.
Balancing
Head movement swirl fluid insde the semicircular canals. They are sensory cells that fire nerve signals to the brain. They are arranged in pairs and each detects motion in one of the three dimensions.
Atmospheric Pressure
The Eustachian tube allows air from the throat to flow into the middle ear cavity, so as atmospheric pressure changes, the air pressure on either side of the eardrum can equalize, allowing the eardrum to vibrate without any restrictions. This is why our ear ‘pops’ when we go downhill, because the pressure is increasing.
Hearing
Sound waves funnel into the canal and strike the eardrum. Then vibrations are created. The movement travels along then three tiny ear bones, ossicles. They span in the middle ear and are our body’s smallest bones. They contract when sound hits the eardrum. The ossicles vibrate the oval window into the cochlea. Then the membrane shake, which then pulls microscopic hairs, and the hairs transfer nerve signals to the brain.
Damage
The Royal National Institute for Deaf People accused manufactures of MP3 players failed to put warning messages on the packaging to urge customers not to crank the volume to high up. They also recommended customers should invest in in-ear canal filters or noise-isolating headphones, thus reducing the need to increase volume.
http://en.wikipedia.org/wiki/Ear
http://news.bbc.co.uk/2/hi/health/6982184.stm
Book: '€˜Human Body'€™ Author: Steve Parker
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