THE HEARING MECHANISM

The hearing mechanism consists of 3 parts: 1) the outer, 2) middle and 3) inner ear chambers.

Deafness is typed by the doctors according to the part of the mechanism involved.

Air conduction deafness means that the outer and middle earchambers are not functioning normally, whereas perceptive or nerve deafness indicates that the cochlear section (inner ear) is at fault.

There are two mechanisms to be considered in the physiology of hearing:

a) the sound conducting mechanism;

b) the sound perceiving mechanism.

The outer ear mechanism consists of the auricle, and the canal leading to the membrane called the ear drum. The collec­tion and concentration of sound waves is performed by the auricle and the external auditory canal. The auricle reflects the sound waves into the auditory canal.

One of the most difficult problems is that of abnormali­ty of development of the auricle and the external ear canal. In complete absence of the ear canal there is about 50 db hearing loss.

The middle ear is air filled, and connected with the throat by the Eustachian tube. Its purpose is to provide ventilations and drainage for the middle ear and to equalize air pressure on both sides of the drum.

When we yawn or swallow, the Eustachian tube opens and the air pressure on both sides of the drum is equalized again.

There are 3 bones in the middle ear: the hammer, the anvil, the stirrup. They serve as a protection against damage to the ear from very loud sounds.

The inner ear is the vital organ of hearing. It consists of 2 sections: the cochlea which looks like a snail and the system of semicircular canals. Unlike the air-filled middle ear, the inner ear is filled with fluid. The motion of the fluid in the cochlea agitates the nerve endings in the mem­brane dividing the inner ear cavern. The stimulation of these nerves is then transmitted to the brain.

So, the action of the middle ear is mechanical. Its function is to conduct sound vibrations.

The action of the inner ear is to transfоrm mechanical energy into the electrical energy of nerve impulses and its function is to perceive sound. Loss of hearing is most com­monly caused by the acute infections of nose and throat usual­ly described as “colds”, “catarrh” and “sinus trouble”.

The nose, throat, sinuses and ears are all connecting cavities in the bony structure of the head. A certain number of germs exist in them all the time and they may produce inflammation, which may damage the ear.

T E R M S

the hearing mechanism слуховой аппарат, орган

outer ear chamber внешняя полость уха

middle ear chamber средняя полость уха, среднеe ухо

inner ear chamber внутренняя полость yxa, внутреннее ухо

air conduction deafness глyxoта вследствие воздушной непроводимости

perceptive deafness восприимчивая глухота

cochlear улитка /уха/

to be at fault быть в затруднении

auricle наружное ухо

ear drum барабанная перепонка

sound waves звуковые волны

throat горло

Eustachian tube евстахиева труба

bone кость

the hammer молоточек

the anvil наковальня

the stirrup стремя

the cochlea улитка /уха/

snail улитка

fluid жидкость, жидкая среда

acute infections острые инфекционные заболевания

colds простуда

sinus trouble болезнь пазух

germ микроб

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