The human ear perceives sound waves, transforms them into signals which reach a brain where they are analyzed and interpreted. Probably, the best mode to explain ear work is to describe a way, which sound passes through various parts of an ear.
1 – The external ear. Assembles sound waves and directs them to the acoustical pass where they amplify thanks to its funneled form. An acoustical pass terminates in an eardrum.
2 – The middle ear. The middle ear is the chamber filled with air connected with nasal and throat passes by a Eustachian tube which is intended for the alignment of sound pressure on either side of an eardrum. The Eustachian tube is usually closed and opens naturally when you swallow or yawn. Sound waves cause vibrations of an eardrum which are transferred on a chain of the acoustical stones attached to it. These smallest bones of the person are called a hammer, an anvil and a stirrup. They mechanically connect an eardrum with an oval window of an internal ear.
3 – The internal ear. The basic part of the internal ear filled with a liquid is curtailed by a coil and consequently is called a snail. In a snail there are approximately 20 000 microscopic sensor cells connected to the fibers of an acoustical nerve and having the termination in the form of hairs. Different groups of these hair cells react to various frequencies of vibrations. Getting to a snail, the transformed sound waves cause liquid vibrations. Thus hair cells, being bent and being unbent, generate nervous electric impulses which are sent to a brain. Here these impulses are interpreted as significant sounds.
In 90 % of cases a hearing loss occurs because of hair cells destruction in an internal ear – owing to ageing, illness or influence of very loud sounds. This hearing disorder is called sensor neural (or perceptive) hearing loss.
Relative deafness consequences are almost always identical – it is getting much more difficult for the person to distinguish speech in a noise, some high-pitched sounds, such as singing of birds, completely vanish, a human speech seems muffled, and it is necessary to ask again often.
The problem consists in the fact that brain does not receive the signals corresponding to sounds on different frequencies, necessary, for example, to make speech clear. It reminds a situation when all highly-sounding keys have been removed on a piano and somebody have been asked to play a known melody. Even if there are no 6 or 7 keys, the melody becomes difficult to recognize and will sound absolutely incorrectly.
If hair cells are damaged in an internal ear, they cannot be restored. However the hearing aid can considerably raise your ability to hear. You can also prevent the further deterioration of hearing, avoiding too long influence of loud sounds and noise.
Other kinds of loss of hearing. Conductive hearing loss. At this kind of hearing loss there is an impassability of sound waves in an internal ear. It can be caused by a sulphur accumulation in acoustical pass, eardrum punching, liquid accumulation on the average an ear or wrong growth of a bone on the average ear (otosclerosis). Conductive hearing loss, as a rule, is subject to medical or surgical treatment.
Tinnitus (a noise in ears). Some people with sensor neuro hearing loss a constant noise or hissing are observed in ears. This phenomenon is called tinnitus. The nature of tinnitus is many-sided and demands additional attention of doctors and treatment.
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