ANATOMY AND PHYSIOLOGY OF THE EAR
Hearing is a complex process designed to receive sound waves that propagate in the air, convert them into electrical nerve stimuli and transmit them to the cerebral cortex, which processes and identified as sound.
The ear is the organ responsible for hearing. Schematically presents each of its parts and its operation.
The ear is divided into three parts clearly differentiated
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-OUTER EAR MIDDLE EAR INNER EAR
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OUTER EAR
What is "ear" or pinna, whose function is to "collect" and amplify the sound wave, and channel it into the ear canal, which ends at the eardrum.
The eardrum is an elastic membrane that completely seals the pipe and makes the border between the outer ear and middle ear. The tympanum
healthy upon receipt of the sound wave vibration occurs. MIDDLE EAR
is a cavity carved into the thick skull, connected with the pharynx through a passage called the Eustachian tube, which serves to atmospheric pressure existing in the external ear and middle ear pressure are equal.
Going up or down mountain passes will notice a "deafening" because it decreases or increases, respectively, the atmospheric pressure outside.
This implies that the eardrum bulges to stress, decreasing its ability to vibrate. When spontaneously or by some movement of the jaw is "open" the eustachian tube is roughly equal pressures in the middle ear and the outside, and produces the typical "popping." Part "noble" is the middle ear ossicular transmission system ": the tiny bones that are responsible for transmitting the vibration to the inner ear. The Hammer, has a thin extension attached to the eardrum, which receives the vibrations from it. Hammer transmits this vibration to Yunque, in which is articulado.Este, in turn, contact the stirrup, a small bone that fits perfectly into a closed window with a membrane, the oval window. The oval window separates the middle ear, inner ear, and she applies the movement vibration of the eardrum, transmitted and amplified by the ossicles. INNER EAR
The inner ear is the ear neurological, where the receptors that convert mechanical vibrations into nerve impulses. The inner ear is also called "Caracol" or "Cochlea" because it is a coiled tubular-shaped shell, dug into the skull. The vibrations of the stirrup are transmitted via the oval window to the inner ear.
In this one, filled with liquid, is a "wave" which introduces the vibration vibrating in all inner ear structures and ending at the round window, which gives the middle ear.
The wave liquid in its path, vibrates the cochlear duct.
Facing a court given transverse level, understand the ultimate mechanism of hearing: The vibration wave in the inner ear, "go" in one direction by the scala vestibuli and "back" by the tympanic membrane vibrates the Basilar, so that the hair cells in the Organ of Corti "rub" with the tectorial membrane.
This friction causes the nerve impulse is transmitted to the brain, where it identifies the drive as sound. Snail Along this mechanism works, but not all cells of Corti are capable of collecting all the sounds: The closer to the window pick up sounds sharper and more distant the most serious.
hearing impairment BUSINESS
noise damages the inner ear, high tones being more harmful than the bass.
The tones are those which occur more frequently in the industrial environment. Hence
audiometric examination of workers who have been subjected to prolonged exposure to high noise levels reveals, loss of hearing acuity in the higher frequency ranges: between 3,000 and 6,000 Hz, and in particular, about of 4,000 Hz
The lesion begins around 4,000 Hz, and then spreads to nearby frequencies. Over time will expand to involve the Conversational BANDA (are the frequencies between 500 and 2,000 Hz). These frequencies correspond with which "normally" gives the human voice.
According to reports from the International Organization for Standardization (ISO), workers who have been exposed to intensities above 85 dB, is characteristic of hearing loss by noise.
noise destroys the hair cells of the organ of Corti (in the inner ear), resulting in a PURA Sensorineural hearing loss (of perception), with decreased levels of hearing both by air (via the ear) or via bone (transmission of sound through the skull). This deafness, besides being perception, is irreversible, that is permanent, and that does not recover the hearing and no treatment.
The use of headphones (sound amplifiers) only enhances the subjective feeling of the person, especially in the early stages of evolution of deafness, but it is not effective because the lesion is in the perception, not the transmission of sonidos.Por other hand, is a progressive lesion, depending on the intensity and duration of noise exposure, progresses inexorably.
To understand the changes in the perception of sounds, often used the following example: It is as if the intention is to listen to the recording on a disc, which is in good conditions, in suitable equipment, without deterioration, connect the buttons ... etc. but it is impossible to hear if there is no network connection. The defect in the connection will prevent hearing the recording, but they operate the volume control.
preventive purposes, it is interesting to note that the beginning of this hearing loss, typically in the range of 4,000 Hz (scotoma), some people in the 6,000 Hz indicative of the onset of injury.
frequencies of 4,000 - 6,000 Hz are not included among those used in conversational band, therefore, the person is unaware of hearing loss in the beginning, it does not have any difficulties to hear the human voice. When he feels that there is some difficulty hearing the voice, it's a very advanced stage, and from there the sense of loss evolution was affecting even the social sphere of the individual.
As already mentioned, is an irreversible hearing loss, no treatment, and affects both ears (bilateral) similar (symmetrical). This is the most common, but do not exclude that in some cases affects only one ear. For example, when the sound source is not environmental but comes from one side only. A typical example is the deaf driver's left ear when the noise from outside the factory receive it on that side the open window, staying healthy, the other ear because the head itself performs the function of shielding.
Demonstration of one-sidedness of the injury, it is easy to check by examining the conditions of the job.
professional to confirm the origin of this hearing, in addition to the features described, is added the existence of a history of occupational exposure to high levels of ruido.Una way to facilitate this data is done by including in the file of Occupational Health, the results of the measurements at the workplace (sonometrías). It is also necessary to rule out hearing loss from another source, such as transmission or those caused by infectious or toxic causes. (You can also find a hearing professional association with other injuries added, for example, a repetition otitis (infection) by the improper use of a shield with deafness ... etc.
It should be noted that adds natural aging ear with age, affecting differently.
hearing loss or deafness PROFESSIONAL (Royal Decree 1995/1978, of 12 May, BY ADOPTING THE TABLE OCCUPATIONAL DISEASES IN THE SOCIAL SECURITY SYSTEM - BOE of 25 August)
is a definitive injury caused by occupational disease (Article 140 of the LAW OF SECURITY SOCIAL of 05/30/1974). And susceptible to financial compensation, as described in "Bodies of the hearing" of the INJURY UPDATE SCALE mutilations and deformities final and non-disabling (MO April 5, 1974).
can also be classified as PERMANENT DISABILITY RATING OF STAY (LAW OF THE SOCIAL SECURITY) when incapacitated for the performance of at least 33% of the main tasks of his usual occupation, and / or poses an additional risk in office (Example: unable to communicate or understand notices, not hearing alarms ... etc.), and depending on the degree of injury. In this case correspond to an indemnity equal to 24 months of their basic salary (depending on price), not leading either to the termination of employment.
In some conventions, and seeking improved protection worker, is articulated the possibility of changing jobs to get rid of the risk exposure that has been injured. In this case, you should remember as well that do not cause detrimental effects on wage perception.
The economic compensation has been cast previously mentioned, in any case fall within the company (unless it is self-insurance), and correspond to the insurance company (Mutual), or ultimately to the INSS. (Cited as: there are conventions which mentions that this compensation the company can deduct the salary of the employee / a. This situation, which could be a source of interpretation error, or failure of information needs to be avoided, since in practice becomes an economic asset for the Company and not for the worker, that is precisely who treated. Would be a strange situation that encourages increased risks at work, because the more injured there, increase the economic contribution to the payment of their wages).
Also important to take precautions, is that the permanent partial disability rating, or "diminished capacity" (in Conventions) by deafness, may be supported to take up or stay in some jobs.
This aspect is referred to the "scales of competence" that determine some companies for internal application. Union intervention is essential in this field, avoiding situations such discriminatory procedures, or reduction of jobs, among others. Types of hearing loss
The occupational deafness is hearing loss caused by certain conditions job.The entitled to compensation varies across countries, for example in Italy, there is a list of 22 types of activities, and treble sound trauma considered as work accidents.
In Spain the right to compensation for deafness is contained in box Permanent non-disabling injuries)
DEAFNESS OR HEARING LOSS TYPES OF BUSINESS:
· HEARING LOSS BY EXPOSURE TO NOISE
· HEARING LOSS FOR MIDDLE EAR TRAUMA BAROMETRIC
· HEARING LOSS FOLLOWING embolism
· BIPOACUSIA cranial trauma or craniofacial
· HEARING LOSS BY EXPOSURE TOXIC AGENTS
INDUSTRIAL NOISE EXPOSURE FOR HEARING LOSS HEARING LOSS BY TRAUMA BAROMETRIC
is an injury to the tympanic membrane middle ear caused by sudden changes in barometric pressure associated with changes in the normal function of the eustachian tube. Can be produced in two similar forms, by increasing pressure or by decreasing it in fast sea diving, or when a diver rises to the surface, intense chopped aviation and landing at excessive speed. There is a blockage of the middle ear with moderate to severe pain, and bleeding in case of eardrum rupture. Prevention is based on the proper execution of the decompression endotimpánica and treatment of rhino-pharyngeal any condition that may cause stenosis of the uterine decompression sickness Eustaquio.HIPOACUSIA
When air is breathed at high pressure, large quantities of nitrogen dissolved in the blood. If the return to normal pressure is not successful, strokes arise by the passage of this nitrogen from the blood into the tissues. Symptoms include hearing loss arises, it will be irreversible, with buzzing and balance disorders.
HEARING LOSS BY CRANIAL TRAUMA OR CRANIOFACIAL
is due to a fracture of the skull (by a blow to the chin that causes fouling of the mandibular condyle, breaking the eardrum or middle ear, causing hearing loss ... transmission) or a concussion without fracture. In the latter case, the hearing loss is sensory type, usually monolateral. HEARING LOSS BY TOXIC AGENTS
toxicants are nervous structures of the ear: source industrial (ototoxicity), certain drugs or drug ingestion (the manufacture of drugs not known to cause deafness), for example, alcohol, lead, carbon monoxide, mercury, carbon disulfide, and certain solvents such as benzene and trichlorethylene.
HEARING LOSS CALCULATION OF EARLY LOSS
INDEX (ELI). An index of early loss of occupational origin. Assesses the loss in dB at 4000Hz, subtracting the estimate of Presbycusis: Presbycusis
VALUE OF AGE dB dB MEN WOMEN
25 0 0 35 30 2 March
March 7
45 40 May 11 August 15 50 December 20
55 26 60 32 17 15 65 38 18
LOSS ELI GRADE CLASSIFICATION HEARING
CORRECTED - 8dB A
Excellent - Good
8-14 dB B - 15 - Normal 22 dB C
- 23-29 dB hearing loss suspected
D - + 30 dB E Deafness clear
AVERAGE SPEECH LOSS (SAL). Conversational rate of loss. It is estimated the average loss for each ear conversational frequencies (DB dB 500 Hz + 1000 Hz + 2000 Hz)
SAL GRADE HEARING LOSS CONVERSATIONAL MEDIA
- 16 dB (worse ear) A Normal
- 17-30 dB (one ear) B Difficulty hearing the whisper
- 31 -45 dB (better ear) C Difficulty hearing normal tone of voice
- 46-60 dB (better ear) D Difficulty hearing high-pitched voice
- 61-90 dB (better ear) hearing difficulty except E
amplified voice - 91 -100 dB (better ear) F Difficulty hearing even with amplification
CLASSIC GRADE: for rapid assessment in the light of audiometry. HEARING LOSS
GRADE I: Scotoma to 4000 Hz, 6000Hz recovery. HEARING LOSS
GRADE II: Scotoma to 4000 Hz, expanded to treble. HEARING LOSS
GRADE III: Scotoma broad band conversational interest.