Hearing Disorders Due to Noise

Definition

Noise is a sound or noise that bothers or undesirable. From this definition suggests that the actual noise is very subjective, depending on each individual, time and place of occurrence of noise. While in audiology, noise is a mixture of pure tone sound with different frequencies.
Hearing disability caused by work (occupational deafness / noise induced hearing loss) is the loss of the entire hearing sebahagian or someone who is a permanent, on one or both ears caused by the continuous noisy workplace environment. In industrial environments, the higher the intensity noise and the longer time noise exposure experienced by the workers, the more severe hearing loss inflicted on these workers. 

Etiology
Factors that affect the noise exposure:
1. The intensity noise
2. frequency noise
3. The length of time noise exposure
4. individual susceptibility
5. gender
6. age
7. Abnormalities in the middle ear

Distribution
In general, the effect of noise on hearing can be divided into two categories namely:
1. Noise Induced Temporary Threshold Shift (TTS)
2. Noise Induced Permanent Threshold Shift (NIPTS)

NOISE INDUCED TEMPORARY THRESHOLD SHIFT (NITTS)
Someone who was first exposed to loud noise will experience a variety of changes, which at first appears is taller hearing thresholds at high frequencies. In the audiometric picture appears as " notch "which is steep on the frequency of 4000 Hz, which is also called acoustic notch. At the initial level of hearing threshold shift is temporary, which is also called NITTS. If the rest outside the noisy environment usually can return to normal hearing.

INDUCED PERMANENT NOISE THRESHOLD SHIFT (NIPTS)
In everyday practice often found in cases of hearing loss due to noise, and this is called "occupational hearing loss" or loss of hearing due to work or any other names noise induced deafness industri. It is said that to change the time required NITTS be NIPTS noisy work environment for 10 - 15 years, but this depends also to:
1. noise level
2. person's sensitivity to noise
 

NIPTS usually occur around the frequency of 4000 Hz and slowly frequency increased and spread to surrounding areas. NIPTS initially without complaint, but if it has spread to the lower frequencies (2000 and

3000 Hz) complaints will arise. At first a person would have difficulty to hold a conversation in a crowded place, but when it is spread to a lower frequency will give rise to difficulty in hearing the voice very weak. Notch starts at frequencies 3000 - 6000 Hz, and after some time picture of a flat audiogram at frequencies more high. Frequency hearing loss at 4000 Hz will continue to grow and settled after 10 years and later development into a more lambat.

Pathogenesis

Deafness due to noise affecting the organ of Corti in the cochlea, especially the cells the hair. The first area affected is the outer hair cells that show the degeneration which increases with the intensity and duration of exposure. Stereosilia on outer hair cells become less rigid, thereby reducing response to stimulation. With increasing intensity and duration of exposure will be found more damage like loss stereosilia. areas that first exposed to the basal region. With the loss stereosilia, hair cells die and be replaced by scar tissue. The higher intensity of exposure sound, hair cells in and supporting cells are also damaged. with the growing extent of damage to the hair cells, can occur in nerve degeneration can also be found in the brainstem auditory nuclei. 

Clinical features
Deafness due to noise can affect discrimination in speech (Speech discrimination) and social functioning. Disturbances at high frequencies can cause difficulties in receiving and distinguishing consonant sounds. sound with a high tone, like a baby crying or a ringing phone can not be heard at all. Deafness is usually bilateral. Additionally tinnitus is symptoms are frequent complaint and may eventually interfere with the sharpness hearing and concentration.
In general overview on deaf deafness due to noise (noise induced hearing loss) are:
1. is sensorineural
2. Almost always bilateral
3. Rarely cause a very severe degree of deafness (profound hearing loss) The degree of hearing loss ranging between 40 s / d of 75 dB.
4. If the noise exposure is stopped, no longer found a decrease Significant hearing.
5. Ear damage in the first place on the frequency 3000, 4000 and 6000 Hz, where the most severe damage occurred on the frequency of 4000 Hz.
6. With constant exposure to noise, frequency deafness in 3000, 4000 and 6000 Hz will reach a maximum level in 10-15 years.
 

Besides the effect on hearing (auditory), excessive noise also has a non-auditory effects such as the influence of communication speech, impaired concentration, sleep disturbances due to stress triggers hearing loss who terjadi.

Management
In accordance with the causes of deafness, the patient should be transferred works from noisy environments. If not impossible to remove the tool can be used ear protectors that form the ear plugs (ear plugs), closed ear (ear muffs) And protective headgear (helmet).
Therefore, noise induced deafness is the cochlear nerve deafness that are settled (irreversible), when the hearing loss has resulted in difficulties communicate with the volume of ordinary conversation, can be tried installation of equipment hearing aids (ABD). If the hearing has been so bad, so using ABD was not able to communicate adequately, it is necessary done so that patients can receive psychotherapy situation. exercise hearing (auditory training) can also be done so that patients can use of residual hearing with ABD efficiently assisted by speech lip reading (lip reading), expression and movement of limbs and sign language to be berkomunikasi.

Prognosis
Because this type of deafness caused by exposure to noise is deaf cochlear nerve sedentary nature, and can not be treated as medical or surgery, the prognosis is less good. Therefore the most important is the prevention of deafness.

Posted in: Disease,Ear