December 26, 2018
Noise Systemic harm to the human body, can cause changes in the auditory system, can also have an impact on a non-auditory system. These early effects mainly physiological change, long-term exposure to relatively strong noise, can cause pathological changes. In addition, the noise in the workplace can also interfere with the language exchange, affecting work efficiency, and even cause accidents.
Effect of noise on the auditory system
Effect of noise on auditory organs is a physiological process from migrating to the pathology, caused by pathological damage to a hearing must reach a certain strength and contact time. The noise is caused by long-term exposure to strong changes of auditory organ damage is generally from the temporary threshold shift gradually to the permanent threshold shift.
(1) temporary threshold shift. Temporary threshold shift is temporary threshold shift caused by a person or animal after exposure to noise from noise after a period of time after the hearing can be restored to the original level.
The auditory adaptation: short time exposure in strong noise environment, harsh voice, feeling unwell after cessation of exposure, decreased hearing organ sensitivity, disengagement of the voice of the outside world is "small" or "far" feeling, hearing threshold check can be increased by 10 ~ 15dB, can restore the out noise environment within 1min this phenomenon is called. Auditory adaptation.
Auditory fatigue: a long time continuously exposed to strong noise or repeatedly accepted impulse noise-induced hearing decreased, after leaving the noisy environment, hearing thresholds increased more than 15 ~ 30dB, take a few hours or even tens of hours listening to recover, called Auditory fatigue. In more than ten hours can be completely restored to physiological auditory fatigue. In the practical work often 16h limited in contact to work second days before the time interval during which returned to normal level. With the time of noise continued, if the first contact failed to fully recover the hearing changes caused by contact again, can cause hearing fatigue gradually increased, the final hearing did not recover and become permanent threshold shift. Auditory adaptation and auditory fatigue are reversible hearing loss, can be regarded as a physiological protective effect. The occurrence of auditory adaptation and auditory fatigue, hearing loss, can hear the sound of the threshold is increased, thereby reducing the noise damage.
The permanent threshold shift (2). To cause noise or other harmful factors increased hearing threshold permanent threshold shift, cannot be restored to the original level. The auditory organs with varying organic. Permanent threshold shifts It can be divided into hearing loss, noise deafness and explosive acoustic trauma.
The hearing loss: refers to a [>85 to more than hearing protection standard of environmental 90dB (A)] in the long term, it is difficult to restore auditory fatigue, continuous cumulative results, a pathological process can make the threshold by physiological migrate to unrecoverable. Mainly in the high frequency (3000Hz, 4000Hz, 6000Hz) either band appears permanent threshold shift is greater than 30dB, but no language hearing disorder, also known as high-frequency hearing loss. High-frequency hearing loss (especially in the 3000 ~ 6000Hz) can be used as an early indicator of noise deafness.
The noise deafness: when high-frequency hearing loss extended to language frequency three-band (500Hz, 1000Hz, 2000Hz), the average threshold shift is greater than 25dB, with a subjective hearing disorder, called noise deafness. And there is a sudden hearing loss to exist in the 4000Hz valley. Noise deafness is due to prolonged exposure to noise stimulation caused by a slow, progressive sensorineural hearing loss.
The explosive deafness and explosive acoustic trauma. Hearing loss resulting in a strong noise under the action of blasting operations, such as firearms or other sudden noise emissions by the formation of strong pulse composite noise and weak shock waves, the canal pressure peak, strong pressure can make the tympanic membrane hyperemia, hemorrhage or perforation can cause serious ossicular chain fracture. The instantaneous pressure into the inner ear, causing hearing impairment occurred in the lymph to basement membrane injury, strong oscillation and may be due to vestibular stimulation accompanied by dizziness, nausea, vomiting and other symptoms. The physical protection structure the reaction has been completely ineffective, it is necessary to strengthen the protection of individual auditory organs.
(3) cochlear morphological changes. The damage of auditory system caused by noise is the physical (Mechanical), multiple factors of physiological, biochemical and metabolic results. In these factors, can cause damage to hair cells, severe Corti (Corti) disappeared or destroyed. The injury often occurs in the oval window from 9 to 13mm.