Noise-induced hearing loss

Lower noise induced hearing loss is defined as a chronic noise exposure (usually at work ) resulting sensorineural hearing loss. Makes it one of the bell raumen.

Ear Fatigue

If noise of high intensity (> 85 dB ( A)) acts on the ear, this leads after hours at a hearing impairment (synonyms: listening fatigue, temporary Hörschwellenabwanderung, English: Temporary Threshold Shift, short TTS). This hearing loss is reversible, in the course of hours or days it comes back to the normalization of hearing threshold. The duration of the recovery time depends on the extent of the TTS.

Noise Induced Hearing Loss

Does high-intensity noise (> 85 dB ( A)) for a long time, that is, over the years several hours each day to the hearing organ, a, so there is a permanent and irreversible damage to the auditory apparatus ( noise induced hearing loss ).

Location of the damage, the hair cells in the organ of Corti of the screw. The sinking of the hair cells begins largely independent of the physical characteristics of the damaging noise in that area of the lowermost turn of the screw ( basal turn ), corresponding to the analysis of about 4000 Hz. From here the process over time spreads out in both directions. In the area of the screw tip (apex) it never comes to a complete destruction of the hair cells, an absolute deafness is not produced as a result of chronic exposure to noise. Very often the noise induced hearing loss associated with tinnitus, but is rarely the focus of complaints.

The development of a noise induced hearing loss is dependent

• On the duration of noise exposure,
• The level and frequency spectrum of the noise acting,
• The presence of any noise breaks during the daily exposure and their distribution and
• Individual factors.

With a sound intensity below 85 dB ( A) any hearing loss is to be expected, with increasing sound intensity increases the risk of damage to the auditory apparatus and the extent of the expected hearing loss. At particularly high sound levels is a noticeable hearing loss may take a few years the result while such evolved at lower exposure only in decades.

The sensitivity of the ear is considerably higher than for lower and higher frequencies for frequencies between about 1000 and 6000 Hz.

If during the daily exposure to frequent disruptions (noise breaks), so the ear can recover again in each case, in any event, this increases the tolerance of the auditory apparatus to noise considerably.

Ultimately, the individual susceptibility to noise is not uniform. Only a small proportion of the noise exposed suffered such damage hearing that speech understanding is greatly restricted.

The audiogram shows a symmetrical sensorineural hearing loss ( sensorineural hearing loss ) at high frequencies with recruitment. The noise damage manifests itself first in the form of a valley of minimum audible at about 4000 Hz noticeable ( " c5 - sink" ), in the further course of this sink is deeper and wider and will also affect lower and higher frequencies. In extreme cases, lead to an Hochtontaubheit, the hearing for medium or even low tones is affected less or not at all.

Years or decades of exposure to noise can be found practically only in professional life. The noise induced hearing loss is therefore a typical occupational disease and considered as such according to law. Workers who are exposed to a noise level of 85 dB (A) daily noise exposure level or more, a screening exam before starting the activity must undergo in the noise area ( aptitude test ), and periodically monitoring studies. 13,546 cases of occupational diseases were recognized in Germany in 2008, of which it was in 5158 cases to noise induced hearing loss. In 2011, the number rose to 15,262 already, with 5,700 reported cases are in the noise-induced hearing about the most common recognized occupational disease in Germany.

The daily noise exposure level ( LEX, 8h ) is as defined in the Noise and Vibration OSH Regulation ( LärmVibrationsArbSchV ) § 2 (2 ) of the time-weighted average noise exposure level based on an eight-hour shift. It covers all noises present at work events.

The use of individual hearing protection ( ear muffs, pre-formed or formable earplugs, ear molds = fitted hearing protection) is from a daily noise exposure level of 85 dB ( A) or peak sound pressure level of 137 dB ( C) ( Upper trip level - noise area ) mandatory in professional activities. The employer shall make available on a daily noise exposure level of 80 dB ( A) or 135 dB (C) peak sound pressure level (lower trigger threshold ) Hearing protection and offer a voluntary screening of "noise ".

For private noise exposure, the use of hearing protection is strongly recommended.