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Environment Module > Noise - 2 of 5

Hearing Loss

Excessive noise exposure can cause noise induced hearing loss (NIHL). Such loss can occur gradually over a number of years or occur as the result of a one time acoustic trauma.

  • NIHL - Noise induced hearing loss begins subtly and is often not recognized by the individual. The first indication is a temporary shift in hearing ability before and after exposure. This is termed a temporary threshold shift (TTS). It is termed "temporary" because hearing returns to normal after a period of time away from the noise that caused the shift. However, over time with repeated exposure, the temporary threshold shift become a permanent threshold shift (PTS). PTS is permanent, irreversible sensorineural loss.
  • Acoustic Trauma - Hearing loss due to acoustic trauma is caused by head or ear trauma or a one time exposure to a very intense sudden noise, such as an explosion. The eardrum can be perforated or the middle ear ossicles affected. Usually, this type of hearing loss is temporary and recoverable.

Because noise induced hearing loss begins slowly and imperceptibly to the individual, limits have been set for occupational exposure to noise. These exposure limits are established in the United States by the Occupational Safety and Health Administration (OSHA).



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