noise damage

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  • noise trauma is the most common preventable cause of sensorineural hearing loss (1)
  • the noise source may be (1)
    • occupational
      • prolonged industrial exposure
    • recreational
      • loud music
    • accidental
      • blast injury
      • gunfire
  • oocupational noise damage may be : (2)
    • occupational acoustic trauma
      • is a sudden change in hearing
      • is caused by a single exposure to a sudden loud sound
        • e.g. explosion
    • occupational noise-induced hearing loss
      • develops gradually over a long period of time
      • is caused by exposure to continuous or intermittent loud sound
  • characteristics of occupational noise-induced hearing loss: (2)
    • always sensorineural
    • often accompanied by high-pitched tinnitus (1)
    • affects hair cellsof the inner ear
    • typically bilateral
    • high frequencies are affected first (1)
    • earliest change noticed on audiogram is
      • “notching” at 3000, 4000, or 6000 Hz, with recovery at 8000 Hz
      • precise location of the notch depends on:
        • the frequency of the damaging noise
        • the length of the ear canal (2)
    • rate of hearing loss
      • is highest during the first 10-15 years of exposure
      • reduces as the hearing threshold increases
        • but, age-related loss, accelerates over time
    • loss of hearing is not reversible
    • diagnosis
      • clinical
      • based on the history of noise exposure
  • treatment
    • the condition cannot be treated - damaged hair cells do not recover
    • early detection is vital to improve prevention (2)
    • a 10 dB threshold shift from baseline in pure tone average at 2000, 3000, and 4000 Hz is an significant early sign of permanent hearing loss
  • prevention (1)
    • needs aggressive use of noise protection
    • foam-insert earplugs
      • decreases noise exposure by 30 dB
  • medico-legal
    • noise damage is an acknowledged industrial disease
    • can be compensated for under the 1975 Industrial Injuries Act in the UK
    • there is an exposure limit in industry of 90dB for an 8 hour shift

Reference:

(1) differential diagnosis and treatment of hearing loss, Jon E. Isaacson, American Family Physician

(2) noise-induced hearing loss, Copyright ©  American College of Occupational and Environmental Medicine

Last reviewed 01/2018

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