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What level of received noise can cause Noise Induced Hearing Loss (NIHL)?
  • A
    Exposure to loud, intense sounds above 85 dB and low, continuous frequencies below 20 Hz.
  • B
    Exposure to sudden, low frequencies below 20 Hz and/or continuous, high frequencies above 20 kHz.
  • C
    A one-time exposure to impulse noise above 120 dB and/or continuous exposure to noise above 85 dB.
  • D
    Exposure to continuous, high frequencies above 10 kHz and intense sounds above 120 dB.


Sounds can be harmful when they are too loud, even for a brief time, or when they are both loud and long-lasting. These sounds can damage sensitive structures in the inner ear, such as the membrane and sensitive hair cells in the cochlea, and cause Noise-induced Hearing Loss (NIHL).

  • Sound is measured in units called decibels. Sounds at or below 70 decibels, even after long exposure, are unlikely to cause hearing loss. However, long or repeated exposure to sounds at or above 85 dB can cause hearing loss. NIHL can be caused by a one-time exposure to an intense “impulse” sound (above 120 dB), such as an explosion, or by continuous exposure to loud sounds over an extended period of time.

The early symptoms are an inability to hear high pitched notes as these notes are normally detected by the finer cells which suffer the greatest damage. NIHL is an occupational hazard for those of us in the aviation industry. In order to prevent NIHL, one is strongly encouraged to wear earplugs or other protective devices when involved in a loud activity. If you can’t reduce the noise or protect yourself from it, move away from it.

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