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Which statement is true about non-conductive or noise induced hearing loss?

  • A

    It only affects the pilot’s ability to hear low-frequency sounds.

  • B

    It is caused by a blockage of the Eustachian tube.

  • C

    It is associated with the outer ear and can be cured by surgery.

  • D

    It is associated with the inner ear and is usually irreversible.

Refer to figure. 
NOISE INDUCED HEARING LOSS (NIHL)

Noise Induced Hearing Loss is caused due to loud sounds. It occurs when the individual is exposed to a very loud sound (above 120 dB) momentarily such as an explosion, or when the individual is exposed to loud noises (above 85 dB) for prolonged periods of time such as working in a noisy environment. The hearing loss may at first be temporary but if the individual keeps being exposed to loud noise (above 85 dB) the problem will become permanent. The cochlea contains delicate hair cells responsible for hearing. When hearing loss is temporary, the hair cells are not permanently damaged, but they are temporarily impaired or “stressed”. Damage to the cochlea hair cells (inner ear) leads to permanent hearing loss because damage to these cells is usually irreversible. The individual loses the ability to hear the higher frequencies first, since they are detected at the outer part of the cochlea which is more sensitive to damage.

Let's examine the given options:

It only affects the pilot’s ability to hear low-frequency sounds. → INCORRECT. The individual loses the ability to hear the higher frequencies first when damage to the cochlea occurs, so it does not only affect the low frequency sounds.

It is caused by a blockage of the Eustachian tube. → INCORRECT. The Eustachian tube is located in the middle ear and it is responsible to equalize pressure with the middle ear and the environment. Blockage leads to pain (barotrauma) but it does not cause hearing loss. The cochlea is in the inner ear responsible for hearing, which works independently of the Eustachian tube.

It is associated with the outer ear and can be cured by surgery. → INCORRECT. Noise Induced Hearing Loss is caused due to damage to the cochlea hair cells in the inner ear. These cells is usually irreversible and cannot be cured by surgery.

It is associated with the inner ear and is usually irreversible. → CORRECT. Damage to the cochlea hair cells (inner ear) leads to permanent hearing loss because damage to these cells is usually irreversible.

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