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Otolaryngology

Noise-Induced Hearing Loss

Noise and hearing loss:

When the ears are exposed to extremely loud noises, or to prolonged loud noises, inner ear structures can be damaged, leading to noise-induced hearing loss. Noise-induced hearing loss is quite common, affecting about one-third of the nearly 36 million Americans who suffer from hearing loss.

What constitutes a loud noise?

Noise, or sound intensity, is measured in decibels. Normal conversation levels occur at about 60 decibels. Anything above 120 decibels can harm the ears and lead to hearing loss. Examples of noises that reach 120 decibels or above include firecrackers, gunshots, and motorcycles. According to the American Academy of Otolaryngology, noise is damaging if:

  • you have to shout to be heard.
  • your ears hurt.
  • your ears ring.
  • you have difficulty hearing for a couple of hours after the exposure.

What is pitch?

Another measurement of noise, pitch, is the frequency of sound vibrations per second. The lower the pitch (deeper sound), the fewer vibrations per second. Pitch is measured in Hertz (Hz), which means cycles per second. Small children tend to have better hearing than adults and can hear sounds as low as 20 Hz (a large pipe organ) or as high as 20,000 Hz (a special dog whistle that most humans cannot hear). When hearing loss begins, a person will, generally, first have trouble hearing high-pitched noises.

How does a loud noise cause hearing loss?

Loud noises can cause damage to the hair cells in the inner ear and to the hearing nerve, called sensorineural hearing loss or nerve deafness. (Sensorineural hearing loss also can be caused by infection, head injury, aging, certain medications, birth defects, tumors, problems with blood circulation or high blood pressure, and stroke.)

Damage can occur from a brief, intense noise such as an explosion, or from continuous loud noises such as noises in a loud work environment. Hearing loss from loud noises may be immediate or occur slowly over years of continuous exposure.

Immediate hearing loss is often accompanied by tinnitus, or ringing in the ears or head. Immediate hearing loss can occur in one or both ears and often involves severe damage to the inner ear structure.

Prolonged exposure to noise can actually change the structure of the hair cells in the inner ear, resulting in hearing loss. Tinnitus, which is the sound of ringing, roaring, buzzing, or clicking inside the head, often occurs with prolonged noise exposure damage, as well.

Hearing loss from noise can be permanent or temporary. If the hearing loss is temporary, hearing usually recovers within 16 hours of loud noise exposure.

Noises that cause hearing loss:

Hearing loss can occur after a one-time exposure to a loud noise or after repeated exposure to varying loud noises. Exposure to loud noises can occur at work, at home, or at play. Examples of noises that can cause hearing loss either immediately or over time include:

  • Recreational activities
    • firing guns and other weapons
    • snowmobiles
    • go-carts
    • motorcycles
    • power horns
    • model airplanes
    • cap guns
  • At home
    • garbage disposal
    • vacuum cleaner
    • lawn mower
    • leaf blower
    • shop tools
  • At work
    • woodworking equipment
    • chain saws
    • sandblasting
    • heavy construction
    • jet engine
    • other noisy machinery

Preventing noise-induced hearing loss:

When you know you will be exposed to loud noises, either temporarily or over a longer period, using ear plugs or ear muffs can help prevent hearing loss. Ear plugs, which fit into the outer ear canal, and ear muffs, which fit over the entire outside of the ear, decrease the intensity of the sound that reaches the eardrum. Properly fitted ear plugs and ear muffs can reduce noise by 15 to 30 decibels. Other preventive measures include:

  • Protect small children from loud noises.

  • Be aware of hazardous noises in your environment.

  • Know which noises are too loud and can cause damage.

  • Undergo a medical examination to measure hearing.

In addition, the Occupational Safety and Health Administration (OSHA) requires hearing conservation programs in noisy work environments. Workers exposed to 85 decibels or more each day are required to have an annual hearing test. If more than 10 decibels of hearing loss are indicated by the annual hearing test, the employee must be informed and is required to wear some type of hearing protectors.

Which noises can affect hearing?

Level of safety Decibels (Approximately) Type of noise
Danger: Permanent hearing loss may occur 140 Firecrackers; rock concert
120 Snowmobiles
110 Chain saw
100 Wood shop
Warning: Gradual hearing loss may occur over time 90 Lawnmower; motorcycle
Safe 80 Traffic noise
60 Normal conversations
40 Refrigerator humming
20 Whispering
Source: National Institute on Deafness and other Communication Disorders

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