Description
Noise-induced hearing loss (NIHL) is diminished hearing ability due to damage to the inner ear by exposure to a very loud sound or long term exposure to reasonably loud sound. Regardless of the frequency of sound exposure, the usual range of hearing frequencies affected is 4000-6000 Hertz and gradually lower frequencies can be impaired.
Noise has the potential to damage the hearing cells of the cochlea in the inner ear. The hair cells can tolerate no more than 85dB of sound for 8 hours. Every 3dB increase in sound halves the amount of time the ear can tolerate sound before damage occurs. So sounds of 100dB can cause damage in just over 15 minutes hours and sounds of 103dB in just 7 minutes 30 seconds.
The hair cells can be permanently damaged from a sudden or one-off exposure to 130-140dB. This might occur in gunfire close to the ear or a blast injury and is termed acoustic trauma.
You may have experienced a change in your hearing after a few hours in a loud environment, such as a concert. Typically this is dullness in hearing that recovers over time and is termed temporary threshold shift. It occurs due to fatigue of the hair cells, which can recover depending on how long and loud the exposure to noise was.
In prolonged exposure to excessive noise or shorter periods of exposure to very high sound levels, a permanent threshold shift can occur. This is often not detected until 48 hours after the exposure and can become increasingly worse for up to five years after the original damage occurred.
Symptoms
Tinnitus (ringing in the ears, especially in quiet environments) is often an early symptom of NIHL but can occur in many conditions. The ear may also have a sensation of fullness. The hearing loss associated with noise is often gradual and affects high-pitched sounds first. Problems may be identified in understanding speech on the telephone, television or in situations with background noise.
Statistics
Noise induced hearing loss is the second most common type of hearing loss after presbyacusis (old age associated hearing loss), and all age groups can be affected. There is a slight male bias, but it is still unknown if this is a result of occupational status (such as working with heavy machinery) or an increased vulnerability to NIHL.
Diagnosis
Noise-induced hearing loss is diagnosed using the usual hearing assessments employed by an audiologist.
Treatment
Damage to the hair cells of the inner ear is irreversible, so noise induced hearing loss will not improve on its own. However, damage to the hair cells will not progress provided exposure to noise is ceased. Hearing aids or assisted listening devices may help amplify the areas where there is hearing damage.
It is best to prevent NIHL by limiting your exposure to loud noises and wearing ear plugs in situations of excessive noise exposure.
The information contained on this page is not meant to be a substitute for the advice from the surgeon or other clinical specialist. This is not a complete discussion of ear disease and is not a complete explanation of the risks of surgery and/or treatments.
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