Causes of hearing loss
Hearing loss caused by exposure to loud noises (noise pollution) is an increasing problem in our society today. When the delicate mechanisms of the inner ear are assaulted by loud noises, a phenomenon called temporary threshold shift (TIS) occurs. If you have ever walked away from a concert or a construction site with a buzzing or hissing in your ears, or with everything sounding as if you are underwater, you have experienced temporary threshold shift. When this condition occurs, you hear only noises above a certain level. While overnight rest usually restores normal hearing, this is a sign that damage has occurred to the hair cells in your inner ear. If this type of damage is lengthy and/or repeated, permanent threshold shift (PTS), with permanent damage and hearing loss, is the result.

There are a number of terms-some clinical, some informal-used to distinguish among the sources of noise­related hearing loss. Boilermaker's ear is a condition caused by heavy exposure to broad-band noise. The affected individual loses the ability to hear high-frequency sounds and has difficulty in understanding spoken words. Diplacusis is a form of hearing loss experienced as sound distortion­the pitch of a given tone is heard differently by each ear. Hyperacusis is an extreme sensitivity to loud noises that can be caused by damage to the eardrum. Sociocusis is a term used to denote hearing loss from non-work-related exposure to noise. Most people who develop noise-related hearing loss say they were unaware that anything was wrong until they developed tinnitus or speech became inaudible, but in fact, the damage begins long before that and temporary threshold shift is a clear sign of it.

Noise-related hearing loss is common in train engineers, military personnel, and workers subjected to constant industrial noise, as well as in hunters and musicians, especially rock musicians.
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