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Hearing loss, also known as hearing impairment, or anacusis, is a partial or total inability to hear. An affected person may be described as hard of hearing. A deaf person has little to no hearing.〔 Hearing loss may occur in one or both ears.〔 In children hearing problems can affect the ability to learn language and in adults it can cause work related difficulties. In some people, particularly older people, hearing loss can result in loneliness.〔 Hearing loss can be temporary or permanent. Hearing loss may be caused by a number of factors, including: genetics, ageing, exposure to noise, some infections, birth complications, trauma to the ear, and certain medications or toxins. A common condition that results in hearing loss is chronic ear infections. Certain infections during pregnancy such as rubella may also cause problems. Hearing loss is diagnosed when hearing testing finds that a person is unable to hear 25 decibels in at least one ear.〔 Testing for poor hearing is recommended for all newborns.〔 Hearing loss can be categorised as mild, moderate, severe, or profound.〔 Half of hearing loss is preventable. This includes by immunisation, proper care around pregnancy, avoiding loud noise, and avoiding certain medications.〔 The World Health Organization recommends that young people limit the use of personal audio players to an hour a day in an effort to limit exposure to noise. Early identification and support are particularly important in children. For many hearing aids, sign language, cochlear implants and subtitles are useful. Lip reading is another useful skill some develop. Access to hearing aids, however, is limited in many areas of the world.〔 Globally hearing loss affects about 10% of the population to some degree. It causes disability in 5% (360 to 538 million) and moderate to severe disability in 124 million people.〔(【引用サイトリンク】url=http://www.who.int/mediacentre/factsheets/fs300/en/ )〕〔 Of those with moderate to severe disability 108 million live in low and middle income countries. Of those with hearing loss it began in 65 million during childhood. Those who speak sign language and are members of Deaf culture see themselves as having a difference rather than an illness.〔 Most members of Deaf culture oppose attempts to cure deafness and some within this community view cochlear implants with concern as they have the potential to eliminate their culture. The term hearing impairment is often viewed negatively as it emphasises what people cannot do. ==Definition== *Hearing loss exists when there is diminished sensitivity to the sounds normally heard.〔 The terms hearing impairment or hard of hearing are usually reserved for people who have relative insensitivity to sound in the speech frequencies. The severity of a hearing loss is categorized according to the increase in volume above the usual level necessary before the listener can detect it. *Deafness is defined as a degree of loss such that a person is unable to understand speech even in the presence of amplification.〔 In profound deafness, even the loudest sounds produced by an audiometer (an instrument used to measure hearing by producing pure tone sounds through a range of frequencies) may not be detected. In total deafness, no sounds at all, regardless of amplification or method of production, are heard. *Speech perception - Another aspect of hearing involves the perceived clarity of a sound rather than its amplitude. In humans, that aspect is usually measured by tests of speech perception. These tests measure one's ability to understand speech, not to merely detect sound. There are very rare types of hearing loss which affect speech understanding alone.〔eBook: ''Current Diagnosis & Treatment in Otolaryngology: Head & Neck Surgery'', Lalwani, Anil K. (Ed.) Chapter 44: Audiologic Testing by Brady M. Klaves, PhD, Jennifer McKee Bold, AuD, Access Medicine〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Hearing loss」の詳細全文を読む スポンサード リンク
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