Hearing loss is either a partial inability to hear, or a total inability termed deafness. Hearing loss may be present at birth or acquired at any time afterwards. Hearing loss may occur in one or both ears. In children, hearing problems can affect the ability to acquire spoken language. In adults, it can create difficulties with social interaction and at work. Hearing loss can be temporary or permanent. Hearing loss related to age usually affects both ears and is due to cochlear hair cell loss. In some people, particularly older people, hearing loss can result in isolation and loneliness. Hearing loss may be caused by a number of factors, including: genetics, ageing, exposure to noise, some infections, birth complications, trauma to the ear or brain, and certain medications or toxins. A common condition that results in hearing loss is chronic ear infections. Certain infections during pregnancy, such as cytomegalovirus, syphilis and rubella, may also cause hearing loss in the child. 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 categorized as minimal/slight (15 to 25 dB), mild (25 to 40 dB), moderate (41 to 55 dB), moderate-severe (56 to 70 dB), severe (71 to 90 dB), or profound (greater than 90 dB). There are three main types of hearing loss: conductive hearing loss, sensorineural hearing loss, and mixed hearing loss. About half of hearing loss globally is preventable through public health measures. Such practices include immunization, proper care around pregnancy, avoiding loud noise, and avoiding certain medications. The World Health Organization recommends that young people limit exposure to loud sounds and the use of personal audio players to an hour a day to limit noise exposure. 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.
Access and affordability Access to hearing aids and hearing care varies widely by country, with affordability often cited as a major barrier to treatment. In New Zealand, public funding schemes provide partial or full subsidies for hearing aids depending on eligibility criteria, such as age, severity of hearing loss, and financial need. To further improve access, some providers in New Zealand, such as Resonate Health, have introduced subscription-based hearing aid models. These typically bundle device costs, servicing, and follow-up care into a monthly fee, reducing the upfront cost of treatment. As of 2013, hearing loss affects about 1.1 billion people to some degree. It causes disability in about 466 million people (5% of the global population), and moderate to severe disability in 124 million people. Of those with moderate to severe disability 108 million live in low and middle-income countries. Of those with hearing loss, it began during childhood for 65 million. Those who use sign language and are members of Deaf culture may see themselves as having a difference rather than a disability. Many members of Deaf culture reject cochlear implants and some within this community view them with concern as they have the potential to eliminate their culture.
Definition
Hearing loss is defined as diminished acuity to sounds which would otherwise be heard normally. The terms hearing impaired or hard of hearing are usually reserved for people who have a relative inability to hear sound in the speech frequencies. Hearing loss occurs when sound waves enter the ears and damage the sensitive tissues The severity of hearing loss is categorized according to the increase in intensity of sound above the usual level required for the listener to 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 highest intensity 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, can be heard. Speech perception is another aspect of hearing which involves the perceived clarity of a word rather than the intensity of sound made by the word. In humans, this is usually measured with speech discrimination tests, which measure not only the ability to detect sound, but also the ability to understand speech. There are very rare types of hearing loss that affect speech discrimination alone. One example is auditory neuropathy, a variety of hearing loss in which the outer hair cells of the cochlea are intact and functioning, but sound information is not faithfully transmitted by the auditory nerve to the brain. Use of the terms "hearing impaired", "deaf-mute", or "deaf and dumb" to describe deaf and hard-of-hearing people is discouraged by many in the deaf community as well as advocacy organizations, as they are offensive to many deaf and hard-of-hearing people.
Hearing standards
Human hearing extends in frequency from 20 to 20,000 Hz, and in intensity from 0 dB to 120 dB HL or more. 0 dB does not represent the absence of sound, but rather the softest sound an average unimpaired human ear can hear; some people can hear down to −5 or even −10 dB. Sound is generally uncomfortably loud above 90 dB and 115 dB represents the threshold of pain. The ear does not hear all frequencies equally well: hearing sensitivity peaks around 3,000 Hz. There are many qualities of human hearing besides frequency range and intensity that cannot easily be measured quantitatively. However, for many practical purposes, normal hearing is defined by a frequency versus intensity graph, or audiogram, charting sensitivity thresholds of hearing at defined frequencies. Due to the cumulative impact of age and exposure to noise and other acoustic insults, 'typical' hearing may not be normal.
Signs and symptoms
The presentation is as follows:
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