A stylized white ear, with two white bars surrounding it, on a blue background. Hearing loss, also known preparing for school children with speech disorders hearing impairment, is a partial or total inability to hear.
A deaf person has little to no hearing. Hearing loss may occur in one or both ears. 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. Half of hearing loss is preventable. This includes by immunization, proper care around pregnancy, avoiding loud noise, and avoiding certain medications.
As of 2013 hearing loss affects about 1. 1 billion people to some degree. Hearing loss exists when there is diminished sensitivity to the sounds normally heard. The terms hearing impaired 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. Another aspect of hearing involves the perceived clarity of a word rather than the amplitude of sound made by the word.
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 perception alone. Use of the terms “hearing impaired”, “deaf-mute”, or “deaf and dumb” to describe deaf and hard of hearing people is discouraged by advocacy organizations as they are offensive to many deaf and hard of hearing people. 20,000 Hz, and in amplitude from 0 dB to 130 dB or more. 130 dB represents the threshold of pain. Hearing loss has multiple causes, including ageing, genetics, perinatal problems and acquired causes like noise and disease.
For some kinds of hearing loss the cause may be classified as of unknown cause. There is a progressive loss of ability to hear high frequencies with aging known as presbycusis. For men, this can start as early as 25 and women at 30. Although genetically variable it is a normal concomitant of ageing and is distinct from hearing losses caused by noise exposure, toxins or disease agents.