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Occupational noise exposure is the main risk factor for work-related hearing loss. One study examined hearing test results obtained between 2000 and 2008 for workers ages 18–65 who had a higher occupational noise exposure than the average worker. [153] Of the sample taken, 18% of the workers had hearing loss.
Noise-induced hearing loss is a permanent shift in pure-tone thresholds, resulting in sensorineural hearing loss. The severity of a threshold shift is dependent on duration and severity of noise exposure. Noise-induced threshold shifts are seen as a notch on an audiogram from 3000 to 6000 Hz, but most often at 4000 Hz. [16]
Ototoxicity-induced hearing loss typically impacts the high frequency range, affecting above 8000 Hz prior to impacting frequencies below. [8] There is not global consensus on measuring severity of ototoxicity-induced hearing loss as there are many criteria available to define and measure ototoxicity-induced hearing loss.
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. [citation needed] There is a progressive loss of ability to hear high frequencies with aging known as presbycusis. For men, this can start as ...
PTA can be used to differentiate between conductive hearing loss, sensorineural hearing loss and mixed hearing loss. A hearing loss can be described by its degree i.e. mild, moderate, severe or profound, or by its shape i.e. high frequency or sloping, low frequency or rising, notched, U-shaped or 'cookie-bite', peaked or flat.
Normal human ears can discriminate between two frequencies that differ by as little as 0.2%. [14] If one ear has normal thresholds while the other has sensorineural hearing loss (SNHL), diplacusis may be present, as much as 15–20% (for example 200 Hz one ear => 240 Hz in the other).
Auditory fatigue is defined as a temporary loss of hearing after exposure to sound. This results in a temporary shift of the auditory threshold known as a temporary threshold shift (TTS). The damage can become permanent ( permanent threshold shift , PTS) if sufficient recovery time is not allowed before continued sound exposure. [ 1 ]
The most common type of congenital hearing loss in developed countries is DFNB1, also known as connexin 26 deafness or GJB2-related deafness. The most common dominant syndromic forms of hearing loss include Stickler syndrome and Waardenburg syndrome. The most common recessive syndromic forms of hearing loss are Pendred syndrome and Usher syndrome.