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Because of the cumulative impact of age and exposure to noise and other acoustic insults, 'typical' hearing may not be normative.
Hearing loss has multiple causes, including ageing, genetics, perinatal problems and acquired causes like noise and disease.
Studies of primitive peoples indicate that much of what has been attributed to age-related hearing loss may be long term cumulative damage from all sources, especially noise.
People living in preindustrial societies have considerably less hearing loss than similar populations living in modern society.
Noise-induced hearing loss (NIHL) typically manifests as elevated hearing thresholds (i.e.
less sensitivity or muting) between 30 Hz, centered at 4000 Hz.
There are many qualities of human hearing besides frequency range and amplitude that can't easily be measured quantitatively.
By correcting for age in assessing hearing, one tends to overestimate the hearing loss due to noise for some and underestimate it for others.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.Estimation of a "safe" duration of exposure is possible using an exchange rate of 3 d B.As 3 d B represents a doubling of intensity of sound, duration of exposure must be cut in half to maintain the same energy dose.
For example, at 100 d B (nightclub music level), a 3 d B exchange rate would limit exposure to 15 minutes; the 5 d B exchange rate allows an hour.