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The Hearing Loss Prevention Research Program is designed to reduce occupational hearing loss through research and the application of the research to real-world situations. [3] This database advances this goal by informing buyers and users of power tools of the dangerous levels of noise and vibrations that they are exposed to while using the tools.
The first research on the topic of how the ear hears different frequencies at different levels was conducted by Fletcher and Munson in 1933. Until recently, it was common to see the term Fletcher–Munson used to refer to equal-loudness contours generally, even though a re-determination was carried out by Robinson and Dadson in 1956, which became the basis for an ISO 226 standard.
In many industrial settings noise exposure metrics have been established to quantify human exposure to sound. In aerospace settings the Speech Intelligibility Index (SII), published in 1986 by the American National Standards Institute, is a major revision of the AI standard and defines computational methods "that produce results highly correlated with the intelligibility of speech under a ...
The same methodology was used to estimate the prevalence of hearing loss for noise-exposed U.S. workers within the Health Care and Social Assistance sector. [155] The prevalence of hearing loss in the Medical Laboratories subsector was 31% and in the Offices of All Other Miscellaneous Health Practitioners subsector was 24%.
Audiograms are unable to measure hidden hearing loss, [15] [16] which is the inability to distinguish between sounds in loud environments such as restaurants. Hidden hearing loss is caused by synaptopathy in the cochlea, [17] as opposed to sensorineural hearing loss caused by hair cell dysfunction. Audiograms are designed to "estimate the ...
When sensorineural hearing loss (damage to the cochlea or in the brain) is present, the perception of loudness is altered. Sounds at low levels (often perceived by those without hearing loss as relatively quiet) are no longer audible to the hearing impaired, but sounds at high levels often are perceived as having the same loudness as they would for an unimpaired listener.
A noise or sound dose is the amount of sound a person is exposed to in a day. The dose is represented by a percentage. A noise dose of 100% means that a person has exceeded the permissible amount of noise. Any noise exposure after the 100% noise dose may damage hearing. The exchange rate is the rate at which exposure accumulates.
The shape of the audiogram resulting from pure-tone audiometry gives an indication of the type of hearing loss as well as possible causes. Conductive hearing loss due to disorders of the middle ear shows as a flat increase in thresholds across the frequency range. Sensorineural hearing loss will have a contoured shape depending on the cause.
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