M00000390
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ISO 1999 3rd Edition, October 1, 2013 Acoustics - Estimation of noise-induced hearing loss
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Availability date: 07/13/2021
Description / Abstract:
This International Standard specifies a method for calculating
the expected noise-induced permanent threshold shift in the hearing
threshold levels of adult populations due to various levels and
durations of noise exposure; it provides the basis for calculating
hearing disability according to various formulae when the hearing
threshold levels at commonly measured audiometric frequencies, or
combinations of such frequencies, exceed a certain value.
NOTE 1 This International Standard does not specify frequencies,
frequency combinations, or weighted combinations to be used for the
evaluation of hearing disability; nor does it specify a hearing
threshold level (fence) which it is necessary to exceed for hearing
disability to exist. Quantitative selection of these parameters is
left to the user. All sound pressure levels stated in this
International Standard do not consider the effect of hearing
protectors which would reduce effective exposure levels and modify
the spectrum at the ear.
The measure of exposure to noise for a population at risk is the
noise exposure level normalized to a nominal 8 h working day,
LEH,8h, for a given number of years
of exposure. This International Standard applies to noise at
frequencies less than approximately 10 kHz which is steady,
intermittent, fluctuating, irregular. Use of this International
Standard for sound pressures exceeding 200 Pa (140 dB relative to
20 μPa) is recognized as extrapolation.
Formulae are presented to calculate the hearing loss, including
statistical distribution, at a range of audiometric frequencies due
to exposure to noise as a function of level of noise exposure and
duration of exposure (in years). The formulae do not distinguish
between male and female populations.
NOTE 2 Although the models of hearing loss are based on data
assumed to stem primarily from populations exposed to occupational
noise, they may be used, with some caution, for estimating the
effects of comparable nonoccupational and combined exposures.
NOTE 3 The prediction method presented is based primarily on
data collected with essentially broadband, steady, non-tonal
noise.
To calculate hearing threshold levels and the risk of acquiring
hearing loss due to noise exposure, it is necessary to make use of
a comparable population. This International Standard contains a
definition of a highly screened otologically normal population (in
accordance with ISO 7029) and three examples of unscreened
populations of three typical industrialized societies. The users of
this International Standard may choose a comparable population
according to their particular requirements.
NOTE 4 All data and procedures presented in this International
Standard are based on deliberate simplifications of experimental
data where the daily sound exposure duration did not exceed 12 h.
The resulting approximations restrict the validity to the stated
ranges of the variables, percentages, sound exposure levels, and
frequency ranges.
This International Standard is based on statistical data and
therefore cannot be applied to the prediction or assessment of the
hearing loss of individual persons except in terms of statistical
probabilities.