This International Standard prescribes a practical relationship between occupational nois exposure, expressed in terms of A-weighted sound level in dB (commonly referred to as dB (A)) and duration of exposure to during a normal working week (assumed to be 40 hours), and the percentage of workers who can be expected to have an increased hearing threshold of 25 dB or more, this threshold being an average calculated for the three frequencies 500, 1000 and 2000 Hz based exclusively on exposure to nois . This International Standard is not applicable to impulsive nois s, i.e. of a duration of less than 1 s, or to is lated high-level transients of very short duration, for example from gunshots. .
NBN S 01-015-1979 history
1979NBN S 01-015-1979 Acoustics - Assessment of occupational noise exposure for hearing conservation purposes