This standard specifies a method for calculating the permanent noise-induced threshold shift that is expected to occur at the hearing threshold levels of an adult population as a result of exposure to noise of different levels and durations; It provides the basis for calculating the hearing deficit according to various formulas, when the hearing threshold levels, measured at the usual audiometric frequencies or in combinations of these frequencies, exceed a certain value. NOTE- This standard does not specify the frequencies, combinations of frequencies or weighted combinations that should be used to evaluate hearing impairment; Nor does it specify the hearing threshold level ("limit") that must be exceeded for a hearing deficit to exist. The quantitative selection of such parameters is left to the discretion of the user. All sound pressure levels specified in this standard do not take into account the effect of hearing protectors that would reduce effective exposure levels at the ear.