[ISO 1999:2013 part 1 : Revised probability model for calculating noise-induced hearing loss]

The ISO 1999:2013 norm describes a method of calculating the statistically expected permanent threshold shift (PTS) due to noise. Input parameters are noise level L_EX,8h related to an 8‑hour working day, duration of noise exposure in years, gender, and age. The background is a formula based on four datasets of measured values from larger surveys. Within its defined scope, ISO 1999 provides audiometric hearing curves for the frequencies 0.5, 1, 2, 3, 4, and 6 kHz for probability percentiles 5 to 95. This international standard is a useful additional tool for estimating the most probable cause of hearing disability when compared to the hearing curve in a noise worker's threshold audiogram and thus for deciding whether an occupational noise-induced hearing loss is likely to be present or not. According to the formula given in ISO 1999, sets of curves were recalculated separately for women and men to make them easily accessible in a new, expanded, and modernized graphical representation in this publication. Thus, according to ISO 1999, the following applies for the assessment: The higher the age, the more likely a noise-induced hearing threshold shift is to recede behind an age-related hearing threshold shift.