Assessment of mean auditory hazard incurred by occupational exposure to impulse noise.

OBJECTIVES

To assess the collective hearing hazard entailed by occupational noise exposure.

METHODS

The Late Audio-Sonometric Index (LASI) is a global score recommended for following up hearing loss in groups of workers exposed to traumatic noise, combining: daily noise exposure level (L(EX,8h) in dB(A)); individual hearing threshold level at 3 kHz (HTL (3kHz) in dB); HTL(0)(3)(kHz) targeted at retirement; and 5 (or 10) years age bracket between 50 and 59 years of age. LASI=HTL(0)(3kHz) - HTL (3kHz)+10 log (age - 20) - 10 log (0.23×L(EX,8h) - 17.36).

RESULTS

When L(EX,8h) exceeds 80dB(A) and HTL(0)(3kHz) is at 25dB, occasional audiometric surveillance may be recommended for workers exposed to hazardous impulse noise: e.g., should the median and the mean LASI values fall below 20 for men or 23 for women (indicative threshold values).

CONCLUSION

This exponential model thus integrates the fact that daily exposure to impulse noise may be more harmful for hearing than eight hours exposure to continuous noise of equivalent energy.