Modified correction curves for noise hazard estimation

Abstract

The harmful effect of noise at work stands is established by the ISO Standard of noise which gives the maximum permissible and the mean permissible values of the sound-level expressed in dB (A). Application of the correction curve A does not account for the effects of the temporary threshold shift (TTS) and the permanent threshold shift (PTS) in hearing which results from physiological aging of the hearing organ. Both effects influence the noise induced permanent hearing loss (NIPTS), depending only on the exposure to noise. In addition there is no correspondence between the noise spectrum corrected by the curve A and the distribution of hearing loss established on the basis of the audiogram of a person exposed to this noise. The present proposal of modified correction curves for noise hazard estimation accounts for the effects mentioned above. Contrary to the previously used methods of noise spectrum correction (by the curves A and D), the distribution of the values of the sound level for individual frequencies, obtained by using the modified correction curves, accounts for the hearing lots induced by the noise. In particular, what is essential here is a good agreement between the position of the spectral maxima and the maximum hearing loss on the frequency scale. The correction curves proposed were used in the estimation of the noise hazard at the work stand of a cutter-loader.