A cross-sectional study of the relationship between background noise and hearing threshold among Indian mine workers: formulating regression equations to reduce the false- positive hearing impairment cases

Abstract Background noise is believed to affect audiometry results conducted particularly in non-soundproof booth in various occupational settings. The present study first of its kind investigated the effect of background noise on the results of audiometry among mine workers. Furthermore, the study formulated regression equations to rationalise audiometry conducted in a non-soundproof audiometry booth. In this cross-sectional study, audiometry was performed on mineworkers (n=388) divided into four groups with variable background noise outside the soundproof booth and then within the soundproof booth. The hearing levels of audiograms obtained outside and inside the soundproof booth were compared. A graph was plotted based on the differences in hearing level and background noise outside the audiometry booth. The relationship between variations in hearing level and background noise was explored using a coefficient of correlation. When the outside background noise level increased from 26 dB to 62 dB, the difference in hearing level increased from 2 dB to 27 dB across all groups. The mean hearing levels were found to be more affected at lower frequencies than at higher frequencies. Based on background noise and the variance in hearing level for each frequency, the study proposed regression equations. The study concluded that background noise had a greater impact on audiometry results at lower frequencies. Formulated regression equations may have the advantage of reducing the number of false positive hearing impairment cases that would have been identified in non-soundproof booths. The findings of the study are important particularly among mine workers in developing countries like India.