Impact of Environmental Noise on Hearing Threshold in Soundproof and Non Soundproof Booths amongst Mine Workers in Rajasthan India – A Cross sectional Comparative Study

BACKGROUND: In many industrial dispensaries, audiometric testing is often conducted in small, enclosed rooms, where ambient noise exceeds the maximum permissible ambient noise level (MPANL). This environmental noise can interfere with accurate audiometric testing, leading to overestimated hearing thresholds and false-positive diagnoses of hearing impairments. AIM: The study aimed to compare audiometric results obtained in soundproof booths versus field settings with ambient noise and to assess the impact of environmental noise on hearing threshold assessments in the occupational settings. SUBJECT AND METHODS: This cross-sectional study was conducted amongst 164 mine workers in Rajasthan, India. Audiometric tests were performed using a portable calibrated audiometer across frequencies ranging from 0.5 kHz to 8 kHz. Each participant underwent two audiometric assessments: One in a soundproof booth adhering to standards and the other in a field setting with ambient noise. Background noise levels were measured using a sound-level meter. Hearing impairment was determined based on the average hearing threshold across all the tested frequencies. RESULTS: The soundproof booth maintained acceptable background noise levels (International Organisation for Standardisation 8253-1:2010), while the field noise exceeded the MPANL. The mean hearing threshold differences between the booth and field conditions were statistically significant for all frequencies (P < 0.0001). The largest difference was at 0.5 kHz (21.22 dB) and the smallest at 4 kHz (7.52 dB). In the booth, 41.46% of participants showed hearing impairment, whereas 100% exhibited hearing loss in the field setting. CONCLUSION: This study found that environmental noise in field conditions significantly increased hearing thresholds, leading to false-positive diagnoses of hearing impairment. These findings emphasise the need for soundproof booths in occupational audiometric testing to ensure accurate hearing assessment and avoid unnecessary diagnostic referrals.