The content of acoustic signals and biological effects of noise in conditions of high level of work intensity

BACKGROUND: The biological effects of noise depend on its physical parameters, combination with other hazards, the content of acoustic signals. This article aimed to analyze the difference in biological effects caused by the selection of nonverbal and verbal signals in conditions of a high level of work intensity. METHODS: Work conditions, physical characteristics of noise, levels of work intensity were studied among 75 telephone operators and 96 geophone operators. Levels of permanent hearing thresholds, evaluated by pure-tone audiometry, and results of self-estimation of operators’ health were compared. The contribution of the content of acoustic signals in the shifting of hearing thresholds was evaluated by the one-way analysis of variance. RESULTS: Selection of acoustic signals in the noise background (< 65 dB), in conditions of high work intensity, causes a significant increase of permanent hearing thresholds in both studied groups comparing to the non-noise exposed population. A combination of the high level of work intensity and distinguishing of nonverbal acoustic messages leads to significant deterioration of health resulting in decreasing of hearing sensitivity and a number of complaints on the state of health (p < 0.05). The content of acoustic signals significantly contributes to the biological effects of the nose. CONCLUSION: Obtained results testify necessity to revise safe criteria of noise levels for workers, engaged in selection, recognition and distinguishing of acoustic messages in the noise background combined with a high level of work intensity. In case when the energy of the acoustic field cannot be reduced, occupational safety measures should focus on decreasing of work intensity.