Models for Estimating the Hearing Threshold of Quarry Workers at High Frequencies

Abstract

It is widely known that quarry industry has great importance in developing countries, such as Nigeria. There is paucity of information regarding effects of noise experienced by quarry workers during their working time. Therefore, this study investigated the influence of age of workers, years of exposure of workers and noise level of the machine used in quarry on hearing threshold. A factorial design of experiment was employed for the investigation. Two hundred and four quarry workers volunteered for this study from four quarries in South western Nigeria. Emitted noise, which quarry workers were exposed to during machinery operation, was measured with a digital sound level meter and workers hearing threshold was measured in an audiogram sound proofing testing booth at standard conditions. Predicted models were established from experimental design to determine main and interactions effects towards the response (hearing threshold). These were statistically analysed using analysis of variance (ANOVA). All terms of the models were significant at p<0.05. The best fitted model was at 4kHz (R2 = 0.639, p<0.05). The magnitudes of the main effect of the factors are in ascending order of noise level >years of exposure>age. The analysis of the experimental response indicated that there is no interaction of any factors on the hearing threshold. It can be concluded that age, years of exposure and noise level have main effects at various capacities at different frequency to predict the hearing threshold of the quarry workers. This work determined the factors and the predicted model to spell out safe hearing threshold of quarry workers that fitted for the job at a particular noisy workstation as well as ensuring comfortable, safe and effective workstation design.